Lithologic Reservoirs

Helium resource in Weihe Basin is abundant and holds great potential for exploration and development. Based on the research process related to helium resource in Weihe Basin，the exploration history，helium source rock，helium carrier and groundwater system，theoretical models of helium accumulation，resource quantity forecast，and prospect priority were summarized，and the existing issues and countermeasures for key techniques in helium exploration and development were discussed. Research findings show that：（1）Helium resource in Weihe Basin was discovered in 1970s，including methods of gravity，magnetics，geochemistry，seismics，and drilling，as well as the latest deployed five helium exclusive exploration wells. However，the exploration level remains low.（2）Helium source rocks widely distributed in the basement and south margin of Weihe Basin show significant potential for helium generation. The effectiveness is closely related to key factors，such as the content of radioactive elements of Th and U，formation age and characteristics of geological structure. The Late Paleozoic coal-bearing strata may remain in the deep basin，providing a carrier gas source for the upward migration of deep helium. Helium-rich natural gas is closely associated with groundwater，and the carrier gas and formation pore-pore water are important carriers for helium migration and enrichment. Based on the genetic method，the effective helium resources in Weihe Basin are estimated to be 33.8×108 m3. Considering the overlapping characteristics of geothermal energy，biogenic gas and helium resource in Weihe Basin，Huazhou-Tongguan area is identified as an important target area for comprehensive exploration and development of multiple resources.（3）The helium exploration well drilled into Archean metamorphic rock basement and IndosinianYanshannian granite. Formation conditions of helium-rich natural gas in Huazhou exploration area are controlled by various factors，such as helium source rock，deep faults，and effective sealing conditions.（4）The exploration and development of helium resource in Weihe Basin still faces several problems and challenges，such as inability to accurately assess helium reserve，significant difficulties in exploration，need for improvement in key engineering technologies，and the requirement for further study of economic sustainability. In response，the related countermeasures have been proposed，including strengthening seismic data processing and technology research of helium downhole engineering，optimizing the matching technique of safe drilling，and trying to carry out the related work about extraction and concentration of helium at wellhead.

Thermal-hydraulic-mechanical coupling model for development of CO₂-EGS hot dry rock horizontal wells under multi-cluster fracturing condition

YANG Yonghong, ZHANG Shiming, CUI Yingbin, YANG Wanqin, YI Hongxia, LIU Wei, ZHANG Lisong

2025, Vol.37(5): 12–21 Abstract ( 10 ) PDF (1237 KB) ( 12 )

doi: https://doi.org/10.12108/yxyqc.20250502

Through the incorporation of bedrock governing equations，fracture governing equations，and thermal-hydraulic-mechanical（THM）coupling relationships，and aidded by COMSOL software，numerical simulation research on the development of CO2-EGS hot dry rock reservoirs via horizontal wells under multicluster fracturing conditions was conducted. The results show that：（1）The established mathematical model reconstructed THM coupling relationships，modified the functional relationships between fracture porosity/permeability and stress，and improved the variations of CO2 density，viscosity，and specific heat capacity with pressure and temperature.（2）Considering the thermal compensation effects of bedrock，cap rock，and surrounding rock，a multi-source thermal compensation numerical simulation method was proposed，and a numerical model for CO 2-EGS hot dry rock reservoir development via horizontal wells under multi-cluster fracturing conditions was established.（3）Using the numerical model，the evolutions of the temperature field，seepage field，and stress field of hot dry rock were discussed，revealing that the horizontal well patterns，the configuration of multicluster fracture networks，and the properties of supercritical CO2 directly influence the evolution process of CO2- EGS.（4）The controlling factors for CO2-EGS hot dry rock reservoir development via horizontal wells were identified as the THM coupling mechanism，horizontal well pattern parameters，and multi-cluster fracture network parameters. Compared with TH coupling，THM coupling increases the produced fluid mass flow rate by 5.76%， shortens the heat extraction period by 3.3 years. The reasonable horizontal well pattern parameters are one injection well and two production wells，with a horizontal well length of 1 250 m，and a well spacing of 300 m. While the optimal fracture network parameters are a fracture spacing of 75 m，fracture width of 3 mm，and fracture height of 40 m.

