Fan-delta sandstones or conglomerates constitute important reservoirs for oil and gas worldwide. The Early to Middle Triassic succession in the Xiazijie area of the Mahu Sag of the Junggar Basin represents a critical hydrocarbon-bearing interval, yet its detailed sedimentary evolution and facies architecture remain insufficiently understood. This study integrates core descriptions, well-log analysis, grain-size data, and heavy mineral indices from 105 wells in the Xiazijie area to reconstruct the depositional environments and evolutionary trends. Results indicate that the strata were deposited in a fan-delta environments, with lithofacies ranging from particle-supported conglomerates (channel fills) to horizontally-bedded mudstones (interchannel deposits). Planar facies mapping reveals that during T1b2, T1b3, and T2k13 periods, sediment was supplied from both northern and northwestern sources, forming dominant NE- and near-SN-trending channel belts. By the T2k12 period, sediment input simplified to a dominant NE direction. This study reveals that a clear retrogradational trend during the Early to Middle Triassic, marked by the shrinkage of the delta front and expansion of lacustrine deposits. This is a local response to the shallow unified Junggar basin, which is characterized by gradually increasing water depth during the Triassic. These findings provide a facies framework for reservoir prediction in this prolific exploration target.

The formation mechanisms of deep high-quality reservoirs in the Dibei area of Kuqa Depression foreland thrust belt were investigated through an integrated multidisciplinary approach combining petrographic analysis (thin section and cathodoluminescence microscopy), geochemical characterization (fluid inclusion microthermometry, stable isotope analysis) and structural modeling (2D finite element simulation). Systematic analysis reveals that the Ahe Formation reservoirs exhibit superior storage capacity characterized by: (1) high fracture density (0-8 m(-1), based on imaging log interpretation and core analysis), (2) intensive feldspar dissolution (resulting in up to 5% porosity enhancement, derived from thin section point counting-derived), and (3) limited authigenic clay mineral content (<3 vol%, thin section point counting-derived). Reservoir heterogeneity is mechanistically controlled by structural-lithofacies-fluid interactions, with optimal reservoir development occurring in sandstone-mudstone interbeds of back thrust structures. These units display composite pore networks composed of dissolution pores (50-500 mu m) interconnected by shear-induced microfractures (aperture: 5-15 mu m). Two-dimensional finite element simulations demonstrate that differential deformation between ductile lithofacies (mudstones and coals) and brittle sandstones promotes fracture proliferation in interbedded sequences, with increasing fracture density by 40%-60% compared to massive sandstone units. Organic acid migration induces LREE-MREE enrichment in calcite and kaolinite, coupled with depleted delta C-13 (-15.2 parts per thousand to -9 parts per thousand) and delta D (-96.8 parts per thousand to -84.1 parts per thousand) values, indicative of redox-driven diagenetic alteration. Open fracture networks in shear-tension zones (mid-upper sections of back thrust structures) provide effective migration pathways for organic acids, establishing localized open geochemical systems that drive feldspar dissolution while inhibiting authigenic clay precipitation (kaolinite <0.5 vol%, illite <1 vol%). Conversely, weakly deformed opposing thrust structures in compression-dominated regimes exhibit reduced fracture connectivity (aperture <5 mu m), limited dissolution (dissolution porosity <3%), and pervasive pore-filling cements (authigenic quartz >1 vol%, kaolinite >1 vol%), collectively degrading reservoir quality.

