To address the challenges in studying the pore formation and evolution processes,and unclear preservation mechanisms of deep to ultra-deep carbonate rocks,a high-temperature and high-pressure visualization simulation ...To address the challenges in studying the pore formation and evolution processes,and unclear preservation mechanisms of deep to ultra-deep carbonate rocks,a high-temperature and high-pressure visualization simulation experimental device was developed for ultra-deep carbonate reservoirs.Carbonate rock samples from the Sichuan Basin and Tarim Basin were used to simulate the dissolution-precipitation process of deep to ultra-deep carbonate reservoirs in an analogous geological setting.This unit comprises four core modules:an ultra-high temperature,high pressure triaxial stress core holder module(temperature higher than 300°C,pressure higher than 150 MPa),a multi-stage continuous flow module with temperature-pressure regulation,an ultra-high temperature-pressure sapphire window cell and an in-situ high-temperature-pressure fluid property measurement module and real-time ultra-high temperature-pressure permeability detection module.The new experimental device was used for simulation experiment,the geological insights were obtained in three aspects.First,the pore-throat structure of carbonate is controlled by lithology and initial pore-throat structure,and fluid type,concentration and dissolution duration determine the degree of dissolution.The dissolution process exhibits two evolution patterns.The dissolution scale is positively correlated to the temperature and pressure,and the pore-forming peak period aligns well with the hydrocarbon generation peak period.Second,the dissolution potential of dolomite in an open flow system is greater than that of limestone,and secondary dissolved pores formed continuously are controlled by the type and concentration of acidic fluids and the initial physical properties.These pores predominantly distribute along pre-existing pore/fracture zones.Third,in a nearly closed diagenetic system,after the chemical reaction between acidic fluids and carbonate rock reaches saturation and dynamic equilibrium,the pore structure no longer changes,keeping pre-existing pores well-preserved.These findings have important guiding significance for the evaluation of pore-throat structure and development potential of deep to ultra-deep carbonate reservoirs,and the prediction of main controlling factors and distribution of high-quality carbonate reservoirs.展开更多
Burial dissolution is a critical diagenetic process influencing ultra-deep carbonate reservoir development and preservation.Artificial carbonate samples with different internal structures were prepared,and high-temper...Burial dissolution is a critical diagenetic process influencing ultra-deep carbonate reservoir development and preservation.Artificial carbonate samples with different internal structures were prepared,and high-temperature and highpressure dissolution kinetic simulations were conducted.The results demonstrate that the intensity of burial dissolution is controlled by temperature and pressure,while tectonic-fluid activity influences the development pattern of burial dissolution,ultimately determining the direction of its differential modification.Extensive burial dissolution is likely to occur primarily at relatively shallow depths,significantly influencing reservoir formation,preservation,modification,and adjustment.The development of faults facilitates the maintenance of the intensity of burial dissolution.The maximum intensity of burial dissolution occurs at the tips and overlap zones of faults and intersections of multiple faults.The larger the scale of the faults,the more conducive it is to the development of burial dissolution.Burial dissolution fosters the formation of fault networks characterized by enhanced reservoir capacity and permeability.Burial dissolution controlled by episodic tectonic-fluid activity is a plausible explanation for forming the Tarim Basin's ultra-deep fault-controlled“stringbead-like”reservoirs.展开更多
Based on the waterflooding development in carbonate reservoirs in the Middle East,this study analyzes the geological characteristics and waterflooding behaviors/patterns of different types of high permeability zones(H...Based on the waterflooding development in carbonate reservoirs in the Middle East,this study analyzes the geological characteristics and waterflooding behaviors/patterns of different types of high permeability zones(HPZs),and proposes rational waterflooding strategies and modes.Four types of HPZs,i.e.sedimentation-dominated,sedimentation-diagenesis coupling,biogenic and composite,are identified in the carbonate reservoirs in the Middle East.Based on their distribution patterns,flow mechanisms,and waterflooding behaviors/patterns,five waterflooding modes are established:(1)the mode with stepwise-infilled areal vertical well pattern,for composite HFZs in patchy distribution;(2)the mode with regular row vertical well pattern for TypeⅠchannel“network”HFZs(with dominant water flow pathways at the base),and the mode with irregular differentiated vertical well pattern for TypeⅡchannel“network”HFZs(where multi-stage superimposition leads to“layered flooding”),for sedimentation-diagenesis coupling HFZs;(3)the mode with row horizontal wells through bottom injection and top production,for biogenic HFZs characterized by thin,contiguous distribution and rapid advancing of injected water along a工-shaped path;and(4)the mode with progressive waterflooding through edge water injection via vertical well and oil production via horizontal well,for sedimentation-dominated HFZs characterized by thick,contiguous distribution and flood first in upper anti-rhythmic reservoirs.Development practices demonstrate that the proposed waterflooding modes are efficient in the highly heterogeneous carbonate reservoirs in the Middle East,with balanced employment of reserves in the adjacent reservoirs and enhanced oil recovery.展开更多
This study explores the application of machine learning techniques for predicting permeability,porosity,and flow zone indicator(FZI)in carbonate reservoirs using well log data,aiming to overcome the limitations of tra...This study explores the application of machine learning techniques for predicting permeability,porosity,and flow zone indicator(FZI)in carbonate reservoirs using well log data,aiming to overcome the limitations of traditional empirical methods.Six machine learning algorithms are utilized:support vector machine(SVM),backpropagation(BP)neural network,gaussian process regression(GPR),extreme gradient boosting(XGBoost),K-nearest neighbor(KNN),and random forest(RF).The methodology involves classifying pore-permeability types based on the flow index,leveraging logging curves and geological data.Models are trained using seven logging parameters—spectral gamma rays(SGR),uranium-free gamma rays(CGR),photoelectric absorption cross-section index(PE),lithologic density(RHOB),acoustic transit time(DT),neutron porosity(NPHI),and formation true resistivity(RT)—along with corresponding physical property labels.Machine learning models are trained and evaluated to predict carbonate rock properties.The results demonstrate that GPR achieves the highest accuracy in porosity prediction,with a coefficient of determination(R~2)value of 0.7342,while RF proves to be the most accurate for permeability prediction.Despite these improvements,accurately predicting lowpermeability zones in heterogeneous carbonate rocks remains a significant challenge.Application of cross-validation techniques optimized the performance of GPR,resulting in an accuracy index(ACI)value of 0.9699 for porosity prediction.This study provides a novel framework that leverages machine learning techniques to improve the characterization of carbonate reservoirs.展开更多
Carbonate reservoirs are known for their complex pore structures,which lead to variable elastic behaviors and seismic responses.These variations pose significant challenges for seismic interpretation of carbonate rese...Carbonate reservoirs are known for their complex pore structures,which lead to variable elastic behaviors and seismic responses.These variations pose significant challenges for seismic interpretation of carbonate reservoirs.Therefore,quantitative characterization of pore structure is crucial for accurate fluid detection and reservoir property estimation.To address the complexity of pore geometry and the uneven fluid distribution in tight carbonate reservoirs,we develop a triple-pore effective medium model by integrating the extended Keys-Xu model with the Gassmann-Hill equation.Comparison between the theoretical modeling results and an available laboratory data set verifies the effectiveness of this model in pore type quantification.Based on this calibrated model,we propose a novel two-step triple pore-type inversion strategy with varying pore aspect ratio via a grid-searching algorithm.We apply this method to well logs and 3D seismic data from the tight carbonate reservoirs of the Ordovician Majiagou formation in the Ordos Basin.The good agreement between pore-type estimates and logging interpretation results suggests that our method significantly improves the accuracy of porosity estimates for different pore types,outperforming the pore-type inversion method with fixed pore aspect ratios.The successful application to seismic data also demonstrates that the proposed method provides a reliable distribution of pore types in tight carbonate reservoirs,confirming its applicability and feasibility in seismic pore-type estimation.This method not only facilitates the recognition of complex pore geometries but also provides valuable insights for accurate detection of high-quality reservoirs.展开更多
