Factors Controlling Organic Matter Enrichment in Alkaline Lacustrine Source Rocks:A Case Study of the Late Paleozoic Fengcheng Formation in the Junggar Basin,NW China

The late Paleozoic Fengcheng Formation shale(LPF shale)in the Junggar Basin,NW China,is the oldest alkaline source rock discovered in the world,providing a unique perspective with which to explore organic matter(OM)enrichment in alkaline lake environments.Combined with the organic carbon isotope profile and paleoenvironmental proxies,this study reveals that the LPF shale was deposited in an arid climate with high salinity and a strong reducing environment,accompanied by frequent volcanic activity.High TOC values are concentrated in two intervals with frequent fluctuations in OM types.A negative excursion due to changes in sedimentary OM source is found in the δ^(13)C_(org) profile.The excursion corresponds to the OM enrichment interval and is accompanied by abnormally high values of Sr/Ba and Sr/Cu.This implies that the extreme arid climate has led to high salinity,resulting in strong reducibility and changes in paleontological assemblages,which in turn controlled the differential enrichment of OM.The Fengcheng Fm.high-quality source rocks are the result of the combined action of climatic events,volcanism,high-salinity water environment and superior hydrocarbon-generating organisms.The results provide new insights into the formation conditions of terrestrial alkaline high-quality source rocks and the factors controlling alkaline OM enrichment.

Simulation for the Controlling Factors of Structural Deformation in the Southern Margin of the Junggar Basin

According to the differences of structural deformation characteristics, the southern margin of the Junggar basin can be divided into two segments from east to west. Arcnate thrust-and-fold belts that protrude to the north are developed in the eastern segment. There are three rows of en echelon thrust-and-fold belts in the western segment. Thrust and fold structures of basement-involved styles are developed in the first row, and decollement fold structures are formed from the second row to the third row. In order to study the factors controlling the deformation of structures, sand-box experiments have been devised to simulate the evolution of plane and profile deformation. The planar simulation results indicate that the orthogonal compression coming from Bogeda Mountain and the oblique compression with an angle of 75° between the stress and the boundary originating from North Tianshan were responsible for the deformation differences between the eastern part and the western part. The Miquan-Uriimqi fault in the basement is the pre-existing condition for generating fragments from east to west. The profile simulation results show that the main factors controlling the deformation in the eastern part are related to the decollement of Jurassic coal beds alone, while those controlling the deformation in the western segment are related to both the Jurassic coal beds and the Eogene clay beds. The total amount of shortening from the Yaomoshan anticline to the Gumudi anticline in the eastern part is -19.57 km as estimated from the simulation results, and the shortening rate is about 36.46%; that from the Qingshuihe anticline to the Anjihai anticline in the western part is -22.01 km as estimated by the simulation results, with a shortening rate of about 32.48%. These estimated values obtained from the model results are very close to the values calculated by means of the balanced cross section.

Controlling factors and models of shale oil enrichment in Lower Permian Fengcheng Formation,Mahu Sag,Junggar Basin,NW China

Based on the combination of core observation,experimental analysis and testingand geological analysis,the main controlling factors of shale oil enrichment in the Lower Permian Fengcheng Formation in the Mahu Sag of the Junggar Basin are clarified,and a shale oil enrichment model is established.The results show that the enrichment of shale oil in the Fengcheng Formation in the Mahu Sag is controlled by the organic abundance,organic type,reservoir capacity and the amount of migration hydrocarbon in shale.The abundance of organic matter provides the material basis for shale oil enrichment,and the shales containing typesⅠandⅡorganic matters have good oil content.The reservoir capacity controls shale oil enrichment.Macropores are the main space for shale oil enrichment in the Fengcheng Formation,and pore size and fracture scale directly control the degree of shale oil enrichment.The migration of hydrocarbons in shale affects shale oil enrichment.The shale that has expelled hydrocarbons has poor oil content,while the shale that has received hydrocarbons migrated from other strata has good oil content.Lithofacies reflect the hydrocarbon generation and storage capacity comprehensively.The laminated felsic shale,laminated lime-dolomitic shale and thick-layered felsic shale have good oil content,and they are favorable lithofacies for shale oil enrichment.Under the control of these factors,relative migration of hydrocarbons occurred within the Fengcheng shale,which leads to the the difference in the enrichment process of shale oil.Accordingly,the enrichment mode of shale oil in Fengcheng Formation is established as"in-situ enrichment"and"migration enrichment".By superimposing favorable lithofacies and main controlling factors of enrichment,the sweet spot of shale oil in the Fengcheng Formation can be selected which has great significance for the exploration and development of shale oil.