Carbonate cementation is a key factor in the densification of sandstone reservoirs in the Yangxia Formation of the Kuqa Depression; however, the formation mechanisms are not yet fully understood. The carbonate cements in the tight sandstones of the Yangxia Formation are primarily composed of siderite, ferroan calcite, ferroan dolomite, and ankerite. The delta 18O, delta 13C, and 87Sr/86Sr data indicate that the formation of these carbonate cements was controlled by the thermal evolution of the coal-bearing source rocks of the Yangxia Formation. Early-phase ferroan siderite (S1) and ferroan dolomite (D1) formed between 199.5 Ma and 170.54 Ma, with carbon derived from the reduction of CO2 by methanogenic bacteria and calcium from the original formation water. Mid- phase ferroan calcite (C1) and ankerite (D2) formed between 72 Ma and 50 Ma, with carbon sourced from a mixture of inorganic CO2 and CO2 released during the thermal degradation of organic matter in the coal-bearing source rocks of the Yangxia Formation. Late-phase ferroan calcite (C2) formed between 18.6 Ma and 13.6 Ma, with carbon derived from a mixture of inorganic CO2 and CO2 released by the thermal decarboxylation of organic matter in the coal-bearing source rocks of the Yangxia Formation. The calcium in both mid-phase and late-phase carbonate cements was sourced from the smectite-to-illite transformation in the coal-bearing source rocks of the Yangxia Formation. Clumped isotope and fluid inclusion thermometry reveal that, prior to hydrocarbon charging, carbonate cementation significantly reduced the porosity and permeability of the sandstones in the Yangxia Formation, resulting in reservoir densification.

Fluids generated from the source rocks containing various kerogen types at different thermal maturity stages control diagenetic processes and reservoir quality in adjacent sandstone reservoirs. This study focuses on the carbonate cements in the sandstones of the Lower Jurassic Yangxia Formation and the Ahe Formation in the Tarim Basin. The d18 O, d13 C, and 87 Sr/86 Sr data indicate that low temperature ferroan calcite and manganoan calcite-characterized by strongly negative d13 C values and enrichment in light rare earth elements (LREEs)-record CO2 released during the thermal degradation of organic matter predominantly composed of Type III kerogen in coal bearing source rocks and of Type II kerogen in mudstone source rocks, respectively. High temperature ferroan calcite and manganoan calcite, which exhibit similarly strongly negative d13 C values and enrichment in middle rare earth elements (MREEs), record organic acids and CO2 produced during the thermal decarboxylation of these same source rocks. The diagenetic fluid evolution sequence comprises early stage CO2 from thermal degradation of both coal bearing and mudstone source rocks; mid stage organic acids and CO2 from thermal decarboxylation of coal bearing source rocks; and late stage organic acids and CO2 from thermal decarboxylation of mudstone source rocks. Fluids generated during the thermal degradation of mudstone and coal bearing source rocks precipitated extensive calcite cements, leading to reservoir densification. Clumped isotope thermometry indicates that the primary generation periods of late stage mudstone derived fluids coincided with the formation of effective fractures. Feldspar dissolution along these fractures produced an interconnected network of fractures and dissolution pores, significantly enhancing reservoir quality in the Ahe Formation. (c) 2025 China University of Geosciences (Beijing) and Peking University. Published by Elsevier B.V. on behalf of China University of Geosciences (Beijing). This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

Kuqa Depression is an important oil-bearing tectonic unit in the Tarim Basin, and the Mesozoic tectonic setting is of great significance for hydrocarbon exploration in the deep-seated strata of the depression. In this paper, the Mesozoic tectonic setting and evolution processes of Kuqa Depression have been studied by using petrology, seismic interpretation, zircon chronology, and geochemistry methods, combined with the analysis of rock properties and age composition of potential provenance areas. The results show that the zircon ages of the sandstones of Triassic Taliqike Formation range from 251 to 2816 Ma, the zircon ages of the sandstones from the Jurassic Yangxia and Ahe formations range from 241 to 2600 Ma, and most of the zircon ages are concentrated in 241-485 Ma. The Mesozoic Triassic and Jurassic strata in the Kuqa Depression are mainly derived from the Yili-Central Tianshan orogenic belt and the Southern Tianshan orogenic belt, and the tectonic background is the passive continental margin. The main provenance of the Cretaceous Kuqa Depression is Southern Tianshan. In the Mesozoic, the provenance of the Kuqa Depression has changed significantly, and there is a trend of strengthening tectonic activity, which is mainly controlled by the interaction between the Central Tianshan and South Tianshan terranes and the Tarim plate. This paper provides a new idea for the tectonic evolution of the Kuqa Depression during the Mesozoic, which will be useful in exploring hydrocarbon accumulations in deep-seated strata.

