The black shales of Wufeng and Longmaxi Formation(Late Ordovician-Early Silurian period)in Sichuan Basin are the main strata for marine shale gas exploration,which have a yearly shale gas production of 228×10^(8)...The black shales of Wufeng and Longmaxi Formation(Late Ordovician-Early Silurian period)in Sichuan Basin are the main strata for marine shale gas exploration,which have a yearly shale gas production of 228×10^(8)m^(3)and cumulative shale gas production of 919×10^(8)m^(3).According to the lithological and biological features,filling sequences,sedimentary structures and lab analysis,the authors divided the Wufeng/Guanyinqiao and Longmaxi Formations into shore,tidal flat,shoal,shallow water shelf and deep water shelf facies,and confirmed that a shallow water deposition between the two sets of shales.Although both Formations contain similar shales,their formation mechanisms differ.During the deposition of Wufeng shale,influenced by the Caledonian Movement,the Central Sichuan and Guizhou Uplifts led to the transformation of the Sichuan Basin into a back-bulge basin.Coinstantaneous volcanic activity provided significant nutrients,contributing to the deposition of Wufeng Formation black shales.In contrast,during the deposition of Longmaxi shale,collisions caused basement subsidence,melting glaciers raised sea levels,and renewed volcanic activity provided additional nutrients,leading to Longmaxi Formation black shale accumulation.Considering the basic sedimentary geology and shale gas characteristics,areas such as Suijiang-Leibo-Daguan,Luzhou-Zigong,Weirong-Yongchuan,and Nanchuan-Dingshan are identified as key prospects for future shale gas exploration in the Wufeng-Longmaxi Formations.展开更多
The Govanda Formation was deposited during the Miocene in the intermontane areas between the Zagros suture and imbricate zones.The Govanda Formation was studied in the Sherwan Mazin area within Mergasor district,Erbil...The Govanda Formation was deposited during the Miocene in the intermontane areas between the Zagros suture and imbricate zones.The Govanda Formation was studied in the Sherwan Mazin area within Mergasor district,Erbil Governorate to identify the lithostratigraphy and microfacies analysis in order to determine the depositional environment of the formation.The formation in the studied section is 116 m thick and mainly consists of reddish-brown,hard,thickbedded,chert-bearing conglomerate,pinkish shale and yellowish-grey,thick-bedded,detrital,fossiliferous limestone.The formation is unconformably underlain by the Upper Cretaceous Tanjero Formation and conformably overlain by the Merga Red Beds series.Four different lithostratigraphic units were identified,based on field observation and petrographic analysis,including a basal conglomerate unit(A),a shale unit(B),a well-bedded limestone unit(C)and a thick and massively-bedded limestone unit(D).The presence of a thick conglomerate bed at the base of the formation indicates a large unconformity that lasted nearly 40 million years.Based on detailed microfacies analysis of carbonate rocks,five main microfacies and 15 submicrofacies are recognized.The main microfacies types include mudstone,wackestone,packstone,grainstone and boundstone microfacies.Based on the microfacies types the depositional environment are defined as open lagoon,reef,fore-reef and back-reef environments of normal to saline,nutrient rich water.展开更多
In Switzerland,the Opalinus Clay has been selected as a potential host rock for the deep geological disposal of radioactive waste due to its low hydraulic conductivity and favorable swelling properties.During the oper...In Switzerland,the Opalinus Clay has been selected as a potential host rock for the deep geological disposal of radioactive waste due to its low hydraulic conductivity and favorable swelling properties.During the operational phase of the repository,the host rock will be exposed to pH values as high as 13.5 due to concrete degradation,which will certainly affect its hydraulic properties.This study investigates the effect of pH increase on the water retention properties of Opalinus Clay.A series of samples from the lower sandy facies of the Mont Terri site in Switzerland,at initial dry state,were exposed to a hyperalkaline solution of pH=13.5 and to the synthetic water of pH=7.5 at different water contents.After equilibrium,the total suction was measured with a dew point potentiometer and microstructural analyses were conducted via mercury intrusion porosimetry(MIP)and nitrogen adsorption-desorption technique.It was found that the total suction decreased with hydration and pH increase.Since the two investigated solutions have the same osmotic suction,the decrease in total suction was attributed to the decrease in matric suction.Indeed,the total porosity increased with saturation and pH increase.This was confirmed by MIP data that evidenced an increase in the proportion of macropores,and by Barret eJoynereHalenda(BJH)data that showed mesopore generation.The specific surface area(SSA)also increased.The previous results were due to mineral hydration and,exclusively in the case of alkaline solution,to(1)the dissolution of quartz and calcite and(2)the acid-base reactions,which were concentrated at the edges of the clay particles,leading to an increase in negatively charged groups and thus to a face-to-face association of the clay particles(dispersion),causing an increase in the repulsive forces between the clay particles.In addition,the weakening of covalent bonds led to the primary dissolution of clay minerals,i.e.silicon and aluminum detachment.展开更多
0 INTRODUCTION Sulfur(S)and carbon(C)are essential volatile elements in both interior and surficial systems of the Earth.The cycling of S and C in subduction zones plays a fundamental role in modulating global S-C flu...0 INTRODUCTION Sulfur(S)and carbon(C)are essential volatile elements in both interior and surficial systems of the Earth.The cycling of S and C in subduction zones plays a fundamental role in modulating global S-C fluxes and exerts a significant influence on the climate evolution,mantle's redox budget,and ore deposit formation(Bekaert et al.,2021).展开更多
A new polarization–interference biomedical diagnostic three-dimensional(3D)Jones-matrix technology with digital Fourier reconstruction of layered maps of optical anisotropy(thesiograms)of dehydrated films(facies)of b...A new polarization–interference biomedical diagnostic three-dimensional(3D)Jones-matrix technology with digital Fourier reconstruction of layered maps of optical anisotropy(thesiograms)of dehydrated films(facies)of biological fluids of human organs is presented and experimentally tested.An original model of layered phase scanning of polycrystalline architectonics of supramolecular networks of biological fluid facies is proposed for the purpose of theoretical justification and prognostic use of the obtained results.On its basis,algorithms of Jones-matrix reconstruction of thesiograms of birefringence and dichroism of facies of synovial fluid,bile and blood are found.As a result,layered thesiograms of linear and circular birefringence and dichroism of facies with different spatial–angular architectonics of supramolecular networks are experimentally obtained for the first time.Within the framework of statistical analysis of experimental data,new objective markers(asymmetry and excess of optical anisotropy parameter distributions)for diagnostics of pathological changes in the optical anisotropy of biological fluid facies were defined and clinically tested.As a result,an excellent level of balanced accuracy of the developed polarization–interference Jones-matrix method of layer-by-layer reconstruction of thesiograms of polycrystalline supramolecular networks in differential diagnostics of bile facies(cholelithiasis),synovial fluid(reactive synovitis–septic arthritis)and whole blood(follicular adenoma–papillary thyroid cancer)was achieved.展开更多
Fan deltas are usually constructed through episodic flood event with debris flow transforming to hyper-concentrated flow during sediments proceeding. However, the role of topography in controlling the flow transformat...Fan deltas are usually constructed through episodic flood event with debris flow transforming to hyper-concentrated flow during sediments proceeding. However, the role of topography in controlling the flow transformation and sediments aggradation has been less studied. This constrain studies of sediment distribution and understanding of graded profile. For lake basin sequences, geomorphological control is much stronger than lake level rise and fall. Under extreme conditions, sediments can still prograde when the lake level rises. Therefore, describing the influence of geomorphology on the flow transformation and stacking pattern of the lobes can provide a deeper understanding of the controlling factors of the lake basin stratigraphy sequence. Xiligou lake (XLG) fan delta from Xisai Basin provides an optimal case for addressing this issue. Three lobes developed on the XLG fan delta with significant differences in their morphologies, architectures, lithofacies, sediment distributions and topographies. Through trenching, drone photography, and satellite data, we analyzed the structure of the sediments and the distribution of sedimentary facies. Based on the analysis of debris flow and hyper-concentrated flow deposits, two transformation models corresponding to different topographies were established. Sediment unloading is caused by a frictional reduction or a sudden momentum loss in the sediments flow's carrying capacity, allowing the debris flow transforms to hyper-concentrated flow and then to stream flow during the movement. The role of topography in controlling sediment flow transformation and sediment distribution is clarified through forces analysis of sediment grain. The topographic gradient of the linear slope is constant, so the direction of fluid movement is consistent with the topographic direction. Therefore, sediment flows move on linear slope without collision with the bed and there is no sudden loss of momentum. The gradual or sudden reduction in topographic gradient of concave slopes forces a constant or sudden change in the direction of fluid movement, which facilitates the unloading of sediments and the transformation of flow. The sudden change of topography forces unloading of viscous component, and the non-viscous component pass over to form hyper-concentrated flow, often accompanied by remobilized large gravels. The graded profile was an equilibrium between the dynamics and resistance of sediment transport. Changes in lake level affect the graded profile by changing the elevation of sediment transport, which is the total gravitational potential energy. The instantaneous graded profile and temporary graded profile are different scales of equilibrium corresponding to hydrodynamic equilibrium and depositional trend respectively. This study reveals the role of geomorphological dynamics in controlling sedimentary body progradation, thus providing a new perspective on the analysis of lake basin stratigraphy sequence.展开更多