Coalbed Methane Enrichment Regularity and Major Control Factors in the Xishanyao Formation in the Western Part of the Southern Junggar Basin

There are abundant coal and coalbed methane(CBM)resources in the Xishanyao Formation in the western region of the southern Junggar Basin,and the prospects for CBM exploration and development are promising.To promote the exploration and development of the CBM resources of the Xishanyao Formation in this area,we studied previous coalfield survey data and CBM geological exploration data.Then,we analyzed the relationships between the gas content and methane concentration vs.coal seam thickness,burial depth,coal reservoir physical characteristics,hydrogeological conditions,and roof and floor lithology.In addition,we briefly discuss the main factors influencing CBM accumulation.First,we found that the coal strata of the Xishanyao Formation in the study area are relatively simple in structure,and the coal seam has a large thickness and burial depth,as well as moderately good roof and floor conditions.The hydrogeological conditions and coal reservoir physical characteristics are also conducive to the enrichment and a high yield of CBM.We believe that the preservation of CBM resources in the study area is mainly controlled by the structure,burial depth,and hydrogeological conditions.Furthermore,on the basis of the above results,the coal seam of the Xishanyao Formation in the synclinal shaft and buried at depths of 700-1000 m should be the first considered for development.

Geological characteristics and high production control factors of shale gas reservoirs in Silurian Longmaxi Formation, southern Sichuan Basin, SW China

Marine shale gas resources have great potential in the south of the Sichuan Basin in China.At present,the high-quality shale gas resources at depth of 2000–3500 m are under effective development,and strategic breakthroughs have been made in deeper shale gas resources at depth of 3500–4500 m.To promote the effective production of shale gas in this area,this study examines key factors controlling high shale gas production and presents the next exploration direction in the southern Sichuan Basin based on summarizing the geological understandings from the Lower Silurian Longmaxi Formation shale gas exploration combined with the latest results of geological evaluation.The results show that:(1)The relative sea depth in marine shelf sedimentary environment controls the development and distribution of reservoirs.In the relatively deep water area in deep-water shelf,grade-I reservoirs with a larger continuous thickness develop.The relative depth of sea in marine shelf sedimentary environment can be determined by redox conditions.The research shows that the uranium to thorium mass ratio greater than 1.25 indicates relatively deep water in anoxic reduction environment,and the uranium to thorium mass ratio of 0.75–1.25 indicates semi-deep water in weak reduction and weak oxidation environment,and the uranium to thorium mass ratio less than 0.75 indicates relatively shallow water in strong oxidation environment.(2)The propped fractures in shale reservoirs subject to fracturing treatment are generally 10–12 m high,if grade-I reservoirs are more than 10 m in continuous thickness,then all the propped section would be high-quality reserves;in this case,the longer the continuous thickness of penetrated grade-I reservoirs,the higher the production will be.(3)The shale gas reservoirs at 3500–4500 m depth in southern Sichuan are characterized by high formation pressure,high pressure coefficient,well preserved pores,good pore structure and high proportion of free gas,making them the most favorable new field for shale gas exploration;and the pressure coefficient greater than 1.2 is a necessary condition for shale gas wells to obtain high production.(4)High production wells in the deep shale gas reservoirs are those in areas where Long11-Long13 sub-beds are more than 10 m thick,with 1500 m long horizontal section,grade-I reservoirs penetration rate of over 90%,and fractured by dense cutting+high intensity sand injection+large displacement+large liquid volume.(5)The relatively deep-water area in the deep-water shelf and the area at depth of 3500–4500 m well overlap in the southern Sichuan,and the overlapping area is the most favorable shale gas exploration and development zones in the southern Sichuan in the future.With advancement in theory and technology,annual shale gas production in the southern Sichuan is expected to reach 450×108 m3.

