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    01 February 2024, Volume 45 Issue 1 Previous Issue    Next Issue
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    OIL AND GAS EXPLORATION
    Distribution Patterns and Significance of Salt in Deep Cretaceous Subsalt Reservoirs in Kuqa Depression,Tarim Basin
    LUO Danting, LUO Jinglan, DENG Chao, NIAN Tao, HAN Jianfa, CHENG Daojie, YUAN Long
    2024, 45 (1):  1-12.  doi: 10.7657/XJPG20240101
    Abstract ( 148 )   HTML ( 17 )   PDF (2908KB) ( 86 )   Save

    The Cretaceous Bashijiqike formation in the Kelasu structural belt in the Kuqa depression of Tarim basin hosts a number of high- and steady-yield subsalt gas reservoirs in ultra-deep,high-temperature,and overpressure environment. For these subsalt tight sandstone reservoirs,the higher the porosity,the higher the salt content and the lower the apparent resistivity. The distribution of salt in the reservoirs not only significantly affects fluid identification but also has a noticeable impact on the reservoir physical properties. The distribution of salt in the subsalt reservoirs in the Bashijiqike formation were systematically analyzed based on the data of cores,cast thin sections,scanning electron microscopy,salt content,and conventional logs. According to the differences in salt content,resistivity,and salt source,three distribution patterns of salt in subsalt reservoirs were proposed: top source,lateral source and local sealing. For the top and lateral source patterns,the reservoir resistivity is only affected by salt content. In the reservoirs with the top source pattern,the salt content shows a vertical zonality,and the reservoir resistivity increases as the salt content decreases. In the reservoirs with the lateral source pattern,the salt content shows a lateral zonation,and the reservoir resistivity shows a trend of high to low and then to high value from the edge of structural belt towards its center. In the reservoirs with the local sealing pattern,the resistivity is influenced jointly by stress and salt content,and changes greatly because the distribution of salt content is sporadic. According to well logging responses,the reservoir is divided into intervals for each pattern. In an ideal top source pattern,the reservoir comprises a salt interval,a mudstone barrier,an interval strongly affected by saturated salt,an interval strongly affected by unsaturated salt,a transition interval affected by unsaturated salt,and a salt-unaffected interval from top to bottom. In an ideal lateral source pattern,there are several intervals affected by oversaturated salt. In an ideal local sealing pattern,the reservoir includes a salt interval,a mudstone barrier,a salt-unaffected interval with strongly compressed stress,a salt-stress hybrid affected interval,and a salt-stress unaffected interval.

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    A Method for Predicting Hydrocarbon Accumulation Period Under Source-Fault-Caprock Configuration and Its Application
    CONG Yan
    2024, 45 (1):  13-18.  doi: 10.7657/XJPG20240102
    Abstract ( 89 )   HTML ( 7 )   PDF (1547KB) ( 58 )   Save

    To determine hydrocarbon enrichment degree around the faults connecting oil and source rocks in petroliferous basins,based on the study of source rock-fault-caprock configuration,and the hydrocarbon accumulation mechanism,a method for predicting hydrocarbon accumulation period under source-fault-caprock configuration was established,which considers the activity period of the fault connecting oil and source rocks,the hydrocarbon expulsion period of source rock,and the formation period of mudstone caprock. The method was applied to predict the hydrocarbon accumulation period in the lower Sha 1 member within the Qikou sag of the Bohai Bay basin. The results show that during the deposition period of the Guantao formation-Minghuazhen formation,the source rock in Sha 3 member expelled hydrocarbons,the Nandagang fault was opened,and the regional mudstone caprock in the middle Sha 1 member was formed. The source rock,fault and caprock were configured well for a long period,which allowed the hydrocarbons expelled from the source rock in Sha 3 member to effectively accumulate in the lower Sha 1 member. The prediction results are consistent with the exploration results.