PETROLEUM EXPLORATION

Oil and gas exploration history and drilling enlightenment of Yin’e Basin

CUI Haifeng, HAN Xiaofeng, HUANG Yuanyi, ZHANG Huiyuan

2025, Vol.37(5): 22–33 Abstract ( 10 ) PDF (1565 KB) ( 13 )

doi: https://doi.org/10.12108/yxyqc.20250503

Yin’e Basin exhibits relative low degree of hydrocarbon exploration，and the distribution law and exploration direction of oil and gas require further clarification. By analyzing the oil and gas exploration history of Yin’e Basin，the exploration progress and existing problems in different stages were sorted out，the drilling understanding was summarized，and the reservoir types and exploration direction were clarified. The results show that：（1）Yin’e Basin has experienced four exploration stages：reconnaissance，comprehensive evaluation，key depression exploration and overall understanding. Taking Cretaceous-Jurassic and Carboniferous-Permian as the target layers，as the research of oil and gas accumulation conditions in the basin gradually deepen，and great progress has been made.（2）During the stage of reconnaissance，gravity-magnetic，electrical，and seismic were applied to delineate the distribution range of key sags and deployed two-dimensional seismic. In the stage of comprehensive evaluation，taking Mesozoic as the target layer，the tectonic units of the basin were divided，and the low-yield oil flow was discovered in Chagan and Lujing sags according to the high-point hydrocarbon-controlling model of fault structure. In the stage of key depression exploration，taking Mesozoic and Upper Paleozoic as the target layers，and the industrial oil and gas flows were achieved in Hari Sag，Guaizihu Sag and Tiancao Sag. However，debates persist on whether oil-producing series belong to Mesozoic or Late Paleozoic. In the stage of overall understanding the basin and the re-division of tectonic units，the current structure of the basin were clarified. It was pointed out that Carboniferous-Permian was the fold basement of the Mesozoic faulted basin，and hydrocarbon accumulation models of Mesozoic lithologic reservoir and pre-Mesozoic buried hill were established. The oil and gas are mainly distributed in small-scale area of the lower part of each Mesozoic dustpan-shaped faulted gentle slope，and the resources are relatively scattered.（3）Yin’e Basin is a Mesozoic faulted basin developed on the folded basement of the Hercynian orogenic belt. The main oil and gas producing strata and oil and gas sources are Mesozoic，and Upper Paleozoic has experienced different degree of deformation and metamorphism，with limited hydrocarbon potential. The unconventional oil and gas reservoirs，such as thick lacustrine mudstone and argillaceous shale in Mesozoic Cretaceous and Jurassic are the key targets for next-phase exploration of the basin.

Exploration potential of shale gas in Ordovician Wulalike Formation in the western margin of Ordos Basin

LU Jiang, WANG Jian, WU Nan, LI Chengshan, FENG Zifei

2025, Vol.37(5): 34–48 Abstract ( 9 ) PDF (1562 KB) ( 12 )

doi: https://doi.org/10.12108/yxyqc.20250504

Combined with well logging data analysis，mineral composition testing，scanning electron microscopy analysis，thin section observation，pore permeability analysis，nitrogen adsorption testing，and methane adsorption testing，the research of petrological characteristics，physical properties，pore structure characteristics，gas potential，and gas-bearing properties of Ordovician Wulalike Formation shale reservoir in the western margin of Ordos Basin were conducted. The results show that：（1）Ordovician Wulalike Formation in the western margin of Ordos Basin is dominated by dark gray to gray black mud shale，these mud shales exhibit stable distribution and have a thickness of about 78.9 m. The mineral composition is mainly quartz，with a brittle mineral mass fraction of 70.98%-90.32% and a brittleness index of 50.03%-71.16%.（2）The porosity of shale reservoirs in the research area is generally less than 0.1%，and the permeability is generally less than 0.01 mD. The pore types are mainly fractures，nano-micron micropores，and intergranular dissolved pores. The microscopic pore volume is 0.016 27-0.033 73 cm3/g，mainly micropores and mesopores. （3）In the research area，main types of organic matter of Wulalike Formation shale are Type Ⅰ and Type Ⅱ1，and TOC can reach to 1.54%，the organic matter is in high maturity to over maturity stage，with a maximum methane adsorption mass volume of 0.99 m3/t under experimental conditions of 30 ℃. The highest shale gas mass volume in logging interpretation is 3.4 m3/t. Compared with typical high-quality shale reservoirs at home and abroad，its organic matter abundance is relatively low，the content of brittle minerals is relatively high，and the gas content is at a moderate level，indicating great potential for shale gas exploration.

Reservoir characteristics and main controlling factors for hydrocarbon accumulation of the fourth member of Sinian Dengying Formation in the west side of Deyang-Anyue Rift，Sichuan Basin

LUO Bing, ZHOU Gang, MA Kui, WANG Wenzhi, XU Shaoli, WU Luya, WANG Yueyun, ZHANG Xin