Geological Controls on the CBM Productivity of No.15 Coal Seam of Carboniferous–Permian Taiyuan Formation in Southern Qinshui Basin and Prediction for CBM High-yield Potential Regions

Coalbed methane(CBM) resources in No.15 coal seam of Taiyuan Formation account for 55% of the total CBM resources in southern Qinshui Basin(SQB), and have a great production potential. This study aims at investigating the CBM production in No.15 coal seam and its influence factors. Based on a series of laboratory experiments and latest exploration and development data from local coal mines and CBM companies, the spatial characteristics of gas production of No.15 coal seam were analyzed and then the influences of seven factors on the gas productivity of this coal seam were discussed, including coal thickness, burial depth, gas content, ratio of critical desorption pressure to original coal reservoir pressure(RCPOP), porosity, permeability, and hydrogeological condition. The influences of hydrological condition on CBM production were analyzed based on the discussions of four aspects: hydrogeochemistry, roof lithology and its distribution, hydrodynamic field of groundwater, and recharge rate of groundwater. Finally, a three-level analytic hierarchy process(AHP) evaluation model was proposed for predicting the CBM potentials of the No.15 coal seam in the SQB. The best prospective target area for CBM production of the No.15 coal seam is predicted to be in the districts of Panzhuang, Chengzhuang and south of Hudi.

四川盆地南部地区五峰组—龙马溪组深层页岩气富集控制因素新认识

近年来,随着四川盆地五峰组—龙马溪组页岩气勘探开发迈向深层(埋深介于3500~4500 m),在四川盆地南部(下文简称川南)地区的泸州、长宁和渝西等区块深层页岩气不断取得了重要突破,展现了深层页岩气良好的开发前景。为了准确认识川南地区深层页岩在局部地区出现的低电阻率、高含水饱和度、测试微气现象,分别从页岩有机质成熟演化、页岩气源内运移特征和区域多期断裂活动影响等3个方面系统地分析了页岩气富集控制因素。研究结果表明:①高—过成熟度有机质石墨化造成了页岩电阻率和含气量明显降低,在有机质成熟度(Ro)大于3.6%以后,有机质生气能力衰竭,颗粒孔隙度明显降低,含水饱和度明显升高;②页岩气存在“源内侧向运移”特征,含气性与现今构造区带构造位置相对高低相关,表现为相对海拔高部位含气饱和度高,相对海拔低部位含气饱和度低;③Ⅰ级断裂对天然气的散失有显著的控制作用,建议距离Ⅰ级断裂1.5 km范围内勿部署实施井位,Ⅱ级断裂对含气性影响范围有限,距离Ⅱ级断层700 m以外时对页岩气体积压裂的影响较小。结论认为,充分考虑页岩有机质热演化程度、构造位置相对高低关系以及断裂发育特征等因素对深层页岩气富集的影响,有利于完善深层页岩气评价标准,对认识深层页岩气资源潜力以及优选有利区,具有重要现实意义,并可为推动实现深层页岩气规模增储和效益开发提供理论支撑。

玛湖凹陷及周缘白碱滩组勘探突破与新认识

为明确玛湖凹陷白碱滩组砂体分布规律和油气成藏模式,评价其油气勘探前景,综合钻井、测井、地震、分析化验等资料,系统梳理白碱滩组二段沉积规律和成藏特征。白碱滩组二段为辫状河三角洲—滩坝—浊积扇沉积序列,发育水下分流河道砂、滩坝砂和浊积砂3种不同类型的砂体,辫状河三角洲前缘亚相以河道砂为主,滨—浅湖发育滩坝砂,半深湖—深湖受坡折带控制发育多个浊积扇体,浊积砂呈朵叶状分布,建立了水下分流河道—滩坝—浊积扇的沉积控砂模式。研究区发育9大走滑断裂体系,其中,走滑断裂直通型、走滑断裂伴生型和走滑断裂接力型3种断裂组合能够有效沟通二叠系风城组烃源岩,作为油气垂向高效运移通道,白碱滩组二段整体具有走滑断裂通源、断裂砂体配置控藏和优质储集层富集的成藏模式。

