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
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
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
Understanding diagenetic processes plays a crucial role in evaluating the quality of tight reservoirs.In this study,we aimed to examine diagenetic facies and thereby assess reservoir quality by conducting an integrate...Understanding diagenetic processes plays a crucial role in evaluating the quality of tight reservoirs.In this study,we aimed to examine diagenetic facies and thereby assess reservoir quality by conducting an integrated analysis of porosity,petrology,permeability,mineralogy,mercury injection,and stable isotopic data in core samples from the Permian Shan 2 and He 1 members(Shan 2—He 1 Mbr)in China's Ordos Basin.Early compaction and precipitation of diagenetic minerals have significantly reduced primary pore space in these members,although certain sandstones have retained anomalously high porosity.These high-porosity reservoirs have been shaped by many factors,with dissolution identified as the predominant mechanism.Detailed petrographic observations and assessments of the primary minerals,the minerals'genesis,and associated diagenetic processes revealed seven distinct diagenetic facies differentiated by their sand-grain populations,types of cementation,clay matrix contents,and volcanic tuffaceous sediment(VTS).The main interstitial fillings consist of VTS,clay minerals,quartz overgrowths,and calcite(ferrocalcite).Clasts and VTS-dissolved sandstone have mainly formed Class I reservoirs with highly unstable grains and good secondary pores resulting from the dissolution of the grains and VTS.VTS tight sandstone,siliceous cementation tight sandstone,illite-siliceous cementation tight sandstone,and calcite cementation tight sandstone have formed Class II reservoirs with high rates of interstitial filling and cementation.Sandstone tightly cemented by illite has poor reservoir properties and has mainly formed Class III reservoirs.This classification underscores the critical importance of understanding diagenesis,diagenetic facies,and especially the diagenetic features of VTS for accurately assessing reservoir quality.A comprehensive understanding of these factors may facilitate more effective hydrocarbon exploration and exploitation in this area.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
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
The close relationship between the structure,evolution,and resources environment of the South China Sea is a current research focus and also a focal point of our study.In this paper,we use regional seismic sections to...The close relationship between the structure,evolution,and resources environment of the South China Sea is a current research focus and also a focal point of our study.In this paper,we use regional seismic sections to analyze the relationship between seismic facies and the structure and tectonic evolution of the northeastern South China Sea and propose new points about the structure and the direction of block（land mass） motion.First,the tectonic features are clear and can be divided into five different structural units which are both linked and independent of each other.Second,it doesn＇t matter if the South China Sea basin pattern is extensional,weakly compressive,or strongly compressive,the regional tectonic stress field is unified.For the first time we find that two shallow subduction zones are recognized in the seismic profiles.All the tectonic blocks have accordion-fold-style structures,converging in the east,and the South China Sea exhibits different stages of basin development：growth, maturity,end,and termination.The block subduction and regional block dip directions are all aligned with the regional stress field.展开更多
Seismic texture attributes are closely related to seismic facies and reservoir characteristics and are thus widely used in seismic data interpretation.However,information is mislaid in the stacking process when tradit...Seismic texture attributes are closely related to seismic facies and reservoir characteristics and are thus widely used in seismic data interpretation.However,information is mislaid in the stacking process when traditional texture attributes are extracted from poststack data,which is detrimental to complex reservoir description.In this study,pre-stack texture attributes are introduced,these attributes can not only capable of precisely depicting the lateral continuity of waveforms between different reflection points but also reflect amplitude versus offset,anisotropy,and heterogeneity in the medium.Due to its strong ability to represent stratigraphies,a pre-stack-data-based seismic facies analysis method is proposed using the selforganizing map algorithm.This method is tested on wide azimuth seismic data from China,and the advantages of pre-stack texture attributes in the description of stratum lateral changes are verified,in addition to the method＇s ability to reveal anisotropy and heterogeneity characteristics.The pre-stack texture classification results effectively distinguish different seismic reflection patterns,thereby providing reliable evidence for use in seismic facies analysis.展开更多
