Tidal sand ridges are the most typical and extensive products of tidal processes and the large-scale layered structures that occur in the coastal area. Although there are abundant sand-riched reservoirs developed in tidal sand ridges, surprising that few people can intuitively identify the distribution in ancient strata. By comparing the seismic microfacies and seismic Root Mean Square Amplitude attribute of high-precision 3-D seismic data, we summarized a new method to identify and describe their superposition and plane distribution. Application examples of the Pingbei Slope Belt in the East China Sea Shelf Basin show the detailed analysis process and the results show that 6 sets of tidal sand ridges have been identified in three intervals of LST, TST, and HST, 5 sets of sand ridges with the same extension direction (342–358°) in LST and HST intervals are obviously affected by tides. This method and application example provides a new meticulous process for tidal sand ridges identification according to the superimposition relationship of seismic microfacies and the plane extension direction of the Root Mean Square Amplitude attribute. The seismic microfacies of it is very easy to be distinguished compared to that of other similar sediments and can accomplish the spatial morphology and parameters characterization of tidal sand ridges in ancient sedimentary strata which buried several kilometers depth in a large-scale area. This method is suitable for most sedimentary basins with tidal background, just need the aid of high-precision 3-D seismic data, and provides practical guidance for the petroleum exploration related to sandstone.

渤海海域近几年在太古界潜山领域获得了多个大型油气田发现,其中,渤中19-6构造天然气储量超过千亿方,展示了该领域巨大的勘探潜力.变质岩潜山储层规模是制约变质岩勘探的关键因素,落实规模性潜山储层形成条件具有重要的理论和实际意义.综合应用岩心、薄片、扫描电镜等实验资料以及地震资料分析了渤海海域太古界大型变质岩潜山储层形成条件.研究结果表明:富脆性长英质矿物是渤海海域太古界变质岩大型潜山储层发育的重要物质基础,长英质矿物含量控制了裂缝发育程度,也为风化淋滤和深部流体等的溶蚀作用提供了基础条件;多类型压性构造控制了大型裂缝型储层的形成;风化淋滤作用对太古界潜山储层纵向发育的明显控制作用,是影响太古界潜山储层纵向分带的主要因素;深部流体对太古界潜山储层具有重要改善作用,扩大了裂缝的规模.在上述形成条件指导下,建立了太古界大型潜山储层成因模式.

Based on the practice of oil and gas exploration and the analysis of shallow lithologic reservoirs, combined with the allocation relationship and enrichment law of oil and gas accumulation factors, main controlling factors and models of hydrocarbon accumulation of large lithologic reservoirs in shallow strata around the Bozhong sag are summarized, and favorable exploration areas are proposed. The coupling of the four factors of “ridge-fault-sand-zone” is crucial for the hydrocarbon enrichment in the shallow lithologic reservoirs. The convergence intensity of deep convergence ridges is the basis for shallow oil and gas enrichment, the activity intensity of large fault cutting ridges and the thickness of cap rocks control the vertical migration ability of oil and gas, the coupling degree of large sand bodies and fault cutting ridges control large-scale oil and gas filling, the fault sealing ability of structural stress concentration zones affects the enrichment degree of lithologic oil and gas reservoirs. Three enrichment models including uplift convergence type, steep slope sand convergence type and depression uplift convergence type are established through the case study of lithologic reservoirs in shallow strata around the Bozhong sag.

Based on anatomy of key reservoirs, and configuration relationship of oil &gas migration factors and enrichment laws, main controlling factors and accumulation models of large lithologic oil reservoirs in shallow strata of Bozhong sag and its surrounding area are examined, and favorable areas for lithologic oil reservoir exploration are predicted. Four factors, deep convergence ridge, big fault cutting the ridge, large scale sand body with good internal connectivity coupling highly with ridge-cutting fault, and sealing degree of lithologic trap in the updip direction, are the major factors controlling enrichment of these reservoirs. Four main enrichment models, QHD33-1S uplift convergence type, KL6-1 low uplift hidden convergence type, KL10-2 steep slope convergence type and BZ28-34 depression uplift convergence type, are established. It is predicted that the anticlines, monoclines, steep slopes in hydrocarbon generation subsags, and uplift areas in subsags around Bozhong sag are favorable exploration zones for large lithologic oil reservoirs in shallow strata.