Light hydrocarbons(LHs)are key components of petroleum,and the carbon isotopes composition(δ^(13)C)of individual LHs contains a wealth of geochemical information.Forty-four oil samples from five different basins were...Light hydrocarbons(LHs)are key components of petroleum,and the carbon isotopes composition(δ^(13)C)of individual LHs contains a wealth of geochemical information.Forty-four oil samples from five different basins were analyzed using gas chromatography(GC),gas chromatography-mass spectrometry(GC–MS),and gas chromatography-isotope ratio mass spectrometry(GC-IRMS).Theδ^(13)C values of forty-three LHs were recognized and determined by comparing the GC and GC-IRMS methods.The results revealed significant differences inδ^(13)C distribution characteristics among different LH compounds.Theδ^(13)C variation of individual LHs in iso-paraffins showed the widest range,followed by cycloalkanes and aromatics,whereas theδ^(13)C variation in n-paraffins showed the narrowest range.Theδ^(13)C values of most individual LHs are primarily affected by the source facies and thermal evolution.Among them,c-1,3-dimethylcyclohexane(c-1,3DMCH)is mainly sourced from higher plants but may also form through abiotic mechanisms such as catalysis or cyclization.Theδ^(13)C values of c-1,3DMCH(δ^(13)Cc-1,3DMCH)primarily exhibit parental genetic characteristics,enabling effective distinction of oil from different source facies.Specifically,theδ^(13)Cc-1,3DMCH in marine oils,lacustrine oils,terrigenous oils,and coal-formed oils are<–22‰,from–22‰to−20.2‰,from−20.2‰to−18.4‰,and>−18.4‰,respectively.Moreover,maturity is the primary controlling factor forδ^(13)C values of 3MC7(δ^(13)C3MC7,3MC7:3-methylheptane),while the source facies serve as a secondary influence.The plot ofδ^(13)Cc-1,3DMCH andδ^(13)C3MC7 was introduced to classify source facies.Asδ^(13)Cc-1,3DMCH andδ^(13)C3MC7 increase,the source facies transits from marine to lacustrine,then terrigenous,and finally coal facies.Additionally,increasingδ^(13)C3MC7 indicates a relative increase in maturity.Therefore,theδ^(13)Cc-1,3DMCH vs.δ^(13)C3MC7 plot serves as an effective tool for distinguishing source facies and assessing relative maturity.展开更多
Cone penetration testing(CPT)and its variant with pore pressure measurements(CPTu)are versatile tools that have been traditionally used for in situ geotechnical site investigations.These investigations are among the m...Cone penetration testing(CPT)and its variant with pore pressure measurements(CPTu)are versatile tools that have been traditionally used for in situ geotechnical site investigations.These investigations are among the most challenging yet indispensable tasks,providing a crucial reference for infrastructure planning,design and construction.However,data obtained through the CPT/CPTu testing often exhibit significant variability,even at closely spaced test points.This variability is primarily attributed to the complex mineral compositions and sedimentary process of the Quaternary sediments.Problems induced by the scattering data include the difficulties in estimating the shear strength of the sediments and determining the appropriate bearing stratum for pile foundations.In this paper,the conventional interpretation methods of the CPT/CPTu data are enhanced with sedimentary facies knowledge.The geotechnical investigation mainly involves 42 CPTu tests(39 essential data sets available)and 4 boring samples.Sediment types are interpreted from the CPTu data and calibrated by the nearby boring samples.Sedimentary facies are derived from the interpreted sequence stratigraphy,for which the interpretation skills are summarized in the form of characteristic curves of the CPTu data.Scattering distribution of the sediment types and their mechanical parameters are well explained by the sedimentary facies.The sediments are then categorized into a few groups by their sedimentary facies,resulting in reduced uncertainties and scattering in terms of shear strength.Bearing stratum of pile foundations is also suggested based on the sedimentary regulations.展开更多
Machine learning techniques and a dataset of five wells from the Rawat oilfield in Sudan containing 93,925 samples per feature(seven well logs and one facies log) were used to classify four facies. Data preprocessing ...Machine learning techniques and a dataset of five wells from the Rawat oilfield in Sudan containing 93,925 samples per feature(seven well logs and one facies log) were used to classify four facies. Data preprocessing and preparation involve two processes: data cleaning and feature scaling. Several machine learning algorithms, including Linear Regression(LR), Decision Tree(DT), Support Vector Machine(SVM),Random Forest(RF), and Gradient Boosting(GB) for classification, were tested using different iterations and various combinations of features and parameters. The support vector radial kernel training model achieved an accuracy of 72.49% without grid search and 64.02% with grid search, while the blind-well test scores were 71.01% and 69.67%, respectively. The Decision Tree(DT) Hyperparameter Optimization model showed an accuracy of 64.15% for training and 67.45% for testing. In comparison, the Decision Tree coupled with grid search yielded better results, with a training score of 69.91% and a testing score of67.89%. The model's validation was carried out using the blind well validation approach, which achieved an accuracy of 69.81%. Three algorithms were used to generate the gradient-boosting model. During training, the Gradient Boosting classifier achieved an accuracy score of 71.57%, and during testing, it achieved 69.89%. The Grid Search model achieved a higher accuracy score of 72.14% during testing. The Extreme Gradient Boosting model had the lowest accuracy score, with only 66.13% for training and66.12% for testing. For validation, the Gradient Boosting(GB) classifier model achieved an accuracy score of 75.41% on the blind well test, while the Gradient Boosting with Grid Search achieved an accuracy score of 71.36%. The Enhanced Random Forest and Random Forest with Bagging algorithms were the most effective, with validation accuracies of 78.30% and 79.18%, respectively. However, the Random Forest and Random Forest with Grid Search models displayed significant variance between their training and testing scores, indicating the potential for overfitting. Random Forest(RF) and Gradient Boosting(GB) are highly effective for facies classification because they handle complex relationships and provide high predictive accuracy. The choice between the two depends on specific project requirements, including interpretability, computational resources, and data nature.展开更多
The Lower Cambrian shale gas in the western Hubei area,South China has a great resource prospect,but the gas-in-place(GIP)content in different sedimentary facies varies widely,and the relevant mechanism has been not w...The Lower Cambrian shale gas in the western Hubei area,South China has a great resource prospect,but the gas-in-place(GIP)content in different sedimentary facies varies widely,and the relevant mechanism has been not well understood.In the present study,two sets of the Lower Cambrian shale samples from the Wells YD4 and YD5 in the western Hubei area,representing the deep-water shelf facies and shallowwater platform facies,respectively,were investigated on the differences of pore types,pore structure and methane adsorption capacity between them,and the main controlling factor and mechanism of their methane adsorption capacities and GIP contents were discussed.The results show that the organic matter(OM)pores in the YD4 shale samples are dominant,while the inorganic mineral(IM)pores in the YD5 shale samples are primary,with underdeveloped OM pores.The pore specific surface area(SSA)and pore volume(PV)of the YD4 shale samples are mainly from micropores and mesopores,respectively,while those of the YD5 shale samples are mainly from micropores and macropores,respectively.The methane adsorption capacity of the YD4 shale samples is significantly higher than that of the YD5 shale samples,with a maximum absolute adsorption capacity of 3.13 cm^(3)/g and 1.31 cm^(3)/g in average,respectively.Compared with the shallow-water platform shale,the deep-water shelf shale has a higher TOC content,a better kerogen type and more developed OM pores,which is the main mechanism for its higher adsorption capacity.The GIP content models based on two samples with a similar TOC content selected respectively from the Wells YD4 and YD5 further indicate that the GIP content of the deep-water shelf shale is mainly 34 m^(3)/t within a depth range of 1000—4000 m,with shale gas exploration and development potential,while the shallow-water platform shale has normally a GIP content of<1 m^(3)/t,with little shale gas potential.Considering the geological and geochemical conditions of shale gas formation and preservation,the deep-water shelf facies is the most favorable target for the Lower Cambrian shale gas exploration and development in the western Hubei area,South China.展开更多
