碳酸盐岩地层-岩性大油气田是一种重要的油气田类型，勘探已经证实其在全球范围内有着大量的油气资源及油气产量。通过对全球94个碳酸盐岩地层-岩性大油气田的区域展布、层系分布、圈闭类型、储层埋深及储量规模等参数的分析，探讨了其分布的主控因素。这类油气田主要分布于北美、中东和中亚地区，其中北美含油气域的油气最为富集，主要富集层系为奥陶系、石炭系、古近系和新近系。圈闭类型主要为生物礁类、颗粒滩类、成岩圈闭和不整合与风化壳型；埋深一般小于5 000 m，埋深超过5 000 m的油气田仅占6.4%。本文重点探讨了以下5个关键因素对碳酸盐岩地层-岩性大油气田的形成与分布：①稳定局限的浅水环境、中低纬度有利于有机质的生成和保存；②构造运动不但会产生大量断裂和裂缝带而增加储层的储集空间，而且会促进油气的运聚（往往与生烃期相匹配），也为古岩溶作用提供有利背景；③古岩溶等成岩作用改善了储集性能；④蒸发岩起到了良好的封盖油气作用；⑤圈闭定型时间与烃源岩的生、排烃时间需在时空上达到良好的匹配关系。

Giant carbonate stratigraphic-lithologic oil and gas field is an important type of oil and gas field in the world. It has been proved to be rich in oil and gas resources and production. Ninety-four carbonate stratigraphiclithologic oil and gas fields were theoretically analyzed, including their geographical distribution, strata distribution, trap types, buried depth and reserve scale of reservoirs,and the main controlling factors of their distribution were discussed. Such oil and gas fields are mainly distributed in the North America, Middle East and Central Asia, among which North America has the most abundant oil and gas,and the oil and gas resources of carbonate reservoirs are mainly accumulated in the Ordovician, Carboniferous, Paleogene and Neogene. The traps can be classified as biological reef, grain beach, diagenetic trap, unconformity and weathering crust. The reservoir burial depth of these oil and gas fields is generally less than 5 000 m,and the oil and gas fields with reservoir burial depth of more than 5 000 m account for only 6.4%. The effects of the following five key factors on the formation and distribution of giant carbonate stratigraphic-lithologic oil and gas fields were discussed:(1) The stable and confined shallow water environment and mid-low latitude are conducive for the generation and preservation of organic matter.(2) Tectonic movement not only increases the reservoir spaces by producing a large number of faults and fracture zones, but also promotes the migration and accumulation of hydrocarbon(usually matching with the hydrocarbon generation stage), and provides a favorable background for paleo-karstification(. 3) Diagenesis such as paleo-karst improves reservoir performance.(4) Evaporite plays an important role in sealing oil and gas.(5) Trap finalization time and hydrocarbon generation and expulsion time of source rocks need to achieve a good matching relationship in time and space.

The Lower Triassic Feixianguan sedimentary system of carbonate platform that develops in Sichuan basin consists of six sedimentary facies, including restricted platform facies, open platform facies, evaporite platform facies, platform margin facies, platform foreslope facies and trough basin facies.According to the single-well and outcrop se-quence division and the well-to-well sequence correlation, the Lower Triassic Feixianguan Formation can be divided into a SQ1 and a SQ2 third-order sequences and corresponding HST and TST system tracts. Feixianguan sequence-based lithofacies and paleogeographic maps at each system tract in the whole basin are compiled. It is shown that Feixianguan sedimentary facies presents obvious differentiation from the southwest to the northeast of the basin. During the SQ1 peri-od, the open platform facies and the restricted platform facies commonly developed in the basin but the intraplatform oolitic beach microfacies and the platform-margin shoal microfacies developed in the central and the east of the basin, and during the SQ2 period, the restricted platform tidal flat subfacies widely developed in the central and northeast of the basin. It is concluded that the oolitic beach microfacies deposited in the HST (SQ1) and the TST (SQ2) may be the good reservoirs for exploration potential.