2025, Vol.37(5): 49–58 Abstract ( 10 ) PDF (1538 KB) ( 17 )

doi: https://doi.org/10.12108/yxyqc.20250505

Based on core observations of hand specimens，rock thin section identification，well logging data analysis，and seismic profile interpretation，the petrological characteristics，sedimentary facies distribution，reservoir characteristics，and source-reservoir configuration relationship of the fourth member of Sinian Dengying Formation in the west part of Deyang-Anyue Rift of Sichuan Basin were characterized，and the main controlling factors for reservoir formation and hydrocarbon accumulation were clarified. The results show that：（1）The fourth member of Dengying Formation in the west part of Deyang-Anyue Rift develop two subfacies：restricted platform and platform margin. The restricted platform subfacies can be further divided into three microfacies： mound-shoal，platform flat，and platform depression. The platform margin subfacies can be divided into two microfacies：mound-shoal and inter-shoal sea.（2）High-quality reservoirs of the fourth member of Dengying Formation are mainly composed of the algal grainstone，algal-clotted dolomite，and algal-laminated dolomite in the mound-shoal microfacies. The types of reservoir spaces are diverse，such as pore type，karst cave-pore type，and fracture type，mainly consisting of framework pores，intergranular dissolution pores，intercrystalline pores，intercrystalline dissolution pores，and karst cave. The reservoirs of the fourth member have undergone multistage diagenetic modification，the main destructive diagenetic processes include compaction，cementation，and filling， while the constructive diagenetic process is multiphase dissolution.（3）The main controlling factors for hydrocarbon accumulation in the fourth member of Dengying Formation in the west side of the rift mainly are paleo-rift control on source rocks，lithofacies and karst control on reservoir quality，paleo-uplift control on hydrocarbon accumulation，and late-stage structural control on traps.

Characteristics and reservoir control of Cenozoic tectonic evolution of Nanpu Sag，Bohai Bay Basin

ZHAO Baoyin, YANG Xiaoli, XU Yingxin, MENG Lingjian, CUI Zixuan, WANG Fanglu, LIU Jianlun, YU Fusheng

2025, Vol.37(5): 59–69 Abstract ( 11 ) PDF (1544 KB) ( 17 )

doi: https://doi.org/10.12108/yxyqc.20250506

Based on the analysis of the latest 3D seismic data，combined with the evidence of regional geological background，unconformity surface and paleontological fossils，sedimentary period（fault depression stage）tectonic episodes of Paleogene Shahejie Formation in Nanpu Sag were redivided from two aspects：the development characteristics of synsedimentary faults and migration rule of sedimentary centers，and its control effects on reservoir was studied. The results show that：（1）The fourth member of Paleogene Shahejie Formation（Es4）in Nanpu Sag mainly distribute in the eastern part of the sag. Es3 is angular unconformity contact with underlying Es4 and overlying Es2，and Es1 is integrated contact with Es2.（2）In the study area，Cenozoic experienced six stages of tectonic evolution，such as three episodes of fault depression（Paleogene Es4，Es3，Es1-Es2），faultdepression conversion（Paleogene Ed），thermal depression（Neogene Ng），and depression fault（Neogene Nm）. The tectonic stress field rotated clockwise from NW-SE to near SN，and the superimposion of extension and strike-slip structures formed a tensional-torsional deformation zone. The sedimentary center controlled by the synsedimentary fault exhibits the migration law of SE-NW-SEE.（3）Cenozoic tectonic evolution of the study area controls the development of source rocks，reservoirs and traps. Four sets of main source rocks，such as Es4， Es3，Es1 and Ed3 are developed，and development models of sand body can clasified as three types：“conversion slope”“conversion nose-bulge”and“fault trough-slope break”. Faults and traps are across developed，and three sets of accumulation combinations are developed vertically，which constitute a multi-layer superimposed composite oil and gas accumulation zone dominated by layered oil and gas reservoirs. Laoyemiao fan body，Gaoliu fault downthrown wall and Nanpu No. 1 fault，Nanpu No. 2 fault and Nanpu No. 4 slope break belt faulted anticline，fault nose structural trap are prioritized as the next-phase exploration targets.

Origin of overpressure and natural gas accumulation characteristics of Miocene Meishan Formation in the deepwater area，Qiongdongnan Basin

LIU Haiyu, HU Lin, LIU Bing, TUO Lei, LI Hu, JIANG Rufeng, WU Shijiu

2025, Vol.37(5): 70–82 Abstract ( 6 ) PDF (1582 KB) ( 13 )