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    Shale Gas Accumulation Characteristics of Wufeng Formation-Longmaxi Formation in Luzhou Area
    LIU Honglin, WANG Huaichang, LI Xiaobo
    2024, 45 (1):  19-26.  doi: 10.7657/XJPG20240103
    Abstract ( 104 )   HTML ( 3 )   PDF (3755KB) ( 55 )   Save

    To find favorable areas for shale gas accumulation in the Wufeng formation-Longmaxi formation in the Luzhou area of the Sichuan basin,fluid inclusion detection,shale micropore observation,and gas bubble-pore evolution simulation were performed. On this basis,the tectonic burial process and the hydrocarbon generation and thermal evolution process in the Luzhou area were investigated,and the characteristics and patterns of shale gas accumulation in the Luzhou area were summarized. The results show that the Wufeng formation-Longmaxi formation in the Luzhou area has a set of thick organic-rich shales. During the Permian to Early Triassic,oil was generated from the shale which then experienced two tectonic uplift events during the Middle Triassic and the Yanshanian-Himalayan movement. The gentle uplifting of the formation in the Middle Triassic did not induce extensive hydrocarbon loss,while the uplifting during the Yanshanian-Himalayan movement was later than that of the structure in the southeastern part of Sichuan basin,with a small magnitude,which was favorable for shale gas preservation. The organic pores in the shales were developed as a result of the fact that the uplifting with short duration and low intensity in the Middle Triassic did not cause massive hydrocarbon expulsion,leaving a large quantity of liquid hydrocarbons in the reservoirs and allowing well preservation of organic pores during the Late Triassic to Middle Cretaceous,when liquid hydrocarbons were cracked to gas along with deep burial,and the strata were universally under overpressure. Although the Triassic uplifting in the Luzhou area was short-lived and of low intensity,the simulation results suggest that it led to crude oil thickening and gas pore formation,which was beneficial for shale gas accumulation. The uplifting in the Indosinian period resulted in crude oil thickening,facilitating shale gas accumulation. The late strata uplifting together with a short period of shale gas loss,developed low-angle bedding fractures,and fewer vertical fractures all contribute to the formation of overpressured shale gas accumulation zones in the Luzhou area. The proposed patterns of shale gas accumulation in the Wufeng formation-Longmaxi formation in the Luzhou area are of great reference significance in guiding oil and gas exploration for similar reservoirs.

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    Main Controlling Factors of Shale Oil and Gas Enrichment in Chang 7 Member, Southeastern Ordos Basin
    SONG Haiqiang, LIU Huiqing, WANG Jing, SI Shanghua, YANG Xiao
    2024, 45 (1):  27-34.  doi: 10.7657/XJPG20240104
    Abstract ( 97 )   HTML ( 5 )   PDF (728KB) ( 58 )   Save

    In order to clarify the main controlling factors of shale oil and gas enrichment,the degree and mechanisms of shale oil and gas enrichment in the Chang 7 member in southeastern Ordos basin were analyzed using the data of drilling,logging,and core. Desorbed shale gas content is positively correlated with the total organic carbon content (TOC) of source rocks,the organic matter content controls the total content of shale oil and gas,and abundant pores are developed in organic matter,and shale oil and gas exist in both adsorbed and free states in these organic pores. The pore structure and porosity of the reservoir affect the content and occurrence state of shale oil and gas. Adsorbed oil and gas mainly exist in micropores,while free oil and gas in mesopores and macropores. The content of free gas in mesopores is higher than that in macropores,and the larger the porosity,the higher the absolute content of oil and gas in shale. The configuration between sandstone interlayers and organic-rich shale controls the enrichment positions of shale oil and gas. Based on the distribution of siltstone,fine sandstone and shale in the reservoir,the shale oil and gas in Chang 7 member can be classified into two types:near-source and in-source. The in-source shale oil and gas can be further divided into hydrocarbons from sandstone interbedded with shale,shale intercalated with sandstone,and pure shale. Sand bodies underlying the organic-rich shale and lenticular sand bodies exhibit the best potential of oil and gas,followed by sand bodies overlying the organic-rich shale or those tongue-shaped or finger-shaped ones in contact with shale.

