Differential Hydrocarbon Enrichment and its Main Controlling Factors in Depressions of the Bohai Bay Basin

Significant differential hydrocarbon enrichment occurs in depressions in a petroliferous basin. There are multiple depressions in the Bohai Bay Basin, and each depression as a relatively independent unit of hydrocarbon generation, migration and accumulation, contains significantly different hydrocarbon generation conditions and enrichment degree. On the basis of previous documents and a large number of statistical data, this work comparatively analyzed the differential hydrocarbon enrichment and its major controlling factors in depressions of the Bohai Bay Basin. The results show that depressions in the Bohai Bay Basin have various hydrocarbon enrichment degrees, and can be categorized into four types, namely enormously oil-rich, oil-rich, oily and oil-poor depressions. In general, the enormously oil-rich and oil-rich depressions are distributed in the eastern part of the basin along the Tan–Lu and Lan–Liao faults, whereas depressions in the western part of the basin are poor in hydrocarbons. Moreover, the vertical distribution of hydrocarbons is also highly heterogeneous, with Pre-Paleogene strata rich in hydrocarbons in the northern and western depressions, Paleogene strata rich in hydrocarbons in the entire basin, and Neogene strata rich in hydrocarbons in the off-shore areas of the Bohai Bay Basin. From early depressions in onshore areas to the late depressions in offshore areas of the Bohai Bay Basin, the source rocks and source-reservoir-cap rock assemblages gradually become younger and shallower, and the hydrocarbon resource abundance gradually increases. Hydrocarbon supplying condition is the key factor constraining the hydrocarbon enrichment for different depressions, while the main source-reservoir-cap rock assemblage, sufficient hydrocarbons and the transportation capacity of faults control the vertical distribution of hydrocarbons. The main factors controlling hydrocarbon enrichment are different for different layers. The hydrocarbon supplying condition of source rocks is the key controlling factor, whereas the source-reservoir configuration, the main source-reservoir-cap rock assemblages, and the fault transportation are the main factors of hydrocarbon enrichment in the Paleogene, Paleogene and Neogene, respectively.     

Differential Hydrocarbon Enrichment and its Main Controlling Factors in Depressions of the Bohai Bay Basin Differential Hydrocarbon Enrichment and its Main Controlling Factors in Depressions of the Bohai Bay Basin

Significant differential hydrocarbon enrichment occurs in depressions in a petroliferous basin.There are multiple depressions in the Bohai Bay Basin, and each depression as a relatively independent unit of hydrocarbon generation, migration and accumulation, contains significantly different hydrocarbon generation conditions and enrichment degree. On the basis of previous documents and a large number of statistical data, this work comparatively analyzed the differential hydrocarbon enrichment and its major controlling factors in depressions of the Bohai Bay Basin. The results show that depressions in the Bohai Bay Basin have various hydrocarbon enrichment degrees, and can be categorized into four types, namely enormously oil-rich, oil-rich, oily and oil-poor depressions. In general, the enormously oil-rich and oil-rich depressions are distributed in the eastern part of the basin along the Tan-Lu and Lan-Liao faults, whereas depressions in the western part of the basin are poor in hydrocarbons. Moreover, the vertical distribution of hydrocarbons is also highly heterogeneous, with Pre-Paleogene strata rich in hydrocarbons in the northern and western depressions, Paleogene strata rich in hydrocarbons in the entire basin, and Neogene strata rich in hydrocarbons in the off-shore areas of the Bohai Bay Basin. From early depressions in onshore areas to the late depressions in offshore areas of the Bohai Bay Basin, the source rocks and source-reservoir-cap rock assemblages gradually become younger and shallower, and the hydrocarbon resource abundance gradually increases. Hydrocarbon supplying condition is the key factor constraining the hydrocarbon enrichment for different depressions,while the main source-reservoir-cap rock assemblage, sufficient hydrocarbons and the transportation capacity of faults control the vertical distribution of hydrocarbons. The main factors controlling hydrocarbon enrichment are different for different layers. The hydrocarbon supplying condition of source rocks is the key controlling factor, whereas the source-reservoir configuration, the main sourcereservoir-cap rock assemblages, and the fault transportation are the main factors of hydrocarbon enrichment in the Paleogene, Paleogene and Neogene, respectively.     