准噶尔盆地中拐凸起东斜坡上乌尔禾组常规—致密油藏主控因素及成藏模式

准噶尔盆地中拐凸起东斜坡上乌尔禾组油气资源丰富,是效益勘探及建产的重要领域。应用测录井、生产测试及岩心分析化验资料,研究中拐凸起东斜坡上乌尔禾组储层特征,明确储层差异性的主控因素,建立中拐凸起东斜坡常规—致密油藏序次分布的成藏模式。结果表明:自北部向南部,研究区逐步由常规油藏转化为致密油藏,沉积作用是造成储层差异性的物质基础,控制储层岩性及原始物性,压实作用和浊沸石胶结作用加剧储层常规—致密差异演化;研究区成岩相带划分为泥质充填带、贫泥—弱胶结带、浊沸石胶结带和强压实—弱溶蚀带4种相带,其中贫泥—弱胶结带为有利储层发育带。该结果为研究区致密油藏勘探提供指导。

准噶尔盆地南缘西段齐古组深层储层特征及物性控制因素

准噶尔盆地南缘西段齐古组深层碎屑岩储层油气勘探潜力巨大,但目前针对其储层特征及物性控制因素尚缺乏系统研究,制约了后期油气勘探进程。本文综合利用铸体薄片、扫描电镜、物性、压汞及包裹体等资料,并结合区域埋藏史及古地温等相关成果,对齐古组储层岩石学特征、物性特征、成岩作用特征及物性控制因素进行系统研究。结果表明,齐古组储层具有低成分成熟度、高塑性岩屑含量及中等结构成熟度的岩石学特征。尽管储层主体埋深大于3500 m,但储集空间仍以粒间孔为主,平均孔隙度为10.29%,平均渗透率为34.12×10^(-3)μm^(2),总体上属低孔低渗储层,但仍发育部分中-高孔渗储层。储层成岩作用主要有压实作用、胶结作用及溶蚀作用,成岩强度相对较弱,主体处于早成岩B期—中成岩A期,并表现为压实强度中等、胶结物含量较低且晚期发育酸性溶蚀的特征。富石英与长石、贫岩屑以及分选好等特征有利于储层物性的保存,而储层物性损失以压实减孔最为显著,但储层内部绿泥石包壳及中成岩期的酸性溶蚀作用可有效改善储层物性。此外,齐古组地层早期长期浅埋、后期短期快速深埋、地层超压及较低的古地温梯度等因素延缓了储层成岩进程,进而降低成岩作用强度,导致齐古组优质储层得以有效保存。

准噶尔盆地深层-超深层碎屑岩致密气储层特征及其控制因素

为寻找准噶尔盆地深层-超深层有利碎屑岩致密气储层,利用钻井、录井、薄片及化验资料,研究了碎屑岩致密气储层发育特征、储集空间类型、物性变化特征及有利储层控制因素。研究结果表明:①深层-超深层有利碎屑岩致密气储层储集岩主要为三角洲砾岩和砂岩,以细砾(砂)岩、中砾(砂)岩及中-细砾(砂)岩为主,为岩屑类砂岩。砾石成分和砂岩岩屑以凝灰岩为主,胶结物主要为方解石,局部富集沸石类。②储集空间为孔隙和裂缝,以孔隙为主。储集空间有孔隙型、裂缝型和孔隙-裂缝混合型3种组合类型。孔隙主要为原生剩余孔隙和次生溶蚀孔隙,以次生溶蚀孔隙为主。裂缝以成岩压实微裂缝和构造裂缝为主。③碎屑岩致密气储层垂向上形成了3个次生孔隙发育带。④岩石成分、建设型成岩作用和异常高压是控制有利储层的主要因素,3个主要因素控制了盆地深层-超深层碎屑岩致密气有利储层的发育和分布。