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    Origin of Crude Oil From Coal Mine of Yan’an Formation in Huangling-Tongchuan Area,Ordos Basin
    KONG Lingyin, LI Jianfeng, WU Kai, MA Jun
    2024, 45 (1):  35-46.  doi: 10.7657/XJPG20240105
    Abstract ( 78 )   HTML ( 5 )   PDF (1020KB) ( 64 )   Save

    To clarify the geochemical characteristics and origin of the crude oil from the coal mine in Yan’an formation in Huangling-Tongchuan area,southeastern Ordos basin,a comparative study was conducted on the biomarker compositions and carbon isotope distribution of n-alkane monomers in extracts from crude oil,coal,and mudstone in the study area using gas chromatography,chromatography-mass spectrometry,and isotope mass spectrometry techniques. The oil from coal mine is characterized by equilibration of pristane and phytane,high sesquiterpene content,relatively high Ts/Tm and C29Ts/C29 norhopane ratios,relatively low ratios of C30 moretane/C30 hopance,C30 norhopane/C30 hopance,and 22S/(22S+22R) for C31 homohopane and C32 homohopane,“V”-shaped distribution of ααα-20R regular sterane,and relatively light carbon isotopic values of crude oil and n-alkane monomers. The extracts from the Jurassic coal-bearing source rocks exhibit high Pr/Ph ratio,low sesquiterpene content,low Ts/Tm and C29Ts/C29 norhopane ratios,relatively high ratios of C30 moretane/C30 hopance,C30 norhopane/C30 hopance,and high 22S/(22S+22R) values for C31 homohopane and C32 homohopane,inverted “L”-shaped distribution of ααα-20R regular sterane,and relatively heavy carbon isotopic values of crude oil and n-alkane monomers. The characteristics of crude oil significantly differ from those of the potential coal-bearing source rocks,which is consistent with the deep lacustrine source rocks and the generated hydrocarbons of Chang 7 member in the basin. The coal of the Jurassic Yan’an formation is at a low maturity stage,and it is incapable of expelling liquid hydrocarbons,since the generated liquid hydrocarbons cannot even fully meet its adsorption needs. The crude oils in the Cuijiagou Coal Mine in Tongchuan and the Diantou Coal Mine in Huangling are both originated from the source rocks of the underlying Chang 7 member.

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    RESERVOIR ENGINEERING
    Establishment and Application of Type Ⅱ Generalized Gas-Water Miscible Flooding Characteristic Curve
    CHU Fujian, GOU Tuobin, HAN Yuetao, GAO Wenjun
    2024, 45 (1):  47-52.  doi: 10.7657/XJPG20240106
    Abstract ( 62 )   HTML ( 2 )   PDF (594KB) ( 31 )   Save

    Based on the Type Ⅱ generalized water drive characteristic curve,the concept of underground gas-water cut was introduced,and the Type Ⅱ generalized gas-water miscible flooding characteristic curve was established on the basis of analogy. The mathematical model of gas-water cut corresponding to the Type Ⅱ generalized gas-water miscible flooding characteristic curve can be transformed to describe the S-shaped gas-water cut variation and also the convex,S-convex,S-concave,concave,and other shapes of gas-water cut variations,when the characteristic values n and m take different values. This provides additional methods for evaluating development effects of gas-water miscible flooding. The paper put forward a general formula for the Type Ⅱ gas-water miscible flooding characteristic curve and corresponding methods for solving the mathematical model of gas-water cut,and evaluated the development effects of the water-alternating-gas miscible flooding in the reservoir of Sanjianfang formation in Pubei oilfield and the gas cap + edge water miscible flooding in S31 reservoir in Jinzhou oilfield,respectively,showing a high fitting accuracy. This work provides a valuable reference for developing other oil reservoirs.