Marine carbonate rocks in China are characterized by aging, developing in small-scale cratons and locating in the lower tectonic layer of superimposed basins. Reservoir genesis and distribution are among the many scientific problems in hydrocarbon exploration. This paper summarizes three innovative achievements made by the project team of the Key Laboratory of Carbonate Reservoir in the past five years in the field of marine carbonate sedimentary reservoir research in China as follows: (1) based on the analysis of tectonic-lithophase paleogeography of the Sinian-Cambrian, Changxing Formation-Feixianguan Formation in Sichuan Basin, it is found that the intra-platform rifts in small-scale craton were generally developed, and thus the carbonate platform sedimentary models of bi-margin ＆ bi-shoal were established. This discovery reveals that the source rocks and large-scale reservoirs can also develop in the intra-platform, which provides a theoretical basis for the exploration field expansion from the margin to the internal of the platform, and it was confirmed by the discovery of the Anyue gas field; (2) based on the exploration practice of karst reservoirs in the Tarim Basin, innovations in the genesis of karst reservoirs and the type ＆ distribution of karst reservoirs of intra-carbonate rocks broke the traditional view that the karst reservoirs mainly develope in the buried hills. This view extends the exploration realm from the buried hill areas to intra-carbonate rocks areas, and it was confirmed by the discovery of Harahatang and Shunbei oilfield on the south slope of North Tarim Basin; (3) the old and deep-buried marine carbonate reservoirs are still facie-controlled and the pores are more inherited from pre-buried stage than modificated in buried stage, which laid the foundation for the scale and predicatability for deep-buried and ancient marine carbonate reservoirs, which promote the exploration values of these reservoirs. This view was confirmed by the hydrocarbon exploration practice in Tarim and Sichuan Basins. Reef-shoal(mound) facies, evaporite tidal flats, sequence boundaries, exposure surfaces and unconformities, paleo-uplifts and fault systems control the distribution of high-quality and large-scale reservoirs of deep-buried and ancient marine carbonates. These understandings not only have important theoretical significance for the development of carbonate sedimentary reservoir discipline, but also provide basis for the expansion of exploration field.

通过岩心精细描述、薄片鉴定、测井和地震特征及古地貌等分析，认为塔里木盆地古城地区寒武—中晚奥陶世主要处在台地—台地边缘—台缘斜坡相带，发育台内滩、台地边缘滩（礁滩复合体）、滩间海、台缘斜坡等微相类型。中下奥陶统鹰山组三段台缘滩和中上寒武统发育的纵向叠置的台缘丘滩体是有利的沉积相带，也是下一步勘探的重点。古地貌特征及其演化控制着沉积相带及礁滩体的分布，台缘坡折带决定了台缘带的分布位置，古地貌高隆区控制着台缘滩的发育。塔东地区沉积相演化主要受海平面升降控制，表现为台地类型的变化和台地边缘相带的迁移。探讨古城地区碳酸盐岩台地沉积微相特征及主控因素，圈定有利沉积相带，对于该区下步油气勘探具有重要的指导意义。

. The quality of geothermal carbonate reservoirs is controlled by, for instance, depositional environment, lithology, diagenesis, karstification, fracture networks, and tectonic deformation. Carbonatic rock formations are thus often extremely heterogeneous, and reservoir parameters and their spatial distribution difficult to predict. Using a 3D seismic dataset combined with well data from Munich, Germany, we demonstrate how a comprehensive seismic attribute analysis can significantly improve the understanding of a complex carbonate reservoir. We deliver an improved reservoir model concept and identify possible exploitation targets within the Upper Jurassic carbonates. We use seismic attributes and different carbonate lithologies from well logs to identify parameter correlations. From this, we obtain a supervised neural-network-based 3D lithology model of the geothermal reservoir. Furthermore, we compare fracture orientations measured in seismic (ant-tracking analysis) and well scale (image log analysis) to address scalability. Our results show that, for example, acoustic impedance is suitable to identify reefs and karst-related dolines, and sweetness proves useful to analyse the internal reef architecture, whereas frequency- and phase-related attributes allow the detection of karst. In addition, reef edges, dolines, and fractures, associated with high permeabilities, are characterized by strong phase changes. Fractures are also identified using variance and ant tracking. Morphological characteristics, like dolines, are captured using the shape index. Regarding the diagenetic evolution of the reservoir and the corresponding lithology distribution, we show that the Upper Jurassic carbonate reservoir experienced a complex evolution, consisting of at least three dolomitization phases, two karstification phases, and a phase of tectonic deformation. We observe spatial trends in the degree of dolomitization and show that it is mainly facies-controlled and that karstification is facies- and fault-controlled. Karstification improves porosity and permeability, whereas dolomitization can either increase or decrease porosity. Therefore, reservoir zones should be exploited that experienced only weak diagenetic alteration, i.e. the dolomitic limestone in the upper part of the Upper Jurassic carbonates. Regarding the fracture scalability across seismic and well scales, we note that a general scalability is, due to a combination of methodological limitations and geological reasons, not possible. Nevertheless, both methods provide an improved understanding of the fracture system and possible fluid pathways. By integrating all the results, we are able to improve and adapt recent reservoir concepts, to outline the different phases of the reservoir's structural and diagenetic evolution, and to identify high-quality reservoir zones in the Munich area. These are located southeast at the Ottobrunn Fault and north of the Munich Fault close to the Nymphenburg Fault.