渤海湾盆地古近纪古地理特征与油气*

渤海湾盆地是一个典型的内陆裂谷盆地,内部发育6个坳陷、4个隆起、54个凹陷和44个凸起。沉积盆地的含油气性与其古地理分布有密切的关系。利用渤海湾盆地各坳陷大量的录井、岩心、古生物、测井、地震资料及前人的大量文献和数据,对渤海湾盆地各坳陷古近系孔店组、沙河街组沙四段、沙三段、沙二段、沙一段、东营组进行了全区对比和统层。在此基础上,对冀中坳陷、济阳坳陷、临清坳陷内东濮凹陷各组段的沉积相进行了分析,编制了这些区域的古地理图;充分利用前人文献和科研报告中所编制的辽河坳陷、黄骅坳陷、渤海海域古近系各组段的古地理图,编制了渤海湾盆地孔店组、沙河街组沙四段、沙三段、沙二段、沙一段、东营组的古地理图。渤海湾盆地发育数十个含油气凹陷,每个凹陷中心的深湖亚相泥岩构成烃源岩,而在凹陷的边缘发育近岸水下扇、扇三角洲、三角洲、滩坝等砂体,构成重要的储集层,在有利的成藏条件下,凹陷中央的烃源岩向周围与之互层的储集层供烃形成油藏,在凹陷中央的烃源岩中,还发育了页岩油、页岩气、致密油气等非常规油气。因此,每个凹陷就是油气生成、运聚的基本单元,是一个独立的油气运移—聚集系统。生油凹陷的分布及其古地理特征控制了油气在渤海湾盆地古近系中的平面分布。     

渤海湾盆地古近纪古地理特征与油气*

渤海湾盆地是一个典型的内陆裂谷盆地,内部发育6个坳陷、4个隆起、54个凹陷和44个凸起。沉积盆地的含油气性与其古地理分布有密切的关系。利用渤海湾盆地各坳陷大量的录井、岩心、古生物、测井、地震资料及前人的大量文献和数据,对渤海湾盆地各坳陷古近系孔店组、沙河街组沙四段、沙三段、沙二段、沙一段、东营组进行了全区对比和统层。在此基础上,对冀中坳陷、济阳坳陷、临清坳陷内东濮凹陷各组段的沉积相进行了分析,编制了这些区域的古地理图;充分利用前人文献和科研报告中所编制的辽河坳陷、黄骅坳陷、渤海海域古近系各组段的古地理图,编制了渤海湾盆地孔店组、沙河街组沙四段、沙三段、沙二段、沙一段、东营组的古地理图。渤海湾盆地发育数十个含油气凹陷,每个凹陷中心的深湖亚相泥岩构成烃源岩,而在凹陷的边缘发育近岸水下扇、扇三角洲、三角洲、滩坝等砂体,构成重要的储集层,在有利的成藏条件下,凹陷中央的烃源岩向周围与之互层的储集层供烃形成油藏,在凹陷中央的烃源岩中,还发育了页岩油、页岩气、致密油气等非常规油气。因此,每个凹陷就是油气生成、运聚的基本单元,是一个独立的油气运移—聚集系统。生油凹陷的分布及其古地理特征控制了油气在渤海湾盆地古近系中的平面分布。     

Characteristics and Genetic Mechanisms of Overpressure in the Depressions of Bohai Bay Basin, China