doi: https://doi.org/10.12108/yxyqc.20250507

Comprehensively utilizing overpressure logging response characteristics，basin numerical simulation， fluid inclusion analysis，drilled core observation，and thin section identification，combined with the analysis of geological conditions for natural gas accumulation，the overpressure characteristics and genesis mechanism of Miocene Meishan Formation gas reservoir in Ledong-Lingshui Sag of the deep water area in Qiongdongnan Basin were analyzed. The coupling relationship between reservoir strong overpressure formation and natural gas accumulation process was explored，and the reservoir formation mode was clarified. The results show that：（1）The pressure of Meishan Formation in Ledong-Lingshui Sag ranges from 49.74 to 95.76 MPa，with a pressure coefficient of 1.37-2.09，which is overpressure-strong overpressure. The pressure structure of a single well shows a typical double-layer overpressure structure. In the early stage，overpressure was mainly controlled by un‐dercompaction，while in the late stage，it was jointly controlled by hydrocarbon fluid pressurization and undercompaction.（2）Natural gas in the study area is jointly sourced by Oligocene and Miocene source rocks，with three stages of oil and gas charging. The first stage（6.0 Ma）was liquid hydrocarbon charging，the second stage （2.7 Ma）was hydrocarbon gas charging，and the peak period of reservoir formation was 1.9-1.0 Ma. The third stage（1.8-1.2 Ma）was CO2 charging.（3）The strong overpressure in Meishan Formation reservoir in the study area is closely related to the process of natural gas migration and accumulation. Overpressure provides a key driving force for oil and gas migration，which is conducive to the formation of pressure relief channels，such as fractures and microcracks. The multi-stage injection of hydrocarbon containing acidic fluids leads to organic acid dissolution and transformation，effectively promoting the development of secondary dissolution pores. Late overpressure has a positive impact on the preservation of reservoir pores. Meishan Formation natural gas reservoir has the characteristics of“multi-source hydrocarbon supply-overpressure drive-vertical fracture transport-multistage filling-large sand body aggregation-preferential enrichment of near source overpressure dissolution type reservoirs”

Gas generation potential and reservoir formation condition of Permian Fengcheng Formation source rock in Mazhong structural belt of Mahu Sag

LIU Guanbo, CHEN Shijia, LI Shihong, ZOU Yang, LI Yong

2025, Vol.37(5): 83–96 Abstract ( 8 ) PDF (1814 KB) ( 12 )

doi: https://doi.org/10.12108/yxyqc.20250508

The deep to ultra-deep oil and gas exploration of Mazhong structural belt in Mahu Sag has gradually become a hot field in Junggar Basin. Based on organic geochemical analysis data of rock cores and hightemperature thermal simulation experiments，the organic matter abundance（TOC），hydrocarbon generation potential（S1 + S2），hydrogen index（HI）of Permian Fengcheng Formation source rocks in Mazhong structural belt of Mahu Sag were systematically analyzed，and the hydrocarbon conversion rate and gas generation potential of the source rocks were estimated.The results show that：（1）The average TOC of Permian Fengcheng Formation source rocks in Mazhong structural belt is 1.2%，the average hydrocarbon generation potential（S1 + S2）is 5.6 mg/g， and the average hydrogen index（HI）is 380 mg/g.The hydrocarbon conversion rate of organic matter is high upto 90%，mainly for oil generation，with a cumulative oil production rate of 829 mg/g. The cumulative gas production rate during the high-mature to over-mature stage is 40 mL/g，and the gas production is relatively low，accounting for only 4.3% of the total hydrocarbon generation.（2）The structural formation period of Mahu and Mabei anticlines is earlier than the main hydrocarbon generation and expulsion period of Fengcheng Formation source rocks，and the reservoir properties were poor，with weak intensity of oil and gas charging.（3）The burial depth of source rocks in Mahu anticline is generally greater than 6 000 m（Ro greater than 1.6%），and hydrocarbon generation has basically stagnated. Moreover，a lack of temperature and pressure conditions for crude oil cracking into gas results in insufficient gas supply and a lack of material basis for forming large-scale gas reservoirs. The burial depth of Mabei anticline is relatively shallow，and the surrounding source rocks are in the mature to high mature stage（Ro being 1.0%-1.5%），which has the potential to form tight light oil reservoirs.

Stratigraphy subdivision and exploration implications of Cambrian Qiongzhusi Formation in Deyang-Anyue aulacogen，Sichuan Basin

WANG Zhen, WANG Xingzhi, ZHU Yiqing, YANG Yuran, YANG Yiming, KANG Jiahao, HUANG Baiwen, LYU Hao

2025, Vol.37(5): 97–110 Abstract ( 9 ) PDF (1530 KB) ( 14 )

doi: https://doi.org/10.12108/yxyqc.20250509

Significant breakthroughs of shale gas exploration of Cambrian Qiongzhusi Formation in Deyang-Anyue aulacogen and its periphery of Sichuan Basin have obtained，which exhibit substantial exploration potential. Based on data of drilling core，well logging，and seismic profile，a study was conducted on subdivision and distribution characteristics of Qiongzhusi Formation，and the controlling effects of aulacogen paleogeomorphology on sedimentation was deeply analyzed.The results show that：（1）Cambrian Qiongzhusi Formation in DeyangAnyue Sichuan Basin can be divided into eight sub-layers，sub-layers 1，3，5 and 7 are dominated by mudstones， while sub-layers 2，4，6 and 8 are mainly siltstones. Each sub-layer can be accurately identified through sedimentary cycli-city，logging curve characteristics，lithology（color and composition），and biogenic features.（2）The geomorphic units（intratrough deep-water zone，intratrough slope zone，and uplift zone extratrough）within DeyangAnyue sub-layers exert decisive control on the development of Cambrian Qiongzhusi Formation. Qiong-1 Member （sub-layers 1-6）is a filling deposition controlled by a rift trough，with high-value thickness areas in both the north and south，and the sedimentation range gradually expands over time. In contrast，Qiong-2 Member（sublayers 7-8）has transformed into a widespread sedimentation，with high-value thickness areas distinctly shifted eastward.（3）The aulacogen governs the development and distribution of high-quality source rocks from Qiongzhusi Formation. Four organic-rich shale reservoirs（sub-layers 1，3，5，7）and their overlying tight argillaceous siltstone caps（sub-layers 2，4，6，8）form an effective source-reservoir-cap assemblage，with“source-reservoir inversion”accumulation model. Multiple sets of stacked source-reservoir-cap assemblages inside the aulacogen and along its margins dominated the formation of large-scale lithological oil and gas reservoirs in Sinian-Cambrian. High-quality shale reservoirs within the aulacogen and mound-shoal body lithological traps along the trough margin platform zone are the two key targets for next-phase exploration.