The Calloviane-Oxfordian carbonates in the northeastern Amu Darya Basin of southeastern Turkmenistan are composed of medium- to thick-bedded, mostly grainy limestones with various skeletal (bivalves, brachiopods, echinoderms, foraminifera, corals, and sponge) and non-skeletal grains (intraclasts, ooids and peloids). Two facies zones, six standard facies belts and some microfacies types were recognized, and sedimentary model “carbonate ramp-rimmed platform” was proposed and established that can be compared with the classical carbonate sedimentary models. In this model, favorable reservoirs not only developed in the intraplatform shoal of open platform, or reef and shoal on the platform margin, but also in the patch reefs, shoal and mound facies on the upper slope. The reservoir’s pore space is dominated by intergranular and intragranular pores and fissure-pore reservoirs exist with medium porosity and medium to low permeability. Sedimentary facies and diagenetic dissolution are the key controlling factors for the development of high-quality reservoirs.

The Cenomanian–Early Turonian Mishrif Formation is a great contributor to oil production in Iraq. Integrating petrographic, mineralogical, and wireline logging data from 52 wells, this study provides an improved understanding of the sequence stratigraphy, depositional evolution, and reservoir characteristics of the Mishrif Formation in the Mesopotamian Basin, south Iraq. Five types of facies associations are classified: lagoon, shoal, rudist bioherm, shallow marine, and deep marine. Such a classification allows convenient differentiation and interpretation of wireline logs. A sequence stratigraphic framework including five third-order sequences (Mhf 1 to Mhf 5) for the Mishrif Formation is established mainly using wireline logging data of close-distance wells, with the aid of cores and thin sections. Two end-member depositional evolution stages are recognized, from clinoform-like progradational shoal complexes in Mhf 1 within a shallow marine environment, to tidal channels in Mhf 2–3 within a lagoon environment. For Mhf 4–5, abrupt changes in facies associations from north to south indicate the development of an intra-shelf basin where organic-rich mudstones directly overlie the shallow marine grainstone shoals and lagoonal wackestones. Reservoir characteristics and compartmentalization are directly controlled by the sequence stratigraphic framework. Sequence boundaries are featured by wackestones and mudstones overprinted by cementation; they are regionally correlatable and work as regional barriers. Shoal complexes in Mhf 1 and tidal channels in Mhf 2–3 are the main reservoir units. Mudstones and wackestones are intra-reservoir baffles and become more frequently developed towards the south, reflecting the increasing water depth towards south. The characterization of the tidal channels, clinoform-like shoals, and intrashelf basinal deposits in the current study could benefit later development of the Mishrif Formation.