The system of sediment dispersal of the continental margin has always been a hot and difficult study topic because of its diversity and complexity, and its dispersal processes and influence on the exploration of reservoirs have puzzled most researchers. Based on the comprehensive analysis of the seismic geomorphology and fault combinations, the seismic facies, and the sum of positive amplitude attributes, we describe the characteristics of the sediment dispersal pathways, and discussing its influence on the exploration of sand-rich reservoirs of the middle part of Pinghu Formation in the Pingbei Slope Belt of Xihu Depression (East China Sea Shelf Basin). The results showed that three modes of sediment dispersal system were established by comparing the geological background and the sediment dispersal pathways of the Pingbei Slope Belt. 1) The "straight mode" developed in the Tuanjieting area is characterized by a group of effective pathways directly connected to the channels developed in the land, then go through the marginal fault and ended in the gentle slope. The sand-rich lobes consisted of rapid accumulation of sediments are the most important target for the exploration of reservoirs, the scale of reservoirs could be easily recorded by the measurement of the area and the thickness of the chaotic reflectors developed in this area. 2) The "restricted mode" developed in the Baoyunting area is largely limited by the depression bounded by the uplift, the sediment dispersal pathways are genetically related to the scale and shape of this depression. The depocenters could be a guidance for the development of sand-rich reservoirs, large-scale sand-rich reservoirs could be formed as long as the depression is large enough. 3) The "migration mode" developed in the Kongqueting area is controlled by the slope and normal fault combinations, the long-distance and short-distance sediment dispersal pathways are developed. The area that developed the long-distance sand-rich sediments in the background of relatively low fault growth ratio shall be the most important target for reservoir exploration and easy to form large-scale sand-rich reservoirs.

Eocene coal-bearing source rocks of the Pinghu Formation from the W-3 well in the western margin of the Xihu Sag, East China Sea Shelf Basin were analyzed using Rock-Eval pyrolysis and gas chromatography–mass spectrometry to investigate the samples’ source of organic matter, depositional environment, thermal maturity, and hydrocarbon generative potential. The distribution patterns of n-alkanes, isoprenoids and steranes, high Pr/Ph ratios, abundant diterpanes, and the presence of non-hopanoid triterpanes indicate predominant source input from higher land plants. The contribution of aquatic organic matter was occasionally slightly elevated probably due to a raised water table. High hopane/sterane ratios and the occurrence of bicyclic sesquiterpanes and A-ring degraded triterpanes suggest microbial activity and the input of microbial organisms. Overwhelming predominance of gymnosperm-derived diterpanes over angiosperm-derived triterpanes suggest a domination of gymnosperms over angiosperms in local palaeovegetation during the period of deposition. The high Pr/Ph ratios, the plot of Pr/n-C17 versus Ph/n-C18, the almost complete absence of gammacerane, and the distribution pattern of hopanes suggest that the samples were deposited in a relatively oxic environment. Generally, fluctuation of redox potential is coupled with source input, i.e., less oxic conditions were associated with more aquatic organic matter, suggesting an occasionally raised water table. Comprehensive maturity evaluation based on Ro, Tmax, and biomarker parameters shows that the samples constitute a natural maturation profile ranging from marginally mature to a near peak oil window. Hydrogen index and atomic H/C and O/C ratios of kerogens suggest that the samples mainly contain type II/III organic matter and could generate mixed oil and gas.