深层致密砂岩储层非均质性特征及控制因素——以准噶尔盆地永进地区侏罗系齐古组为例

以准噶尔盆地永进地区侏罗系齐古组为例,根据岩心、薄片、储层物性和测井数据等资料,分析深层致密砂岩储层非均质性特征并进行综合表征,明确储层非均质性控制因素。结果表明:研究区齐古组自下而上分为1~6小层,粒度韵律和渗透率韵律以正韵律为主,在层内非均质性方面,3小层的非均质性最强;在层间非均质性方面,1~3小层砂体展布面积大且连通性好,3小层砂体最发育;在平面非均质性方面,1~4小层具有较强非均质性。3小层的非均质性最强,其次分别为2小层、4小层和1小层的。沉积作用影响砂体展布及物质组成,是导致储层非均质性的基础,成岩作用能够改善孔隙结构和类型,是影响储层非均质性的关键因素。该结果对准噶尔盆地永进地区油气勘探具有指导意义。

中拐凸起南斜坡八道湾组油层低阻成因及识别

准噶尔盆地中拐凸起南斜坡下侏罗统八道湾组低阻油层与一般低阻油层对比,储集层具有形成时期早、埋藏深度大、岩石粒度较大、泥质含量低等特点,低阻成因具有较强特殊性。在对国内外典型低阻油层成因机理综合研究的基础上,利用该区钻井、录井、测井、试井、岩心化验分析等资料,从构造、沉积、成岩作用、储集层特征、成藏条件等多角度,开展八道湾组油藏低阻主控因素研究。该区油藏低阻的形成受宏观因素和微观因素共同控制,低构造幅度、弱水动力沉积等宏观背景下,低油水分异程度、高地层水矿化度及低凝灰岩岩屑含量,是油藏低阻的主控因素;束缚水饱和度偏低,是油藏低阻的次要控制因素。在此基础上,建立地层电阻率与油气指示系数关系图版,与该区试油和试采资料对比,符合率92.9%,为中拐凸起南斜坡八道湾组低阻油层的识别提供了依据。

沙湾凹陷上乌尔禾组储层特征及控制因素分析

沙湾凹陷上乌尔禾组成藏条件同玛湖凹陷相似,但储层基本特征以及控制因素较为模糊,阻碍了该地区目的储层进一步勘探和开发。在前人研究基础上,利用岩芯观察、薄片、扫描电镜、压汞及物性等研究手段,对研究区上乌尔禾组分段的储层岩石学特征、储集特征及控制因素进行详细分析。结果表明,乌一段岩性以砂砾岩为主,储集空间以原生粒间孔为主,普遍见片状片弯状喉道,属于特低孔特低渗储层;乌二段岩性以含砾砂岩为主,储集空间以原生粒间孔和粒间溶孔为主,发育片状喉道,属于低孔中低渗储层。沉积和成岩因素为储层质量主要控制因素,沉积环境和凝灰质含量控制优质储层的分布和储集性能,成岩因素中压实作用对储层物性影响最大,胶结和溶蚀作用造成储层物性进一步产生差异,异常压力对储层质量有一定的改善。以上因素造成乌二段孔隙结构较为复杂,储层质量相对较好。