Based on the analysis of field outcrops, well logging and core data, the sedimentary facies types and features of the Lower Cambrian Longwangmiao Formation in northern Sichuan Basin are discussed, and their influences on reservoirs are analyzed. During Early Cambrian Longwangmiao period, the sedimentary environment in northern Sichuan Basin was carbonate platform, which developed three types of facies including tidal flat, restricted platform and open platform, which were further subdivided into four types of subfacies: mixed tidal flat, intra-platform shoal, lagoon and interbank sea. The mixed tidal flat was mainly composed of sandy dolomite and dolomite, and tidal channels were visible in some areas. The intra-platform shoal was mainly composed of doloarenite with small deposition thickness. The lagoon mainly consisted of dolomite lagoon and dolomitic-limy lagoon with large distribution area. The deposition of interbank sea was mainly composed of dark gray massive limestone with intercalated dolomitic mottled limestone. The Longwangmiao period is composed of two regressive cycles in most areas, and lagoon mainly developed in the middle and lower part of a single sedimentary cycle, and intra-platform shoal mainly developed in the middle and upper part of a sedimentary cycle with thin single layer, and the mixed tidal flat mainly developed at the top of a sedimentary cycle. Due to the influence of paleocontinents, the sediment source supply decreased and the water depth gradually deepened, and the sedimentary facies translated from tidal flat to restricted platform to open platform successively from west to east in the study area. The intra-platform shoal mainly distributed around the restricted lagoon. Combined with the analysis of reservoir property of different sedimentary faces, it is concluded that grain dolomite depositing on the intra-platform shoal have the best reservoir property, followed by the crystalline dolomite, and the gypsum was the worst. Therefore, the most favorable sedimentary environment for reservoir development in Longwangmiao Formation is intra-platform shoal.

近年来，在特提斯构造域油气富集带中的四川盆地、塔里木盆地及阿姆河盆地的台内滩油气田勘探取得了重要进展，展示了良好的勘探前景。以阿姆河盆地阿姆河右岸地区中上侏罗统盐下碳酸盐岩台内滩气田为例，通过地震层拉平技术、残余地层厚度法和补偿厚度印模法等对古地貌特征进行了研究及恢复，并重点分析了沉积古地貌对台内滩储集体分布及气藏特征的控制作用。结果表明:研究区发育2个大的基底古隆起，隐伏基底隆起形成的台内沉积古地貌差异对台内滩储层的发育具有明显的控制作用，在基底古隆起发育的古地貌高部位台内滩单层厚度大，垂向上多期叠置，横向连片，储层物性条件好，形成大规模的叠合台内滩储集体;在古地貌低洼部位台内滩单层厚度薄，总厚度小，储层物性条件相对较差，形成的台内滩储层规模有限。同时，隐伏隆起形成的台内沉积古地貌差异对台内滩气藏气水系统、产能特征及气田规模也有重要的影响，沉积古地貌高部位台内滩储层垂向连通性较好，内部隔夹层相对不发育，气水系统相对简单，单井产量高;沉积古地貌低洼部位台内滩储层纵向连通性差，内部发育多套隔夹层，气水系统复杂，单井产量较低。继承性隆起上的地貌高地易形成大型叠合台内滩气田。

阿姆河右岸区块位于中亚阿姆河盆地东北部，天然气资源丰富，盐下中—上侏罗统碳酸盐岩是主要的油 气富集层位。通过对盐下大中型气田的地质特征和成藏因素进行分析，结果表明：①盐下碳酸盐岩大中型气田可划分 为叠合台内滩气田、缓坡礁滩气藏群和逆冲构造缝洞型气田3 类，其中叠合台内滩气田发育孔隙（洞）型台内滩储集 体，纵向叠置且隔夹层发育，形成多套气水系统；缓坡礁滩气藏群发育裂缝—孔隙（洞）型斜坡礁滩储集体，平面表 现为“一礁一藏”；逆冲构造缝洞型气田发育碳酸盐岩缝洞型储集体，气水系统复杂，距主控断层越近、充注强度越 高，气水界面越低。②叠合台内滩气田分布于蒸发台地—局限台地—开阔台地，气田规模受古地貌和现今构造幅度控 制；缓坡礁滩气藏群位于台缘上斜坡带，天然气富集程度与古地貌高和礁滩体类型密切相关；缝洞型气田分布于山前 逆冲构造带，气田内断层发育规模是高产富集主控因素。③深层中—下侏罗统碎屑岩形成了自生自储的成藏组合，具 有大中型气田形成条件，喜马拉雅期改造较弱的继承性构造圈闭和凹陷带地层—岩性圈闭是有利的勘探目标。