The deep Lower Jurassic Ahe Formation (J1a) in the Dibei-Tuzi area of the Kuqa Depression has not been extensively explored because of the complex distribution of fractures. A study was conducted to investigate the relationship between the natural fracture distribution and structural style. The J1a fractures in this area were mainly high-angle shear fractures. A backward thrust structure (BTS) is favorable for gas migration and accumulation, probably because natural fractures are more developed in the middle and upper parts of a thick competent layer. The opposing thrust structure (OTS) was strongly compressed, and the natural fractures in the middle and lower parts of the thick competent layer around the fault were more intense. The vertical fracture distribution in the thick competent layers of an imbricate-thrust structure (ITS) differs from that of BTS and OTS. The intensity of the fractures in the ITS anticline is similar to that in the BTS. Fracture density in monoclinic strata in a ITS is controlled by faulting. Overall, the structural style controls the configuration of faults and anticlines, and the stress on the competent layers, which significantly affects deep gas reservoir fractures. The enrichment of deep tight sandstone gas is likely controlled by two closely spaced faults and a fault-related anticline.

Determining the timing of fracturing is crucial for understanding reservoir evolution and hydrocarbon accumulation in foreland basins. Using fracturing data from cores, borehole images, and outcrops, combined with the clumped isotope (Delta(47)) and fluid inclusion analyses of carbonate minerals filled in pores and fractures, this study ascertained the fracturing timing of the Jurassic reservoirs in the Dibei-Tuziluoke Gas Field, Kuqa Foreland Basin. Data from outcrops and borehole images show two dominant fracture sets in the study area: W-E and NE-SW striking fractures. Some W-E striking fractures are carbonate-filled, while NE-SW striking fractures lack mineral fillings. Bitumen veins, not easy to be identified in borehole images, are prevalent in cores. The petrographic analysis reveals that these bitumen veins formed before the calcite cementation in pores and display high viscosity and low maturity. Homogenization temperatures (T-h) from primary fluid inclusion assemblages in two representative calcite vein samples were notably lower than T-Delta(47) values from corresponding samples. This suggests the Delta(47) signature underwent alteration due to partial reordering during burial. Thus, Delta(47)-derived temperatures (apparent temperatures) may not faithfully represent the mineral precipitation temperatures. When plotting these apparent temperatures vs. the burial history, only the possible latest ages of fracturing emerged. These ages were further refined by considering petroleum charging, tectonic evolution, and stress orientation. Bitumen-filled fractures likely resulted from the Late Cretaceous uplift, marking the migration of low-maturity hydrocarbons in the study area. Carbonate-filled E-W striking fractures emerged during the late Miocene (similar to 13-6.5 Ma) alongside fold development. NE-striking fractures that crosscut W-E ones possibly formed recently due to stress reorientation. (c) 2024 Sinopec Petroleum Exploration and Production Research Institute. Publishing services by Elsevier B.V. on behalf of KeAi Communications Co. Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

We investigated diagenesis of the sandstones from the DN2 Gas Field of the Kuqa Foreland Basin (KFB), in order to infer the timing of fluid migration and discuss the linkage between fluids and tectonics. The textures and chemical composition of authigenic minerals, fluid evidence from fluid inclusions and formation water measurements were all used to fulfill this aim. Eodiagenesis occurred with the participation of meteoric water and connate water. Mesodiagenesis is related to high salinity fluids, which were attributed as originating from the overlying Neogene Jidike Formation evaporite (principal minerals including halite, anhydrite, glauberite, carnallite and thenardite). The onset of high salinity fluid migration is inferred to occur during the late Miocene (12.4–9.2 Ma) through the use of homogenization temperatures measured in the present study and K‐Ar dating of authigenetic illites from previous work. This period is consistent with the crucial phase (13–10 Ma) that witnessed the rapid uplift of the southern Tianshan Mts and the stage when calcite and anhydrite veins formed in the studied strata. We thus argue that diagenesis related to high salinity fluids occurred as a response to the Tianshan Mts' rapid uplift and related tectonic processes. The flow of high salinity fluids was probably driven by a density gradient and channeled and focused by fractures formed contemporaneously.