The Middle Permian Qixia Formation in the Shuangyushi area,northwestern Sichuan Basin,develops shoal-facies dolomite reservoirs.To pinpoint promising reservoirs in the Qixia Formation,deep thin shoal-facies dolomite r...The Middle Permian Qixia Formation in the Shuangyushi area,northwestern Sichuan Basin,develops shoal-facies dolomite reservoirs.To pinpoint promising reservoirs in the Qixia Formation,deep thin shoal-facies dolomite reservoirs were predicted using the techniques of pre-stack Kirchhoff-Q compensation for absorption,inverse Q filtering,low-to high-frequency compensation,forward modeling,and facies-controlled seismic meme inversion.The results are obtained in six aspects.First,the dolomite reservoirs mainly exist in the middle and lower parts of the second member of Qixia Formation(Qi2 Member),which coincide with the zones shoal cores are developed.Second,the forward modeling shows that the trough energy at the top and bottom of shoal core increases with increasing shoal-core thickness,and weak peak reflections are associated in the middle of shoal core.Third,five types of seismic waveform are identified through waveform analysis of seismic facies.Type-Ⅰ and Type-Ⅱ waveforms correspond to promising facies(shoal core microfacies).Fourth,vertically,two packages of thin dolomite reservoirs turn up in the sedimentary cycle of intraplatform shoal in the Qi2 Member,and the lower package is superior to the upper package in dolomite thickness,scale and lateral connectivity.Fifth,in plane,significantly controlled by sedimentary facies,dolomite reservoirs laterally distribute with consistent thickness in shoal cores at topographical highs and extend toward the break.Sixth,the promising prospects are the zones with thick dolomite reservoirs and superimposition of horstegraben structural traps.展开更多
The saline lacustrine hybrid sedimentary rocks are complex in lithology and unknown for their sedimentary mechanisms.The hybrid sedimentary rocks samples from the Neogene upper Ganchaigou Formation to lower Youshashan...The saline lacustrine hybrid sedimentary rocks are complex in lithology and unknown for their sedimentary mechanisms.The hybrid sedimentary rocks samples from the Neogene upper Ganchaigou Formation to lower Youshashan Formation(N_(1)-N_(2)^(1))in the Fengxi area Qaidam Basin,were investigated through core-log and petrology-geochemistry cross-analysis by using the core,casting thin section,scanning electron microscope,X-ray diffraction,logging,and carbon/oxygen isotopic data.The hybrid sedimentary rocks in the Fengxi area,including terrigenous clastic rock and lacustrine carbonate rock,were deposited in a shallow lake environment far from the source,or occasionally in a semi-deep lake environment,with 5 lithofacies types and 6 microfacies types recognized.Stable carbon and oxygen isotopic compositions reveal that the formation of sedimentary cycles is controlled by a climate-driven compensation-undercompensation cyclic mechanism.A sedimentary cycle model of hybrid sedimentary rocks in an arid and saline setting is proposed.According to this model,in the compensation period,the lake level rises sharply,and microfacies such as mud flat,sand-mud flat and beach are developed,with physical subsidence as the dominant sedimentary mechanism;in the undercompensation period,the lake level falls slowly,and microfacies such as lime-mud flat,lime-dolomite flat and algal mound/mat are developed,with chemical-biological process as the dominant sedimentary mechanism.In the saline lacustrine sedimentary system,lacustrine carbonate rock is mainly formed along with regression,the facies change is not interpreted by the accommodation believed traditionally,but controlled by the temporary fluctuation of lake water chemistry caused by climate change.The research results update the interpreted high-resolution sequence model and genesis of hybrid sedimentary rocks in the saline lacustrine basin and provide a valuable guidance for exploring unconventional hydrocarbons of saline lacustrine facies.展开更多
Fault zones have always drawn attention from the industry,and the performance of a quantitative interpretation of the fault interior structure on seismic data has remained as a big challenge.In this work,we focus on q...Fault zones have always drawn attention from the industry,and the performance of a quantitative interpretation of the fault interior structure on seismic data has remained as a big challenge.In this work,we focus on quantitatively populating the heterogeneity of the fault interior structure in a three-dimensional space on seismic data.To realize this goal,we take the South Wuerxun sub-depression in Hailar Basin as an example of a faulted basin.First,based on a heterogeneity analysis using the drilling and logging information from wells,we establish fault zone geologic models and perform seismic forward modeling to determine the relationship between different fault zone models with different fault dips,internal fillings,and P wave responses.Next,the fault interior structure index(FIS)is constructed,and the response features on the FIS from the fault facies and the host rock are observed.Finally,the FIS is applied to perform the quantitative interpretation and prediction of the heterogeneity in the FIS on seismic data.The results show that the FIS response from the fault zone is higher than that of the host rock in plane,indicating that the former is quantitatively separated from the surrounding host rocks.The FIS values greater than 26 represent the feedback from the fault facies,whereas those less than 26 represent the response from the host rocks.The FIS shows segmented features in the strike,banded in dip on plane.On the slip surface,the FIS indicates the shale smear zone and the location where low-graded and small-scaled faults are densely developed.The heterogeneity prediction result is proven by oil and gas exploration activities.The study results imply that the FIS could indicate a favorable path of the hydrocarbon migration in the fault zone and evaluate the fault sealing parts.The method can explore the quantitative characterization of fault facies and has essential popularization and application values in similar geological application fields,including hydrocarbon exploration,development of faulted reservoirs,and geological engineering evaluation related to faults.展开更多
With the successful application and breakthrough of deep learning technology in image segmentation,there has been continuous development in the field of seismic facies interpretation using convolutional neural network...With the successful application and breakthrough of deep learning technology in image segmentation,there has been continuous development in the field of seismic facies interpretation using convolutional neural networks.These intelligent and automated methods significantly reduce manual labor,particularly in the laborious task of manually labeling seismic facies.However,the extensive demand for training data imposes limitations on their wider application.To overcome this challenge,we adopt the UNet architecture as the foundational network structure for seismic facies classification,which has demonstrated effective segmentation results even with small-sample training data.Additionally,we integrate spatial pyramid pooling and dilated convolution modules into the network architecture to enhance the perception of spatial information across a broader range.The seismic facies classification test on the public data from the F3 block verifies the superior performance of our proposed improved network structure in delineating seismic facies boundaries.Comparative analysis against the traditional UNet model reveals that our method achieves more accurate predictive classification results,as evidenced by various evaluation metrics for image segmentation.Obviously,the classification accuracy reaches an impressive 96%.Furthermore,the results of seismic facies classification in the seismic slice dimension provide further confirmation of the superior performance of our proposed method,which accurately defines the range of different seismic facies.This approach holds significant potential for analyzing geological patterns and extracting valuable depositional information.展开更多
To solve the problems in restoring sedimentary facies and predicting reservoirs in loose gas-bearing sediment,based on seismic sedimentologic analysis of the first 9-component S-wave 3D seismic dataset of China,a four...To solve the problems in restoring sedimentary facies and predicting reservoirs in loose gas-bearing sediment,based on seismic sedimentologic analysis of the first 9-component S-wave 3D seismic dataset of China,a fourth-order isochronous stratigraphic framework was set up and then sedimentary facies and reservoirs in the Pleistocene Qigequan Formation in Taidong area of Qaidam Basin were studied by seismic geomorphology and seismic lithology.The study method and thought are as following.Firstly,techniques of phase rotation,frequency decomposition and fusion,and stratal slicing were applied to the 9-component S-wave seismic data to restore sedimentary facies of major marker beds based on sedimentary models reflected by satellite images.Then,techniques of seismic attribute extraction,principal component analysis,and random fitting were applied to calculate the reservoir thickness and physical parameters of a key sandbody,and the results are satisfactory and confirmed by blind testing wells.Study results reveal that the dominant sedimentary facies in the Qigequan Formation within the study area are delta front and shallow lake.The RGB fused slices indicate that there are two cycles with three sets of underwater distributary channel systems in one period.Among them,sandstones in the distributary channels of middle-low Qigequan Formation are thick and broad with superior physical properties,which are favorable reservoirs.The reservoir permeability is also affected by diagenesis.Distributary channel sandstone reservoirs extend further to the west of Sebei-1 gas field,which provides a basis to expand exploration to the western peripheral area.展开更多