The right bank block of the Amu Darya River is located in the northeastern part of the Amu Darya Basin in Central Asia and has abundant gas resources. The sub-salt carbonate rocks of the Middle-Upper Jurassic are the main hydrocarbon enrichment formations. Analysis of the geological characteristics and hydrocarbon accumulation factors of sub-salt large and medium gas fields show that: ① The sub-salt large and medium carbonate gas fields can be divided into three types: gas fields of superimposed inner-platform shoals, gas reservoir groups of ramp reef shoals, and fracture-cavity type gas fields in thrust structures. Pore (vug) type inner-platform shoal reservoirs are developed in the gas fields of superimposed inner-platform shoals. They are vertically superimposed, with development of barrier layers and interlayers, forming multiple sets of gas-water systems. Fracture- pore (vug) type ramp reef shoal reservoirs are developed in the gas reservoir groups of ramp reef shoals. In the plane, this is characterized as “one reservoir in one reef”. Carbonate fracture-cavity reservoirs are developed in fracture-cavity type gas fields in thrust structures with complicated gas-water systems. The closer to the main faults, the higher the charging intensity and the lower the gas-water contact. ② Gas fields of superimposed inner-platform shoals are distributed in evaporate platform–restricted platform–open platform. The scale of this type of gas field was controlled by paleogeomorphology and structural amplitude. The gas reservoir groups of ramp reef shoals were located on upper ramp zones of platform margins, with the gas enrichment degree being closely related to the paleogeomorphic high and to the type of reef-shoal. Fracture-cavity type gas fields are distributed in piedmont thrust structural zones. The development scale of faults in the gas fields is the main controlling factor of high gas production and enrichment. ③ The deep clastic rocks of the Middle-Lower Jurassic form a hydrocarbon accumulation assemblage of self-generation and self-storage, which has the conditions required for the formation of large and medium gas fields. Successive structural traps with less reconstruction in the Himalayan and stratigraphic-lithologic traps in the sag zones are favorable exploration targets.

阿姆河右岸阿盖雷气田中上侏罗统卡洛夫—牛津阶碳酸盐岩储层勘探难度大、地震反射能量弱、地震资料信噪比低。以储层特征及岩石物理分析为基础，通过叠前道集优化处理、井-震联合低频阻抗建模以及叠前射线域弹性阻抗反演方法，对该地区含气储层进行了预测。研究结果表明：①阿盖雷气田中上侏罗统卡洛夫—牛津阶储层主要为台地前缘缓坡相碳酸盐岩，岩性主要为砂屑灰岩和生屑灰岩，储集空间以孔隙-裂缝型为主，具有低孔、低渗和非均质性强的特征；有效含气储层主要表现为低纵波阻抗、低剪切模量、低体积模量特征，剪切模量对含气储层的敏感程度最高。②通过预测剔除去噪，奇异值分解去噪和谱平衡能量补偿手段对叠前道集进行处理可以有效去除异常振幅等高频及随机噪音，提升有效信号强度并增强远偏移距AVO特征；井-震联合建模方法通过引入低频层速度解决因地震数据低频信息缺失而造成的反演多解性问题，提高了反演精度的同时有效表征了储层横向变化；叠前射线域弹性阻抗反演方法在研究区应用效果好，纵、横波阻抗反演体在纵、横向上均表现出较高的分辨能力，预测的含气储层厚度与测井解释的成果吻合度达85%以上，反演体显示气层的横向连续性较差，符合缓坡滩沉积特征。③研究区碳酸盐岩储层具有良好的勘探开发潜力，东部和西南部的未钻区域有多处明显的含气显示；上部Gap—XVhp段含气显示更好。