Understanding diagenetic fluid types and their effects on diagenesis is important to identify the main control factors of reservoir characteristics and predict reservoir sweet spots. Reservoir space destruction caused by strong cementation is notable in the Lower Jurassic Ahe Formation sandstones near the deep-rooted fault (Yiqikelike Fault) in the Kuqa depression. Different authigenic minerals and widely varying cementation contents indicate the complexity of diagenetic fluids. Therefore, we investigated strong cementation using petrographic and geochemical methods, including cathodoluminescence, scanning electron microscopy, laser ablation inductively coupled plasma mass spectrometry, and stable isotope analysis. The contents of authigenic quartz and calcite increased as they approached the deep-rooted fault, with maximum concentration of quartz and calcite of up to 8.73% and 8.92%, respectively. Abnormally high homogenization temperatures of the fluid inclusions were observed in the quartz overgrowth, one of which reached 156 degrees C. In calcite, the rare earth element Eu exhibited abnormal characteristics, and the carbon isotopes ranged from-8.00%o to-2.00%o. Therefore, it is likely that deep fluids are involved in reservoir diagenesis near a deep-rooted fault. This study provides a good example of diagenetic evolution in deep sandstone reservoirs and the negative effects of the involvement of deep fluids in diagenetic processes.

The Kuqa Foreland Basin, adjacent to the southern Tianshan Mountains, is an important gas-producing basin in northwestern China. The development of the basin is dominated by a regional stress field with orientations of the maximum horizontal stress (SHmax) in the north-south direction, as a result of the collision between the Indian and Eurasian Plates. Previous studies have noted variations in the stress state in the Kuqa Foreland Basin; however, little attention has been paid to understanding the mechanisms causing such variations. In this study, a systematic analysis of in-situ SHmax orientations and fractures has been carried out using image logs from eight wells and XMAC/DSI logs from five wells. These wells are located in an East-West (E-W) trending fold-thrust in the foreland basin. The SHmax orientations (having quality ranked between A and D) obtained from borehole breakouts and drilling-induced fractures are highly variable and occur as two evidently different stress patterns on a scale of less than 10 km. The first stress pattern with SHmax orientations between NNW and NNE (165.08 and 188.59 degrees N) is broadly comparable to the regional stress field inferred from earthquake focal mechanism solutions in northwestern China from the World Stress Map (WSM). The stress pattern is interpreted to be controlled by plate boundary forces related to the collision between the Indian and Eurasian Plates. The SHmax orientations for the second stress pattern, however, ranging from NNE to ENE (26.65-57.77 degrees N), are clearly inconsistent with the regional stress filed and have been influenced by local geological factors. Faults and hinge-parallel fractures (trending in an approximately W-E direction) formed during the syn-folding stage probably resulted in heterogeneity of elastic properties and thus deflected SHmax orientations, both laterally and vertically, to generate the second stress pattern. The NE-striking hinge-oblique fractures are interpreted to have formed in response to the stress reorientation. Observations in this study suggest that there may exist a close relationship between fracturing (faulting) and stress variations, and pre-existing faults and fractures can influence subsequent fracturing by regulating local stress fields on a scale of several kilometers. The coupling between fracturing or faulting and stress produced fracture swarms, which can significantly enhance fluid flow and hence petroleum production.

&lt;p&gt;We used the textures and chemical composition of authigenic cements in Paleogene sandstones from DN2 Gas Field of Kuqa Foreland Basin (KFB) and evidence of associated fluids from fluid inclusions and formation water measurements to infer timing of fluid migration and discuss link between fluids and tectonics. Eodiagenesis occurred with the participation of meteoric waters and connate waters. Mesodiagenesis operated in the context of high salinity fluids, which were interpreted to originate from overlying Neogene evaporite. Halite, anhydrite, glauberite, carnallite and thenardite are major minerals for the evaporite. Homogenization temperatures measured in this study and K-Ar dating performed on authigenetic illites by previous study indicate that initial migration of high salinity fluid occurred during the late Miocene (12.4&amp;#8211;9.2 Ma). The period is consistent with the crucial phase (13&amp;#8211;10 Ma) witnessing the rapid development of southern Tianshan and the stage when calcite and anhydrite veins formed in the studied strata. These results suggest that diagenesis related to high salinity fluids probably occurred as a response to Tianshan&amp;#8217;s rapid uplift and related tectonic processes. The flow of high salinity fluids was probably driven by density gradient and channeled and focused by fractures formed contemporaneously.&lt;/p&gt;