Natural fractures controlled by faults in ultradeep carbonate strata play substantial roles as both fluid migration channels and storage spaces.However,characterizing the heterogeneous distribution of underground frac...Natural fractures controlled by faults in ultradeep carbonate strata play substantial roles as both fluid migration channels and storage spaces.However,characterizing the heterogeneous distribution of underground fractures within the complex three-dimensional geometry of strike-slip fault zones remains challenging.This study investigates the characteristics of natural fractures controlled by strike-slip faults in the fractured Middle and Lower Ordovician reservoirs of the central and northern Tarim Basin,China.Seismics,cores,and image logs were integrated to quantitatively analyze the intensity and dip angle of natural fractures and findings were verified using published sandbox simulations.The carbonate reservoir contains three main types of natural fractures:tectonic fractures,abnormal high-pressure-related fractures,and stylolites.Strike-slip faults control the distribution and characteristics of tectonic fractures across various scales.Generally,both fracture intensity and porosity exhibit a decreasing trend as the distance from the main fault surface increases.Compared with those in non-stepover zones along a strike-slip fault,natural fractures and faults in stepover zones are more developed along the fault strike,with significantly greater development intensity in central stepover regions than that at its two ends.Furthermore,strike-slip faults influence the dip angles of both natural fractures and secondary faults.The proportion of medium-to-low-dip angle fractures and faults in the stepover zone is greater than that in the non-stepover zone.Additionally,the proportion of medium-to low-dip angle fractures and faults in the middle of the stepover is greater than that at both ends.Therefore,strike-slip fault structures control the dip angle of natural fracture and the heterogeneity of secondary fault and fracture intensity.The linking damage zone in the stepover contains a larger volume of fractured rocks,making it a promising petroleum exploration target.The development of stepovers and the orientation of present-day in-situ stress substantially influence the productivity of fractured reservoirs controlled by strike-slip faults.The analysis in this study reveals that reservoir productivity increases as the angle between the strike-slip fault segment and the maximum horizontal principal stress decreases.This study provides valuable insights for quantitatively evaluating fracture heterogeneity in fractured reservoirs and establishing optimized selection criteria for favorable targets in fault-related fractured reservoirs.展开更多
Recent exploration has highlighted the critical role of strike-slip faults in shaping ultra-deep carbonate reservoirs in the Tarim Basin.This study integrates satellite imagery,UAV photogrammetry,outcrop surveys and m...Recent exploration has highlighted the critical role of strike-slip faults in shaping ultra-deep carbonate reservoirs in the Tarim Basin.This study integrates satellite imagery,UAV photogrammetry,outcrop surveys and microscopic analysis to investigate the architecture of these faults and their impact on reservoir petrophysical properties.The strike-slip faults exhibit cores consisting of calcite bands,fault breccias and fractures,while the damage zones are predominantly fractured.Thicker fault cores and fault zones are associated with more extensive reservoir development.Individual strike-slip fault zones are primarily characterized by two sets of fractures intersecting the fault at small angles.When two fault systems interact,the dominant pattern is two sets of fractures intersecting the main fault at small angles and one set at larger angles,facilitating the formation of large-scale reservoirs.We propose a model for the fault core,which primarily consists of a calcite band and fault breccias.These breccias are composed of original host rock,calcite cement and quartz,which exhibit poor physical properties,while fractures and vugs show favorable reservoir characteristics.This model offers valuable insights into the development of fault-controlled reservoirs,particularly in the Tarim Basin.展开更多
Wellbore instability is one of the significant challenges in the drilling engineering and during the development of carbonate reservoirs,especially with open-hole completion.The problems of wellbore instability such a...Wellbore instability is one of the significant challenges in the drilling engineering and during the development of carbonate reservoirs,especially with open-hole completion.The problems of wellbore instability such as downhole collapse and silt deposit in the fractured carbonate reservoir of Tarim Basin(Ordovician)are severe.Solid destabilization and production(SDP)was proposed to describe this engineering problem of carbonate reservoirs.To clarify the mechanism and mitigate potential borehole instability problems,we conducted particle size distribution(PSD)analysis,X-ray diffraction(XRD)analysis,triaxial compression tests,and micro-scale sand production tests based on data analysis.We found that the rock fragments and silt in the wellbore came from two sources:one from the wellbore collapse in the upper unplugged layers and the other from the production of sand particles carried by the fluid in the productive layers.Based on the experimental study,a novel method combining a geomechanical model and microscopic sand production model was proposed to predict wellbore instability and analyze its influencing factors.The critical condition and failure zone predicted by the prediction model fit well with the field observations.According to the prediction results,the management and prevention measures of wellbore instability in carbonate reservoirs were proposed.It is suggested to optimize the well track in new drilling wells while upgrading the production system in old wells.This study is of great guiding significance for the optimization of carbonate solid control and it improves the understanding of the sand production problems in carbonate reservoirs.展开更多
Mesozoic-Palaeozoic marine carbonate rocks are crucial hydrocarbon reservoirs in the Central Uplift area of the South Yellow Sea Basin(SYSB).Due to the scarcity of boreholes and the significant heterogeneity of carbon...Mesozoic-Palaeozoic marine carbonate rocks are crucial hydrocarbon reservoirs in the Central Uplift area of the South Yellow Sea Basin(SYSB).Due to the scarcity of boreholes and the significant heterogeneity of carbonate reservoirs,the distribution of porous carbonate reservoirs and their related key controlling factors remain unclear.In this study,factors affecting the distribution of porous Carboniferous-Early Permian carbonate reservoirs in the SYSB were investigated through seismic inversion and isotope analysis.The log-seismic characteristics of porous carbonate reservoirs,sensitive lithology parameters,and physical property parameters were extracted and analyzed.The pre-stack simultaneous inversion technique was applied to predict the lithology and physical properties of porous carbonate reservoirs.Moreover,the sedimentary of carbonate was analyzed using isotopes of carbon,oxygen,and strontium.The results show that porous carbonate reservoirs are mainly developed in the open platform sediments with porosities of 3%-5%and are mainly distributed in the paleo-highland(Huanglong Formation and Chuanshan Formation)and the slope of paleo-highland(Hezhou Formation).The porous carbonate reservoirs of the Qixia Formation are only locally developed.In addition,the negativeδ13C excursions indicate a warm and humid tropical climate with three sea-level fluctuations in the study area from the Carboniferous to Early Permian.The favorable conditions for developing porous carbonate rocks include the sedimentary environment and diagenetic process.The primary pore tends to form in high-energy environments of the paleo-highland,and the secondary pore is increased by dissolution during the syngenetic or quasi-syngenetic period.According to the hydrocarbon potential analysis,the Late Ordovician Wufeng Formation and Lower Silurian Gaojiabian Formation are the source rocks in the high-maturity-over-maturity stage,the Carboniferous-Lower Permian carbonate is the good reservoirs,and the Late Permian Longtan-Dalong Formation is the stable seal,ensuring a huge hydrocarbon accumulation potential in SYSB.The methods proposed in this study can be applied to other carbonate-dominated strata worldwide.展开更多
Based on the analysis of geological characteristics of ultra-deep fault-controlled fracture-cavity carbonate reservoirs and division of reservoir units, two physical models were made, and physical simulations of oil d...Based on the analysis of geological characteristics of ultra-deep fault-controlled fracture-cavity carbonate reservoirs and division of reservoir units, two physical models were made, and physical simulations of oil displacement by water injection were carried out to find out water flooding mechanism in the fault-controlled fracture-cavity carbonate reservoir under complex flow state. On this basis, a mathematical model of fault-controlled carbonate reservoir with coexisting seepage and free flow has been established. Pilot water injection tests have been carried out to evaluate the effects of enhancing oil recovery by water injection. The results show that: fault-controlled fracture-cavity carbonate reservoir units can be divided into three types:the strong natural energy connected type, the weak natural energy connected type and the weak natural energy isolated type;the fault-fracture activity index of the fault-controlled fractured-cavity body can effectively characterize the connectivity of the reservoir and predict the effective direction of water injection;the mathematical model of fault-controlled carbonate reservoir with coexisting seepage and free flows can quantitatively describe the fluid flow law in the fracture-cavity body;the water injected into the fault-controlled fracture-cavity body is weakly affected by the capillary force of the lithologic body, and the oil-water movement is mainly dominated by gravity. The development modes of single well water injection, unit water injection,and single well high pressure water injection proposed based on the connection structure of fracture-cavity space and well storage space configuration are confirmed effective by pilot tests, with obvious water injection gravity flooding effect.展开更多
