The Upper Urho Formation (P3w) of the Permian in Central Zhongguai Rise, Junggar Basin is a key target for deep hydrocarbon exploration and exploitation. Based on cores, wireline logs, thin sections, scanning electron microscopy (SEM), and 3D seismic sections, this study systematically investigates sedimentary facies, petrological characteristics and physical properties of glutenite reservoirs, and discusses controlling factors on glutenite reservoir properties. The results reveal that fan delta deposits are developed in Central Zhongguai Rise. Braided channels dominate the first member of Urho Formation (P3w1), while subaqueous distributary channels dominate the second member of Urho Formation (P3w2). The two members show distinct petrological features. In P3w1, residual intergranular pores and dissolved pores are predominant, with clay minerals mainly consisting of kaolinite and illite-smectite mixed layers. In contrast, P3w2 is composed of mixed grain types, and its pore spaces are primarily residual intergranular and intragranular pores. Porosity and permeability data indicate that both reservoir intervals exhibit similar average porosity and permeability, and both are generally classified as low to medium-low permeability reservoirs. However, P3w2 has a higher maximum porosity, a greater proportion of high-quality reservoirs, and more abundant tight low-permeability end members, indicating stronger heterogeneity. Reservoir quality is primarily controlled by sedimentation, followed by diagenesis. Sedimentation governs the distribution of sand bodies and their original fabric, providing the material basis for subsequent diagenetic alterations. Diagenetic processes such as compaction, cementation, and dissolution further modify the pore structure. The subaqueous distributary channel sand bodies in P3w2 possess a favorable original fabric, which, combined with dissolution-induced porosity enhancement, is key to the formation of high-quality “sweet spot” reservoirs.

The Fengcheng Formation of Junggar Basin has been demonstrated as an essential target interval for fine-grained sedimentary rocks and shale oil exploration-exploitation in ancient alkaline lacustrine basin in China. However, the volcanic activities have influenced alkaline lacustrine environment to a large extent. Therefore, the characteristics and distributions of alkaline-volcanic lithofacies remain unclear. The cores, thin sections, scanning electron microscope (SEM) and wireline logs are employed to conduct research on the type, characteristics, distribution and evolution model of lithofacies in Fengcheng Formation. The results indicate that seven lithofacies are developed, including basalt, tuff aceous conglomerate/sandstone, massive/laminated/alkaline tuffaceous fine-grained sedimentary rocks, and alkaline rocks. Among them, basalt is mainly developed in lower part. The massive/laminated/alkaline tuffaceous fine-grained sedimentary rocks are mainly developed in middle part. The tuff aceous conglomerate/sandstone and alkaline rocks are mainly developed in upper part. The wireline responses of diff erent lithofacies/sub-lithofacies vary significantly in stacking patterns and value scope. However, the lithofacies/sub-lithofacies with similar genesis share similarity in wireline responses. The lithofacies/sub-lithofacies distribution generally show progradation in the northwest and retrogradation in the southwest. The lithofacies/sub-lithofacies scope of fine-grained sedimentary rocks are to a large extent related to tuff aceous conglomerate/sandstone distribution. In addition, the lithofacies/sublithofacies are influenced by paleo-environment (paleo-salinity, paleo-climate, paleo-water depth) changes and volcanic activities. The climate in early depositional period has turned into dry and hot. Subsequently, the scope of lacustrine basin starts to shrink, resulting in gradually-increasing salinity. The lithology during this period is dominated by dolomite and dolomitic rocks. However, the climate in late depositional period remains dry and hot. The lake level continues to fall and the salinity continues to increase. The alkaline minerals such as alkali are precipitated, marking the final formation of alkaline lakes and alkaline rocks..