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    Characteristics of Dominant Flowing Channels and Throat Volume of Multi-Layer Sandstone Reservoirs in Liuzan Oilfield
    CAO Tongfeng, GAO Donghua, LI Zhandong, WANG Tianyang, JIANG Feng
    2024, 45 (1):  53-57.  doi: 10.7657/XJPG20240107
    Abstract ( 69 )   HTML ( 2 )   PDF (1018KB) ( 49 )   Save

    For continental reservoirs with strong heterogeneity,long-term water injection may create dominant flowing channels,which will cause rapid water breakthrough in oil wells,thereby reducing the displacement efficiency and resulting in poor development results. Taking the Paleogene Oligocene Shahejie formation of Liuzan oilfield as an example,the litho-electric logging responses,reservoir heterogeneity,injection-production performance,and reservoir pore characteristics were analyzed,the characteristics of dominant flowing channels in the multi-layer sandstone reservoirs of the oilfield were described,and the conditions for the formation of dominant flowing channels in this area were determined. A calculation method for the throat volume of dominant flowing channels was established. With this method,the amount of profile control agent used in the subsequent operations was clarified to effectively plug the channels. The research results provide a technical support for subsequent oil production stabilization and water control in oilfields.

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    Numerical Simulation of Grid-Like Fragmented Structure of Fault-Karst Reservoirs in Southern Tuoputai Block
    ZHANG Rujie, YUE Ping, ZHANG Ying, LI Xiaobo, HUANG Nan, ZHAO Liming, FAN Qingzhen
    2024, 45 (1):  58-64.  doi: 10.7657/XJPG20240108
    Abstract ( 66 )   HTML ( 0 )   PDF (3074KB) ( 51 )   Save

    The fault-karst reservoirs in the southern Tuoputai block of the Tahe oilfield exhibit a high initial production capacity,but a sharply declining production in the late development stage due to serious water flood and rapid water breakthrough occurred in many wells. There is no efficient simulation method for this phenomenon. Based on the karst features,seismic characteristics,actual well-reservoir configuration,and three-zone structure of fault-karst reservoirs,a grid-like fragmented structure of the fault-karst reservoirs was proposed. Accordingly,by combining the automatic fault extraction (AFE) technology with the ant body attributes,the fracture indicator was derived for characterizing the grid-like fragmented reservoir. Tensor attributes were used for characterizing the karst-vug reservoir,and a dual-porosity compositional model was established for numerical simulation. The results indicate that the grid-like fragmented structure serves as the primary flow channel in fault-karst reservoirs. The fracture indicator is better applicable to characterize the grid-like fragmented structure than AFE and maximum likelihood,and it is highly compatible with tensor attributes in water source zone but poorly compatible in other areas. Compared to single-porosity model,the dual-porosity model based on the grid-like fragmented structure can offer higher matching accuracy and better reflect the production performance of the fault-karst reservoirs.

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    Thermally Recovered Reservoir Management and EOR for a Multi-Layered Sandstone Oilfield
    LYU Xiaoguang, LI Wei
    2024, 45 (1):  65-71.  doi: 10.7657/XJPG20240109
    Abstract ( 80 )   HTML ( 5 )   PDF (674KB) ( 49 )   Save

    This paper presents the characteristics and development history of the multi-layered sandstone heavy oil reservoirs in the Kern River field,USA,and specifically discusses the practices of thermally recovered reservoir management and enhanced oil recovery (EOR). The Kern River field is a monocline reservoir of hydrodynamic trap. In the late stage of steam flooding,the practices such as C/O spectral logging,4D time-lapse dynamic surveillance during thermal recovery,injector-producer performance monitoring,isolated single-channel sandbody identification and tracking,and full-field 3D geological modeling and numerical simulation lay a basis for identifying remaining oil and enhancing oil recovery. Artificial intelligence,steam-foam flooding,and layered steam injection through dual-tubing completion are proved technologies for expanding the swept volume of steam flooding. Infill drilling,horizontal well drilling,and horizontal sidetracking in shallow oil reservoirs provide additional opportunities for significantly increasing the recoverable reserves. These technologies enable the production of horizontal well to be more than three times that of adjacent vertical wells. To exploit “cold reservoirs” near the oil-water contact in the downdip zone of the reservoir,water producers are drilled in the downdip aquifer zone to release reservoir pressure,allowing the remaining oil in this zone to be effectively swept by steam.