Structural-lithologic trap types and main controlling factors of hydrocarbon accumulation of Cretaceous in Longhupao Oilfield，Songliao Basin

ZHANG Yunfeng, SHI Xiaodong, LIU Zongbao, YANG Xuewei, WANG Hongjun, HAO Bin

2025, Vol.37(5): 111–121 Abstract ( 10 ) PDF (1449 KB) ( 12 )

doi: https://doi.org/10.12108/yxyqc.20250510

Based on structural characteristics and sand body geometry features，the structural-lithologic trap types of Cretaceous in Longhupao Oilfield of Songliao Basin were identified and classified by utilizing data from rock cores，master logging，well logging，and production dynamics. The main controlling factors for reservoir formation were studied from three aspects，such as source rock conditions，oil source transport fault，and the relationship between structure and sand body configuration. Oil and gas accumulation models of different types of traps were summarized. The results show that：（1）Cretaceous structural-lithologic traps in Longhupao Oilfield are mainly developed in Putaohua oil layer，with three microfacies ，such as underwater distributary channels，estuary bar，and front sheet sands，which maintain the characteristics of thin and narrow sand bodies in the delta front subfacies controlled by the northern source.（2）The structural-lithologic traps in the study area can be divided into three categories：fault-lithologic traps in the western slope zone，nose shaped structural-lithologic traps in the eastern nose shaped structural zone，and fault-nose shaped structural-lithologic traps in the central subsag zone. They can be further subdivided into eight subtypes：fault-strip sand type，fault-sheet sand type， fault-lens sand type，nose shaped structural-strip sand type，nose shaped structural-sheet sand type，nose shaped structural-lens sand type，fault nose-strip sand type，and fault nose-sheet sand type.（3）The formation of structural-lithologic traps in the study area is jointly controlled by“source-fault-reservoir-potential”. Source rocks from the first member of Qingshankou Formation provide sufficient oil and gas resources，oil source faults serve as vertical migration pathways for oil and gas，and the relationship between structure and sand body configuration controls the enrichment of oil and gas within traps.（4）There are three types of structural-lithologic trap accumulation models developed in the study area：fault-lithologic trap accumulation model of“vertical transport of oil source faults and enrichment of favorable sedimentary microfacies”，nose shaped structure-lithologic trap accumulation model of“lateral transport of sand bodies and enrichment of positive structures”，and faultnose shaped structure-lithologic trap accumulation model of“fault and sand composite transport，and enrichment of connected sand bodies or thick sand bodies”.

Paleogeomorphy restoration of Permian-Jurassic and its hydrocarbon implications in Junggar Basin，NW China

YE Hui, ZHU Feng, WANG Guizhong, SHI Wanzhong, KANG Xiaoning, DONG Guoning, Naziyiman, WANG Ren

2025, Vol.37(5): 122–132 Abstract ( 10 ) PDF (1962 KB) ( 14 )

doi: https://doi.org/10.12108/yxyqc.20250511

Based on the identification of Permian-Jurassic unconformity in Junggar Basin，the erosion amount was estimated through a combination of stratigraphic trend analysis and sedimentation rate methods. Then paleogeomorphology was characterized using impression method，and the impact of ancient landform evolution characteristics on oil and gas accumulation was analyzed. The results show that：（1）Three first-order unconformities（C/P，P/T，J/K）and three second-order unconformities（P1/P2，P2/P3，T/J）can be identified in PermianJurassic of Junggar Basin. The denudation area of Permian is mainly located in the southeast and northwest of Zhongguai uplift and Dabasong uplift，with a small amount of denudation in the eastern uplift zone. The denudation area of Triassic is mainly located in the northwest margin of the basin，while the denudation area of Jurassic is mainly located in Chepaizi-Mosowan paleo-uplift and the eastern part of the basin.（2）In the study area，Early Permian showed fault depression，normal faults controlled the west and the strata terminated，the eastern strata overlaid on the slope，and Middle-Late Permian presented a multi-depositional center pattern of uplift and depression. Triassic experienced overall subsidence，with three relatively large sedimentary centers. In Early-Middle Jurassic period，the terrain was flat with minimal topographical fluctuations. During Middle-Late Jurassic，the southern part of the basin experienced severe subsidence due to tectonic activity，resulting in a topography characterized by high in the north and low in the south.（3）The evolution of Permian-Jurassic paleogeomorphology in the study area has a significant influence on the distribution of sand bodies and source rocks. The source rocks developed in the sedimentary center of Lower Permian basin and the glutenite in the uplift area formed a good near source source-reservoir combination. During Middle Permian，the rapid eastward expansion and the pattern of multiple sedimentary centers provided favorable conditions for the development of source rocks. The paleouplifts at the basin margin in Upper Permian significantly controlled the distribution of sand bodies. In Triassic， rapid basin subsidence led to the formation of a deep-water lake basin，depositing a thick layer of source rocks. The flat terrain during Middle-Lower Jurassic provided favorable conditions for coal seam development.