The southern Zhongguai Rise has gained wide attentions due to its commercial hydrocarbon discoveries from volcanic deposits in Jinlong Oilfield. An integrated analysis of geologic and geophysical data assists in determination and depiction of volcanic lithology and volcanic facie, characterization of volcanic reservoirs, and discussion of constrains on volcanic lithology and lithofacies. The conclusions suggest that two types of volcanic lithology, including volcaniclastic rocks and silicic molten lava, can be identified based on cores. In addition, two types of volcanic lithofacies can be delineated according to cores and wireline responses. Whereas explosive facies are mainly developed in the early depositional period, the effusive facies are developed through the depositional period. Furthermore, the reservoir space predominantly consists of pores and fractures according to thin sections. The physical property varies with time; that is, the porosity distribution varies slightly. In contrast, permeability distribution varies significantly. The volcanic reservoirs can be generally attributed to high-porosity and low-permeability reservoirs in volcaniclastic rocks or silicic molten lava. The volcanic lithofacies, facies distribution, diagenism, and paleogeomorphology exert controls on physical property and reservoir performance of volcanic reservoirs together.

Recent petroleum reserves preserved within reservoirs formed by braided river delta deposits have been confirmed in the Toutunhe Formation. However, sedimentological heterogeneities play a critical role in determining reservoir performance. Geological and geophysical data are utilized to investigate the genetic relationships within the reservoir. The results identify two sedimentary sub-facies and three sedimentary microfacies. The braided river delta plain is characterized by short sediment transport distances, low compositional maturity of rocks, and high structural maturity. The sediment is primarily sandstone, with lithic sandstone being the dominant rock type. Carbonate cementation is prevalent, with pore-filling cement as the main cement type and mud as the primary mixed matrix component. Clay minerals are dominated by kaolinite, followed by illite and chlorite. Kaolinite and chlorite content show a positive correlation with reservoir porosity, while illite content is negatively correlated. Two types of reservoir pores are identified: primary pores and secondary pores. Primary pores are mainly intergranular pores, often associated with quartz and chlorite, while secondary pores are primarily intergranular dissolution pores, associated with feldspar and kaolinite. Insights into sedimentary characteristics and diagenetic processes controlling reservoir heterogeneity in braided river delta deposits can aid in further petroleum exploration in this region and similar areas.

The Fengcheng Formation in Mahu Sag of Junggar Basin has been demonstrated to be an important target interval for shale oil exploration-exploitation deposited in fine-grained sedimentary rocks within alkaline lacustrine basin in northwestern China. The geological-geophysical-geochemical data are used to conduct research on reservoir space characteristics and "sweet spots" distribution in Fengcheng Formation. The results indicate that seven types of lithofacies/sub-facies are identified. The reservoir spaces in different lithofacies/sub-facies either vary significantly or share similarity in geological datasets. The interpretation of reservoir spaces is carried out regarding to pores and throats. The pores include dissolution pore, intergranular pore, intercrystal pore, and fracture. The throats consist of fracture-type throat, air void-type throat, decreasing void-type throat, bending-type throat, decreasing neck-type throat, tube-type throat. The description of vertical petroliferous characteristics and physical property in different kinds of lithofacies indicate that laminated tuffaceous fine-grained sedimentary rocks and tuffaceous sandstone can constitute favorable "sweet spot". The distribution of "sweet spot" decreases from early to late depositional period of second member of Fengcheng Formation due to provenance, sedimentary environment, climate change, and volcanic activities.

The Permian strata in southern Zhongguai Rise are famous for their abundant petroleum reservoirs. The depositional evolution of the Upper Urho Formation has been studied by analyzing the interactions between the sedimentary environments and the diagenetic evolution based on the comprehensive analysis of geologic and geophysical data sets. The obtained results have shown that fan delta deposits, overlain by lacustrine deposits, are deposited. Proceeding upward, the fan delta succession is characterized by retrogradational patterns, such as sandstone facies and conglomeratic facies. These facies have shown different clay mineralogic compositions, porosity, and physical properties. The sandstone facies indicate well-sorted and well-rounded sedimentological textures with good physical properties. In contrast, the conglomeratic facies indicate poorly sorted and poorly rounded sedimentological textures with poor physical properties. All of these characteristics lead to reservoir heterogeneity resulting from sedimentary facies and diagenesis.