The complex pore structure of carbonate reservoirs hinders the correlation between porosity and permeability.In view of the sedimentation,diagenesis,testing,and production characteristics of carbonate reservoirs in th...The complex pore structure of carbonate reservoirs hinders the correlation between porosity and permeability.In view of the sedimentation,diagenesis,testing,and production characteristics of carbonate reservoirs in the study area,combined with the current trends and advances in well log interpretation techniques for carbonate reservoirs,a log interpretation technology route of“geological information constraint+deep learning”was developed.The principal component analysis(PCA)was employed to establish lithology identification criteria with an accuracy of 91%.The Bayesian stepwise discriminant method was used to construct a sedimentary microfacies identification method with an accuracy of 90.5%.Based on production data,the main lithologies and sedimentary microfacies of effective reservoirs were determined,and 10 petrophysical facies with effective reservoir characteristics were identified.Constrained by petrophysical facies,the mean interpretation error of porosity compared to core analysis results is 2.7%,and the ratio of interpreted permeability to core analysis is within one order of magnitude,averaging 3.6.The research results demonstrate that deep learning algorithms can uncover the correlation in carbonate reservoir well logging data.Integrating geological and production data and selecting appropriate machine learning algorithms can significantly improve the accuracy of well log interpretation for carbonate reservoirs.展开更多
The establishment of effective proxies for the differentiation of sedimentary facies in the tide-dominated river mouth is fundamental to the delineation of stratigraphy and the study of paleoenvironments.Geochemical s...The establishment of effective proxies for the differentiation of sedimentary facies in the tide-dominated river mouth is fundamental to the delineation of stratigraphy and the study of paleoenvironments.Geochemical signatures of the acetic acid(HAc)extractive phases of alkaline earth metals,such as Sr,Ba,and Ca,are closely related to sedimentary environments and thus provide a novel method for discriminating the sedimentary facies of river mouth.In this study,50 surface water and surface sediment samples were obtained from different geomorphological units of the Jiulong River mouth,i.e.,river channel,distributary channel,delta front,delta front slope,prodelta,and shallow marine area,and the salinity of the water,the grain size,and the Sr,Ba,and Ca contents and Sr/Ba molar ratio(Sr/Ba)in HAc leachates of the sediments were determined.Contents of alkaline earth metals in HAc leachates of surface sediments from the Changjiang(Yangtze)River coast were also collated.The goals of this study were to reveal the spatial distribution of alkaline earth metals in the Jiulong River mouth,define their depositional mechanisms,and search for effective geochemical proxies for identification of the various sedimentary facies in the fluvial to marine transition zone.The results revealed several land-to-sea gradients.The Ba content decreased rapidly from the distributary channel to the sea,and the Sr and Ca contents and Sr/Ba increased gradually with the increase in salinity.Salinity,marine biomass,and sedimentary dynamic processes,were speculated to be the main reasons for the differences in their spatial distributions.There were significant differences in Ba,Sr,Ca,and Sr/Ba between the river channel and the distributary channel,in Ca and Ba between the distributary channel and the delta front(slope),and in Sr,Ca,and Sr/Ba between the delta front(slope)and the prodelta-shallow marine region.The Sr-Ba scatterplot showed that the sediments of the river channel and alluvial plain were located as a high Ba and low Sr element-defined end-member,whereas samples of the prodelta and shallow marine formed a high Sr and low Ba end-member.These can be used as characteristic end-members indicating terrestrial facies and marine facies,respectively.The sediments of the delta plain,tidal river,distributary channel,delta front,and delta front slope are located between these two end-member regions of the scatterplot,and this region of the diagram can be used to identify land-sea transitional sedimentary facies.展开更多
The geological conditions of offshore shallow water delta oil reservoirs were complex, with limited well data and large well spacing. Taking A Oilfield in the Bohai Sea Area, China as an example, the target sand body ...The geological conditions of offshore shallow water delta oil reservoirs were complex, with limited well data and large well spacing. Taking A Oilfield in the Bohai Sea Area, China as an example, the target sand body was formed in a shallow water delta sedimentary environment, with well-developed underwater distributary channels and frequent branching and diversion. The reservoir was strong non-uniformity and uneven plane water cut pressure. To this end, based on the existing work of predecessors, combined with seismic, logging, and production dynamics data, and based on the genesis mechanism of shallow water delta reservoirs, the boundary of composite river channels was identified through seismic facies, and logging facies were used to subdivide them into single river levels within the composite river channels. Then, seismic waveform characteristics were applied to track and characterize the plane distribution of single river channels, guiding the efficient development of offshore shallow water delta oil fields and achieving increased storage and production in Bohai Oilfield, China.展开更多
Reef-bank reservoirs are an important target for petroleum exploration in marine carbonates and also an essential supplemental area for oil and gas production in China. Due to the diversity of reservoirs and the extre...Reef-bank reservoirs are an important target for petroleum exploration in marine carbonates and also an essential supplemental area for oil and gas production in China. Due to the diversity of reservoirs and the extreme heterogeneity of reef-banks, it is very difficult to discriminate the sedimentary facies and lithologies in reef-bank reservoirs using conventional well logs. The borehole image log provides clear identification of sedimentary structures and textures and is an ideal tool for discriminating sedimentary facies and lithologies. After examining a large number of borehole images and cores, we propose nine typical patterns for borehole image interpretation and a method that uses these patterns to discriminate sedimentary facies and lithologies in reeI^bank reservoirs automatically. We also develop software with user-friendly interface. The results of applications in reef-bank reservoirs in the middle Tarim Basin and northeast Sichuan have proved that the proposed method and the corresponding software are quite effective.展开更多
In the Sichuan Basin,the Middle Permian marine carbonate rocks are important natural gas pay zones with immense exploration potential,but the facies belts and distribution situations of layered dolomite reservoirs are...In the Sichuan Basin,the Middle Permian marine carbonate rocks are important natural gas pay zones with immense exploration potential,but the facies belts and distribution situations of layered dolomite reservoirs are not clear,which hinders the progress in natural gas exploration.In view of the sedimentary background of the Sichuan Basin,field outcrop section,drilling data and seismic data were comprehensively analyzed with the favorable reservoir intervals in the framework of sequence stratigraphy as the key research units.Research results about its lithofacies paleogeography were obtained as follows.First,a gentle slope SW high and NE low was presented during the sedimentation of the Qixia Fm in the Middle Permian.In the Maokou Fm of the Middle Permian,however,a series of the N-W trending intra-platform rifts were developed in this setting,and eventually a paleogeographic pattern of NE-dipping alternative uplift and depression was evolved.Second,in the Qixia Fm,the transgressive tract was in an open platform environment and the highstand system tract evolved into a rimmed platform.And the platform margin beach in the area of Jiange-Ya'an is the favorable reservoir facies belt.And third,in the Maokou Fm,the transgressive tract was in the carbonate shelf environment and the highstand system tract evolved into a rimmed platform.And the platform margin reef flat in the area of Jiange-Ya'an and the syneclise margin beach in the area of YantingeGuang'an are favorable reservoir facies belts.It is concluded that the two grain beach facies belts in the areas of Jiange-Ya'an and YantingeGuang'an were the favorable zones for the large-scale development of Middle Permian layered dolomite reservoirs and they are the main target of subsequent natural gas exploration.展开更多
基金supported by the project of the China Geological Survey(DD20221661).