Carbonate reservoirs worldwide are complex in structure,diverse in form,and highly heterogeneous.Based on these characteristics,the reservoir stimulation technologies and fluid flow characteristics of carbonate reserv...Carbonate reservoirs worldwide are complex in structure,diverse in form,and highly heterogeneous.Based on these characteristics,the reservoir stimulation technologies and fluid flow characteristics of carbonate reservoirs are briefly described in this study.The development methods and EOR technologies of carbonate reservoirs are systematically summarized,the relevant mechanisms are analyzed,and the application status of oil fields is catalogued.The challenges in the development of carbonate reservoirs are discussed,and future research directions are explored.In the current development processes of carbonate reservoirs,water flooding and gas flooding remain the primary means but are often prone to channeling problems.Chemical flooding is an effective method of tertiary oil recovery,but the harsh formation conditions require high-performance chemical agents.The application of emerging technologies can enhance the oil recovery efficiency and environmental friendliness to a certain extent,which is welcome in hard-to-recover areas such as heavy oil reservoirs,but the economic cost is often high.In future research on EOR technologies,flow field control and flow channel plugging will be the potential directions of traditional development methods,and the application of nanoparticles will revolutionize the chemical EOR methods.On the basis of diversified reservoir stimulation,combined with a variety of modern data processing schemes,multichannel EOR technologies are being developed to realize the systematic,intelligent,and cost-effective development of carbonate reservoirs.展开更多
Secondary storage spaces with very complex geometries are well developed in Ordovician carbonate reservoirs in the Tarim Basin,which is taken as a study case in this paper.It is still not clear how the secondary stora...Secondary storage spaces with very complex geometries are well developed in Ordovician carbonate reservoirs in the Tarim Basin,which is taken as a study case in this paper.It is still not clear how the secondary storage space shape influences the P-＆ S-wave velocities （or elastic properties） in complex carbonate reservoirs.In this paper,three classical rock physics models （Wyllie timeaverage equation,Gassmann equation and the Kuster-Toks z model） are comparably analyzed for their construction principles and actual velocity prediction results,aiming at determining the most favourable rock physics model to consider the influence of secondary storage space shape.Then relationships between the P-＆ S-wave velocities in carbonate reservoirs and geometric shapes of secondary storage spaces are discussed from different aspects based on actual well data by employing the favourable rock physics model.To explain the influence of secondary storage space shape on V P-V S relationship,it is analyzed for the differences of S-wave velocities between derived from common empirical relationships （including Castagna＇s mud rock line and Greenberg-Castagna V P-V S relationship） and predicted by the rock physics model.We advocate that V P-V S relationship for complex carbonate reservoirs should be built for different storage space types.For the carbonate reservoirs in the Tarim Basin,the V P-V S relationships for fractured,fractured-cavernous,and fractured-hole-vuggy reservoirs are respectively built on the basis of velocity prediction and secondary storage space type determination.Through the discussion above,it is expected that the velocity prediction and the V P-V S relationships for complex carbonate reservoirs should fully consider the influence of secondary storage space shape,thus providing more reasonable constraints for prestack inversion,further building a foundation for realizing carbonate reservoir prediction and fluid prediction.展开更多
The major storage space types in the carbonate reservoir in the Ordovician in the TZ45 area are secondary dissolution caves.For the prediction of caved carbonate reservoir,post-stack methods are commonly used in the o...The major storage space types in the carbonate reservoir in the Ordovician in the TZ45 area are secondary dissolution caves.For the prediction of caved carbonate reservoir,post-stack methods are commonly used in the oilfield at present since pre-stack inversion is always limited by poor seismic data quality and insufficient logging data.In this paper,based on amplitude preserved seismic data processing and rock-physics analysis,pre-stack inversion is employed to predict the caved carbonate reservoir in TZ45 area by seriously controlling the quality of inversion procedures.These procedures mainly include angle-gather conversion,partial stack,wavelet estimation,low-frequency model building and inversion residual analysis.The amplitude-preserved data processing method can achieve high quality data based on the principle that they are very consistent with the synthetics.Besides,the foundation of pre-stack inversion and reservoir prediction criterion can be established by the connection between reservoir property and seismic reflection through rock-physics analysis.Finally,the inversion result is consistent with drilling wells in most cases.It is concluded that integrated with amplitude-preserved processing and rock-physics,pre-stack inversion can be effectively applied in the caved carbonate reservoir prediction.展开更多
The carbonate reservoirs in the Tarim Basin are characterized by low matrix-porosity,heterogeneity and anisotropy,which make it difficult to predict and evaluate these reservoirs.The reservoir formations in Lundong ar...The carbonate reservoirs in the Tarim Basin are characterized by low matrix-porosity,heterogeneity and anisotropy,which make it difficult to predict and evaluate these reservoirs.The reservoir formations in Lundong area experienced a series of diagenesis and tectonic evolution stages.And secondary storage spaces such as fractures and dissolution caves were developed while nearly all the primary pores have disappeared.Based on a summary of different types of storage spaces and their responses in conventional logs,FMI and full waveform sonic logs which are sensitive to different reservoirs,the comprehensive probability index （CPI） method is applied to evaluating the reservoirs and a standard of reservoir classification is established.By comparing the evaluation results with actual welllogging results,the method has proven to be practical for formation evaluation of carbonate reservoirs,especially for the fractured carbonate reservoirs.In reservoir fluid identification,the multivariate stepwise discriminant analysis （MSDA） method is introduced.Combining the CPI method and MSDA method,comprehensive formation evaluation has been performed for fractured and caved carbonate reservoirs in the Tarim Basin.Additionally,on the basis of secondary pore inversion results,another new method of formation evaluation is also proposed in the discussion part of this paper.Through detailed application result analysis,the method shows a promising capability for formation evaluation of complex carbonate reservoirs dominated by various secondary pores such as holes,caves,and cracks.展开更多
Carbonate reservoirs exhibit strong heterogeneity in the distribution of pore types that can be quantitatively characterized by applying Xu–Payne multi-porosity model.However,there are some prerequisites to this mode...Carbonate reservoirs exhibit strong heterogeneity in the distribution of pore types that can be quantitatively characterized by applying Xu–Payne multi-porosity model.However,there are some prerequisites to this model the porosity and saturation need to be provided.In general,these application conditions are difficult to satisfy for seismic data.In order to overcome this problem,we present a two-step method to estimate the porosity and saturation and pore type of carbonate reservoirs from seismic data.In step one,the pore space of the carbonate reservoir is equivalent to a single-porosity system with an effective pore aspect ratio;then,a 3D rock-physics template(RPT)is established through the Gassmann’s equations and effective medium models;and then,the effective aspect ratio of pore,porosity and fluid saturation are simultaneously estimated from the seismic data based on 3D RPT.In step two,the pore space of the carbonate reservoir is equivalent to a triple-porosity system.Combined with the inverted porosity and saturation in the first step,the porosities of three pore types can be inverted from the seismic elastic properties.The application results indicate that our method can obtain accurate physical properties consistent with logging data and ensure the reliability of characterization of pore type.展开更多
Conventional seismic exploration method based on post-stack data usually fails to identify the distribution of fractured and caved carbonate reservoirs in the Tarim Basin,so the rich pre-stack information should be ap...Conventional seismic exploration method based on post-stack data usually fails to identify the distribution of fractured and caved carbonate reservoirs in the Tarim Basin,so the rich pre-stack information should be applied to the prediction of carbonate reservoirs.Amplitude-preserved seismic data processing is the foundation.In this paper,according to the feature of desert seismic data （including weak reflection,fast attenuation of high frequency components,strong coherent noises,low S/N and resolution）,a set of amplitude-preserved processing techniques is applied and a reasonable processing flow is formed to obtain the high quality data.After implementing a set of pre-stack amplitude-preserved processing,we test and define the kernel parameters of amplitude-preserved Kirchhoff PSTM （pre-stack time migration） and subsequent gathers processing,in order to obtain the amplitude-preserved gathers used to the isotropic pre-stack inversion for the identification of caved reservoirs.The AVO characteristics of obtained gathers fit well with the synthetic gathers from logging data,and it proves that the processing above is amplitudepreserved.The azimuthal processing techniques,including azimuth division and binning enlargement,are implemented for amplitude-preserved azimuthal gathers with the uniform fold.They can be used in the anisotropic inversion to detect effective fractures.The processing techniques and flows are applied to the field seismic data,and are proved available for providing the amplitude-preserved gathers for carbonate reservoir prediction in the Tarim Basin.展开更多