Accurate evaluation of uranium sources and identification of their spatiotemporal correlations with uranium deposits (or sinks) in sedimentary basins are important for exploring sandstone-type uranium deposits. This study examines the source-to-sink system of Mesozoic-Cenozoic sandstone-type uranium deposits in the Qaidam Basin (QB) through a literature review in conjunction with logging and seismic data and yields the following findings. (1) The uranium-supplying capacity of a source rock in the uranium source area depends on primarily its type and to a lesser extent, the tectonic zone where it is located and the episode during which it formed. (2) The initial uranium content, U-0, is the core parameter for classifying and evaluating the uranium-supplying capacity of a source rock. At U-0 > 1.5 ppm, uranium begins to migrate from a source rock. The uranium variation coefficient, & UDelta;U, and the amount of uranium migration, & UDelta;Ut, decrease continuously to -55 % and -5 ppm respectively as U0 increases up to 9.5 ppm, which suggests that at most 5 ppm of uranium in the source rocks can migrate away. As U0 increases beyond 9.5 ppm, & UDelta;U and & UDelta;Ut fluctuate around -55 % and -7 ppm respectively, which suggests that approximately 7 ppm of the uranium in the source rocks can migrate away. (3) Of the different types of rocks, silicic igneous rocks (including both intrusive and volcanic igneous rocks) and granitic gneisses have the highest uranium-supplying capacity; intermediate igneous rocks and gneisses come second; mafic-ultramafic igneous rocks and the other metamorphic rocks (except granitic gneiss and gneiss) come third. Of the sub-source areas (tectonic zones), the western segment of the Eastern Kunlun and the Qiman Tagh have the highest uranium -supplying capacity; the Central and Southern Altyn Tagh come second; the others come third. (4) Uranium sources are the fundamental prerequisite for the formation of uranium sinks. Other geological factors control the specific formation process of uranium sinks as well as their spatiotemporal distribution patterns. For QB, the most economic and prospective uranium sink, Neogene formations of Gy anticline, was fed by the source areas which had the highest uranium-supplying capacity. This suggests that the Neogene of WEK anticline belt, Quaternary of Kumukol Basin and Qarqan River Basin are the most noteworthy metallogenic prospective areas. The uranium-source evaluation scheme and "source-to-sink " ore exploration approach introduced in this study have practical value for advancing the exploration of uranium deposits in sedimentary basins in northern China and other parts of the world.

Investigating the formation and evolution of coarse-grained deposits in modern lakes and the relevant controlling conditions is indispensable to the prediction of reservoir sandbodies, disaster prediction, and limnological research. The source-to-sink system of coarse-grained deposits in Lake Chenghai, a deep, scarped Late Quaternary lake, was investigated in this study based on 62 outcrops, Advanced Land Observing Satellite (ALOS) digital elevation model (DEM) data, and regional geological survey data. The findings include the following: (1) the source areas of coarse-grained deposits in Lake Chenghai were lithologically classified into carbonate source areas, basaltic source areas and siliciclastic source areas, and were geomorphically categorized as scarp type or confluence type. Subaqueous colluvial aprons have formed downstream of the carbonate source areas and scarp-type basaltic source areas, while Gilbert-type deltas have formed downstream of siliciclastic source areas and confluence-type basaltic source areas. (2) The formation and evolution of coarse-grained deposits are controlled by the sediment flux that evolves in synchrony with the geomorphic evolution of the source areas and the sink regimes. Scarps represent the initial landform of the source areas. Source material rolls off or slides down scarps or forms small-scale debris flows before entering the lake. The source material initially formed subaqueous colluvial apron (synonymous with subaqueous fans) where sufficient space was present to accommodate sediments and the basement angle exceeded than the natural angle of repose. As weathering and denudation have progressed, the initial scarps have transformed into confluence-type slopes, and the source material has formed medium- and large-scale debris flows that have entered the lake, resulting in an increase in sediment flux. Consequently, the subaqueous colluvial aprons have rapidly grown and developed subaerial deposits, which have evolved into larger-scale Gilbert-type deltas that overlie the initial aprons. (3) The morphology and distribution of coarse-grained deposits vary in response to differences in quantity and composition of materials from different source areas, which resulting from different rates of weathering and denudation and different sediment input regimes. Firstly, the size and surface slope angle of a subaqueous colluvial apron from a carbonate source are smaller than those of a subaqueous colluvial apron of basaltic origin. Secondly, a Gilbert-type delta from a basaltic source features a greater slope angle and a thicker topset than does a Gilbert-type delta of siliciclastic origin, and the latter exhibits a longer foreset and a thicker bottomset than in the former. Thirdly, the sizes of subaqueous colluvial aprons are not strongly correlated with the sizes of the source areas, while the sizes of Gilbert-type deltas are.