准噶尔盆地东道海子凹陷二叠系下乌尔禾组陆相页岩气形成富集条件及主控因素

为探明准噶尔盆地二叠系下乌尔禾组页岩气富集条件及主控因素,以东道海子凹陷下乌尔禾组为研究对象,通过野外地质观察、录井、测井、地震等资料的收集,结合总有机碳含量测定、X衍射全岩分析、岩心观察、气体吸附(N_(2)、CO_(2))等手段,对下乌尔禾组页岩的分布特征、有机质发育特征、储层特征及含气性特征进行了研究。结果表明:(1)下乌尔禾组页岩总有机碳含量(w(TOC))较高,平均1.58%;有机质类型以Ⅱ_(2)型和Ⅲ型为主;镜质体反射率Ro平均1.46%,处于成熟阶段;烃源岩厚度平均75 m,烃源岩较好,生气潜力大。盆地模拟结果表明下乌尔禾组页岩含气量较好,平均1.89 m^(3)/t。(2)页岩储集层粒内孔和微裂缝较为发育;气体主要吸附于微孔和介孔;孔隙度均值6.10%,渗透率均值为0.27×10^(-3)μm^(2),有利于页岩气的聚集。(3)页岩黏土矿物体积分数较高,均值29.6%,能提供较高的比表面积,增加页岩的气体吸附能力;脆性矿物体积分数均值50.9%,压裂改造性良好。(4)页岩储层压力系数较大,均值为1.58,具有良好的保存条件。结合区域构造—沉积环境以及地化参数的分析表明,东道海子凹陷下乌尔禾组页岩气成藏的主控因素包括地化参数和保存条件,其中有机质热演化成熟度高、页岩厚度大、w(TOC)高、良好的保存条件等是影响页岩气富集的关键因素。基于上述条件,提出东道海子凹陷页岩气勘探开发有利区位于凹陷的腹部偏东北斜坡地区。该研究成果揭示了东道海子凹陷下乌尔禾组页岩气富集条件及主控因素,对准噶尔盆地腹部地区深层油气勘探具有借鉴意义。

吉南凹陷二叠系井井子沟组二段致密砂岩储层特征及影响因素

吉南凹陷是准噶尔盆地东部新发现的含油凹陷,其中二叠系井井子沟组二段是该凹陷最主要的含油层系。基于多口井的岩心常规分析、常规薄片、铸体薄片、扫描电镜及黏土矿物X射线衍射分析等资料,系统开展了吉南凹陷井井子沟组二段砂岩储层岩矿特征、储层物性及孔隙特征、影响储层物性的主要因素研究。研究表明,井井子沟组二段砂岩储层为低矿物成熟度、中等结构成熟度,属于低—特低孔、特低—超低渗、纳米级吼道、处于中成岩A期的致密储层特征。通过定性、半定量分析,认为压实作用、胶结作用,特别是早期碳酸盐胶结作用是导致致密储层形成的主要因素,中成岩期的溶蚀作用有效地改善了储层物性。计算结果表明,井井子沟组二段砂岩储层原始孔隙度平均约27.1%,压实作用及胶结作用减孔量平均为11.3%、9.8%,溶蚀作用增孔量平均约为3.4%。

新疆油田强水敏砾岩油藏二氧化碳驱连通特征

明确CO_(2)驱油藏注采井间连通特征可为后续针对性实施CO_(2)驱波及效率改善技术提供基础支撑。以新疆油田某强水敏砾岩油藏为研究对象,通过现场注采相关数据分析,明确注采连通性判断关键参数,预设关键参数比重后设计评价系数C,确定C值不同取值范围下注采井间连通关系,建立一套强水敏砾岩油藏连通性评判方法。通过该方法可判断该区注采井间弱连通、中等连通、强连通情况,分析不同连通特征主控因素,形成针对性治理对策。研究表明,注采连通性判断关键参数为生产井产油量、油压、气体组分;C值大于8时注采井属于强连通关系,C值在3~8时注采井属于中等连通关系,C值小于3时注采井属于弱连通关系。统计全区注采数据,根据C值判断,区块注采井间连通性呈两种明显连通特征,一是注采连通具有方向性,中强连通主要偏西北方向,但局部连通具有一定差异性,分析主要受构造及前期水驱影响;其次是注采连通具有区域性,区块中心偏东北注采连通性较好,该区22口井中强连通井14口,占比达63.6%,主要受地层渗透性差异及注碳量影响。根据注采连通性判断结果,建议对该区各类连通井分类治理,边缘区弱连通井吞吐补能,核心区弱连通井小规模压裂,强连通井封窜调剖。本研究可对提升强水敏砾岩油藏注水后CO_(2)驱高效开发提供参考和借鉴。