Structural characteristics of Permian Wujiaping Formation，Nanya area， eastern Sichuan Basin and their hydrocarbon reservoir control mechanism

ZHAN Lin, FAN Cunhui, TANG Wen, YANG Xiyan, LIU Dongxi, LI Bo, YANG Xinrui

2025, Vol.37(5): 133–144 Abstract ( 14 ) PDF (1487 KB) ( 21 )

doi: https://doi.org/10.12108/yxyqc.20250512

Permian Wujiaping Formation in Nanya area of eastern Sichuan Basin has obtained high-yield industrial gas flow，which shows great shale gas exploration potential in the study area. Based on the characteristics of regional tectonic evolution，combined with drilling，logging，and seismic data，the structural features and their control over the generation，storage，and preservation of shale gas were analyzed. The results show that：（1）Nanya syncline area in eastern Sichuan Basin has undergone three tectonic movements，shaping the current pattern of barriertype fold belts. Faults can be classified into 5 levels，level Ⅰ faults in NE-SW direction are the main ones，with a fzult space greater than 300 m. This type of fault has a significant destructive effect on shale gas preservation. （2）“Kaijiang-Liangping”trough，formed by extensional stress provides a favorable location for the formation of deep-water shelf facies shale in the study area. Tectonic movements cause uplift and subsidence of the strata， directly affecting the thermal evolution of organic matter within the shale. The primary hydrocarbon expulsion period occurred during Jurassic，while the main gas generation phase was the early period of Middle Jurassic-Early Cretaceous.（3）The micro-fractures and nano-scale pores formed by tectonic activity provide storage space for shale gas. The reticular fracture system matches the direction of the maximum horizontal principal stress，effectively improving the physical properties of shale and facilitating the migration and enrichment of shale gas. Faults are the main channels for the escape of shale gas，and the preservation of shale gas is mainly affected by level Ⅰ faults. The deployment of well locations should be at least 1.5 km away from level I faults.（4）Tectonic activity has an important impact on the generation，storage，and preservation of shale gas，and“moderate structural transformation，effective reticular fractures，and complete sealing system”are the key factors for shale gas reservoir formation. Nanya syncline area is a favorable area for shale gas exploration in eastern Sichuan Basin.

Characteristics and geological significance of volcanic ash of Cretaceous Qingshankou Formation in the central depression of northern Songliao Basin

LIU Lijuan, LI Junhui, FU Xiuli, BAI Yue, ZHENG Qiang

2025, Vol.37(5): 145–154 Abstract ( 7 ) PDF (1391 KB) ( 16 )

doi: https://doi.org/10.12108/yxyqc.20250513

Through analyses of core observation，argon ion polishing-field emission scanning electron microscopy，whole rock X-ray diffraction and zircon U-Pb dating，the types，mineral components，distribution characteristics，and zircon U-Pb dating of rocks contained volcanic ash from Cretaceous Qingshankou Formation in the central depression of Songliao Basin were analyzed. The organic matter enrichment influence of Gulong shale was analyzed from tectonic environment，volcanic eruption period，and global hypoxia event.The results show that：（1）Qingshankou Formation in Songliao Basin mainly develop gray and gray white tuff，with a single layer thickness of 0.5-3.0 cm. The mineral composition is mainly clay（illite-montmorillonite mixed layer），with a mass fraction exceeding 50%，followed by siderite，feldspar，and quartz，and some pyrite. The tuff beds exhibit either abrupt contacts or scalloped contact with adjacent layers.（2）Vertically，the volcanic ash in the study area is mainly distributed in the first and second sections of Qingshankou Formation，and the thickness of the volcanic ash in the first section is larger. While in the plane，the thickness of the volcanic ash exhibits“west thick and east thin”in the first section of Qingshankou Formation，and“east thick and west thin”in the second section，the average age of volcanic ash is 93.820 ± 0.240 Ma.（3）In the study area，during the initial stage of sedimentation of Qingshankou Formation，the dual effects of rapid thermal subsidence and extensional stress tectonic background provided the driving force for volcanic eruptions. The eruption of volcanic ash provided nutrients for the reproduction of creatures，such as lacustrine algae，and the enrichment of organic matter. At least 6 periods of volcanic ash beds have deposited in the shale series of the first and second sections of Qiangshankou Formation，representing 6 volcanic eruption episodes. The volcanic ash in Q1 layer of the first section is formed by magma eruption around the western periphery of the basin，while the volcanic ash of the second section mainly originates from volcanic eruption materials in the eastern part of the basin.（4）The formation time of volcanic ash from Qingshankou Formation in the study area is consistent with the time of global hypoxia event OAE2（93.6-94.3 Ma）. The nutrient materials brought by volcanic ash are the important guarantee for the sustained biological bloom and organic matter enrichment over the subsequent 0.04-0.08 Ma.