Numerous hydrocarbon discoveries in the lower Urho Formation of the western Mahu Slope, China indicate that potential petroliferous reservoirs may exist in that region. However, issues concerning the reservoir characteristics and associated controlling factors remain unclear. To determine the characteristics and associated controlling factors of these reservoirs, we conducted integrated analysis of the 3D seismic volume, wireline logs, mud logs, cores, thin sections, porosity, and permeability data. Several lithologic types were identified from the core, casting thin section, and mud-log data (including mudstone, sandstone, gravity flow-derived glutenite, transitional glutenite, and traction flow-derived glutenite). The contact relationship was determined from the casting thin section data, and it included point contact and lineal contact, followed by concavo-convex contact and suture contact. We found the dominant pore types were found to be intergranular pores, followed by intragranular pores, intramatrix pores, and cracks. The porosity and permeability data reveal that sandstone and traction flow-derived glutenite commonly form low-porosity and low-permeability reservoirs, whereas transitional glutenite commonly forms low-porosity and ultralow-permeability reservoirs and gravity flow-derived glutenite generally forms low-porosity and ultralow-permeability reservoirs. This integrated analysis finds that tectonic movements and a sedimentary environment control the physical properties of the reservoirs. The tectonic movements control reservoir characteristics through thrust fault systems and large-scale provenance, and the sedimentary environment controls reservoir characteristics via facies distribution and lacustrine fluctuation. The insights gained from this study can provide knowledge about the characteristics and associated controlling factors of the reservoirs in the Permian Lower Urho Formation within the western Junggar Basin. These insights can also benefit petroleum reserve and hydrocarbon production exploration in the study area and further petroleum exploration in other areas with similar sedimentary/tectonic settings.

In recent years,breakthroughs have been made in oil and gas exploration in the Mahu Sag,but there is less research on the control of heterogeneous diagenesis in sandy gravel reservoirs.The first member of the Upper Permian Urho Formation in the Mahu1 well block is a typical strongly heterogeneous sandstone reservoir with low compositional and structural maturity.Based on data such as cast thin sections,reservoir physical properties,and scanning electron microscopy,the damage and construction effects of diagenesis on reservoir physical properties were analyzed,and the main reason for the high content of secondary dissolved pores is clarified,which is the dissolution of tuff debris and feldspar in the study area.Zeolites have a strong cementation and destruction effect on reservoirs in the early stage of diagenesis,but after entering the middle diagenetic stage A,a large number of zeolite dissolution pores are formed,becoming an important component of secondary dissolution pores.Meanwhile,there is a large amount of iron calcite and filamen-tous illite in the reservoir of the first member of the Urho Formation,indicating that the first member of the Urhe Formation in the Mahu1 well block is currently in the middle diagenetic stage B.

辫状河沉积具有发育范围广、砂体规模大且非均质性较低等有利储集条件,长期以来一直是世界范围内重要的油气储层类型.准噶尔盆地西北缘红山嘴油田红 003 井区侏罗系齐古组辫状河储层具有高孔、高渗、高含油饱和度的特征,准确认识区域内沉积演化规律与储层特征,是稠油资源高效开发的基础.本次研究根据岩性、颜色、沉积构造、沉积序列、电性特征对比分析,建立了红 003 井区齐古组沉积相标志,明确了齐古组发育辫状河沉积体系,并具有河道主体、河道侧翼、心滩坝、泛滥平原等沉积微相类型,其中由河道与心滩坝组成的主力砂体呈带状分布,是研究区范围内有利的相带类型.通过单井、连井、平面沉积相分析,再现了齐古组辫状河沉积时空演化规律;其中J3q1 和 J3q2 时期是辨状河发育的全盛时期,而J3q3 辫状河沉积规模开始减小.沉积相类型、储层物性、储集空间类型以及孔隙结构特征综合评价,齐古组发育 Ⅰ 类、Ⅱ类、 Ⅲ 类储层,其中 I类储层心滩坝砂体是下一步重点开发目标.