The influence exerted by the linkage and growth of fault segments on the sedimentation pattern in a lacustrine rift subbasin, the northern Bonan Sag in the Jiyang Depression in the Bohai Bay Basin, is studied by integrating drilling cores, wireline logs and 3D seismic data. The NW-trending Guxi Fault formed through the linkage of three fault segments, which display a roughly en echelon arrangement in map view and are probably related to early-stage regional transtensional and slip-strike stress. Between the vertical displacement troughs of normal faults, two narrow relay ramps, attributed to the coherent fault linkage-and-growth model, formed through the linkage of the three fault segments. A relatively wide relay ramp, attributed to the isolated fault linkage-and-growth model, developed due to the linkage of the NW-trending Guxi Fault and E-W-oriented segmented Chengnan Fault. The sedimentation pattern was strongly controlled by the geometry and evolution of the relay ramps. The sediment routing system was dominated by the relay zone, and fan-delta and sublacustrine fan depositional systems developed in the early stage of relay ramp formation. Lateral breaching of the relay ramps through extensive faulting and rifting probably caused an increase in the vertical throw and resulted in deposition of a coarse-grained nearshore subaqueous fan in front of the normal faults. The relay zone that formed from the linkage of independent faults (the Chengnan and Guxi faults) is associated with a broad drainage area and fan-delta and sublacustrine fan deposits, which contain the most effective hydrocarbon reservoirs in this deeply buried setting.

通过精细观察和描述山东灵山岛科学钻探井灵科1井1300余米岩心,系统研究该井沉积岩地层岩石和沉积相的类型、特征和演化,结合前人对灵山岛露头沉积特征的认识成果,梳理和总结该区早白垩世莱阳群沉积特征与演化模式.结果 表明:灵山岛早白垩世莱阳群沉积地层自下而上发育扇三角洲—水下扇—浊积扇—三角洲沉积,构成完整的裂陷盆地沉积充填序列;其中扇三角洲发育于盆地裂陷初期,由3个退积旋回组成;水下扇发育于盆地扩张深陷期,由下部3个退积旋回和顶部1个进积旋回构成;浊积扇发育于深陷稳定期,由两个不明显的退积旋回和两个加积旋回组成;三角洲则发育于莱阳期末盆地抬升期.

Deep-water sandstones related to sediment gravity flows are becoming an increasingly important exploration domain in continental rift basins in China. However, ambiguities remain regarding the initiation, evolution, and deposition of sediment gravity flows on faulted slopes, where step faults are commonly developed. To address the uncertainties related to these processes, grain size analysis, lithofacies analysis, logging interpretation, and seismic interpretation were employed to study Paleogene sediment gravity flow deposits from well cores on a faulted slope in the Zhanhua Sag of the Bohai Bay Basin. Twelve lithofacies related to sediment gravity flows were recognized and attributed to intrabasinal sediment gravity flows (ISGFs) induced by slope failures and extrabasinal sediment gravity flows (ESGFs) generated by floods. Active faults were important triggers for ISGFs on the faulted slope in the Zhanhua Sag. The fault activity rate had a prominent role in determining the volume of re-transported sediments, which further influenced the evolution of the resulting flows. Travelling across multiple faults downslope, ISGFs generally underwent considerable velocity losses, with the result that almost all sediments were deposited in shallow water. Moreover, unconsolidated ISGF deposits could be transported again to generate sediment gravity flows, obscuring the depositional characteristics of ISGFs. ESGFs originated from rivers during floods and involved the transformation of cohesive into turbulent hyperpycnal flows. In humid and warm climates, active sag-border faults favoured the generation of long-lived ESGFs. These flows usually travelled along intra-sag faults and therefore considerable volume of sediments could be transferred into deep water. The resulting thick-bedded hyperpycnites contributed substantially to the reservoirs of Bonan Oilfield. Meanwhile, short-lived ESGFs usually generated in the regions where sag-border faults were extinct. They generally travelled down the faulted slope and deposited sediments in shallow water. These features suggest that the initiation, evolution, and deposition of sediment gravity flows on the faulted slope are mainly controlled by faults and climate. Hyperpycnites can serve as excellent reservoirs for hydrocarbon accumulation and they are probably common in other sags of the Bohai Bay Basin.