An intelligent prediction method for fractures in tight carbonate reservoir has been established by upgrading single-well fracture identification and interwell fracture trend prediction with artificial intelligence,mo...An intelligent prediction method for fractures in tight carbonate reservoir has been established by upgrading single-well fracture identification and interwell fracture trend prediction with artificial intelligence,modifying construction of interwell fracture density model,and modeling fracture network and making fracture property equivalence.This method deeply mines fracture information in multi-source isomerous data of different scales to reduce uncertainties of fracture prediction.Based on conventional fracture indicating parameter method,a prediction method of single-well fractures has been worked out by using 3 kinds of artificial intelligence methods to improve fracture identification accuracy from 3 aspects,small sample classification,multi-scale nonlinear feature extraction,and decreasing variance of the prediction model.Fracture prediction by artificial intelligence using seismic attributes provides many details of inter-well fractures.It is combined with fault-related fracture information predicted by numerical simulation of reservoir geomechanics to improve inter-well fracture trend prediction.An interwell fracture density model for fracture network modeling is built by coupling single-well fracture identification and interwell fracture trend through co-sequential simulation.By taking the tight carbonate reservoir of Oligocene-Miocene AS Formation of A Oilfield in Zagros Basin of the Middle East as an example,the proposed prediction method was applied and verified.The single-well fracture identification improves over 15%compared with the conventional fracture indication parameter method in accuracy rate,and the inter-well fracture prediction improves over 25%compared with the composite seismic attribute prediction.The established fracture network model is well consistent with the fluid production index.展开更多
The GOI(grains containing oil inclusions)index is used to distinguish oil zones,oil-water zones and water zones in sandstone oil reservoirs.However,this method cannot be directly applied to carbonate rocks that may no...The GOI(grains containing oil inclusions)index is used to distinguish oil zones,oil-water zones and water zones in sandstone oil reservoirs.However,this method cannot be directly applied to carbonate rocks that may not have clear granular textures.In this paper we propose the Effective Grid Containing Oil Inclusions(EGOI)method for carbonate reservoirs.A microscopic view under10×ocular and 10 x objective is divided into 10×10 grids,each with an area of 0.0625 mm×0.0625 mm.An effective grid is defined as one that is cut(touched)by a stylolite,a healed fracture,a vein,or a pore-filling material.EGOI is defined as the number of effective grids containing oil inclusions divided by the total number of effective grids multiplied by 100%.Based on data from the Tarim Basin,the EGOI values indicative of the paleo-oil zones,oil-water zones,and water zones are〉5%,1%-5%,and〈1%,respectively.However,the oil zones in young reservoirs(charged in the Himalayan)generally have lower EGOI values,typically 3%-5%.展开更多
Based on comprehensive analysis of tectonic and fault evolution, core, well logging, seismic, drilling, and production data, the reservoir space characteristic, distribution, origin of fault-karst carbonate reservoir ...Based on comprehensive analysis of tectonic and fault evolution, core, well logging, seismic, drilling, and production data, the reservoir space characteristic, distribution, origin of fault-karst carbonate reservoir in Yueman block of South Tahe area, Halahatang oilfield, Tarim Basin, were studied systematically. And the regular pattern of hydrocarbon accumulation and enrichment was analyzed systematically based on development practice of the reservoirs. The results show that fault-karst carbonate reservoirs are distributed in the form of "body by body" discontinuously, heterogeneously and irregularly, which are controlled by the development of faults. Three formation models of fault-karst carbonate reservoirs, namely, the models controlled by the main deep-large fault, the secondary fault and the secondary internal fault, are built. The hydrocarbon accumulation and enrichment of fault-karst carbonate reservoirs is controlled by the spatiotemporal matching relation between hydrocarbon generation period and fault activity, and the size and segmentation of fault. The study results can effectively guide the well deployment and help the efficient development of fault-karst carbonate reservoirs of South Tahe area, Halahatang oilfield.展开更多
Porous carbonate reservoirs,prevalent in the Middle East,are lithologically dominated by bioclastic limestones,exhibiting high porosity,low permeability,intricate pore structure,and strong heterogeneity.Waterflooding ...Porous carbonate reservoirs,prevalent in the Middle East,are lithologically dominated by bioclastic limestones,exhibiting high porosity,low permeability,intricate pore structure,and strong heterogeneity.Waterflooding through horizontal wells is commonly used for exploiting these reservoirs.However,challenges persist,such as significant uncertainty and complex operational procedures regarding adjustment effects during the exploitation.The USH reservoir of the Cretaceous D oilfield,Oman exemplifies typical porous carbonate reservoirs.It initially underwent depletion drive using vertical wells,followed by horizontal well waterflooding in the late stage.Currently,the oilfield is confronted with substantial developmental challenges,involving the understanding of residual oil distribution,effective water cut control,and sustaining oil production since it has entered the late development stage.Employing a microscopic visualization displacement system equipped with electrodes,this study elucidated the waterflooding mechanisms and residual oil distribution in the late-stage development of the USH reservoir.The results reveal that the reservoir's vertical stacking patterns act as the main factor affecting the horizontal well waterflooding efficacy.Distinct water flow channels emerge under varying reservoir stacking patterns,with post-waterflooding residual oil predominantly distributed at the reservoir's top and bottom.The oil recovery can be enhanced by adjusting the waterflooding's flow line and intensity.The findings of this study will provide theoretical insights of waterflooding mechanisms and injection-production adjustments for exploiting other porous carbonate reservoirs in the Middle East through horizontal wells.展开更多
基金Supported by the Joint Fund for Enterprise Innovation and Development of the National Natural Science Foundation of China(U23B20154)General Program of the National Natural Science Foundation of China(42372169)。
文摘To address the challenges in studying the pore formation and evolution processes,and unclear preservation mechanisms of deep to ultra-deep carbonate rocks,a high-temperature and high-pressure visualization simulation experimental device was developed for ultra-deep carbonate reservoirs.Carbonate rock samples from the Sichuan Basin and Tarim Basin were used to simulate the dissolution-precipitation process of deep to ultra-deep carbonate reservoirs in an analogous geological setting.This unit comprises four core modules:an ultra-high temperature,high pressure triaxial stress core holder module(temperature higher than 300°C,pressure higher than 150 MPa),a multi-stage continuous flow module with temperature-pressure regulation,an ultra-high temperature-pressure sapphire window cell and an in-situ high-temperature-pressure fluid property measurement module and real-time ultra-high temperature-pressure permeability detection module.The new experimental device was used for simulation experiment,the geological insights were obtained in three aspects.First,the pore-throat structure of carbonate is controlled by lithology and initial pore-throat structure,and fluid type,concentration and dissolution duration determine the degree of dissolution.The dissolution process exhibits two evolution patterns.The dissolution scale is positively correlated to the temperature and pressure,and the pore-forming peak period aligns well with the hydrocarbon generation peak period.Second,the dissolution potential of dolomite in an open flow system is greater than that of limestone,and secondary dissolved pores formed continuously are controlled by the type and concentration of acidic fluids and the initial physical properties.These pores predominantly distribute along pre-existing pore/fracture zones.Third,in a nearly closed diagenetic system,after the chemical reaction between acidic fluids and carbonate rock reaches saturation and dynamic equilibrium,the pore structure no longer changes,keeping pre-existing pores well-preserved.These findings have important guiding significance for the evaluation of pore-throat structure and development potential of deep to ultra-deep carbonate reservoirs,and the prediction of main controlling factors and distribution of high-quality carbonate reservoirs.