The distribution and genetic mechanisms of abnormal pressures in the Bohai Bay Basin were systematically analyzed. Abnormal pressures are widely developed in the Bohai Bay Basin, primarily in the Paleogene E2s4, E2s3, Es1, and Ed formations. From the onshore area of the Bohai Bay Basin to the center of the Bozhong area, the top depth of the overpressured zone in each depression increases gradually, the overpressured strata in each depression gradually move to younger formations, and the pressure structure successively alters from single-bottom- overpressure to double-bottom-overpressure and finally to double-top-overpressure. The distribution of overpressured area is consistent with the sedimentary migration controlled by the tectonic evolution of the Bohai Bay Basin, which is closely related to the hydrocarbon-generation capability of active source rocks. The overpressured strata are consistent with the source-rock intervals in each depression; the top of the overpressured zone is synchronous with the hydrocarbon generation threshold in each depression; the hydrocarbon generation capability is positively correlated with the overpressure magnitude in each formation. Undercompaction was the main mechanism of overpressure for depressions with fluid pressure coefficients less than 1.2, whereas hydrocarbon generation was the main mechanism for depressions with fluid pressure coefficients greater than 1.5.     

大杨树盆地的构造特征及变形期次

大杨树盆地是叠置于大兴安岭造山带的东部,与松辽盆地紧邻,呈北北东向长条带状展布的中新生代断陷-坳陷型盆地。大杨树盆地经历了多期变形作用,具有以伸展构造为主、并被挤压构造和反转构造叠加的构造特征。早白垩世龙江期主要受到了NWW—SEE向的拉伸作用,形成一系列北北东向控陷犁式正断层组合,在控陷断层的上盘发育小型箕状断陷;早白垩世九峰山期,大杨树盆地受挤压作用控制,使早期形成的断陷盆地发生反转作用,形成正反转构造,同时在某些地段形成逆冲断层和断层传播褶皱;早白垩世甘河期,大杨树盆地再次受到伸展作用,形成了一系列北北东向小型断陷。早白垩世晚期(甘河期之后)—晚白垩世早期,大杨树盆地受到强烈的挤压作用,使早期控陷正断层出现正反转作用,在盆地的浅部形成大型断层传播褶皱,使大杨树盆地全面隆升遭受剥蚀。第四纪大杨树盆地具有伸展的特征,发育一系列小型伸展断陷。     

伸展断陷中的变换构造分析

变换构造分析对于研究伸展断陷盆地的构造格局与油气分布具有重要的意义。在前人研究成果和近年来渤海湾盆地大量地震反射剖面解释的基础上,讨论了变换构造研究中一些有争议和有意义的问题。(1)对变换构造研究中采用的术语,诸如分段构造、变换构造、传递带、调节带和转换带重新进行了定义,并阐述了其基本概念。(2)根据侧列控凹主断层之间连接方式的不同,提出了一个新的分类方案,首先将变换构造划分为传递带、调节带和转换带3类,而后考虑每类变换构造特有的标志细分为若干亚类。(3)传递带和调节带的形成机制一般与侧列的控凹断层位移量沿其走向均匀变化有关。在断层中段位移量最大,在其末端,位移量减至最小。传递带和调节带形成于断层末端,然而,由于侧列断层叠覆程度的差异、位移量是否守恒、断层的倾向状况以及平面上侧列断层末端之间的横向距离等诸多因素,从而产生传递带或者是调节带以及与之有关的多种多样的变换构造样式。与传递带和调节带不同,转换带以连接不同伸展构造段的转换断层为特征,推测其形成是由于地壳伸展速率的巨大差异所致。     

Late-stage Hydrocarbon Accumulation in the Bozhong Depression of the Bohai Bay Basin as Controlled by Neotectonism

Neotectonism occurred intensively in the Bozhong depression in the Bohai Bay Basin, which was reflected vertically by dramatic subsidence and a number of uplifts and laterally by notable fault movements. This particularity has resulted in the special petroleum geological conditions of the Bozhong depression which are different from those of adjacent lands. For example, the source rocks of the Shahejie Formation were overpressured and hydrocarbon generation occurred in the late stage; the Dongying Formation was deeply buried below the hydrocarbon-generating     