The southern Zhongguai Rise, the petroliferous zones in northwestern Junggar Basin, is among the most significant sedimentary basins in China because of its abundant petroleum reserves. The reservoir characteristics and their responses to controlling factors have been complex in the Permian Upper Urho Formation. A systematic investigation has been conducted based on integrated analysis of seismic volumes, wireline logs, mud logs, cores, thin sections, SEM, grain size data, porosity‐permeability data, and mercury injection test results. The results indicate that the Upper Urho Formation consists of five types of lithology (glutenite, coarse‐grained sandstone, medium‐grained sandstone, fine‐grained sandstone, and siltstone). Furthermore, the detrital composition in Upper Urho Formation is predominantly composed of debris (mainly volcanic rocks), with relatively less contents of quartz and feldspar. The cement is dominated by calcite, laumontite, and siliceous. In addition, the reservoir space in Upper Urho Formation includes intergranular pore, intragranular pore, dissolution pore, and microfracture. The intergranular pore and dissolution pore comprise the main reservoirs. The reservoirs in Upper Urho Formation are characterized by micro‐fine pore‐throat and low‐porosity permeability. Diagenesis along with sedimentary facies exerts the controls on the reservoir heterogeneity and physical properties.

The abundant petroleum reserves have been found in the Urho Formation in the past few years in western Mahu Slope, Junggar Basin. A great deal of studies has been carried out regarding tectonic evolution, sequence stratigraphy, reservoir prediction, and mechanism in the Urho Formation. However, little is known concerning the depositional evolution and associated controlling factors in the Upper Urho Formation. In this study, thin sections, cores, wireline logs, and seismic volumes are utilized to identify and describe sedimentary facies/microfacies, analyse mineral components and micro characteristics of microfacies, predict facies/microfacies distributions, and reveal depositional evolution and associated controlling factors. The results indicate the identification of eight sedimentary microfacies and the evolution of fan delta systems in Upper Urho Formation. In addition, depositional evolution of fan delta systems from bottom to top in Upper Urho Formation is characterized by retrogradation during lacustrine transgression period. The controlling factors, including tectonic activities along northwestern thrust fold belt and lacustrine fluctuations together exert influences over depositional evolution of regressive fan delta systems in Upper Urho Formation.

The significant hydrocarbon discoveries have been found during the past few years in Middle Jurassic Xishanyao Formation in Southeastern Xiayan Rise, Junggar Basin. The braided delta front deposits and shore‐shallow lacustrine deposits are well preserved in Xishanyao Formation, their history being documented by integrated analysis of seismic volumes and borehole datasets (wireline logs, cores, grain size etc). The results reveal that five sedimentary microfacies are identified. Among them, the braided delta front deposits include subaqueous distributary channel, inter‐distributary channel and mouth bar, while shore‐shallow lacustrine deposits consist of lacustrine mud and swamp. In addition, depositional evolution of braided delta front deposits and shore‐shallow lacustrine deposits from bottom to top in Xishanyao Formation is characterized by retrogradation and progradation during depositional period. The depositional evolution during depositional period of Xishanyao Formation is controlled by interactions of the source and distribution of provenance, the catchments, the lacustrine fluctuations and the climates.