基金supported by the National Natural Science Foundation of China(Grant No.U21B2062)supported by the Key Laboratory for Carbonate Reservoirs of China National Petroleum Corporation。
文摘Burial dissolution is a critical diagenetic process influencing ultra-deep carbonate reservoir development and preservation.Artificial carbonate samples with different internal structures were prepared,and high-temperature and highpressure dissolution kinetic simulations were conducted.The results demonstrate that the intensity of burial dissolution is controlled by temperature and pressure,while tectonic-fluid activity influences the development pattern of burial dissolution,ultimately determining the direction of its differential modification.Extensive burial dissolution is likely to occur primarily at relatively shallow depths,significantly influencing reservoir formation,preservation,modification,and adjustment.The development of faults facilitates the maintenance of the intensity of burial dissolution.The maximum intensity of burial dissolution occurs at the tips and overlap zones of faults and intersections of multiple faults.The larger the scale of the faults,the more conducive it is to the development of burial dissolution.Burial dissolution fosters the formation of fault networks characterized by enhanced reservoir capacity and permeability.Burial dissolution controlled by episodic tectonic-fluid activity is a plausible explanation for forming the Tarim Basin's ultra-deep fault-controlled“stringbead-like”reservoirs.
基金Supported by the China National Petroleum Corporation Major Science and Technology Project(2023ZZ19-01,2023ZZ19-07).
文摘Based on the waterflooding development in carbonate reservoirs in the Middle East,this study analyzes the geological characteristics and waterflooding behaviors/patterns of different types of high permeability zones(HPZs),and proposes rational waterflooding strategies and modes.Four types of HPZs,i.e.sedimentation-dominated,sedimentation-diagenesis coupling,biogenic and composite,are identified in the carbonate reservoirs in the Middle East.Based on their distribution patterns,flow mechanisms,and waterflooding behaviors/patterns,five waterflooding modes are established:(1)the mode with stepwise-infilled areal vertical well pattern,for composite HFZs in patchy distribution;(2)the mode with regular row vertical well pattern for TypeⅠchannel“network”HFZs(with dominant water flow pathways at the base),and the mode with irregular differentiated vertical well pattern for TypeⅡchannel“network”HFZs(where multi-stage superimposition leads to“layered flooding”),for sedimentation-diagenesis coupling HFZs;(3)the mode with row horizontal wells through bottom injection and top production,for biogenic HFZs characterized by thin,contiguous distribution and rapid advancing of injected water along a工-shaped path;and(4)the mode with progressive waterflooding through edge water injection via vertical well and oil production via horizontal well,for sedimentation-dominated HFZs characterized by thick,contiguous distribution and flood first in upper anti-rhythmic reservoirs.Development practices demonstrate that the proposed waterflooding modes are efficient in the highly heterogeneous carbonate reservoirs in the Middle East,with balanced employment of reserves in the adjacent reservoirs and enhanced oil recovery.
基金funded by Fundamental Research Funds for the Central Universities(No.00007851)。
文摘This study explores the application of machine learning techniques for predicting permeability,porosity,and flow zone indicator(FZI)in carbonate reservoirs using well log data,aiming to overcome the limitations of traditional empirical methods.Six machine learning algorithms are utilized:support vector machine(SVM),backpropagation(BP)neural network,gaussian process regression(GPR),extreme gradient boosting(XGBoost),K-nearest neighbor(KNN),and random forest(RF).The methodology involves classifying pore-permeability types based on the flow index,leveraging logging curves and geological data.Models are trained using seven logging parameters—spectral gamma rays(SGR),uranium-free gamma rays(CGR),photoelectric absorption cross-section index(PE),lithologic density(RHOB),acoustic transit time(DT),neutron porosity(NPHI),and formation true resistivity(RT)—along with corresponding physical property labels.Machine learning models are trained and evaluated to predict carbonate rock properties.The results demonstrate that GPR achieves the highest accuracy in porosity prediction,with a coefficient of determination(R~2)value of 0.7342,while RF proves to be the most accurate for permeability prediction.Despite these improvements,accurately predicting lowpermeability zones in heterogeneous carbonate rocks remains a significant challenge.Application of cross-validation techniques optimized the performance of GPR,resulting in an accuracy index(ACI)value of 0.9699 for porosity prediction.This study provides a novel framework that leverages machine learning techniques to improve the characterization of carbonate reservoirs.
基金supported by the National Engineering Laboratory for Exploration and Development of Low-Permeability Oil and Gas Fields(KFKT2023-20)the National Natural Science Foundation of China(42104121)。
文摘Carbonate reservoirs are known for their complex pore structures,which lead to variable elastic behaviors and seismic responses.These variations pose significant challenges for seismic interpretation of carbonate reservoirs.Therefore,quantitative characterization of pore structure is crucial for accurate fluid detection and reservoir property estimation.To address the complexity of pore geometry and the uneven fluid distribution in tight carbonate reservoirs,we develop a triple-pore effective medium model by integrating the extended Keys-Xu model with the Gassmann-Hill equation.Comparison between the theoretical modeling results and an available laboratory data set verifies the effectiveness of this model in pore type quantification.Based on this calibrated model,we propose a novel two-step triple pore-type inversion strategy with varying pore aspect ratio via a grid-searching algorithm.We apply this method to well logs and 3D seismic data from the tight carbonate reservoirs of the Ordovician Majiagou formation in the Ordos Basin.The good agreement between pore-type estimates and logging interpretation results suggests that our method significantly improves the accuracy of porosity estimates for different pore types,outperforming the pore-type inversion method with fixed pore aspect ratios.The successful application to seismic data also demonstrates that the proposed method provides a reliable distribution of pore types in tight carbonate reservoirs,confirming its applicability and feasibility in seismic pore-type estimation.This method not only facilitates the recognition of complex pore geometries but also provides valuable insights for accurate detection of high-quality reservoirs.