文摘The black shales of Wufeng and Longmaxi Formation(Late Ordovician-Early Silurian period)in Sichuan Basin are the main strata for marine shale gas exploration,which have a yearly shale gas production of 228×10^(8)m^(3)and cumulative shale gas production of 919×10^(8)m^(3).According to the lithological and biological features,filling sequences,sedimentary structures and lab analysis,the authors divided the Wufeng/Guanyinqiao and Longmaxi Formations into shore,tidal flat,shoal,shallow water shelf and deep water shelf facies,and confirmed that a shallow water deposition between the two sets of shales.Although both Formations contain similar shales,their formation mechanisms differ.During the deposition of Wufeng shale,influenced by the Caledonian Movement,the Central Sichuan and Guizhou Uplifts led to the transformation of the Sichuan Basin into a back-bulge basin.Coinstantaneous volcanic activity provided significant nutrients,contributing to the deposition of Wufeng Formation black shales.In contrast,during the deposition of Longmaxi shale,collisions caused basement subsidence,melting glaciers raised sea levels,and renewed volcanic activity provided additional nutrients,leading to Longmaxi Formation black shale accumulation.Considering the basic sedimentary geology and shale gas characteristics,areas such as Suijiang-Leibo-Daguan,Luzhou-Zigong,Weirong-Yongchuan,and Nanchuan-Dingshan are identified as key prospects for future shale gas exploration in the Wufeng-Longmaxi Formations.
文摘The Govanda Formation was deposited during the Miocene in the intermontane areas between the Zagros suture and imbricate zones.The Govanda Formation was studied in the Sherwan Mazin area within Mergasor district,Erbil Governorate to identify the lithostratigraphy and microfacies analysis in order to determine the depositional environment of the formation.The formation in the studied section is 116 m thick and mainly consists of reddish-brown,hard,thickbedded,chert-bearing conglomerate,pinkish shale and yellowish-grey,thick-bedded,detrital,fossiliferous limestone.The formation is unconformably underlain by the Upper Cretaceous Tanjero Formation and conformably overlain by the Merga Red Beds series.Four different lithostratigraphic units were identified,based on field observation and petrographic analysis,including a basal conglomerate unit(A),a shale unit(B),a well-bedded limestone unit(C)and a thick and massively-bedded limestone unit(D).The presence of a thick conglomerate bed at the base of the formation indicates a large unconformity that lasted nearly 40 million years.Based on detailed microfacies analysis of carbonate rocks,five main microfacies and 15 submicrofacies are recognized.The main microfacies types include mudstone,wackestone,packstone,grainstone and boundstone microfacies.Based on the microfacies types the depositional environment are defined as open lagoon,reef,fore-reef and back-reef environments of normal to saline,nutrient rich water.
文摘In Switzerland,the Opalinus Clay has been selected as a potential host rock for the deep geological disposal of radioactive waste due to its low hydraulic conductivity and favorable swelling properties.During the operational phase of the repository,the host rock will be exposed to pH values as high as 13.5 due to concrete degradation,which will certainly affect its hydraulic properties.This study investigates the effect of pH increase on the water retention properties of Opalinus Clay.A series of samples from the lower sandy facies of the Mont Terri site in Switzerland,at initial dry state,were exposed to a hyperalkaline solution of pH=13.5 and to the synthetic water of pH=7.5 at different water contents.After equilibrium,the total suction was measured with a dew point potentiometer and microstructural analyses were conducted via mercury intrusion porosimetry(MIP)and nitrogen adsorption-desorption technique.It was found that the total suction decreased with hydration and pH increase.Since the two investigated solutions have the same osmotic suction,the decrease in total suction was attributed to the decrease in matric suction.Indeed,the total porosity increased with saturation and pH increase.This was confirmed by MIP data that evidenced an increase in the proportion of macropores,and by Barret eJoynereHalenda(BJH)data that showed mesopore generation.The specific surface area(SSA)also increased.The previous results were due to mineral hydration and,exclusively in the case of alkaline solution,to(1)the dissolution of quartz and calcite and(2)the acid-base reactions,which were concentrated at the edges of the clay particles,leading to an increase in negatively charged groups and thus to a face-to-face association of the clay particles(dispersion),causing an increase in the repulsive forces between the clay particles.In addition,the weakening of covalent bonds led to the primary dissolution of clay minerals,i.e.silicon and aluminum detachment.
基金financially supported by the National Natural Science Foundation of China(Nos.92355301,42302061)the China Postdoctoral Science Foundation(No.2023M743471)+1 种基金the Key Research Program of the Institute of Geology and Geophysics,Chinese Academy of Sciences(No.IGGCAS-202204)the Youth Innovation Promotion Association of Chinese Academy of Sciences(No.Y2021026)。
文摘0 INTRODUCTION Sulfur(S)and carbon(C)are essential volatile elements in both interior and surficial systems of the Earth.The cycling of S and C in subduction zones plays a fundamental role in modulating global S-C fluxes and exerts a significant influence on the climate evolution,mantle's redox budget,and ore deposit formation(Bekaert et al.,2021).
文摘A new polarization–interference biomedical diagnostic three-dimensional(3D)Jones-matrix technology with digital Fourier reconstruction of layered maps of optical anisotropy(thesiograms)of dehydrated films(facies)of biological fluids of human organs is presented and experimentally tested.An original model of layered phase scanning of polycrystalline architectonics of supramolecular networks of biological fluid facies is proposed for the purpose of theoretical justification and prognostic use of the obtained results.On its basis,algorithms of Jones-matrix reconstruction of thesiograms of birefringence and dichroism of facies of synovial fluid,bile and blood are found.As a result,layered thesiograms of linear and circular birefringence and dichroism of facies with different spatial–angular architectonics of supramolecular networks are experimentally obtained for the first time.Within the framework of statistical analysis of experimental data,new objective markers(asymmetry and excess of optical anisotropy parameter distributions)for diagnostics of pathological changes in the optical anisotropy of biological fluid facies were defined and clinically tested.As a result,an excellent level of balanced accuracy of the developed polarization–interference Jones-matrix method of layer-by-layer reconstruction of thesiograms of polycrystalline supramolecular networks in differential diagnostics of bile facies(cholelithiasis),synovial fluid(reactive synovitis–septic arthritis)and whole blood(follicular adenoma–papillary thyroid cancer)was achieved.
基金the Natural Science Foundation of China(42272124)the National Key R&D Program of China(2023YFF0804302)Quantitative anatomy of shallow fan deltas in western China project directed by Research Institute of Petroleum Exploration and Development(2020D-5008-03).