The hydrocarbon discoveries are increasing in deltaic systems in Jurassic Sangonghe Formation in southern Mahu Slope of Junggar Basin in recent years. However, different scales of sedimentological heterogeneities influence reservoir quality and architecture. Consequently, the study aims to employ thin sections, core logs and wireline logs to conduct research to address the issues. The results show that the integrated analysis of conventional cores reveals three facies groups in Sangonghe Formation which are deposited in braided deltaic and lacustrine environment. Each facies group contains several lithofacies given their grain size, sedimentary structures. In addition, the lithofacies types, associations, and wireline responses indicates that Lower, Middle, and Upper Sangonghe Formation is deposited in braided delta plain, braided delta front, and pro‐delta respectively. Moreover, the Sangonghe Formation is characterized by variations regarding sandbody, thickness, geometry, and architecture. The facies distribution and sedimentary environment indicate that accommodation space plays essential controls. The sedimentological heterogeneity controls reservoir quality and architecture from macro‐ to micro‐scale. The macro‐scale insights reflect that the lower and middle Sangonghe Formation shows high connectivity of sandbodies while the upper Sangonghe Formation shows low connectivity of sandbodies. The micro‐scale insights indicate that sandstone types, texture, composition all plays significantly role in controlling reservoir porosity and permeability. Finally, the understandings and insights of reservoir sedimentological heterogeneities assist in better prediction and assessment of reservoir quality and architecture. Finally, it will make contributions to reservoir development, recovery, and productivity for areas with similar sedimentological settings.

Significant hydrocarbon discoveries that resulted from conglomerate reservoirs in the Baikouquan Formation have been found in the last few years in Mahu Sag, Junggar Basin. Many studies have been conducted to describe the sedimentological complexity of reservoirs. However, few of them have been focused on the depositional characteristics and associated controlling factors in Baikouquan Formation. In this study, analysis of cores, thin sections, wireline logs, and seismic volume were carried out obtain detailed descriptions and interpretations of sedimentary microfacies, depositional evolution, and associated controlling factors. The results indicate that seven sedimentary microfacies are identified in Baikouquan Formation. Furthermore, depositional evolution of fan delta systems from bottom to top of Baikouquan Formation shows retrogradation in general. Tectonic activities along the northwestern fault zone, rising lake levels, arid climate, and high temperature together exert the controls on depositional evolution of fan delta systems in Baikouquan Formation.

The Ke‐Bai Fault Belt in northwestern Junggar Basin has gained robust insights and wide attention on large‐scale hydrocarbon discoveries in the Carboniferous volcanic rocks. The integrated analysis of wireline logs, image logs, core photographs, thin sections, and scanning electron microscope allows the description and interpretation of volcanic facies and volcanic reservoirs, as well as their responses to controlling factors. The results indicate that three types of lithology are identified based on cores, including volcanic rocks, followed by sedimentary rocks and metamorphic rocks. In addition, explosive facies, effusive facies, volcanic sedimentary facies, and sub‐volcanic facies are delineated according to spatial distribution, occurrence condition, and appearance characteristics of volcanic products. Furthermore, the characteristics of reservoir space (including pores and fractures) are analysed and described. Finally, the controls on the characteristics of volcanic reservoirs are revealed, including volcanic lithofacies, tectonic movements, and diagenesis.

利用烟道气进行稳定重力驱在国外油田开发试验中取得较好的应用效果.新疆油田在稠油热采过程中产生了大量烟道气,在气源附近存在大量高倾角、厚层块状油藏,如果这些油藏可以进行烟道气稳定重力驱,不但可以大幅度提高原油采收率,还将减少温室气体排放,保护生态环境.为此,通过详细分析国外气体辅助稳定重力驱现场实例,总结了气体辅助稳定重力驱技术的应用条件,在此基础上,结合新疆油田的资源现状,以具有可操作性为原则,按必要性和重要性分级确定烟道气稳定重力驱油藏筛选评价指标及标准,建立油藏筛选评价方法,并通过11个油藏实例验证该方法的可靠性.利用所建方法,对照油藏筛选标准,从气源和井况条件及地质条件方面论证新疆油田红153油藏开展烟道气稳定重力驱的可行性,最终计算烟道气稳定重力驱油藏筛选指数为9.39,说明该区块实施烟道气稳定重力驱在技术上是可行的.新疆油田分公司于2017年12月在红153油藏顶部开展了注气试验,注气井临井产油量由9.5 t/d提高至20.3 t/d,效果明显,证实了油藏筛选方法的准确性.