基金supported by the National Natural Science Foundation of China(No.U21B2062)funding from the Chinese Scholarship Council(CSC)and the American Association of Petroleum Geologists Foundation Grantsin-Aid Program.
文摘Natural fractures controlled by faults in ultradeep carbonate strata play substantial roles as both fluid migration channels and storage spaces.However,characterizing the heterogeneous distribution of underground fractures within the complex three-dimensional geometry of strike-slip fault zones remains challenging.This study investigates the characteristics of natural fractures controlled by strike-slip faults in the fractured Middle and Lower Ordovician reservoirs of the central and northern Tarim Basin,China.Seismics,cores,and image logs were integrated to quantitatively analyze the intensity and dip angle of natural fractures and findings were verified using published sandbox simulations.The carbonate reservoir contains three main types of natural fractures:tectonic fractures,abnormal high-pressure-related fractures,and stylolites.Strike-slip faults control the distribution and characteristics of tectonic fractures across various scales.Generally,both fracture intensity and porosity exhibit a decreasing trend as the distance from the main fault surface increases.Compared with those in non-stepover zones along a strike-slip fault,natural fractures and faults in stepover zones are more developed along the fault strike,with significantly greater development intensity in central stepover regions than that at its two ends.Furthermore,strike-slip faults influence the dip angles of both natural fractures and secondary faults.The proportion of medium-to-low-dip angle fractures and faults in the stepover zone is greater than that in the non-stepover zone.Additionally,the proportion of medium-to low-dip angle fractures and faults in the middle of the stepover is greater than that at both ends.Therefore,strike-slip fault structures control the dip angle of natural fracture and the heterogeneity of secondary fault and fracture intensity.The linking damage zone in the stepover contains a larger volume of fractured rocks,making it a promising petroleum exploration target.The development of stepovers and the orientation of present-day in-situ stress substantially influence the productivity of fractured reservoirs controlled by strike-slip faults.The analysis in this study reveals that reservoir productivity increases as the angle between the strike-slip fault segment and the maximum horizontal principal stress decreases.This study provides valuable insights for quantitatively evaluating fracture heterogeneity in fractured reservoirs and establishing optimized selection criteria for favorable targets in fault-related fractured reservoirs.
基金supported by the National Natural Science Foundation of China(Grant No.U21B2062).
文摘Recent exploration has highlighted the critical role of strike-slip faults in shaping ultra-deep carbonate reservoirs in the Tarim Basin.This study integrates satellite imagery,UAV photogrammetry,outcrop surveys and microscopic analysis to investigate the architecture of these faults and their impact on reservoir petrophysical properties.The strike-slip faults exhibit cores consisting of calcite bands,fault breccias and fractures,while the damage zones are predominantly fractured.Thicker fault cores and fault zones are associated with more extensive reservoir development.Individual strike-slip fault zones are primarily characterized by two sets of fractures intersecting the fault at small angles.When two fault systems interact,the dominant pattern is two sets of fractures intersecting the main fault at small angles and one set at larger angles,facilitating the formation of large-scale reservoirs.We propose a model for the fault core,which primarily consists of a calcite band and fault breccias.These breccias are composed of original host rock,calcite cement and quartz,which exhibit poor physical properties,while fractures and vugs show favorable reservoir characteristics.This model offers valuable insights into the development of fault-controlled reservoirs,particularly in the Tarim Basin.
基金financially supported by the National Natural Science Foundation of China(Grant No.52074331).
文摘Wellbore instability is one of the significant challenges in the drilling engineering and during the development of carbonate reservoirs,especially with open-hole completion.The problems of wellbore instability such as downhole collapse and silt deposit in the fractured carbonate reservoir of Tarim Basin(Ordovician)are severe.Solid destabilization and production(SDP)was proposed to describe this engineering problem of carbonate reservoirs.To clarify the mechanism and mitigate potential borehole instability problems,we conducted particle size distribution(PSD)analysis,X-ray diffraction(XRD)analysis,triaxial compression tests,and micro-scale sand production tests based on data analysis.We found that the rock fragments and silt in the wellbore came from two sources:one from the wellbore collapse in the upper unplugged layers and the other from the production of sand particles carried by the fluid in the productive layers.Based on the experimental study,a novel method combining a geomechanical model and microscopic sand production model was proposed to predict wellbore instability and analyze its influencing factors.The critical condition and failure zone predicted by the prediction model fit well with the field observations.According to the prediction results,the management and prevention measures of wellbore instability in carbonate reservoirs were proposed.It is suggested to optimize the well track in new drilling wells while upgrading the production system in old wells.This study is of great guiding significance for the optimization of carbonate solid control and it improves the understanding of the sand production problems in carbonate reservoirs.
基金This study was supported by the project ofthe Science and Technology Innovation Fund of Command Center of Natural Resources Intergrated Survey entitled“Temporal and spatial distribution of paleochannel and origin of organic carbon burial in the Western Bohai Sea since 2.28Ma”(KC20220011)the project entitled“Characterization of Carboniferous-Early Permian heterogeneous porous carbonate reservoirs and hydrocarbon potential analysis in the central uplift of the South Yellow Sea Basin”(KLSG2304)+3 种基金by the Key laboratory of Submarine Science,Ministry of Natural Resources,the project entitled“1∶50000 Marine regional Geological survey in Caofeidian Sea Area,Bohai Sea”(ZD20220602)“1∶250000 Marine regional Geological survey in Weihai Sea Area,North Yellow Sea”(DD20230412)“Geological survey on tectonic and sedimentary conditions of Laoshan uplift”(DD2016015)by the China Geological Survey,and the project entitled“Study on Hydrocarbon Accumulation Failure and Fluid Evolution Reduction of the Permian Reservoir in the Laoshan Uplift,South Yellow Sea”(42076220)organized by the National Natural Science Foundation of China.
文摘Mesozoic-Palaeozoic marine carbonate rocks are crucial hydrocarbon reservoirs in the Central Uplift area of the South Yellow Sea Basin(SYSB).Due to the scarcity of boreholes and the significant heterogeneity of carbonate reservoirs,the distribution of porous carbonate reservoirs and their related key controlling factors remain unclear.In this study,factors affecting the distribution of porous Carboniferous-Early Permian carbonate reservoirs in the SYSB were investigated through seismic inversion and isotope analysis.The log-seismic characteristics of porous carbonate reservoirs,sensitive lithology parameters,and physical property parameters were extracted and analyzed.The pre-stack simultaneous inversion technique was applied to predict the lithology and physical properties of porous carbonate reservoirs.Moreover,the sedimentary of carbonate was analyzed using isotopes of carbon,oxygen,and strontium.The results show that porous carbonate reservoirs are mainly developed in the open platform sediments with porosities of 3%-5%and are mainly distributed in the paleo-highland(Huanglong Formation and Chuanshan Formation)and the slope of paleo-highland(Hezhou Formation).The porous carbonate reservoirs of the Qixia Formation are only locally developed.In addition,the negativeδ13C excursions indicate a warm and humid tropical climate with three sea-level fluctuations in the study area from the Carboniferous to Early Permian.The favorable conditions for developing porous carbonate rocks include the sedimentary environment and diagenetic process.The primary pore tends to form in high-energy environments of the paleo-highland,and the secondary pore is increased by dissolution during the syngenetic or quasi-syngenetic period.According to the hydrocarbon potential analysis,the Late Ordovician Wufeng Formation and Lower Silurian Gaojiabian Formation are the source rocks in the high-maturity-over-maturity stage,the Carboniferous-Lower Permian carbonate is the good reservoirs,and the Late Permian Longtan-Dalong Formation is the stable seal,ensuring a huge hydrocarbon accumulation potential in SYSB.The methods proposed in this study can be applied to other carbonate-dominated strata worldwide.