The Cenozoic offshore Bohai Bay basin has similar graben-horst configurations as in many rift basins, however, different areas of it have different stratigraphic fill, resulted from jointly effects of basement fabrics, rifting and strike-slipping. Within the Liaodongwan subbasin, the Liaodong rise is a transpressional structural belt bounded by the Tanlu strike-slip fault. The Bodong rise is similar to the Liaodong rise. The eastern Bozhong subbasin has a graben-horst configuration caused by extensional stress. The southern and northwestern parts of the Bozhong subbasin are characterized by large-scale horsts that are limited by south-dipping listric normal faults. The Bozhong subbasin shows many similarities with the faulted sag basin. The southern Bohai Bay basin is characterized by EW-oriented half-grabens and horsts resulted from S-N extensional stress. The Cenozoic evolution of the basin began with Paleogene rifting, followed by the Neogene-Quaternary thermal subsidence stage. The main rifting episode, caused by the upwelling of the mantle, is characterized by strong differential block-faulting during the deposition of the Eocene Sha-3 member. During the deposition of the Oligocene Dongying Formation, previously isolated and scattered sags connected with each other and became a broad and unified lake basin. In addition, the dextral movement of the Tanlu fault zone initiated the development of several transpressional structural belts in fault bends. In the eastern basin, extensional systems were also superimposed by strike-slip systems. During thermal subsidence, neotectonic movement produced many secondary faults in shallower strata, and the dextral movement of the Tanlu fault zone also altered the eastern basin architecture.

The Northeastern Laizhouwan Sag (NLS) is a marginal sag in the Bohai Bay Basin, China. Paleogene source rocks from 3 wells (K-a, K-b and K-c) in this region, i.e., the third to the first member of the Shahejie Formation (Es-3, Es-2, and Es-1), and the third member of the Dongying Formation (Ed(3)) were investigated for their petroleum potentials and depositional environments using geochemical and palynological methods. Among these members, the Es-3 and Es-1 members hold considerable hydrocarbon potential, while the rest are relatively fair. Although there are variations between the wells, the organic matter (OM) in the Es-3 member is primarily composed of low mature or mature type I-II1 kerogen, which were primarily contributed by lower aquatic organisms and prokaryotes. During the Es-3 stage, saline, stratified, and anoxic bottom water prevailed in the K-a well, while freshwater and weak reducing conditions dominated the K-b well. The OM in the Es-1 member was contributed more by lower aquatic organisms than that in the Es-2 member, but both are primarily composed of types II1-II2 kerogen; further, OM in the Es-2 member is low mature, while that for the Es-1 member ranges from immature to low mature, and higher maturity is expected in deeper buried places for the two members. Saline and anoxic bottom water prevailed during the both Es-2 and Es-1 members. Compared with other members, noticeable terrigenous OM was deposited during the Ed(3) stage, which is dominated by immature type II2 kerogen. Lower salinity and weak reducing depositional conditions occurred in the Ed(3) member. OM enrichment in the Es-3 member was mainly determined by primary productivity, while that of the K-a well was also enhanced by the anoxic bottom water condition. The accumulations of OM in other members are speculated to have been controlled by the deposition rate.

Late Jurassic‐Early Cretaceous strike‐slip faults play an important role in basin formation and igneous activities in eastern China and the adjacent areas. Because of the lack of seismic data, their distribution and effect on the formation of basins and igneous activities in the Subei‐South Yellow Sea Basin (SB‐SYSB) are still poorly understood. In this study, based on systematic analyses of the acquired seismic data, the Late Jurassic‐Early Cretaceous strike‐slip faults in the SB‐SYSB were identified and characterized. The strike‐slip faults can be divided into two sets, a NE‐NNE trending sinistral strike‐slip fault system and a NW trending dextral fault system. They present in seismic sections as a flower structure or Y/V‐shaped structure, respectively. In map view, they show horsetail splay faults, en echelon reverse faults, pull‐apart structure, linear structure, or curvilinear structure. These faults resulted in different types of subbasins in the SB‐SYSB, such as transpressional/transtensional subbasins and pull‐apart subbasins. The close relationship between the strike‐slip faults and the distribution of igneous rocks in the SB‐SYSB suggest that the strike‐slip faults probably acted as efficient pathways for magma intrusion during the Late Jurassic‐Early Cretaceous. The sinistral displacement was characterized by thrusting‐folding deformation structures, which show a tendency to decrease toward the Sulu orogenic belt, indicating that the Sulu orogenic belt has probably weakened the strike‐slip movement in the basin. We infer that the sinistral strike‐slip movement in the SB‐SYSB was most likely controlled by the subduction of the paleo‐Pacific plate and the Tan‐Lu strike‐slip faulting.