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    Geometry of Hydraulic Fractures in Fractured Horizontal Wells in Shale Reservoirs of Jimsar Sag,Junggar Basin
    FANG Zheng, CHEN Mian, WANG Su, LI Jiacheng, LYU Jiaxin, YU Yanbo, JIAO Jibo
    2024, 45 (1):  72-80.  doi: 10.7657/XJPG20240110
    Abstract ( 90 )   HTML ( 3 )   PDF (4519KB) ( 60 )   Save

    The side-view images of microseismic monitoring in horizontal wells in the shale reservoirs in the Jimsar sag of Junggar basin and in the southern Sichuan basin exhibit a phenomenon that the density and extent of the data points parallel to bedding direction are much greater than those perpendicular to the bedding direction. This phenomenon contradicts the hydraulic fracture interpretation results from conventional processing. However,there is no clear explanation for this phenomenon in terms of 3D geometry of hydraulic fractures. A method of microseismic inversion was established,and the inversion results were reconstructed to obtain 3D geometry of the fractures induced by horizontal well hydraulic fracturing in shale reservoirs. Finally,the fracture geometry and the microseismic inversion method were verified through physical simulation experiments on fracturing under true triaxial stress. The results show that the fractures from inversion primarily exhibit a geometrical pattern of one main fracture intersecting with multiple secondary fractures in three dimensional space. Combining with the results of fracturing physical simulation experiments under true triaxial stress,it is found that the hydraulic fractures are horizontally and vertically intersected. The results of acoustic emission experiments and the fracture geometry presented after true-triaxial fracturing physical simulation of outcrop samples from the Jimsar sag validate that the microseismic inversion method is reliable and the fractures induced by horizontal well hydraulic fracturing in shale reservoirs are complex.

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    Water Production Mechanism in Tight Sandstone Gas Reservoirs After Fracturing in Linxing Gas Field
    SHI Xuefeng, YOU Lijun, GE Yan, HU Yunting, MA Litao, WANG Yijun, GUO Sasa
    2024, 45 (1):  81-87.  doi: 10.7657/XJPG20240111
    Abstract ( 68 )   HTML ( 4 )   PDF (678KB) ( 62 )   Save

    The tight sandstone gas reservoirs in the Linxing gas field,Ordos basin,are key targets for onshore gas development. Due to the structural complexity,reservoir physical properties,and complicated gas-water relationship,most gas wells produce water continuously after fracturing,and their water production rates are very different. Understanding the reasons for irreducible water saturation variation after fracturing is of great significance for formulating effective water control and gas recovery measures to increase well productivity. In this study,representative tight sandstone samples from the Linxing gas field were tested by using the gas displacement method to clarify how reservoir properties,production pressure difference,and fracturing fluid affect irreducible water saturation. The results show that the difference in the irreducible water saturation between matrix and fractures is 13.32%~18.36% for Class Ⅰ reservoirs,28.28%~34.19% for Class Ⅱ reservoirs,and 39.10%~48.15% for Class Ⅲ reservoirs. Hydraulic fractures can significantly improve the water flow capacity of reservoirs,and provide additional water flow pathways. The increased production pressure difference,reduced flow pressure loss and weakened hydrophilic degree are the main mechanisms leading to the weakening capacity of the reservoir in bounding water and water production of gas wells after fracturing. To control water and produce gas efficiently in tight sandstone gas reservoirs with high water cut after fracturing,measures such as controlling fracturing scale,optimizing production systems,and adjusting fracturing additive amount can be implemented,which will help delay the onset of water breakthrough in gas wells and reduce the overall water production.

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    Well Location Optimization and Potential Tapping Strategy for Reservoirs With Narrow Oil Ring and Gas Cap in JZ-X Oilfield, Bohai Bay Basin
    YUE Baolin, MENG Zhiqiang, FANG Na, ZHENG Yang, QU Zhaozhao, WANG Shuanglong
    2024, 45 (1):  88-93.  doi: 10.7657/XJPG20240112
    Abstract ( 78 )   HTML ( 4 )   PDF (2148KB) ( 35 )   Save