塔南凹陷南屯组油藏类型及其分布特征

塔南凹陷南屯组现今的复合箕状断陷结构,是由盆地内部的多个断块、翘倾掀斜分割改造的缓坡—沉积中心—沉降中心—陡坡组成大型断陷盆地后形成的。通过构造、沉积、反演和试油资料的综合分析,发现区内油气藏类型及其展布受沉积过程、同生断层及后期构造的控制,与普通的陆相箕状断陷盆地明显不同。缓坡一侧的翘倾掀斜部位主要为三角洲前缘储集砂体,发育断层分割或遮挡的构造-岩性油气藏;沉积中心的储集砂体主要为远岸扇和三角洲前缘成因,多发育透镜状岩性油气藏和构造-岩性油气藏;在沉积和沉降中心之间的翘倾掀斜部位为远岸扇储集砂体,多发育透镜状岩性油气藏和背斜-岩性油气藏;陡坡一侧的沉降中心主要为近岸水下扇储集砂体,以透镜状岩性油气藏为主,也可见到上倾尖灭岩性油气藏和构造-岩性油气藏。     

塔南凹陷岩性油藏成藏条件与4种成藏模式

本文分析了塔南凹陷岩性油藏的成藏条件,结果表明,开阔的复式箕状断陷结构使塔南凹陷形成了多凸多凹、凹隆相间的构造格局,为岩性油藏的形成创造了有利的空间;南屯组多沉积中心发育的优质烃源岩为岩性油藏发育提供了物质基础;同沉积断裂及其配置关系决定了塔南凹陷具有沟谷控源、转换带控扇、断坡控砂的成盆特点,水下扇中扇,三角洲前缘和远...     

含油气盆地盐构造研究进展

简要讨论了近年来含油气盆地盐构造研究的主要进展,这些进展主要表现在盐构造地质建模、三维可视化、物理模拟和数值模拟、平衡剖面分析和构造复原以及盐构造形成机制等方面。盐构造是一类与油气聚集关系极为密切的构造类型,在波斯湾、北海、墨西哥湾、北欧和非洲大陆边缘等油气资源丰富的地区有大量分布。中国在塔里木、渤海湾、江汉、四川等盆地广泛发育多期盐岩层和多种类型的盐构造,但国内盐构造研究相对较少,对盐及其相关构造的变形组合样式、三维地质建模和三维可视化、盐构造形成机理和动力学演化的研究是薄弱环节。对于塔里木、渤海湾盆地以及中国南方海相碳酸盐岩层系来说,区域性盐岩盖层的存在和分布将是油气藏得以保存的关键。深入探讨盐构造特征将有助于深化对中国含油气盆地构造演化、构造样式和油气成藏过程的认识。     

Distribution Characteristics and Accumulation Model for the Coal‐formed Gas Generated from Permo‐Carboniferous Coal Measures in Bohai Bay Basin,China: A Review

Coal-formed gas generated from the Permo-Carboniferous coal measures has become one of the most important targets for deep hydrocarbon exploration in the Bohai Bay Basin, offshore eastern China. However, the proven gas reserves from this source rock remain low to date, and the distribution characteristics and accumulation model for the coal-formed gas are not clear. Here we review the coal-formed gas deposits formed from the Permo-Carboniferous coal measures in the Bohai Bay Basin. The accumulations are scattered, and dominated by middle-small sized gas fields, of which the proven reserves ranging from 0.002 to 149.4×108 m3 with an average of 44.30×108 m3 and a mid-point of 8.16×108 m3. The commercially valuable gas fields are mainly found in the central and southern parts of the basin. Vertically, the coal-formed gas is accumulated at multiple stratigraphic levels from Paleogene to Archaeozoic, among which the Paleogene and PermoCarboniferous are the main reservoir strata. According to the transporting pathway, filling mechanism and the relationship between source rocks and reservoir, the coal-formed gas accumulation model can be defined into three types: "Upward migrated, fault transported gas" accumulation model, "Laterally migrated, sandbody transported gas" accumulation model, and "Downward migrated, sub-source, fracture transported gas" accumulation model. Source rock distribution, thermal evolution and hydrocarbon generation capacity are the fundamental controlling factors for the macro distribution and enrichment of the coal-formed gas. The fault activity and the configuration of fault and caprock control the vertical enrichment pattern.     