基金Supported by China National Science and Technology Major Project (2017ZX05008-004)PetroChina Science and Technology Major Project (2018E-18)。
文摘Based on the analysis of geological characteristics of ultra-deep fault-controlled fracture-cavity carbonate reservoirs and division of reservoir units, two physical models were made, and physical simulations of oil displacement by water injection were carried out to find out water flooding mechanism in the fault-controlled fracture-cavity carbonate reservoir under complex flow state. On this basis, a mathematical model of fault-controlled carbonate reservoir with coexisting seepage and free flow has been established. Pilot water injection tests have been carried out to evaluate the effects of enhancing oil recovery by water injection. The results show that: fault-controlled fracture-cavity carbonate reservoir units can be divided into three types:the strong natural energy connected type, the weak natural energy connected type and the weak natural energy isolated type;the fault-fracture activity index of the fault-controlled fractured-cavity body can effectively characterize the connectivity of the reservoir and predict the effective direction of water injection;the mathematical model of fault-controlled carbonate reservoir with coexisting seepage and free flows can quantitatively describe the fluid flow law in the fracture-cavity body;the water injected into the fault-controlled fracture-cavity body is weakly affected by the capillary force of the lithologic body, and the oil-water movement is mainly dominated by gravity. The development modes of single well water injection, unit water injection,and single well high pressure water injection proposed based on the connection structure of fracture-cavity space and well storage space configuration are confirmed effective by pilot tests, with obvious water injection gravity flooding effect.
基金supported by the Innovation Project for Graduates in UPC(Grant YCX2019016)the National Natural Science Foundation of China(Nos.51774306 and 51974346)+1 种基金the Science and Technology Support Plan for Youth Innovation of University in Shandong Province under Grant 2019KJH002the Major Scientific and Technological Projects of CNPC under Grant ZD2019-183-008。
文摘Carbonate reservoirs worldwide are complex in structure,diverse in form,and highly heterogeneous.Based on these characteristics,the reservoir stimulation technologies and fluid flow characteristics of carbonate reservoirs are briefly described in this study.The development methods and EOR technologies of carbonate reservoirs are systematically summarized,the relevant mechanisms are analyzed,and the application status of oil fields is catalogued.The challenges in the development of carbonate reservoirs are discussed,and future research directions are explored.In the current development processes of carbonate reservoirs,water flooding and gas flooding remain the primary means but are often prone to channeling problems.Chemical flooding is an effective method of tertiary oil recovery,but the harsh formation conditions require high-performance chemical agents.The application of emerging technologies can enhance the oil recovery efficiency and environmental friendliness to a certain extent,which is welcome in hard-to-recover areas such as heavy oil reservoirs,but the economic cost is often high.In future research on EOR technologies,flow field control and flow channel plugging will be the potential directions of traditional development methods,and the application of nanoparticles will revolutionize the chemical EOR methods.On the basis of diversified reservoir stimulation,combined with a variety of modern data processing schemes,multichannel EOR technologies are being developed to realize the systematic,intelligent,and cost-effective development of carbonate reservoirs.
基金co-supported by the National Basic Research Program of China(Grant No.2011CB201103)the National Science and Technology Major Project(Grant No.2011ZX05004003)
文摘Secondary storage spaces with very complex geometries are well developed in Ordovician carbonate reservoirs in the Tarim Basin,which is taken as a study case in this paper.It is still not clear how the secondary storage space shape influences the P-＆ S-wave velocities （or elastic properties） in complex carbonate reservoirs.In this paper,three classical rock physics models （Wyllie timeaverage equation,Gassmann equation and the Kuster-Toks z model） are comparably analyzed for their construction principles and actual velocity prediction results,aiming at determining the most favourable rock physics model to consider the influence of secondary storage space shape.Then relationships between the P-＆ S-wave velocities in carbonate reservoirs and geometric shapes of secondary storage spaces are discussed from different aspects based on actual well data by employing the favourable rock physics model.To explain the influence of secondary storage space shape on V P-V S relationship,it is analyzed for the differences of S-wave velocities between derived from common empirical relationships （including Castagna＇s mud rock line and Greenberg-Castagna V P-V S relationship） and predicted by the rock physics model.We advocate that V P-V S relationship for complex carbonate reservoirs should be built for different storage space types.For the carbonate reservoirs in the Tarim Basin,the V P-V S relationships for fractured,fractured-cavernous,and fractured-hole-vuggy reservoirs are respectively built on the basis of velocity prediction and secondary storage space type determination.Through the discussion above,it is expected that the velocity prediction and the V P-V S relationships for complex carbonate reservoirs should fully consider the influence of secondary storage space shape,thus providing more reasonable constraints for prestack inversion,further building a foundation for realizing carbonate reservoir prediction and fluid prediction.
基金supported by National Basic Research Program(2006CB202304)of Chinaco-supported by the National Basic Research Program of China(Grant No.2011CB201103)the National Science and Technology Major Project of China(Grant No.2011ZX05004003)
文摘The major storage space types in the carbonate reservoir in the Ordovician in the TZ45 area are secondary dissolution caves.For the prediction of caved carbonate reservoir,post-stack methods are commonly used in the oilfield at present since pre-stack inversion is always limited by poor seismic data quality and insufficient logging data.In this paper,based on amplitude preserved seismic data processing and rock-physics analysis,pre-stack inversion is employed to predict the caved carbonate reservoir in TZ45 area by seriously controlling the quality of inversion procedures.These procedures mainly include angle-gather conversion,partial stack,wavelet estimation,low-frequency model building and inversion residual analysis.The amplitude-preserved data processing method can achieve high quality data based on the principle that they are very consistent with the synthetics.Besides,the foundation of pre-stack inversion and reservoir prediction criterion can be established by the connection between reservoir property and seismic reflection through rock-physics analysis.Finally,the inversion result is consistent with drilling wells in most cases.It is concluded that integrated with amplitude-preserved processing and rock-physics,pre-stack inversion can be effectively applied in the caved carbonate reservoir prediction.
基金co-supported by the National Basic Research Program of China(Grant No.2011CB201103)the National Science and Technology Major Project(GrantNo.2011ZX05004003)
文摘The carbonate reservoirs in the Tarim Basin are characterized by low matrix-porosity,heterogeneity and anisotropy,which make it difficult to predict and evaluate these reservoirs.The reservoir formations in Lundong area experienced a series of diagenesis and tectonic evolution stages.And secondary storage spaces such as fractures and dissolution caves were developed while nearly all the primary pores have disappeared.Based on a summary of different types of storage spaces and their responses in conventional logs,FMI and full waveform sonic logs which are sensitive to different reservoirs,the comprehensive probability index （CPI） method is applied to evaluating the reservoirs and a standard of reservoir classification is established.By comparing the evaluation results with actual welllogging results,the method has proven to be practical for formation evaluation of carbonate reservoirs,especially for the fractured carbonate reservoirs.In reservoir fluid identification,the multivariate stepwise discriminant analysis （MSDA） method is introduced.Combining the CPI method and MSDA method,comprehensive formation evaluation has been performed for fractured and caved carbonate reservoirs in the Tarim Basin.Additionally,on the basis of secondary pore inversion results,another new method of formation evaluation is also proposed in the discussion part of this paper.Through detailed application result analysis,the method shows a promising capability for formation evaluation of complex carbonate reservoirs dominated by various secondary pores such as holes,caves,and cracks.