西湖凹陷具有优越的油气地质条件,已发现多个油气田,但多以低渗致密油气藏为主,面临着经济有效开发及常规油气藏勘探方向不明的两大挑战,迫切需要转变勘探思路与拓展勘探领域.2017年以来,通过对西湖凹陷石油地质条件的重新认识和系统研究,明确了以煤系烃源岩为主的物质基础和通源断裂晚期活化的控制因素,基于这两大地质认识创新提出了多层系立体勘探思路,确定了西湖凹陷油气勘探领域及突破方向:斜坡带下层系(始新统平湖组)复合岩性领域与中央洼陷反转带中、上层系(新近系龙井组以上)浅层领域,取得了平湖斜坡带WY中型油气田的发现及中央带CX油气田浅部层系的突破,拉开了西湖凹陷新的勘探序幕,拓宽了西湖凹陷勘探战场,为东海盆地落实“七年行动计划”开辟了新的储量增长点,对西湖凹陷寻找具有经济价值的优质油气指明了方向.

通过分析分支河流体系的基本特征,对分支河流体系在陆相含油气沉积盆地沉积体系研究和油气勘探中的意义进行分析和讨论.分支河流体系是指河流从某一顶点开始进入盆地并呈放射状展布的沉积体系,包括最大规模的巨型扇、中等规模的河流扇以及小规模的冲积扇.分支河流体系广泛发育在拉张、挤压、走滑和克拉通盆地中,占据了沉积盆地大部分地区;河道呈分支状分布,但不一定同时都在活动;河道规模向下游逐渐减小,泛滥平原和河道所占面积之比不断增加,沉积物粒度逐渐变细.分支河流体系的沉积模式与冲积扇模式外形相似,但内容相差很大.河流流域盆地梯度和流域面积与分支河流体系的表面坡降和面积具有正相关性.分支河流体系是随着现代地球信息技术发展而提出的,也是冲积扇沉积学、河流沉积学和陆相沉积体系研究不断深入的结果,是陆相盆地沉积学与现代计算机和地理信息技术融合发展的结果.分支河流体系的研究促进了扇状沉积体系分类描述的系统化,促进了沉积微相和沉积模式的多样化,促进了沉积过程响应解释的精细化,促进了源汇体系分析的定量化.分支河流体系启发了对陆相盆地沉积体系展布模式、陆相沉积体系中河流沉积作用、陆相盆地岩相古地理格局以及陆相盆地油气勘探潜力的再思考.研究分支河流体系对完善中国陆相沉积储层地质理论体系具有重要意义.

A comparative study on organic geochemistry and kinetics was performed on two representative coal measure mudstone and coal samples of the Eocene Pinghu Formation in the Xihu Sag, East China Sea Shelf Basin, China. Gas chromatography-mass spectrometry analysis of the aliphatic fractions of the source rock extracts was performed to characterize the maturity, depositional conditions, and source materials in the samples. The kerogens isolated from the mudstone and coal were pyrolyzed in a closed-system at two heating rates to determine the kinetics for natural gas generation, and the results were extrapolated to geological conditions. Biomarker assemblages show that the mudstone (type III kerogen) and coal (type II/III kerogen) contain predominantly terrigenous source materials with the effect of microbial reworking, and were deposited under oxic conditions within an unstratified water column. The mudstone has slightly more algal material input and less oxic conditions during deposition than the coal. The rocks are at the early-mature stage but the coal is slightly more mature than the mudstone. The activation energies for natural gas generation from the mudstone and coal distribute mainly in the range of 47-62 kcal/mol and 50-69 kcal/mol with a frequency factor of 2.0 x 10(11) s(-1) and 1.0 x 10(13) s(-1), respectively. The lower activation energies for the mudstone than the coal suggests an earlier onset of natural generation. Assuming a constant burial heating rate of 3 degrees C/Ma for the calculated activation energy distributions, the calculated temperature for a given transformation ratio can differ by > 60 degrees C, indicating varying kinetic stability due to different kerogen composition and structure. This significant and unexpected difference suggests that more attentions should be paid to the kinetic heterogeneity of coal bearing source rocks, and we must be particularly cautious about selecting appropriate kinetic models in petroleum system modeling.