The reflection energy of middle-upper Jurassic Karlov-Oxfordian carbonate reservoir in the Agayry gas field on the right bank of the Amu Darya River is weak，and the signal-to-noise ratio of seismic data is low. Based on the analysis of reservoir characteristics and rock physics，the gas-bearing reservoir is predicted by prestack gather conditioning，well-seismic joint low-frequency impedance modeling，pre-stack ray domain elastic impedance inversion. The results show that：（1）The Calllovian-Oxfordian reservoirs in the middle and upper Jurassic of the Agayry gas field are mainly gentle slope carbonate rocks in the front edge of the platform. The lithology is mainly sandy limestone and bioclastic limestone. The reservoir space is dominated by pore-fracture type，which has the characteristics of low porosity，low permeability and strong heterogeneity. The results of rock physics analysis show that the effective gas-bearing reservoirs are mainly characterized by low longitudinal wave impedance，low shear modulus and low bulk modulus，and the shear modulus is the most sensitive to gasbearing reservoirs.（2）The pre-stack gathers are processed by means of prediction elimination denoising，singu lar value decomposition denoising and spectral balance energy compensation，which can effectively remove highfrequency and random noise such as abnormal amplitude，improve the effective signal strength and enhance the AVO characteristics at far offset. The well-seismic joint modeling method solves the problem of multi-solution inversion caused by the lack of low-frequency information of seismic data by introducing low-frequency layer velocity，which improves the inversion accuracy and effectively characterizes the lateral change of reservoir. The pre-stack ray domain elastic impedance inversion method has a good application effect in the study area. The P-wave and S-wave impedance inversion results show high resolution in both vertical and horizontal directions. The predicted gas-bearing reservoir thickness is more than 85% consistent with the results of logging interpreta tion. At the same time，the inversion indicated that lateral continuity of the gas layer is poor，which is consistent of the sedimentary characteristics of the gentle slope beach.（3）The carbonate reservoirs in the study area are favorable areas of exploration and development potential. There are many obvious gas shows in the undrilled areas in the east and southwest. The gas-bearing display of the upper Gap-XVhp is better.

High gamma-radioactivity in carbonates is usually ascribed to uranium of detrital minerals and organic matter, and to thorium and potassium of clays. The present study based on Urgonian marls and marly limestones (France) shows that some of the most radioactive values correspond instead to some ‘pure’ limestones. These peaks are generally associated with a sequence boundary or a maximum flooding surface. Low-level γ-spectrometry and ICP–MS analyses show that although high radioactivities are mostly associated with uranium, there is no obvious correlation between uranium enrichment and lithology. Also, correlation between high radioactivity and argillaceous beds might not be systematic.

松辽盆地北部青山口组页岩油的勘探开发潜力巨大,但目前对其沉积旋回格架及有机质富集响应模式认识不清。对古页1井青山口组的自然伽马测井数据分段开展小波变换分析和频谱分析,并综合岩心、测井资料和地球化学元素分析成果,识别出蕴含在该套沉积地层中的米兰科维奇旋回,建立了理论轨道周期与单井沉积旋回的联系,实现了松辽盆地青山口组高精度沉积旋回的识别与划分。依据400 ka的长偏心率周期建立了青山口组的"浮动"天文年代标尺,计算出青山口组的沉积时间在5.6 Ma,青山口组一段富有机质泥页岩为晚白垩世Cenomanian晚期—Turonian早期的产物。青山口组的米兰科维奇旋回可划分为14个长偏心率旋回和46个短偏心率旋回,长、短偏心率旋回分别对应层序地层学的四级、五级层序,由此可搭建研究区天文旋回层序地层格架,为深、浅水区的统一地层划分提供思路。基于建立的受控于长偏心率旋回的有机质沉积响应模式发现,偏心率接近极大值时对应沉积旋回为富有机质层段,该层段是页岩油勘探的潜在优质层段。

There is great exploration and development potential of shale oil in Qingshankou Formation in the north of Songliao Basin, but its sedimentary cycle framework and organic matter enrichment response model are still unclear. Based on wavelet transform analysis and spectral analysis of the natural gamma logging data of Qingshankou Formation in Well Guye1, in combination with analysis results of the core, logging data and geochemical elements, the paper identifies the Milankovich cycle in the sedimentary strata, establishes the relationship between the theoretical orbital period and the single-well sedimentary cycle, and achieves the identification and division of the high-precision sedimentary cycles of Qingshankou Formation in Songliao Basin. The floating astronomical timescale of Qingshankou Formation is established according to the long eccentricity period of 400 ka. The sedimentary time of Qingshankou Formation is calculated to be 5.6 Ma. The organic-rich mud shale of Member 1 of Qingshankou Formation deposits during Late Cenomanian to Early Turonian of the Late Cretaceous. The Milankovitch cycle of Qingshankou Formation can be divided into 14 long eccentricity cycles and 46 short eccentricity cycles. The long and short eccentricity cycles correspond to the fourth and fifth levels of sequence stratigraphy respectively. On this basis, the sequence stratigraphic framework of astronomical cycles can be built in the study area, thus providing an idea for the unified stratigraphic division of deep and shallow water areas. Based on the established sedimentary model controlled by the long eccentricity cycle, it is found that when the eccentricity is close to the maximum, the corresponding sedimentary cycle will be in the organic-rich interval, which is the potential high-quality interval for shale oil exploration.