Unconformity structures controlling stratigraphic reservoirs in the north-west margin of Junggar basin, North-west China

Tectonic movements formed several unconfor- mities in the north-west margin of the Junggar basin. Based on data of outcrop, core, and samples, the unconformity is a structural body whose formation associates with weath- ering, leaching, and onlap. At the same time, the structural body may be divided into three layers, including upper layer, mid layer, and lower layer. The upper layer with good primary porosity serves as the hydrocarbon migration system, and also accumulates the hydrocarbon. The mid layer with compactness and ductility can play a role as cap rock, the strength of which increases with depth. The lower layer with good secondary porosity due to weathering and leaching can form the stratigraphic truncation traps. A typical stratigraphie reservoir lying in the unconformity between the Jurassic and Triassic in the north-west margin of the Junggar basin was meticulously analyzed in order to reveal the key controlling factors. The results showed that the hydrocarbon distribution in the stratigraphic onlap reservoirs was controlled by the onlap line, the hydro- carbon distribution in the stratigraphic truncation reser- voirs was confined by the truncation line, and the mid layer acted as the key sealing rock. So a conclusion was drawn that ＂two lines （onlap line and truncation line） and a body （unconformity structural body）＂ control the formation and distribution of stratigraphic reservoirs.

Complex Petroleum Migration and Accumulation in Central Region of Southern Junggar Basin,Northwest China

The central region of the southern Junggar basin （Northwest China） is a key exploration target in this petroliferous basin. As there are four sets of potential source rocks （e.g., Permian, Jurassic, Cretaceous and Paleogene sequences）, petroleum migration and accumulation are likely complex. This study represents an attempt to understand this complexity in order to provide fundamental information for future regional petroleum exploration and geological studies. Based on petroleum geology and geochemistry, it is implied that there are mainly three types of hydrocarbons, including Cretaceous- and Paleogene-sourced oils （with the former being dominant） and Jurassic-sourced gas. The petroleum migration and accumulation mainly cover three stages. The first stage is the late period of the Early Pleistocene, in which the Cretaceous-sourced oils migrate and accumulate. Then, in the second stage （from the late period of the Middle Pleistocene to the early period of the Late Pleistocene）, the Cretaceous- sourced oils, together with the Paleogene-sourced oils, participate in the migration and accumulation. At last, in the end of the Late Pleistocene, large quantities of oils remigrate and accumulate, with gas （especially Jurassic- sourced gas） migrating along faults to accumulate. Thus, petroleum charge events in the area are complex, reflecting the control of complex tectonic evolution on petroleum migration and accumulation.

准噶尔盆地玛湖凹陷风城组页岩油富集主控因素与模式

通过岩心观察、实验分析测试和地质剖析等多方法相结合,研究准噶尔盆地玛湖凹陷下二叠统风城组页岩油富集主控因素,建立页岩油富集模式。研究结果表明,玛湖凹陷风城组页岩油的富集受到有机质丰度和类型、储集能力以及运移烃量的联合控制,具体表现为:①高有机质丰度为页岩油的富集提供了物质基础,有机质类型为Ⅰ型和Ⅱ型的页岩含油性较好;②储集能力制约页岩油富集,宏孔是风城组页岩油富集的主要空间,孔隙大小和裂缝规模直接控制了页岩油的富集程度;③页岩层系内烃类的运移影响页岩油富集,发生了排烃作用的页岩含油性差,而接受了外来运移烃的页岩含油性显著更好;④岩相能综合反映页岩油的生烃及储集能力,纹层状长英质页岩、纹层状灰云质页岩和厚层状长英质页岩含油性较好,为页岩油富集的有利岩相。受控于以上因素,风城组页岩层系内部存在烃类的相对运移,导致页岩油富集过程差异,据此建立的风城组页岩油的富集模式为“原地富集”和“运移富集”两种类型。通过有利岩相与富集主控因素叠合,可以优选出风城组页岩油甜点段,对页岩油勘探开发具有重要意义。