文摘Fan deltas are usually constructed through episodic flood event with debris flow transforming to hyper-concentrated flow during sediments proceeding. However, the role of topography in controlling the flow transformation and sediments aggradation has been less studied. This constrain studies of sediment distribution and understanding of graded profile. For lake basin sequences, geomorphological control is much stronger than lake level rise and fall. Under extreme conditions, sediments can still prograde when the lake level rises. Therefore, describing the influence of geomorphology on the flow transformation and stacking pattern of the lobes can provide a deeper understanding of the controlling factors of the lake basin stratigraphy sequence. Xiligou lake (XLG) fan delta from Xisai Basin provides an optimal case for addressing this issue. Three lobes developed on the XLG fan delta with significant differences in their morphologies, architectures, lithofacies, sediment distributions and topographies. Through trenching, drone photography, and satellite data, we analyzed the structure of the sediments and the distribution of sedimentary facies. Based on the analysis of debris flow and hyper-concentrated flow deposits, two transformation models corresponding to different topographies were established. Sediment unloading is caused by a frictional reduction or a sudden momentum loss in the sediments flow's carrying capacity, allowing the debris flow transforms to hyper-concentrated flow and then to stream flow during the movement. The role of topography in controlling sediment flow transformation and sediment distribution is clarified through forces analysis of sediment grain. The topographic gradient of the linear slope is constant, so the direction of fluid movement is consistent with the topographic direction. Therefore, sediment flows move on linear slope without collision with the bed and there is no sudden loss of momentum. The gradual or sudden reduction in topographic gradient of concave slopes forces a constant or sudden change in the direction of fluid movement, which facilitates the unloading of sediments and the transformation of flow. The sudden change of topography forces unloading of viscous component, and the non-viscous component pass over to form hyper-concentrated flow, often accompanied by remobilized large gravels. The graded profile was an equilibrium between the dynamics and resistance of sediment transport. Changes in lake level affect the graded profile by changing the elevation of sediment transport, which is the total gravitational potential energy. The instantaneous graded profile and temporary graded profile are different scales of equilibrium corresponding to hydrodynamic equilibrium and depositional trend respectively. This study reveals the role of geomorphological dynamics in controlling sedimentary body progradation, thus providing a new perspective on the analysis of lake basin stratigraphy sequence.
基金funded by the National Natural Science Foundation of China(Grant No.42173054).
文摘Light hydrocarbons(LHs)are key components of petroleum,and the carbon isotopes composition(δ^(13)C)of individual LHs contains a wealth of geochemical information.Forty-four oil samples from five different basins were analyzed using gas chromatography(GC),gas chromatography-mass spectrometry(GC–MS),and gas chromatography-isotope ratio mass spectrometry(GC-IRMS).Theδ^(13)C values of forty-three LHs were recognized and determined by comparing the GC and GC-IRMS methods.The results revealed significant differences inδ^(13)C distribution characteristics among different LH compounds.Theδ^(13)C variation of individual LHs in iso-paraffins showed the widest range,followed by cycloalkanes and aromatics,whereas theδ^(13)C variation in n-paraffins showed the narrowest range.Theδ^(13)C values of most individual LHs are primarily affected by the source facies and thermal evolution.Among them,c-1,3-dimethylcyclohexane(c-1,3DMCH)is mainly sourced from higher plants but may also form through abiotic mechanisms such as catalysis or cyclization.Theδ^(13)C values of c-1,3DMCH(δ^(13)Cc-1,3DMCH)primarily exhibit parental genetic characteristics,enabling effective distinction of oil from different source facies.Specifically,theδ^(13)Cc-1,3DMCH in marine oils,lacustrine oils,terrigenous oils,and coal-formed oils are<–22‰,from–22‰to−20.2‰,from−20.2‰to−18.4‰,and>−18.4‰,respectively.Moreover,maturity is the primary controlling factor forδ^(13)C values of 3MC7(δ^(13)C3MC7,3MC7:3-methylheptane),while the source facies serve as a secondary influence.The plot ofδ^(13)Cc-1,3DMCH andδ^(13)C3MC7 was introduced to classify source facies.Asδ^(13)Cc-1,3DMCH andδ^(13)C3MC7 increase,the source facies transits from marine to lacustrine,then terrigenous,and finally coal facies.Additionally,increasingδ^(13)C3MC7 indicates a relative increase in maturity.Therefore,theδ^(13)Cc-1,3DMCH vs.δ^(13)C3MC7 plot serves as an effective tool for distinguishing source facies and assessing relative maturity.
基金supported by the National Natural Science Foundation of China(Grant Nos.42272328 and 52108356).
文摘Cone penetration testing(CPT)and its variant with pore pressure measurements(CPTu)are versatile tools that have been traditionally used for in situ geotechnical site investigations.These investigations are among the most challenging yet indispensable tasks,providing a crucial reference for infrastructure planning,design and construction.However,data obtained through the CPT/CPTu testing often exhibit significant variability,even at closely spaced test points.This variability is primarily attributed to the complex mineral compositions and sedimentary process of the Quaternary sediments.Problems induced by the scattering data include the difficulties in estimating the shear strength of the sediments and determining the appropriate bearing stratum for pile foundations.In this paper,the conventional interpretation methods of the CPT/CPTu data are enhanced with sedimentary facies knowledge.The geotechnical investigation mainly involves 42 CPTu tests(39 essential data sets available)and 4 boring samples.Sediment types are interpreted from the CPTu data and calibrated by the nearby boring samples.Sedimentary facies are derived from the interpreted sequence stratigraphy,for which the interpretation skills are summarized in the form of characteristic curves of the CPTu data.Scattering distribution of the sediment types and their mechanical parameters are well explained by the sedimentary facies.The sediments are then categorized into a few groups by their sedimentary facies,resulting in reduced uncertainties and scattering in terms of shear strength.Bearing stratum of pile foundations is also suggested based on the sedimentary regulations.
文摘Machine learning techniques and a dataset of five wells from the Rawat oilfield in Sudan containing 93,925 samples per feature(seven well logs and one facies log) were used to classify four facies. Data preprocessing and preparation involve two processes: data cleaning and feature scaling. Several machine learning algorithms, including Linear Regression(LR), Decision Tree(DT), Support Vector Machine(SVM),Random Forest(RF), and Gradient Boosting(GB) for classification, were tested using different iterations and various combinations of features and parameters. The support vector radial kernel training model achieved an accuracy of 72.49% without grid search and 64.02% with grid search, while the blind-well test scores were 71.01% and 69.67%, respectively. The Decision Tree(DT) Hyperparameter Optimization model showed an accuracy of 64.15% for training and 67.45% for testing. In comparison, the Decision Tree coupled with grid search yielded better results, with a training score of 69.91% and a testing score of67.89%. The model's validation was carried out using the blind well validation approach, which achieved an accuracy of 69.81%. Three algorithms were used to generate the gradient-boosting model. During training, the Gradient Boosting classifier achieved an accuracy score of 71.57%, and during testing, it achieved 69.89%. The Grid Search model achieved a higher accuracy score of 72.14% during testing. The Extreme Gradient Boosting model had the lowest accuracy score, with only 66.13% for training and66.12% for testing. For validation, the Gradient Boosting(GB) classifier model achieved an accuracy score of 75.41% on the blind well test, while the Gradient Boosting with Grid Search achieved an accuracy score of 71.36%. The Enhanced Random Forest and Random Forest with Bagging algorithms were the most effective, with validation accuracies of 78.30% and 79.18%, respectively. However, the Random Forest and Random Forest with Grid Search models displayed significant variance between their training and testing scores, indicating the potential for overfitting. Random Forest(RF) and Gradient Boosting(GB) are highly effective for facies classification because they handle complex relationships and provide high predictive accuracy. The choice between the two depends on specific project requirements, including interpretability, computational resources, and data nature.
基金financially supported by the National Natural Science Foundation of China(Grant Nos.42030804 and 42330811)the“Deep-time Digital Earth”Science and Technology Leading Talents Team Funds for the Central Universities for the Frontiers Science Center for Deep-time Digital Earth,China University of Geosciences(Beijing)(Fundamental Research Funds for the Central UniversitiesGrant No.2652023001)。
文摘The Lower Cambrian shale gas in the western Hubei area,South China has a great resource prospect,but the gas-in-place(GIP)content in different sedimentary facies varies widely,and the relevant mechanism has been not well understood.In the present study,two sets of the Lower Cambrian shale samples from the Wells YD4 and YD5 in the western Hubei area,representing the deep-water shelf facies and shallowwater platform facies,respectively,were investigated on the differences of pore types,pore structure and methane adsorption capacity between them,and the main controlling factor and mechanism of their methane adsorption capacities and GIP contents were discussed.The results show that the organic matter(OM)pores in the YD4 shale samples are dominant,while the inorganic mineral(IM)pores in the YD5 shale samples are primary,with underdeveloped OM pores.The pore specific surface area(SSA)and pore volume(PV)of the YD4 shale samples are mainly from micropores and mesopores,respectively,while those of the YD5 shale samples are mainly from micropores and macropores,respectively.The methane adsorption capacity of the YD4 shale samples is significantly higher than that of the YD5 shale samples,with a maximum absolute adsorption capacity of 3.13 cm^(3)/g and 1.31 cm^(3)/g in average,respectively.Compared with the shallow-water platform shale,the deep-water shelf shale has a higher TOC content,a better kerogen type and more developed OM pores,which is the main mechanism for its higher adsorption capacity.The GIP content models based on two samples with a similar TOC content selected respectively from the Wells YD4 and YD5 further indicate that the GIP content of the deep-water shelf shale is mainly 34 m^(3)/t within a depth range of 1000—4000 m,with shale gas exploration and development potential,while the shallow-water platform shale has normally a GIP content of<1 m^(3)/t,with little shale gas potential.Considering the geological and geochemical conditions of shale gas formation and preservation,the deep-water shelf facies is the most favorable target for the Lower Cambrian shale gas exploration and development in the western Hubei area,South China.