Based on the theory of plate tectonics, the authors combined the concept and analytic methods of tectonic facies, and divided the western Tianshan Mt. and its adjacent area into eight tectonic facies. i. e.① Kuluktag...Based on the theory of plate tectonics, the authors combined the concept and analytic methods of tectonic facies, and divided the western Tianshan Mt. and its adjacent area into eight tectonic facies. i. e.① Kuluktage rejuvenational foreland basement fold-thrust facie, ②Kalpin rejuvenational foreland basement fold-thrust facie,③ Kuqa rejuvenational foreland fold-thrust facie. ④ Southern Tianshan backarc foreland mollasse facie. ⑤ Southern Tianshan Late Paleozoic magmatic arc facie. ⑥ Southern Tianshan backarc melange facie. ⑦ Central Tianshan composite magmatic are facie, and ⑧ Northern Tianshan foreare melange facie. F1nally. we reconstructed the history of the western Tianshan Paleozoic tectonic evolution.展开更多
This paper proposes a novel approach for generating 3-dimensional complex geological facies models based on deep generative models.It can reproduce a wide range of conceptual geological models while possessing the fle...This paper proposes a novel approach for generating 3-dimensional complex geological facies models based on deep generative models.It can reproduce a wide range of conceptual geological models while possessing the flexibility necessary to honor constraints such as well data.Compared with existing geostatistics-based modeling methods,our approach produces realistic subsurface facies architecture in 3D using a state-of-the-art deep learning method called generative adversarial networks(GANs).GANs couple a generator with a discriminator,and each uses a deep convolutional neural network.The networks are trained in an adversarial manner until the generator can create "fake" images that the discriminator cannot distinguish from "real" images.We extend the original GAN approach to 3D geological modeling at the reservoir scale.The GANs are trained using a library of 3D facies models.Once the GANs have been trained,they can generate a variety of geologically realistic facies models constrained by well data interpretations.This geomodelling approach using GANs has been tested on models of both complex fluvial depositional systems and carbonate reservoirs that exhibit progradational and aggradational trends.The results demonstrate that this deep learning-driven modeling approach can capture more realistic facies architectures and associations than existing geostatistical modeling methods,which often fail to reproduce heterogeneous nonstationary sedimentary facies with apparent depositional trend.展开更多
Organic matter(OM)nanopores developed in transitional facies shales,i.e.,the Upper Permian Longtan and Dalong Formations in the Yangtze Platform,China,were investigated to determine the corre-sponding influence of the...Organic matter(OM)nanopores developed in transitional facies shales,i.e.,the Upper Permian Longtan and Dalong Formations in the Yangtze Platform,China,were investigated to determine the corre-sponding influence of thermal maturity and OM types within the geological conditions.A suite of 16 core samples were taken from Type-Ⅲ Longtan shales and Type-Ⅱ Dalong shales from two wells covering a ma-turity(Ro,vitrinite reflectance)ranging from 1.22%to 1.43%and 2.62%to 2.97%,respectively.Integrated analysis of the shale samples was carried out,including field-emission scanning electron microscopy(FESEM),low-pressure N2 and CO2 adsorption,high-pressure CH4 adsorption,and mercury intrusion capillary pressure(MICP)analysis.The fluid inclusions of liquid and gas hydrocarbons trapped in calcite vein samples in Dalong shales of two wells were studied using laser Raman and fluorescence spectroscopy.FE-SEM images indicated that OM pores in different formations varied substantially in terms of shape,size,and distribution density.OM pores in Type-Ⅱ Dalong shales of Well XY1 were mainly micropore,sparsely distributed in the gas-prone kerogen with a spot-like and irregular shape,while bitumen rarely developed observable pores.In contrast,the morphology of OM pores in Type-Ⅲ Longtan shales were significantly different,which was due to differences in the OM type.The primary OM pores in some terrestrial woody debris in Longtan shales had a relatively larger pore diameter,ranging from hundreds of nanometers to a few micrometers and were al-most all rounded in shape,which might be one of the factors contributing to larger pore volume and gas adsorption capacity than Dalong shales of Well XY1.Comparing Dalong shales of Well XY1 with relatively lower thermal maturity,there were abundant spongy-like pores,densely developed in the pyrobitumen in Type-Ⅱ Dalong shales of Well EY1,with an irregular shape and diameter ranging from several to hundreds of nanometers.Many blue fluorescent oil inclusions and a small number of CH4 inclusions mixed with C2H6 could be observed within calcite veins in Dalong shales of Well XY1,whereas only CH4 inclusions could be identified within calcite veins in Dalong shales of Well EJ1.Therefore,thermal maturity not only controlled the type of hydrocarbons generated,but also makes a significant contribution to the formation of OM pores,resulting in larger pore volumes and adsorption capacity of Type-Ⅱ shale samples in the dry gas window.展开更多