The Mahu Depression is an important hydrocarbon-bearing foreland sag located at the northwestern margin of the Junggar Basin, China. On the northern slope of the depression, large coarse-grained proximal fan-delta depositional systems developed in the Lower Triassic Baikouquan Formation (T1b). Some lithologic hydrocarbon reservoirs have been found in the conglomerates of the formation since recent years. However, the rapid vertical and horizontal lithology variations make it is difficult to divide the base-level cycle of the formation using the conventional methods. Spectral analysis technologies, such as Integrated Prediction Error Filter Analysis (INPEFA), provide another effective way to overcome this difficultly. In this paper, processed by INPEFA, conventional resistivity logs are utilized to study the base-level cycle of the fan-delta depositional systems. The negative trend of the INPEFA curve indicates the base-level fall semi-cycles, adversely, positive trend suggests the rise semi-cycles. Base-level cycles of Baikouquan Formation are divided in single and correlation wells. One long-term base-level rise semi-cycle, including three medium-term base-level cycles, is identified overall the Baikouquan Formation. The medium-term base-level cycles are characterized as rise semi-cycles mainly in the fan-delta plain, symmetric cycles in the fan-delta front and fall semi-cycles mainly in the pro-fan-delta. The short-term base-level rise semi-cycles most developed in the braided channels, sub-aqueous distributary channels and sheet sands. While, the interdistributary bays and pro-fan-delta mud indicate short-term base-level fall semi-cycles. Finally, based on the method of INPEFA, sequence filling model of Baikouquan formation is established.

In contrast to marine shale oil reservoirs, lacustrine shale exhibits rapid lithofacies changes and strong mineral compositional heterogeneity, posing new challenges for the evaluation and distribution prediction of shale oil sweet spots. The oiliness, reservoir properties, oil fluidity, and fracability of different lithofacies were analyzed using emission-scanning electron microscopy (FE-SEM) observation, low-pressure nitrogen physisorption (LNP) analysis, mercury intrusion porosimetry (MIP), nuclear magnetic resonance (NMR), and triaxial compression testing. Based on the mineral composition obtained from X-ray diffraction (XRD) analysis, total organic carbon (TOC) content, and sedimentary structure, four lithofacies were classified, which are organic-rich laminated calcareous shale (LC), organic-rich laminated siliceous shale (LS), organic-rich laminated mixed shale (LM), and organic-poor massive calcareous shale (MC). Considering the factors of oiliness, reservoir properties, oil fluidity, and fracability, the LC and LS lithofacies were determined as being high-quality sweet spots (type I). Within the stratigraphic sequence divided by GR-INPEFA curves, multi-resolution graph-based clustering (MRGC) analysis of sensitive well logs was used to classify the lithofacies, after which the distribution of sweet spots was predicted. The results reveal that the sweet spots exhibit regular changes in their vertical distribution and a ring-like pattern in their planar distribution, influenced by variations in the sedimentary environment. This finding can offer valuable guidance for the future exploitation of shale oil in the Guandong region.

The strata of the Shan 2 Member of the Shanxi Formation of Permian(S2)in the LQ Gas Field in the northeast of the Ordos Basin restrict the study of sand body distribution and lateral distribution. The accuracy of sand body prediction is reduced, which greatly affects the exploration and development of oil and gas. In order to accurately characterize the transverse distribution of sand bodies and improve the prediction accuracy of sand bodies, S2 is divided by the sequence stratigraphy method. Research based on the traditional stratigraphic division method includes seismic, logging, and core data. The logging curve is processed by INPEFA and the wavelet transform to reduce artificial division interference. The range of the S2 section is limited by the seismic interpretation surface. The maximum entropy spectral analysis and the wavelet transform are used for fine division, and S2 is divided into 1 long-term base level cycle, 6 medium-term base level cycles, and 11 short-term base level cycles. The fine stratigraphic division improves the exploration accuracy of oil and gas reservoirs.© 2023 The Authors. Published by American Chemical Society.