Fracture effectiveness evaluation of tight reservoir of Cretaceous Yageliemu Formation in Kelasu structural belt，Kuqa piedmont

XU Sihui, ZHAO Jun, ZHAO Xinjian, WANG Junyu, LI Zhaoping, LIN Zongpeng

2025, Vol.37(5): 155–165 Abstract ( 10 ) PDF (1182 KB) ( 13 )

doi: https://doi.org/10.12108/yxyqc.20250514

The geological structures and pressure systems of Cretaceous Yageliemu Formation in Kelasu structural belt of Kuqa piedmont are complex. The development of natural fractures has significant impacts on the reservoir flow capacity. Focused on evaluation effectiveness of fracture reservoirs from Cretaceous Yageliemu Formation， permeability sensitive parameters such as fracture width，stress-fracture angle difference，and friction coefficient were optimized to establish a fracture effectiveness index（FEI）classification standard based on in-situ stress through multi-parameter coupling. The results show that：（1）The permeability boundary between effective fractures（unfilled or semi-filled）and ineffective fractures（fully filled）of reservoirs from Cretaceous Yageliemu Formation is around 0.2 mD. Increasing fracture width can improve the reservoir permeability.（2）High stressfracture angle differences and high normal stress reduce fracture effectiveness by influencing fracture closure. While high friction coefficients improve fracture effectiveness by increasing shear slip between fracture surfaces. （3）Based on the weights of various in-situ stress parameters that affect the fracture effectiveness，the FEI evaluation standard was established. Applying this FEI evaluation standard to classify and evaluate the reservoirs in the study area，the proportion of Class Ⅰ and Class Ⅱ effective fractures in the central part of the study area is higher， indicating better reservoir effectiveness. Towards the east and west，the proportion of such fractures decreases， resulting in poorer reservoir effectiveness.

Source-to-sink system of Paleogene in Huizhou Sag of Pearl River Mouth Basin and its control on reservoir

YAN Yuyang, XIONG Lianqiao, HE Youbin, CHEN Ying, ZHAO Zhongxiang, LIU Shengqian, LUO Jinxiong, FENG Bin

2025, Vol.37(5): 166–177 Abstract ( 6 ) PDF (1757 KB) ( 10 )

doi: https://doi.org/10.12108/yxyqc.20250515

Paleogene tectonic evolution of Huizhou Sag in Pearl River Mouth Basin is complex，and the sourceto-sink elements are variable. Based on data obtained from drilling，seismic，petrographic thin section，detrital zircon geochronology，the source-to-sink system and its control on reservoir was studied. The results show that：（1）Three types of source-to-sink systems developed in Paleogene of Huizhou Sag：the low uplift fault-trough type，the intra-depression transfer zone type，and the extra-depression transfer zone type. The parent rocks of the low uplift fault-trough type source-to-sink system were mainly the granite basement within the basin，transported through the same-direction fault troughs，and developed small-scale braided river deltas. The parent rocks of the intra-depression transfer zone type source-to-sink system were mainly the granite basement，transported via the transfer zone，and developed medium-scale braided river deltas. Affected by the fjord topography，they occasionally superimposed with the adjacent fan deltas sedimentary bodies. The extra-depression transfer zone type source-to-sink system was mainly sourced from the external water system，with a long transport distance and only a small amount of internal source mixing，developed large-scale braided river deltas.（2）The scale and physical properties of reservoirs in the study area are jointly controlled by parent rock composition，transport distance，transport channel morphology，sedimentary facies，and paleogeomorphology of the sedimentary period. （3）There are three types of high-quality reservoirs：the endogenous dissolution type，the mixed-source convergence type，and the low-uplift beach-bar type. The reservoir physical properties of the mixed-source convergence type at the junction of the exogenous transfer zone and the low uplift within the basin are the best.