A systematic analysis of southwestern Ordos Basin's sedimentary characteristics,internal architectural element association styles and depositional model was illustrated through core statistics,well logging data an...A systematic analysis of southwestern Ordos Basin's sedimentary characteristics,internal architectural element association styles and depositional model was illustrated through core statistics,well logging data and outcrop observations in Chang 8 oil-bearing group.This analysis indicates that shallow water delta sediments dominated by a fluvial system is the primary sedimentary system of the Chang 8 oil-bearing group of the Yanchang Formation in southwestern Ordos Basin.Four microfacies with fine grain sizes are identified: distributary channels,sheet sandstone,mouth bar and interdistributary fines.According to the sandbody's spatial distribution and internal architecture,two types of sandbody architectural element associations are identified: amalgamated distributary channels and thin-layer lobate sandstone.In this sedimentary system,net-like distributary channels at the delta with a narrow ribbon shape compose the skeleton of the sandbody that extends further into the delta front and shades into contiguous lobate distribution sheet sandstone in the distal delta front.The mouth bar is largely absent in this system.By analyzing the palaeogeomorphology,the palaeostructure background,sedimentary characteristics,sedimentary facies types and spatial distribution of sedimentary facies during the Chang 8 period,a distinctive depositional model of the Chang 8 shallow water fluvial-dominated delta was established,which primarily consists of straight multi-phase amalgamated distributary channels in the delta plain,net-like distributary channels frequently diverting and converging in the proximal delta front,sheet sandstones with dispersing contiguous lobate shapes in the distal delta front,and prodelta or shallow lake mudstones.展开更多
Sedimentary facies is an important factor influencing shale gas accumulation. It not only controlls hydrocarbon generation, but also affects reservoir characteristics and distribution. This paper discusses the Lower S...Sedimentary facies is an important factor influencing shale gas accumulation. It not only controlls hydrocarbon generation, but also affects reservoir characteristics and distribution. This paper discusses the Lower Silurian Longmaxi Formation in the south of the Sichuan Basin. Outcrop, core, drilling and logging data identify the sedimentary facies of the formation as continental shelf facies, which is divided into two subfacies： an inner shelf and an outer shelf subfacies. These two subfacies can be further divided into seven microfacies： muddy silty shallow shelf, calcareous silty shallow shelf, muddy limy shallow shelf, storm flow, muddy deep shelf, silty muddy deep shelf and contour current microfacies. Vertical and horizontal distribution of microfacies establishes a sedimentation model of the continental shelf facies. Combined with analization or calculation of geochemical, mineralogical, physical and gas-bearing properties of samples, sedimentary microfacies is evaluated using nine parameters： total organic carbon content, effective shale continuous thickness, vitrinite reflectance, kerogen type, mineral components, porosity, permeability, water saturation and gas content. The evaluation revealed that the most favorable facies for shale gas exploration and development are the muddy deep shelf and part of the silty muddy deep shelf microfacies, with TOC more than 2%, siliceous component over 50%, clay less than 30%, porosity more than 3%, water saturation lower than 40%, gas content greater than 2 m3/t. These results provide a theoretical basis for deciston-making on the most promising areas for shale gas exploration in the Sichuan Basin and for marine shale gas exploration and development in South China.展开更多
Hydrothermal mineral assemblages and related hydrothermally enhanced fracturing are common in the Precambrian Dengying Formation of Central Sichuan Basin. Petrographic and geochemical analyses of core samples show tha...Hydrothermal mineral assemblages and related hydrothermally enhanced fracturing are common in the Precambrian Dengying Formation of Central Sichuan Basin. Petrographic and geochemical analyses of core samples show that the hydrothermal dolomite reservoirs of Dengying Formation consist of four main types of pores in the reservoir facies. These include: 1) hydrothermal dissolution vug(or pore), 2) intercrystalline pore, 3) residual inter-breccia vug(or pore), and 4) enlarged dissolved-fracture. There are three different fabrics dolomite in hydrothermal dolomite reservoirs, namely, saddle dolomite, fine-medium dolomite and micritic dolomite. Micritic dolomite is the original lithology of host rock. Saddle dolomite with curved or irregular crystal faces was directly crystallized from hydrothermal fluids(average temperature 192°C). Fine-medium dolomites are the