文摘The Middle Permian Qixia Formation in the Shuangyushi area,northwestern Sichuan Basin,develops shoal-facies dolomite reservoirs.To pinpoint promising reservoirs in the Qixia Formation,deep thin shoal-facies dolomite reservoirs were predicted using the techniques of pre-stack Kirchhoff-Q compensation for absorption,inverse Q filtering,low-to high-frequency compensation,forward modeling,and facies-controlled seismic meme inversion.The results are obtained in six aspects.First,the dolomite reservoirs mainly exist in the middle and lower parts of the second member of Qixia Formation(Qi2 Member),which coincide with the zones shoal cores are developed.Second,the forward modeling shows that the trough energy at the top and bottom of shoal core increases with increasing shoal-core thickness,and weak peak reflections are associated in the middle of shoal core.Third,five types of seismic waveform are identified through waveform analysis of seismic facies.Type-Ⅰ and Type-Ⅱ waveforms correspond to promising facies(shoal core microfacies).Fourth,vertically,two packages of thin dolomite reservoirs turn up in the sedimentary cycle of intraplatform shoal in the Qi2 Member,and the lower package is superior to the upper package in dolomite thickness,scale and lateral connectivity.Fifth,in plane,significantly controlled by sedimentary facies,dolomite reservoirs laterally distribute with consistent thickness in shoal cores at topographical highs and extend toward the break.Sixth,the promising prospects are the zones with thick dolomite reservoirs and superimposition of horstegraben structural traps.
基金Supported by CNPC Prospective and Basic Science and Technology Major Project(2023ZZ02)Petro China Science and Technology Major Project(2021DJ0402.2021DJ0202)。
文摘The saline lacustrine hybrid sedimentary rocks are complex in lithology and unknown for their sedimentary mechanisms.The hybrid sedimentary rocks samples from the Neogene upper Ganchaigou Formation to lower Youshashan Formation(N_(1)-N_(2)^(1))in the Fengxi area Qaidam Basin,were investigated through core-log and petrology-geochemistry cross-analysis by using the core,casting thin section,scanning electron microscope,X-ray diffraction,logging,and carbon/oxygen isotopic data.The hybrid sedimentary rocks in the Fengxi area,including terrigenous clastic rock and lacustrine carbonate rock,were deposited in a shallow lake environment far from the source,or occasionally in a semi-deep lake environment,with 5 lithofacies types and 6 microfacies types recognized.Stable carbon and oxygen isotopic compositions reveal that the formation of sedimentary cycles is controlled by a climate-driven compensation-undercompensation cyclic mechanism.A sedimentary cycle model of hybrid sedimentary rocks in an arid and saline setting is proposed.According to this model,in the compensation period,the lake level rises sharply,and microfacies such as mud flat,sand-mud flat and beach are developed,with physical subsidence as the dominant sedimentary mechanism;in the undercompensation period,the lake level falls slowly,and microfacies such as lime-mud flat,lime-dolomite flat and algal mound/mat are developed,with chemical-biological process as the dominant sedimentary mechanism.In the saline lacustrine sedimentary system,lacustrine carbonate rock is mainly formed along with regression,the facies change is not interpreted by the accommodation believed traditionally,but controlled by the temporary fluctuation of lake water chemistry caused by climate change.The research results update the interpreted high-resolution sequence model and genesis of hybrid sedimentary rocks in the saline lacustrine basin and provide a valuable guidance for exploring unconventional hydrocarbons of saline lacustrine facies.
基金sponsored by the Subordinate subject of the National Major Science and Technology Project“Development of Large Oil and Gas Fields and coalbed methane”(2017ZX05001-003)supported by the Science Research Project from CNPC(2019D-0708)supported by the National Natural Science Foundation of China"Quantitative evaluation of sealing capacity of fault rocks with diff erent structures in clastic strata”(41872153).
文摘Fault zones have always drawn attention from the industry,and the performance of a quantitative interpretation of the fault interior structure on seismic data has remained as a big challenge.In this work,we focus on quantitatively populating the heterogeneity of the fault interior structure in a three-dimensional space on seismic data.To realize this goal,we take the South Wuerxun sub-depression in Hailar Basin as an example of a faulted basin.First,based on a heterogeneity analysis using the drilling and logging information from wells,we establish fault zone geologic models and perform seismic forward modeling to determine the relationship between different fault zone models with different fault dips,internal fillings,and P wave responses.Next,the fault interior structure index(FIS)is constructed,and the response features on the FIS from the fault facies and the host rock are observed.Finally,the FIS is applied to perform the quantitative interpretation and prediction of the heterogeneity in the FIS on seismic data.The results show that the FIS response from the fault zone is higher than that of the host rock in plane,indicating that the former is quantitatively separated from the surrounding host rocks.The FIS values greater than 26 represent the feedback from the fault facies,whereas those less than 26 represent the response from the host rocks.The FIS shows segmented features in the strike,banded in dip on plane.On the slip surface,the FIS indicates the shale smear zone and the location where low-graded and small-scaled faults are densely developed.The heterogeneity prediction result is proven by oil and gas exploration activities.The study results imply that the FIS could indicate a favorable path of the hydrocarbon migration in the fault zone and evaluate the fault sealing parts.The method can explore the quantitative characterization of fault facies and has essential popularization and application values in similar geological application fields,including hydrocarbon exploration,development of faulted reservoirs,and geological engineering evaluation related to faults.
基金funded by the Fundamental Research Project of CNPC Geophysical Key Lab(2022DQ0604-4)the Strategic Cooperation Technology Projects of China National Petroleum Corporation and China University of Petroleum-Beijing(ZLZX 202003)。
文摘With the successful application and breakthrough of deep learning technology in image segmentation,there has been continuous development in the field of seismic facies interpretation using convolutional neural networks.These intelligent and automated methods significantly reduce manual labor,particularly in the laborious task of manually labeling seismic facies.However,the extensive demand for training data imposes limitations on their wider application.To overcome this challenge,we adopt the UNet architecture as the foundational network structure for seismic facies classification,which has demonstrated effective segmentation results even with small-sample training data.Additionally,we integrate spatial pyramid pooling and dilated convolution modules into the network architecture to enhance the perception of spatial information across a broader range.The seismic facies classification test on the public data from the F3 block verifies the superior performance of our proposed improved network structure in delineating seismic facies boundaries.Comparative analysis against the traditional UNet model reveals that our method achieves more accurate predictive classification results,as evidenced by various evaluation metrics for image segmentation.Obviously,the classification accuracy reaches an impressive 96%.Furthermore,the results of seismic facies classification in the seismic slice dimension provide further confirmation of the superior performance of our proposed method,which accurately defines the range of different seismic facies.This approach holds significant potential for analyzing geological patterns and extracting valuable depositional information.
基金Supported by the CNPC Science and Technology Projects(2022-N/G-47808,2023-N/G-67014)RIPED International Cooperation Project(19HTY5000008).