By employing the main techniques of core observation, grain size analysis, thin section examination, log data and seismic data interpretation etc., the major types and sedimentary characteristics of sediment gravity flows in the third member of Shahejie Formation in Gudao west slope zone of Zhanhua sag in the Bobai Bay Basin were studied in this paper. Their control factors under different triggering mechanisms and tectonic activities over the sedimentary process of gravity flows and sand body distribution were discussed, the source-to-sink coupled systems were summa-rized and the development mode of gravity flow sand bodies in the slope zone were established. The results indicated that five types of sediment gravity flow, including hyperpycnal flows, debris flows, turbidity currents, fluidized flows, and slides-slumps were developed during the sedimentary period of the third member of Shahejie Formation in the study area, and involving two triggering mechanisms, namely, flood and slump. The fluid evolution was in general at the early stage of evolution from debris flow to turbidity current, and it is predicted that in the deep waters to the north of the study area, debris flow sediments were still developed and turbidity current sediments started to develop exten-sively. Tectonic action exerts significant control over fluid property and evolution, development and distribution of con-temporaneous deformed structures and sand bodies of gravity flow origin in the third member of Shahejie formation in the study area. In general, there are four major source-to-sink systems occurred, including fault trough gully, fault slope break, fault strike slope, and gentle slope gully, respectively. Vertically, the ( semi) deep lake, nearshore sub-aqueous fan and slump fan deposition were evolved into shore-shallow lake, braided delta and fan delta deposition from the bottom up in the third member of Shahejie Formation. On the plane, fan delta front and nearshore subaqueous fan from Gudao uplift are mainly developed in the east part of the study area whereas braided delta fronts are mainly developed in the west part of the study area, and slump fans in bead string pattern are mainly developed in the middle part of the study area.

构造成岩作用(structural diagenesis)是构造地质学与沉积学交叉融合形成的前沿研究领域,主要研究构造作用、构造和非构造成因的变形构造和变形效应与沉积物(岩)成岩变化之间的相互作用.变形构造及变形过程通过影响成岩流体流动对成岩作用非均质性产生重要影响;与变形构造相关的成岩作用研究则有助于揭示储层成岩演化、流体流动以及构造活动时期、期次及速率等重要信息.构造成岩作用提供了构造—成岩格架下探讨储层演化的新思路,在实际工作中应注意这一思路在储层成因与预测、致密化机制及沉积盆地动力学过程等研究方面的应用.碳酸盐岩变形条带相关研究起步较晚,相对较薄弱,未来应加强这方面的研究;同时亟待建立考虑碳酸盐岩在内的新的变形条带分类体系.目前,不同变形构造之间的研究程度不均衡,变形条带与裂缝几乎构成了构造成岩作用研究的主体;与软沉积物变形构造、砂岩脉等变形构造有关的构造成岩作用研究有待强化.变形构造空间分布预测及其对流体流动影响的研究要综合岩芯、露头及数值模拟等多种资料与方法.国内学者就中国中西部盆地深层系构造作用对储层演化的物理影响开展了研究,并取得了重要进展,构造作用对储层化学变化影响的相关研究已经起步;未来应重视运用构造成岩作用思路探究储层演化与分布的动力机制和过程,推进储层成岩动力学过程和沉积盆地动力学研究.