products of recrystallization of micritic dolomite, resulting in abnormal geochemical characteristics, such as slight depletion of δ^(18)O, significant enrichment of Mn-Fe and ^(87)Sr/^(86)Sr, and positive Eu anomaly. A model for the distribution of various hydrothermal dolomite reservoir facies is proposed here, which incorporates three fundamental geological controls: 1) extensional tectonics and tectono-hydrothermal events(i.e., the Xingkai Taphrogenesis of Late Sinian-Early Cambrian, and Emei Taphrogenesis of Late Permian), 2) hydrothermal fluid storage in clastic rocks with large thickness(e.g., Nanhua System of Chengjiang Formation and part of Doushantuo Formation), and 3) confining bed for hydrothermal fluids(such as, the shale in Qiongzhusi Formation). The supply of hydrothermal fluid is critical. Large basement-rooted faults and associated grid-like fracture system may function as the channels for upward migration of hydrothermal fluid flow. The intersection of the above-mentioned faults(including the conversion fault), especially transtensional sags above negative flower structures on wrench faults can serve as a key target for future hydrocarbon exploration.展开更多
In recent years, deep water areas have become popular exploration fields because of their abundant hydrocarbon resource potential. There are only relatively poor planar seismic profiles and no wells for deepwater area...In recent years, deep water areas have become popular exploration fields because of their abundant hydrocarbon resource potential. There are only relatively poor planar seismic profiles and no wells for deepwater areas of the Lingshui Formation in the Qiongdongnan Basin. A lot of faults developed and strata are fragmented due to high temperatures and high pressure, and this has resulted in dim sequence boundaries. Based on seismic data of the deepwater area and well data of bordering shallow water areas, Lingshui Formation was divided into four third class sequences; namely SI, SII, SIII and SIV, and the three-dimensional isochronous stratigraphic framework of the Lingshui Formation in the studied area was shaped. Based mainly on seismic attributes such as amplitude, continuity, internal structure and external shape, six typical seismic facies were identified, including mat-shaped, filling, wedge-shaped, foreset, moundy-shaped and lenticular-shaped, and a seismic facies distribution map was subsequently drawn. With studies on wells of bordering shallow water areas, regional sedimentary characteristics, and isopach map as references, sedimentary planar distribution features were analyzed. The deepwater area of the Lingshui Formation has mainly developed littoral and shallow sea. Sandstone bodies of fan delta, braided river delta, slope fan, basin floor fan, and turbidite fan are at an interdigitate junction to marine hydrocarbon source rocks and thus are favorable prospecting targets.展开更多
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).
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supported by the National Natural Science Foundation of China:Tethys Dynamics(Grant No.92255302)the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDA14010201)the China Scholarship Council(Grant No.202206400023).
文摘Understanding diagenetic processes plays a crucial role in evaluating the quality of tight reservoirs.In this study,we aimed to examine diagenetic facies and thereby assess reservoir quality by conducting an integrated analysis of porosity,petrology,permeability,mineralogy,mercury injection,and stable isotopic data in core samples from the Permian Shan 2 and He 1 members(Shan 2—He 1 Mbr)in China's Ordos Basin.Early compaction and precipitation of diagenetic minerals have significantly reduced primary pore space in these members,although certain sandstones have retained anomalously high porosity.These high-porosity reservoirs have been shaped by many factors,with dissolution identified as the predominant mechanism.Detailed petrographic observations and assessments of the primary minerals,the minerals'genesis,and associated diagenetic processes revealed seven distinct diagenetic facies differentiated by their sand-grain populations,types of cementation,clay matrix contents,and volcanic tuffaceous sediment(VTS).The main interstitial fillings consist of VTS,clay minerals,quartz overgrowths,and calcite(ferrocalcite).Clasts and VTS-dissolved sandstone have mainly formed Class I reservoirs with highly unstable grains and good secondary pores resulting from the dissolution of the grains and VTS.VTS tight sandstone,siliceous cementation tight sandstone,illite-siliceous cementation tight sandstone,and calcite cementation tight sandstone have formed Class II reservoirs with high rates of interstitial filling and cementation.Sandstone tightly cemented by illite has poor reservoir properties and has mainly formed Class III reservoirs.This classification underscores the critical importance of understanding diagenesis,diagenetic facies,and especially the diagenetic features of VTS for accurately assessing reservoir quality.A comprehensive understanding of these factors may facilitate more effective hydrocarbon exploration and exploitation in this area.