PETROLEUM ENGINEERING AND OIL & GAS FIELD DEVELOPMENT

Derivation and application of material balance equation for abnormal high pressure gas reservoirs with aquifer

CAI Junjun, LIU Wei, HU Yi, LI Qiu, XU Rui, MAO Zhenglin, TIAN Ye, MA Yang

2025, Vol.37(5): 178–185 Abstract ( 8 ) PDF (1257 KB) ( 14 )

doi: https://doi.org/10.12108/yxyqc.20250516

Abnormal high pressure gas reservoirs with aquifer are subjected to the combined action of rock，fluid compressibility and water invasion. As a result，the shape of pressure drop curve is an upward moving“ straight line”. Using the concept of the cumulative effective compaction coefficient defined by Fetkovich，and the powerlaw function of dynamic reserves recovery rate Gp/G and Ce(p)Δp+ω derived from field data，a material balance equation for abnormal high pressure gas reservoirs with aquifer was derived in the form of a power-law function.The results show that：（1）Based on the production data of gas reservoir，the newly derived material balance equation of the abnormal high pressure gas reservoir with aquifer can be used to calculate the dynamic reserves and water influx of the gas reservoirs.（2）The fitting coefficients A and B of the power function Gp/G and Ce(p)Δp+ω derived from production data of 11 abnormal high pressure gas reservoirs with aquifer in China， with A value of 0.3-0.9 and B value of 1.0-2.0.The values of A and B reflect the timing of water invasion in gas reservoirs：if the gas reservoir experiences early water invasion，the A value is larger；if the gas reservoir experiences middle and late water invasion，the B value is larger.（3）The production data calculation and comparison of 6 abnormal high pressure gas reservoirs with aquifer in China show that the newly established material balance equation is reliable.

A new calculation method for dynamic reserves of gas water coproduction volumetric gas reservoirs in Daniudi Gasfield of Ordos Basin

ZHAO Rundong, WANG Jinchang, LUO Yi, ZHOU Ruili, ZHOU Jian

2025, Vol.37(5): 186–192 Abstract ( 11 ) PDF (1248 KB) ( 13 )

doi: https://doi.org/10.12108/yxyqc.20250517

When flowing material balance equation is applied in gas water coproduction volumetric gas reservoirs，as the water-gas ratio increases，the calculated dynamic reserves error gradually tends to increase，and the result affects the evaluation of gas well production potential. To address this problem，a gas-water two-phase material balance equation for volumetric gas reservoir was established by integrating the effects of water saturation， cumulative water production and rock matrix expansion.The results show that：（1）As the equation is an implicit function equation，a corresponding iterative solution method is designed to be constrained by dual parameters of dynamic reserves and pseudo-pressure gas recovery index.（2）Verified by the pressure recovery test results of 3 gas wells，under the same conditions of using wellhead and wellbore production data，the average absolute error of calculating dynamic reserves using the gas-water two-phase material balance equation is 5.0%，and the average absolute error of calculating dynamic reserves using the flowing material balance equation is 111%. By comparison，the accuracy of gas-water two-phase material balance equation is higher.（3）Dynamic reserves decrease as the water-gas ratio increases. And as the water-gas ratio increases，the difference of dynamic reserves calculated by the gas-water two-phase material balance equation and the flowing material balance equation becomes greater.

Well testing interpretation model of vertical injection well with multi flow channels considering high-velocity non-Darcy flow

CUI Yongzheng, ZHOU Wensheng, WEI Zhijie, JIANG Ruizhong

2025, Vol.37(5): 193–200 Abstract ( 7 ) PDF (1279 KB) ( 10 )

doi: https://doi.org/10.12108/yxyqc.20250518

To focus on the issue of high permeability flow channels developed upon long-term strong water erosion in offshore unconsolidated sandstone，the Barree-Conway model was employed to describe the highvelocity non-Darcy flow within flow channels. An iterative method was adopted for the strong nonlinearity caused by high-velocity non-Darcy flow. Then a pressure transient model of vertical injection well with multi flow channels considering high-velocity non-Darcy flow was obtained through line source，Laplace transformation and numerical discretization methods，and the typical pressure dynamic curves and related parameters were analyzed.The results show that：（1）The semi-analytical model for unstable well-testing in vertical injection well with multi flow channels considering high-velocity non-Darcy flow can effectively address both the development of multi high permeability flow channels and high-velocity non-Darcy flow within these channels，and the calculation results are more reliable.（2）The typical pressure curves of vertical injection well with multi flow channels can be divided into six flow stages：wellbore storage，transition flow，bilinear flow，linear flow，flow channel interference，and radial flow. When high-velocity non-Darcy flow is considered，both the early stage pressure and pressure derivative curves move up significantly，and the flow conductivity capacity of the multi flow channels near wellbore shift down significantly. As the numbers of flow channels increase，the pressure and pressure derivative curves decrease significantly，while the influence of high-velocity non-Darcy flow within the flow channels diminishes.（3）The model was successfully applied to the parameters interpretation of an injection well in Bohai Oilfield，then the quantitative characterization of flow channels can be achieved.