    The development of the reservoirs with narrow oil ring, gas cap, and bottom water is often challenged by water coning, gas channeling, and complex remaining oil distribution. This paper discusses the well location optimization and potential tapping strategy for horizontal well development in the Bohai Bay basin. In the basic well pattern arrangement stage, in plane, horizontal wells are arranged perpendicular to the structural lines and penetrating multiple layers for enhancing the recovery of reserves, and the separated-layer production string with intelligent sliding sleeve is equipped to alleviate inter-layer contradiction; vertically, horizontal wells are arranged parallel to the fluid interface and at 1/3 of the oil column height from the water-oil contact for gas channeling prevention and water control. In the comprehensive adjustment stage, according to the numerical reservoir simulation, the remaining oil is enriched in inter-well retention zone in plane in the middle-late development stage, and is vertically enriched in the upper part of the reservoir due to the subsequent dominance of water drive in the late stage. Comparing the oil increment indexes under the schemes of inter-well sidetracking, gas reinjection into the gas cap, and barrier water injection, the former two schemes are preferred for tapping the potential remaining oil. Ineffective and inefficient wells are sidetracked to the zones at high positions between wells, with the expected net oil increment of 3.4×104-4.2×104 m3 per well. For gas reinjection into the gas cap, existing gas production wells are converted for gas reinjection to replenish the energy of the gas cap, so as to displace the remaining oil in the upper part of horizontal wells and enhancing the oil recovery, with the expected net oil increment of 5.2×104 m3 per well.

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    Genesis of Barriers/Interlayers in Braided-River Reservoirs and Its Controls on Remaining Oil Distribution:A Case of N1g3 in Liuguanzhuang Area of Dagang Oilfield
    LI Hang, LI Shengli, ZHOU Lianwu, MA Shuiping, HUANG Xiaodi, HAN Bo, LI Ning
    2024, 45 (1):  94-101.  doi: 10.7657/XJPG20240113
    Abstract ( 91 )   HTML ( 4 )   PDF (2302KB) ( 37 )   Save

    In order to clarify the controls of barriers/interlayers on the distribution of remaining oil in the braided-river reservoirs,taking the sand set Ⅱ in the third member of the Guantao formation (N1g3) in the Liuguanzhuang area of Dagang oilfield as an example,and using the data of core,testing,logging,and production performance,the criteria for quantitative identification of barriers/interlayers were established for the target interval in the study area,and the hierarchy,genesis of barriers/interlayers and their controls on remaining oil distribution were determined. In the study area,the barriers/interlayers in the target interval can be divided into 3 categories such as barriers between sand sets,interlayers between sand bodies,and interlayers within a sand body,which are developed near the architecture boundaries of the 7th-,8th-,and 9th-order sand bodies,respectively. The barriers between sand sets are dominated by floodplain mudstones and silty mudstone,with the thickness ranging from tens of centimeters to several meters. They can efficiently seal oil and gas vertically and allow the edge water to advance preferentially along the formation during development,leading to severe water flooding,and thus the remaining oil is mostly distributed in the upper parts of the complex mid-channel bars and braided channels far from water injection wells. The interlayers between sand bodies are mainly composed of fine-grained sediments in abandoned channels and gullies,with the thickness typically ranging from 0 to 2 meters. They locally hinder vertical fluid migration and laterally control the distribution of remaining oil in different sand bodies,leading to two remaining oil distribution patterns:one is controlled by abandoned channel and the other by gully. The interlayers within a sand body are primarily associated with lateral accreted and interchannel mud deposits,and fall-silt seam,with the thickness reaching tens of centimeters,leading to three remaining oil distribution patterns,which are controlled by laterally-accreted mudstone,fall-silt seam,and interchannel mudstone,respectively.