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the National Hi-Tech Research and Development Program of China(Grant No.2006AA09A101).
文摘The close relationship between the structure,evolution,and resources environment of the South China Sea is a current research focus and also a focal point of our study.In this paper,we use regional seismic sections to analyze the relationship between seismic facies and the structure and tectonic evolution of the northeastern South China Sea and propose new points about the structure and the direction of block（land mass） motion.First,the tectonic features are clear and can be divided into five different structural units which are both linked and independent of each other.Second,it doesn＇t matter if the South China Sea basin pattern is extensional,weakly compressive,or strongly compressive,the regional tectonic stress field is unified.For the first time we find that two shallow subduction zones are recognized in the seismic profiles.All the tectonic blocks have accordion-fold-style structures,converging in the east,and the South China Sea exhibits different stages of basin development：growth, maturity,end,and termination.The block subduction and regional block dip directions are all aligned with the regional stress field.
基金supported by the Scientific Research Staring Foundation of University of Electronic Science and Technology of China(No.ZYGX2015KYQD049)
文摘Seismic texture attributes are closely related to seismic facies and reservoir characteristics and are thus widely used in seismic data interpretation.However,information is mislaid in the stacking process when traditional texture attributes are extracted from poststack data,which is detrimental to complex reservoir description.In this study,pre-stack texture attributes are introduced,these attributes can not only capable of precisely depicting the lateral continuity of waveforms between different reflection points but also reflect amplitude versus offset,anisotropy,and heterogeneity in the medium.Due to its strong ability to represent stratigraphies,a pre-stack-data-based seismic facies analysis method is proposed using the selforganizing map algorithm.This method is tested on wide azimuth seismic data from China,and the advantages of pre-stack texture attributes in the description of stratum lateral changes are verified,in addition to the method＇s ability to reveal anisotropy and heterogeneity characteristics.The pre-stack texture classification results effectively distinguish different seismic reflection patterns,thereby providing reliable evidence for use in seismic facies analysis.
文摘Based on the theory of plate tectonics, the authors combined the concept and analytic methods of tectonic facies, and divided the western Tianshan Mt. and its adjacent area into eight tectonic facies. i. e.① Kuluktage rejuvenational foreland basement fold-thrust facie, ②Kalpin rejuvenational foreland basement fold-thrust facie,③ Kuqa rejuvenational foreland fold-thrust facie. ④ Southern Tianshan backarc foreland mollasse facie. ⑤ Southern Tianshan Late Paleozoic magmatic arc facie. ⑥ Southern Tianshan backarc melange facie. ⑦ Central Tianshan composite magmatic are facie, and ⑧ Northern Tianshan foreare melange facie. F1nally. we reconstructed the history of the western Tianshan Paleozoic tectonic evolution.
文摘This paper proposes a novel approach for generating 3-dimensional complex geological facies models based on deep generative models.It can reproduce a wide range of conceptual geological models while possessing the flexibility necessary to honor constraints such as well data.Compared with existing geostatistics-based modeling methods,our approach produces realistic subsurface facies architecture in 3D using a state-of-the-art deep learning method called generative adversarial networks(GANs).GANs couple a generator with a discriminator,and each uses a deep convolutional neural network.The networks are trained in an adversarial manner until the generator can create "fake" images that the discriminator cannot distinguish from "real" images.We extend the original GAN approach to 3D geological modeling at the reservoir scale.The GANs are trained using a library of 3D facies models.Once the GANs have been trained,they can generate a variety of geologically realistic facies models constrained by well data interpretations.This geomodelling approach using GANs has been tested on models of both complex fluvial depositional systems and carbonate reservoirs that exhibit progradational and aggradational trends.The results demonstrate that this deep learning-driven modeling approach can capture more realistic facies architectures and associations than existing geostatistical modeling methods,which often fail to reproduce heterogeneous nonstationary sedimentary facies with apparent depositional trend.
基金We would like to thank the National Key R&D program of China(No.2017YFE0103600)the National Natural Science Foundation of China(Nos.41830431,41672139)the China National Science and Technology Major Projects(No.2016ZX05034002-003)for financial assistance to this research.