柴达木盆地东缘石灰沟地区上石炭统克鲁克组合煤岩系地层厚度大,分布范围广,具备煤系气资源形成的条件.煤系烃源岩全区分布,矿区中部最厚,以岩性组合特征将克鲁克组划分为四段,总体有机质丰度较高,但克1段有机质丰度较其他三段略差.克鲁克组烃源岩以Ⅱ型干酪根为主,部分为川型,且全段均无差异地表现为成熟-高成熟演化程度的特征.以底界埋深、泥岩累计厚度、灰岩累计厚度等有效信息圈定了研究区石炭系克鲁克组煤系气发育优选区,即CY井以西地区.

西准噶尔地区风化火山期次界面分为两类,Ⅰ类界面自然伽马值高、电阻率值低、密度值低;Ⅱ类界面自然伽马值高、电阻率值高、密度值低.界面发育在火山机构的分界线上,地震剖面上具有超覆、强反射的特征.风化火山期次界面为流体的运移通道,流体对界面两侧的岩石产生强烈的风化作用,使界面附近岩石内部产生微裂缝、溶蚀孔洞,最终使风化火山期次界面区域成为油气成藏的优势区域.

针对玛湖地区储层可压性评价体系缺乏的问题,利用测井资料计算地层应力和破裂压力,定性分析压裂缝延伸情况.结果表明压裂缝的形态取决于地层应力的大小和方向,裂缝的方位垂直于最小水平主应力方向,缝高延伸终止于最小水平主应力高值处.使用应力突进参数模型对缝高进行模拟,建立缝高变化模型,可将玛湖地区百口泉组低渗储层分成三类可压性储层,采用不同的压裂措施.将该方法应用到玛湖地区三叠系百口泉组储层的压裂工程中,提高了该区域的压裂成功率.

Previous studies have not determined the location of the catchment area of the Shanxi Formation and Member 8 of Xiashihezi Formation sediments in the Ordos Basin derived from north and south provenaces.Thin-section analyses of sandstones from 4 outcrops and cores for 18 wells in the southern basin have been carried out in this study on the basis of understanding of the general data of the studied stratigraphic intervals in the Ordos Basin.The location of catchment area for the sediments of the Shanxi Formation and Member 8 of Xiashihezi Formation is defined in the southern Ordos Basin based on the changes of feldspar content and other lithological characters,the characteristics of log curves and rock assemblages,and the facies analyses of across well profiles and outcrops.The "catchment area" refers the area where the rivers transporting the sediments from north and south provenances merge and it is the bordering area which separates the early-derived sediments from the north to the south.It lies roughly in east-west direction.There are obvious differences in feldspar content between the north and south sides of the catchment area.It is put forward that there are "intersection parts" of sediments from the north and south in local places of the catchment area.The "intersection parts" mean the areas where the sediments from the north and south meet and intersect with each other,which are the connecting places of the sediments from the north and south.The intersection parts are located in the catchment area and separate it into different parts.The siderite nodules formed in the early diagenetic stage under reduction conditions were found in the intersection parts of the Member 8 of Xiashihezi Formation.The palaeogeography of the southern basin during the deposition of the Shanxi Formation and Member 8 of Xiashihezi Formation was controlled by sediments from both the north and south.The across-well sections show that the sedimentary facies belts have a symmetrical distribution on the north and south sides of the catchment area.The sedimentary units and facies belts include:1)the catchment area,with three intersection parts;2)the delta facies belt on the south margin of the catchment area,including 3 deltas from the south provenance;3)the delta facies belt on the north margin of the catchment area,including 4-5deltas from the north provenance;4)the fluvial facies belts which are the transitional belts of north and south deltas.The depositional model for the studied intervals in the study area in Ordos Basin is proposed.