基金supported by the China National Key R D plan(2019YFC0605504)Scientific Research&Technology Development Project of China National Petroleum Corporation(Grant Nos.2017D-3504 and 2018D-4305)
文摘Carbonate reservoirs exhibit strong heterogeneity in the distribution of pore types that can be quantitatively characterized by applying Xu–Payne multi-porosity model.However,there are some prerequisites to this model the porosity and saturation need to be provided.In general,these application conditions are difficult to satisfy for seismic data.In order to overcome this problem,we present a two-step method to estimate the porosity and saturation and pore type of carbonate reservoirs from seismic data.In step one,the pore space of the carbonate reservoir is equivalent to a single-porosity system with an effective pore aspect ratio;then,a 3D rock-physics template(RPT)is established through the Gassmann’s equations and effective medium models;and then,the effective aspect ratio of pore,porosity and fluid saturation are simultaneously estimated from the seismic data based on 3D RPT.In step two,the pore space of the carbonate reservoir is equivalent to a triple-porosity system.Combined with the inverted porosity and saturation in the first step,the porosities of three pore types can be inverted from the seismic elastic properties.The application results indicate that our method can obtain accurate physical properties consistent with logging data and ensure the reliability of characterization of pore type.
基金financially supported by National Basic Research Program of China(No.2011CB201100)
文摘Conventional seismic exploration method based on post-stack data usually fails to identify the distribution of fractured and caved carbonate reservoirs in the Tarim Basin,so the rich pre-stack information should be applied to the prediction of carbonate reservoirs.Amplitude-preserved seismic data processing is the foundation.In this paper,according to the feature of desert seismic data （including weak reflection,fast attenuation of high frequency components,strong coherent noises,low S/N and resolution）,a set of amplitude-preserved processing techniques is applied and a reasonable processing flow is formed to obtain the high quality data.After implementing a set of pre-stack amplitude-preserved processing,we test and define the kernel parameters of amplitude-preserved Kirchhoff PSTM （pre-stack time migration） and subsequent gathers processing,in order to obtain the amplitude-preserved gathers used to the isotropic pre-stack inversion for the identification of caved reservoirs.The AVO characteristics of obtained gathers fit well with the synthetic gathers from logging data,and it proves that the processing above is amplitudepreserved.The azimuthal processing techniques,including azimuth division and binning enlargement,are implemented for amplitude-preserved azimuthal gathers with the uniform fold.They can be used in the anisotropic inversion to detect effective fractures.The processing techniques and flows are applied to the field seismic data,and are proved available for providing the amplitude-preserved gathers for carbonate reservoir prediction in the Tarim Basin.
基金Supported by the China Youth Program of National Natural Science Foundation(42002134)The 14th Special Support Program of China Postdoctoral Science Foundation(2021T140735).
文摘An intelligent prediction method for fractures in tight carbonate reservoir has been established by upgrading single-well fracture identification and interwell fracture trend prediction with artificial intelligence,modifying construction of interwell fracture density model,and modeling fracture network and making fracture property equivalence.This method deeply mines fracture information in multi-source isomerous data of different scales to reduce uncertainties of fracture prediction.Based on conventional fracture indicating parameter method,a prediction method of single-well fractures has been worked out by using 3 kinds of artificial intelligence methods to improve fracture identification accuracy from 3 aspects,small sample classification,multi-scale nonlinear feature extraction,and decreasing variance of the prediction model.Fracture prediction by artificial intelligence using seismic attributes provides many details of inter-well fractures.It is combined with fault-related fracture information predicted by numerical simulation of reservoir geomechanics to improve inter-well fracture trend prediction.An interwell fracture density model for fracture network modeling is built by coupling single-well fracture identification and interwell fracture trend through co-sequential simulation.By taking the tight carbonate reservoir of Oligocene-Miocene AS Formation of A Oilfield in Zagros Basin of the Middle East as an example,the proposed prediction method was applied and verified.The single-well fracture identification improves over 15%compared with the conventional fracture indication parameter method in accuracy rate,and the inter-well fracture prediction improves over 25%compared with the composite seismic attribute prediction.The established fracture network model is well consistent with the fluid production index.
基金supported by the project of Research on Fluid Inclusions and Geological Ages of Hydrocarbon Accumulations of Key Reservoirs in the Tarim Basin(No.041014080008)
文摘The GOI(grains containing oil inclusions)index is used to distinguish oil zones,oil-water zones and water zones in sandstone oil reservoirs.However,this method cannot be directly applied to carbonate rocks that may not have clear granular textures.In this paper we propose the Effective Grid Containing Oil Inclusions(EGOI)method for carbonate reservoirs.A microscopic view under10×ocular and 10 x objective is divided into 10×10 grids,each with an area of 0.0625 mm×0.0625 mm.An effective grid is defined as one that is cut(touched)by a stylolite,a healed fracture,a vein,or a pore-filling material.EGOI is defined as the number of effective grids containing oil inclusions divided by the total number of effective grids multiplied by 100%.Based on data from the Tarim Basin,the EGOI values indicative of the paleo-oil zones,oil-water zones,and water zones are〉5%,1%-5%,and〈1%,respectively.However,the oil zones in young reservoirs(charged in the Himalayan)generally have lower EGOI values,typically 3%-5%.
基金Supported by the China National Sicence and Technology Project(2016ZX05004)
文摘Based on comprehensive analysis of tectonic and fault evolution, core, well logging, seismic, drilling, and production data, the reservoir space characteristic, distribution, origin of fault-karst carbonate reservoir in Yueman block of South Tahe area, Halahatang oilfield, Tarim Basin, were studied systematically. And the regular pattern of hydrocarbon accumulation and enrichment was analyzed systematically based on development practice of the reservoirs. The results show that fault-karst carbonate reservoirs are distributed in the form of "body by body" discontinuously, heterogeneously and irregularly, which are controlled by the development of faults. Three formation models of fault-karst carbonate reservoirs, namely, the models controlled by the main deep-large fault, the secondary fault and the secondary internal fault, are built. The hydrocarbon accumulation and enrichment of fault-karst carbonate reservoirs is controlled by the spatiotemporal matching relation between hydrocarbon generation period and fault activity, and the size and segmentation of fault. The study results can effectively guide the well deployment and help the efficient development of fault-karst carbonate reservoirs of South Tahe area, Halahatang oilfield.
基金funded by a Major Science and Technology Project of China National Petroleum Corporation(CNPC)entitled Research on Key Technologies for Efficient Production of Overseas Large Carbonate Reservoir”(2023ZZ19-08).
文摘Porous carbonate reservoirs,prevalent in the Middle East,are lithologically dominated by bioclastic limestones,exhibiting high porosity,low permeability,intricate pore structure,and strong heterogeneity.Waterflooding through horizontal wells is commonly used for exploiting these reservoirs.However,challenges persist,such as significant uncertainty and complex operational procedures regarding adjustment effects during the exploitation.The USH reservoir of the Cretaceous D oilfield,Oman exemplifies typical porous carbonate reservoirs.It initially underwent depletion drive using vertical wells,followed by horizontal well waterflooding in the late stage.Currently,the oilfield is confronted with substantial developmental challenges,involving the understanding of residual oil distribution,effective water cut control,and sustaining oil production since it has entered the late development stage.Employing a microscopic visualization displacement system equipped with electrodes,this study elucidated the waterflooding mechanisms and residual oil distribution in the late-stage development of the USH reservoir.The results reveal that the reservoir's vertical stacking patterns act as the main factor affecting the horizontal well waterflooding efficacy.Distinct water flow channels emerge under varying reservoir stacking patterns,with post-waterflooding residual oil predominantly distributed at the reservoir's top and bottom.The oil recovery can be enhanced by adjusting the waterflooding's flow line and intensity.The findings of this study will provide theoretical insights of waterflooding mechanisms and injection-production adjustments for exploiting other porous carbonate reservoirs in the Middle East through horizontal wells.