文摘Organic matter(OM)nanopores developed in transitional facies shales,i.e.,the Upper Permian Longtan and Dalong Formations in the Yangtze Platform,China,were investigated to determine the corre-sponding influence of thermal maturity and OM types within the geological conditions.A suite of 16 core samples were taken from Type-Ⅲ Longtan shales and Type-Ⅱ Dalong shales from two wells covering a ma-turity(Ro,vitrinite reflectance)ranging from 1.22%to 1.43%and 2.62%to 2.97%,respectively.Integrated analysis of the shale samples was carried out,including field-emission scanning electron microscopy(FESEM),low-pressure N2 and CO2 adsorption,high-pressure CH4 adsorption,and mercury intrusion capillary pressure(MICP)analysis.The fluid inclusions of liquid and gas hydrocarbons trapped in calcite vein samples in Dalong shales of two wells were studied using laser Raman and fluorescence spectroscopy.FE-SEM images indicated that OM pores in different formations varied substantially in terms of shape,size,and distribution density.OM pores in Type-Ⅱ Dalong shales of Well XY1 were mainly micropore,sparsely distributed in the gas-prone kerogen with a spot-like and irregular shape,while bitumen rarely developed observable pores.In contrast,the morphology of OM pores in Type-Ⅲ Longtan shales were significantly different,which was due to differences in the OM type.The primary OM pores in some terrestrial woody debris in Longtan shales had a relatively larger pore diameter,ranging from hundreds of nanometers to a few micrometers and were al-most all rounded in shape,which might be one of the factors contributing to larger pore volume and gas adsorption capacity than Dalong shales of Well XY1.Comparing Dalong shales of Well XY1 with relatively lower thermal maturity,there were abundant spongy-like pores,densely developed in the pyrobitumen in Type-Ⅱ Dalong shales of Well EY1,with an irregular shape and diameter ranging from several to hundreds of nanometers.Many blue fluorescent oil inclusions and a small number of CH4 inclusions mixed with C2H6 could be observed within calcite veins in Dalong shales of Well XY1,whereas only CH4 inclusions could be identified within calcite veins in Dalong shales of Well EJ1.Therefore,thermal maturity not only controlled the type of hydrocarbons generated,but also makes a significant contribution to the formation of OM pores,resulting in larger pore volumes and adsorption capacity of Type-Ⅱ shale samples in the dry gas window.
基金Project(SQ2013CB021013)supported by the National Key Basic Research Program of ChinaProject(41002045)supported by the National Natural Science Foundation of China
文摘A systematic analysis of southwestern Ordos Basin's sedimentary characteristics,internal architectural element association styles and depositional model was illustrated through core statistics,well logging data and outcrop observations in Chang 8 oil-bearing group.This analysis indicates that shallow water delta sediments dominated by a fluvial system is the primary sedimentary system of the Chang 8 oil-bearing group of the Yanchang Formation in southwestern Ordos Basin.Four microfacies with fine grain sizes are identified: distributary channels,sheet sandstone,mouth bar and interdistributary fines.According to the sandbody's spatial distribution and internal architecture,two types of sandbody architectural element associations are identified: amalgamated distributary channels and thin-layer lobate sandstone.In this sedimentary system,net-like distributary channels at the delta with a narrow ribbon shape compose the skeleton of the sandbody that extends further into the delta front and shades into contiguous lobate distribution sheet sandstone in the distal delta front.The mouth bar is largely absent in this system.By analyzing the palaeogeomorphology,the palaeostructure background,sedimentary characteristics,sedimentary facies types and spatial distribution of sedimentary facies during the Chang 8 period,a distinctive depositional model of the Chang 8 shallow water fluvial-dominated delta was established,which primarily consists of straight multi-phase amalgamated distributary channels in the delta plain,net-like distributary channels frequently diverting and converging in the proximal delta front,sheet sandstones with dispersing contiguous lobate shapes in the distal delta front,and prodelta or shallow lake mudstones.