随着地质认识的逐步加深和勘探技术手段的进步,东海陆架盆地西湖凹陷平北斜坡带的勘探领域逐步从构造油气藏转向岩性油气藏.通过系统分析平北斜坡带海陆过渡型沉积体系的层序构成样式、砂体展布特征和油气藏发育模式,指出平北斜坡带存在断裂陡坡型、对向断阶型、反向断阶型和同向断阶型4种层序地层发育样式,对应发育断裂陡坡型潮控三角洲潮道砂岩油气藏、对向断阶型潮控三角洲前缘潮滩砂岩油气藏、反向断阶型河控三角洲前缘水道砂岩油气藏和同向断阶型河控三角洲前缘水道砂岩油气藏4种类型.结合砂体展布规律和油气藏成藏模式预测,对平北斜坡带不同区带岩性油气藏的形成条件和分布规律进行总结,并指出团结亭区断裂陡坡型潮控三角洲潮道砂岩油气藏和孔雀亭区同向断阶型河控三角洲前缘水道砂岩油气藏是该区岩性油气藏勘探重点领域.在该岩性油气藏发育模式指导下,近期针对宝云亭低隆与反向断阶带控制下的宁波19区岩性圈闭钻探取得重大突破.

基于太平洋板块俯冲作用下的东亚陆缘背景,结合盆地结构特征,分析了东海西湖凹陷成盆演化过程.在成盆动力背景上,西湖凹陷新生代断陷盆地发育阶段东亚陆缘中段经历了安第斯型陆缘裂解消亡,并向岛弧型陆缘转变的过程,至断陷结束后的渐新世才逐步开始发育典型沟-弧-盆体系;在成盆演化过程上,中始新世平湖运动、始新世末玉泉运动、渐新世末花港运动和中新世末龙井运动期是西湖凹陷成盆过程转变的关键期,应力背景分别为伸展方向转变、伸展结束、挤压开始和挤压显著增强;在原型盆地演变上,现今盆地为陆缘背景下的分隔型断陷盆地、整体型断-拗转换盆地、大型拗陷盆地和压陷萎缩盆地的垂向叠置.在此基础上,进一步探讨了盆地类型对煤系烃源岩及油气运移的指示意义.

东海盆地西湖凹陷天然气资源丰富,但其成因与来源一直存在较大争议.综合分析天然气组分、碳同位素组成、轻烃指纹以及天然气伴生凝析油地球化学特征,对西湖凹陷天然气的成因、热演化程度与族群划分进行了探讨,在此基础上利用不同烃源岩热模拟产物碳同位素特征与伴生凝析油特征进行了气源分析.西湖凹陷天然气为煤型气,形成于中等成熟—高成熟热演化阶段,对应的Ro值约为1.16％～1.87％.西胡凹陷天然气可以划分为4个族群,其中A、B与C类天然气分别分布于平湖斜坡、黄岩构造带和宁波构造带,D类天然气零星分布于平湖斜坡.西湖凹陷A类天然气主要来源于平湖组煤,B类天然气主要来源于平湖组泥岩,C类天然气主要来源于高热演化阶段的平湖组煤,D类天然气中有3个样品来源于平湖组炭质泥岩,1个气样可能有中下始新统烃源岩贡献.本文研究结果可为西湖凹陷的天然气勘探提供理论依据和技术支持.