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    APPLICATION OF TECHNOLOGY
    Seismic Frequency Enhancement Processing Based on Multi-Layer Residual Network and Its Application to Identification of Thin Reservoirs
    ZHANG Wenqi, LI Chunlei
    2024, 45 (1):  102-108.  doi: 10.7657/XJPG20240114
    Abstract ( 77 )   HTML ( 5 )   PDF (4839KB) ( 49 )   Save

    The seismic frequency enhancement processing method based on multi-layer residual network combines high-frequency well logging information with seismic data through an intelligent network. This method effectively improves vertical resolution while maintaining lateral continuity,facilitating the identification of thin reservoir beds. In the AMH area,the seismic data processed by conventional techniques enable only the identification of carbonates thicker than 30 m,but not of thinner beds. The seismic frequency enhancement processing method based on multi-layer residual network was proposed for application in this area. First,a training was performed using the multi-layer residual network,a deep learning network,with the near-wellbore seismic amplitudes as training data and the relative wave impedance data from well logging as training labels. Thus,a predictive model for relative wave impedance curve was obtained. By using seismic data as input,the deep network training model was solved to obtain a relative wave impedance data cube,and then a data cube of reflection coefficient corresponding to the frequency-enhanced seismic data cube was obtained. After analyzing the geological conditions of the target area,appropriate wide-frequency wavelet was extracted after calibration,and then convolved with the reflection coefficient cube,so that a frequency-enhanced seismic data cube was obtained. Reservoir inversion was performed using the frequency-enhanced seismic data cube. The inversion results are of high resolution vertically,well matching the main target beds,and can be identifiable and traceable laterally. Ultimately,the identification of thin beds in the AMH area was realized through the application of high-resolution seismic inversion results. The seismic frequency enhancement processing based on multi-layer residual network together with the corresponding high-resolution model inversion can identify beds thicker than 10 m in the AMH area. This method effectively addresses the problem of infeasible thin bed identification using low-resolution seismic data,and improves the accuracy in predicting thin beds. It is referential for identifying similar thin beds.

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    Application of Scattered Wave Field in Identifying Fractured Reservoirs
    CHEN Keyang, ZHOU Hui, YANG Wei, WANG Cheng
    2024, 45 (1):  109-117.  doi: 10.7657/XJPG20240115
    Abstract ( 67 )   HTML ( 1 )   PDF (9429KB) ( 42 )   Save

    Fractured reservoirs are important exploration and development targets for increasing oil and gas reserves and production. The conventional post-stack seismic data can not meet the needs of fractured reservoir identification. This paper presents a method for the relative separation of reflected and scattered seismic wave fields based on diffusion filtering. This method predicts fractured reservoirs by adjusting diffusion coefficient and the number of iterations to separate the post-stack seismic data cube into 2 data cubes of reflection wave field and scattered wave field,and then extracting seismic attributes such as coherence,curvature,and ant tracking from the scattered wave field data cube. The method was applied to predict fractures in the weathered crust fractured bedrock reservoirs in the Songliao basin and the fractured reservoirs in the Maokou formation in the Sichuan basin. The results show that the method has higher resolution in predicting fractured reservoirs. The method was verified by the actual drilling data of two wells in the weathered-crust fractured reservoirs in the Daqing exploration area,showing a coincidence rate of 67%. This method can provide references for exploration,development,and well deployment in similar reservoirs.

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    Layered Modeling Algorithms and Cases for Different Reservoir Development Stages
    ZUO Yi, SONG Jing, SHI Zhuoli, QIAO Jingxuan, ZU Xiuran, ZHENG Jie
    2024, 45 (1):  118-125.  doi: 10.7657/XJPG20240116
    Abstract ( 72 )   HTML ( 3 )   PDF (1695KB) ( 38 )   Save

    The simulation methods and model precision adopted for layered modeling in 3D geological modeling vary with reservoir characteristics and research purposes at different development stages. From the perspective of 3D geological modeling,the reservoir development can be divided into three stages: reservoir evaluation,new block development,and existing block adjustment. The layered modeling algorithms were analyzed and selected for the 5th fault block in Gangdong district 2. It is proposed that the Kriging algorithm should be used for modeling at the reservoir evaluation stage,with a grid resolution of 100 m × 100 m × 5.0 m;the Kriging or Global B-spline algorithm should be used for modeling at the new block development stage,with a grid resolution of 50 m × 50 m × 1.5 m;and the Local B-spline or Converging average algorithm should be used for modeling at the existing block adjustment stage,with a grid resolution of 10 m × 10 m × 0.5 m. This modeling approach can provide results in more coincidence with actual geological conditions and can meet requirements for reservoir research at each stage.

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