基金supported by the National Science and Technology Major Projects of China(No.2012ZX05018-006-006)the National Natural Science Foundation of China(No.U1262209)
文摘Sedimentary facies is an important factor influencing shale gas accumulation. It not only controlls hydrocarbon generation, but also affects reservoir characteristics and distribution. This paper discusses the Lower Silurian Longmaxi Formation in the south of the Sichuan Basin. Outcrop, core, drilling and logging data identify the sedimentary facies of the formation as continental shelf facies, which is divided into two subfacies： an inner shelf and an outer shelf subfacies. These two subfacies can be further divided into seven microfacies： muddy silty shallow shelf, calcareous silty shallow shelf, muddy limy shallow shelf, storm flow, muddy deep shelf, silty muddy deep shelf and contour current microfacies. Vertical and horizontal distribution of microfacies establishes a sedimentation model of the continental shelf facies. Combined with analization or calculation of geochemical, mineralogical, physical and gas-bearing properties of samples, sedimentary microfacies is evaluated using nine parameters： total organic carbon content, effective shale continuous thickness, vitrinite reflectance, kerogen type, mineral components, porosity, permeability, water saturation and gas content. The evaluation revealed that the most favorable facies for shale gas exploration and development are the muddy deep shelf and part of the silty muddy deep shelf microfacies, with TOC more than 2%, siliceous component over 50%, clay less than 30%, porosity more than 3%, water saturation lower than 40%, gas content greater than 2 m3/t. These results provide a theoretical basis for deciston-making on the most promising areas for shale gas exploration in the Sichuan Basin and for marine shale gas exploration and development in South China.
基金funded by the National Science and Technology Major Project(grant No.2016ZX05052)the National Natural Science Foundation of China(grant No.41072102)
文摘Hydrothermal mineral assemblages and related hydrothermally enhanced fracturing are common in the Precambrian Dengying Formation of Central Sichuan Basin. Petrographic and geochemical analyses of core samples show that the hydrothermal dolomite reservoirs of Dengying Formation consist of four main types of pores in the reservoir facies. These include: 1) hydrothermal dissolution vug(or pore), 2) intercrystalline pore, 3) residual inter-breccia vug(or pore), and 4) enlarged dissolved-fracture. There are three different fabrics dolomite in hydrothermal dolomite reservoirs, namely, saddle dolomite, fine-medium dolomite and micritic dolomite. Micritic dolomite is the original lithology of host rock. Saddle dolomite with curved or irregular crystal faces was directly crystallized from hydrothermal fluids(average temperature 192°C). Fine-medium dolomites are the products of recrystallization of micritic dolomite, resulting in abnormal geochemical characteristics, such as slight depletion of δ^(18)O, significant enrichment of Mn-Fe and ^(87)Sr/^(86)Sr, and positive Eu anomaly. A model for the distribution of various hydrothermal dolomite reservoir facies is proposed here, which incorporates three fundamental geological controls: 1) extensional tectonics and tectono-hydrothermal events(i.e., the Xingkai Taphrogenesis of Late Sinian-Early Cambrian, and Emei Taphrogenesis of Late Permian), 2) hydrothermal fluid storage in clastic rocks with large thickness(e.g., Nanhua System of Chengjiang Formation and part of Doushantuo Formation), and 3) confining bed for hydrothermal fluids(such as, the shale in Qiongzhusi Formation). The supply of hydrothermal fluid is critical. Large basement-rooted faults and associated grid-like fracture system may function as the channels for upward migration of hydrothermal fluid flow. The intersection of the above-mentioned faults(including the conversion fault), especially transtensional sags above negative flower structures on wrench faults can serve as a key target for future hydrocarbon exploration.
基金sponsored by Ministry of Science and Technology of China (grant No. 2009CB219400)
文摘In recent years, deep water areas have become popular exploration fields because of their abundant hydrocarbon resource potential. There are only relatively poor planar seismic profiles and no wells for deepwater areas of the Lingshui Formation in the Qiongdongnan Basin. A lot of faults developed and strata are fragmented due to high temperatures and high pressure, and this has resulted in dim sequence boundaries. Based on seismic data of the deepwater area and well data of bordering shallow water areas, Lingshui Formation was divided into four third class sequences; namely SI, SII, SIII and SIV, and the three-dimensional isochronous stratigraphic framework of the Lingshui Formation in the studied area was shaped. Based mainly on seismic attributes such as amplitude, continuity, internal structure and external shape, six typical seismic facies were identified, including mat-shaped, filling, wedge-shaped, foreset, moundy-shaped and lenticular-shaped, and a seismic facies distribution map was subsequently drawn. With studies on wells of bordering shallow water areas, regional sedimentary characteristics, and isopach map as references, sedimentary planar distribution features were analyzed. The deepwater area of the Lingshui Formation has mainly developed littoral and shallow sea. Sandstone bodies of fan delta, braided river delta, slope fan, basin floor fan, and turbidite fan are at an interdigitate junction to marine hydrocarbon source rocks and thus are favorable prospecting targets.