郯庐走滑断裂带穿过渤海湾盆地黄河口凹陷和莱西构造带,为了探讨走滑构造带内断裂发育特征、成因机制及其对油气控制作用,依据方差切片、三维可视化及精细地震解释技术对走滑构造带进行研究.结果 表明,渤海湾盆地南部走滑构造带内发育“云梯式”和“栅栏式”两种断裂体系,断裂演化主要经历了中生代左旋走滑、古近纪伸展-走滑和新近纪强烈右旋走滑3个阶段.走滑构造带不仅控制了圈闭的形成,而且还影响了中、深层沉积体系的分布和油气的富集层位.结合不同构造部位油气富集特征,建立了走滑构造带内“中转站式”、“网毯式”、“复合式”及“阶梯式”等4类油气成藏模式,近些年指导发现了一系列大中型油气田,为下一步油气勘探指明了方向.

在回顾渤海海域盆地(渤海湾盆地海域部分)油气勘探历程及相关石油地质理论研究的基础上,总结了渤海海域盆地的新生代构造-沉积演化历程,分析了渤海海域盆地的石油地质条件,着重指出了与相邻陆区的显著差异.首先,渤海海域盆地两期构造旋回相应发育了沙河街组和东营组两套优质烃源岩,其中东营组烃源岩为海域盆地所特有,且晚期快速沉降有助于其成熟,因此,渤海海域盆地具有更为优越的烃源条件;其次,渤海海域盆地新近系广泛发育浅水-极浅水三角洲,是海域特有的一套勘探层系;最后,郯庐断裂带海域部分的长期持续活动最终形成了渤海海域盆地大中型油气田集中分布的油气富集带,是当前渤海油气勘探的重要领域.充分认识渤海海域盆地演化的特殊性及其独特的石油地质条件和油气富集规律,对今后的渤海油气勘探及相关研究具有参考价值.

This research study presents the results of an integrated study employing core samples, wireline logs, and seismic dataset collected in the study area for analysing the syn‐depositional fault's control of the evolution of the axial meandering river delta‐sublacustrine fan deposits during the Ed2x depositional period. The results indicate that the delta deposits that had developed during a retrogressive period, with the characteristics of retrogressive stacking patterns, had resulted from a high subsidence rate caused by the syn‐depositional faults with large fault throw. These appeared to be characterized by strong amplitude, low frequency, and continuous seismic reflections on the seismic profiles, and high‐amplitude serrated cylinder‐shaped stacking patterns in the wireline logs, with no obvious sedimentary structures. In contrast, the delta deposits developed during a progressive period and characterized by progressive stacking patterns were determined to have resulted from a low subsidence rate caused by the syn‐depositional faults with small fault throw. They were found to be characterized by weak‐to‐medium amplitude vermicule‐shaped seismic reflections, as well as low‐amplitude bell‐shaped or funnel‐shaped stacking patterns, with soft‐sediment deformation structures.

The Huanghekou Sag is located at the southeast part of the Bohai Bay Basin, northern China. Large-scale shallow lake delta developed in the Neogene provided suitable geological conditions for the formation of a subtle oil-gas reservoir in this area. The key for analyzing sandstone reservoir and sedimentary facies is by using seismic attributes (amplitude) to establish the relationship between lithology combination and seismic attributes. The lower unit of Late Miocene Minghuazhen Formation at the BZ34 block in the Huanghekou Sag was subdivided into 10 parasequence sets (PSS). Thicker sandstones mainly occurred in PSS1 and PSS10, whereas thin sandstones are mostly observed within other parasequence sets. This study presents statistics and analyses of lithology, i.e., statistics of root-mean-square (RMS) amplitude and lithology of well locations in different parasequence sets of the study area, as well as 1-D forward seismic models of 7 types of lithology combinations, the establishment of a spatial distribution of 2-D sandbody, forward seismic models etc. Our study indicates that high amplitude peaks correspond to thicker sandbodies, while low amplitude indicates non-development of sandbodies (generally less than 2 m), and medium amplitude agrees well with large sets of mudstones interbedded with medium and thinner sandstones. Different sand–mudstone combinations genetically reflect a combination of multiple micro-facies, therefore, amplitude features can predict sandbodies as well as facies characteristics.