文摘To solve the problems in restoring sedimentary facies and predicting reservoirs in loose gas-bearing sediment,based on seismic sedimentologic analysis of the first 9-component S-wave 3D seismic dataset of China,a fourth-order isochronous stratigraphic framework was set up and then sedimentary facies and reservoirs in the Pleistocene Qigequan Formation in Taidong area of Qaidam Basin were studied by seismic geomorphology and seismic lithology.The study method and thought are as following.Firstly,techniques of phase rotation,frequency decomposition and fusion,and stratal slicing were applied to the 9-component S-wave seismic data to restore sedimentary facies of major marker beds based on sedimentary models reflected by satellite images.Then,techniques of seismic attribute extraction,principal component analysis,and random fitting were applied to calculate the reservoir thickness and physical parameters of a key sandbody,and the results are satisfactory and confirmed by blind testing wells.Study results reveal that the dominant sedimentary facies in the Qigequan Formation within the study area are delta front and shallow lake.The RGB fused slices indicate that there are two cycles with three sets of underwater distributary channel systems in one period.Among them,sandstones in the distributary channels of middle-low Qigequan Formation are thick and broad with superior physical properties,which are favorable reservoirs.The reservoir permeability is also affected by diagenesis.Distributary channel sandstone reservoirs extend further to the west of Sebei-1 gas field,which provides a basis to expand exploration to the western peripheral area.
基金funded by the Science and Technology Project of Changzhou City(Grant No.CJ20210120)the Research Start-up Fund of Changzhou University(Grant No.ZMF21020056).
文摘The complex pore structure of carbonate reservoirs hinders the correlation between porosity and permeability.In view of the sedimentation,diagenesis,testing,and production characteristics of carbonate reservoirs in the study area,combined with the current trends and advances in well log interpretation techniques for carbonate reservoirs,a log interpretation technology route of“geological information constraint+deep learning”was developed.The principal component analysis(PCA)was employed to establish lithology identification criteria with an accuracy of 91%.The Bayesian stepwise discriminant method was used to construct a sedimentary microfacies identification method with an accuracy of 90.5%.Based on production data,the main lithologies and sedimentary microfacies of effective reservoirs were determined,and 10 petrophysical facies with effective reservoir characteristics were identified.Constrained by petrophysical facies,the mean interpretation error of porosity compared to core analysis results is 2.7%,and the ratio of interpreted permeability to core analysis is within one order of magnitude,averaging 3.6.The research results demonstrate that deep learning algorithms can uncover the correlation in carbonate reservoir well logging data.Integrating geological and production data and selecting appropriate machine learning algorithms can significantly improve the accuracy of well log interpretation for carbonate reservoirs.
基金The National Natural Science Foundation of China under contract Nos 42476156,41961144022the Natural Science Foundation of Fujian Province,China under contract No.2023J01927+1 种基金the College Students’Innovation and Entrepreneurship Training Program of Fujian Province,China under contract No.S202310402032the Scientific Research Foundation of the Third Institute of Oceanography,SOA,China under contract No.2019018。
文摘The establishment of effective proxies for the differentiation of sedimentary facies in the tide-dominated river mouth is fundamental to the delineation of stratigraphy and the study of paleoenvironments.Geochemical signatures of the acetic acid(HAc)extractive phases of alkaline earth metals,such as Sr,Ba,and Ca,are closely related to sedimentary environments and thus provide a novel method for discriminating the sedimentary facies of river mouth.In this study,50 surface water and surface sediment samples were obtained from different geomorphological units of the Jiulong River mouth,i.e.,river channel,distributary channel,delta front,delta front slope,prodelta,and shallow marine area,and the salinity of the water,the grain size,and the Sr,Ba,and Ca contents and Sr/Ba molar ratio(Sr/Ba)in HAc leachates of the sediments were determined.Contents of alkaline earth metals in HAc leachates of surface sediments from the Changjiang(Yangtze)River coast were also collated.The goals of this study were to reveal the spatial distribution of alkaline earth metals in the Jiulong River mouth,define their depositional mechanisms,and search for effective geochemical proxies for identification of the various sedimentary facies in the fluvial to marine transition zone.The results revealed several land-to-sea gradients.The Ba content decreased rapidly from the distributary channel to the sea,and the Sr and Ca contents and Sr/Ba increased gradually with the increase in salinity.Salinity,marine biomass,and sedimentary dynamic processes,were speculated to be the main reasons for the differences in their spatial distributions.There were significant differences in Ba,Sr,Ca,and Sr/Ba between the river channel and the distributary channel,in Ca and Ba between the distributary channel and the delta front(slope),and in Sr,Ca,and Sr/Ba between the delta front(slope)and the prodelta-shallow marine region.The Sr-Ba scatterplot showed that the sediments of the river channel and alluvial plain were located as a high Ba and low Sr element-defined end-member,whereas samples of the prodelta and shallow marine formed a high Sr and low Ba end-member.These can be used as characteristic end-members indicating terrestrial facies and marine facies,respectively.The sediments of the delta plain,tidal river,distributary channel,delta front,and delta front slope are located between these two end-member regions of the scatterplot,and this region of the diagram can be used to identify land-sea transitional sedimentary facies.
文摘The geological conditions of offshore shallow water delta oil reservoirs were complex, with limited well data and large well spacing. Taking A Oilfield in the Bohai Sea Area, China as an example, the target sand body was formed in a shallow water delta sedimentary environment, with well-developed underwater distributary channels and frequent branching and diversion. The reservoir was strong non-uniformity and uneven plane water cut pressure. To this end, based on the existing work of predecessors, combined with seismic, logging, and production dynamics data, and based on the genesis mechanism of shallow water delta reservoirs, the boundary of composite river channels was identified through seismic facies, and logging facies were used to subdivide them into single river levels within the composite river channels. Then, seismic waveform characteristics were applied to track and characterize the plane distribution of single river channels, guiding the efficient development of offshore shallow water delta oil fields and achieving increased storage and production in Bohai Oilfield, China.
基金sponsored by the National S&T Major Special Project(No.2008ZX05020-01)
文摘Reef-bank reservoirs are an important target for petroleum exploration in marine carbonates and also an essential supplemental area for oil and gas production in China. Due to the diversity of reservoirs and the extreme heterogeneity of reef-banks, it is very difficult to discriminate the sedimentary facies and lithologies in reef-bank reservoirs using conventional well logs. The borehole image log provides clear identification of sedimentary structures and textures and is an ideal tool for discriminating sedimentary facies and lithologies. After examining a large number of borehole images and cores, we propose nine typical patterns for borehole image interpretation and a method that uses these patterns to discriminate sedimentary facies and lithologies in reeI^bank reservoirs automatically. We also develop software with user-friendly interface. The results of applications in reef-bank reservoirs in the middle Tarim Basin and northeast Sichuan have proved that the proposed method and the corresponding software are quite effective.
基金Project supported by the National Major S&T Project(No.2011ZX05004-002)the CNPC Major S&T Project(No.2014E-32).
文摘In the Sichuan Basin,the Middle Permian marine carbonate rocks are important natural gas pay zones with immense exploration potential,but the facies belts and distribution situations of layered dolomite reservoirs are not clear,which hinders the progress in natural gas exploration.In view of the sedimentary background of the Sichuan Basin,field outcrop section,drilling data and seismic data were comprehensively analyzed with the favorable reservoir intervals in the framework of sequence stratigraphy as the key research units.Research results about its lithofacies paleogeography were obtained as follows.First,a gentle slope SW high and NE low was presented during the sedimentation of the Qixia Fm in the Middle Permian.In the Maokou Fm of the Middle Permian,however,a series of the N-W trending intra-platform rifts were developed in this setting,and eventually a paleogeographic pattern of NE-dipping alternative uplift and depression was evolved.Second,in the Qixia Fm,the transgressive tract was in an open platform environment and the highstand system tract evolved into a rimmed platform.And the platform margin beach in the area of Jiange-Ya'an is the favorable reservoir facies belt.And third,in the Maokou Fm,the transgressive tract was in the carbonate shelf environment and the highstand system tract evolved into a rimmed platform.And the platform margin reef flat in the area of Jiange-Ya'an and the syneclise margin beach in the area of YantingeGuang'an are favorable reservoir facies belts.It is concluded that the two grain beach facies belts in the areas of Jiange-Ya'an and YantingeGuang'an were the favorable zones for the large-scale development of Middle Permian layered dolomite reservoirs and they are the main target of subsequent natural gas exploration.