Hydrocarbon Generation Evolution of Permo-Carboniferous Rocks of the Bohai Bay Basin in China

<正>The Bohai Bay Basin is a Mesozoic subsidence and Cenozoic rift basin in the North China Craton.Since the deposition of the Permo-Carboniferous hydrocarbon source rock,the basin has undergone many tectonic events.The source rocks have undergone non-uniform uplift,twisting,deep burying,and magmatism and that led to an interrupted or stepwise during the evolution of hydrocarbon source rocks.We have investigated the Permo-Carboniferous hydrocarbon source rocks history of burying,heating,and hydrocarbon generation,not only on the basis of tectonic disturbance and deeply buried but also with new studies on apatite fission track analysis,fluid inclusion measurements,and the application of the numerical simulation of EASY%R_o.The heating temperature of the source rocks continued to rise from the Indosinian to Himalayan stage and reached a maximum at the Late Himalayan.This led to the stepwise increases during organic maturation and multiple stages of hydrocarbon generation.The study delineated the tectonic stages, the intensity of hydrocarbon generation and spatial and temporal distribution of hydrocarbon generations.The hydrocarbon generation occurred during the Indosinian,Yanshanian,and particularly Late Himalayan.The hydrocarbon generation during the late Himalayan stage is the most important one for the Permo-Carboniferous source rocks of the Bohai Bay Basin in China.     

Post-Neogene Structural Evolution: An Important Geological Stage in the Formation of Gas Reservoirs in China

Tectonic movements since the Neogene have been the major developmental and evolutional stages of the latest global crustal deformation and orogenic movements. China is located in a triangular area bounded by the Indian landmass, the West Siberian landmass and the Pacific Plate, characterized by relatively active tectonic movements since the Neogene, and in this region, natural gas would have been very easy to dissipate, or difficult to preserve. Therefore, the characteristics of post-Neogene tectonic movements offer important geological factors in researching the formation and preservation of gas reservoirs in China. Summarizing the reservoiring history of gas fields in China, although there are some differences between various basins, they are all affected by the tectonic     

纵向伸展断背斜类型及成因

纵向伸展断背斜是伸展断陷中重要的油气勘探领域。按照断背斜的几何形态将纵向伸展断背斜划分为双断型断背斜、单断型断背斜和叠合y型断背斜。根据渤海湾盆地新生代地质资料,讨论这3类纵向伸展断背斜的成因:(1)双断型断背斜发育于裂谷期,受对向双断断陷控制,主要是由于早期伸展过程中岩层局部缩短作用、晚期差异沉降和断块翘倾作用形成,其形成机制不同于前陆盆地的区域挤压作用产生的背斜;(2)单断型断背斜(或称逆牵引背斜)发育于裂谷期,受单断断陷控制,是由于控陷断层下降盘岩层下滑过程中岩层以逆牵引方式回倾、差异沉降和岩层弹性挠曲作用造成的,但岩层长度局部缩短作用仍是一个重要因素;(3)叠合y型断背斜发育于裂谷期后,受对称断陷和其中y形断洼控制,其形成与以纯剪切方式伸展运动和多期次断裂活动有关。它与走滑-伸展断背斜成因存在根本性差别,后者实质上不属于纵向伸展断背斜的范畴。     

合肥盆地地质格架演化及油气条件分析

综合运用大地构造学及沉积学理论与方法,结合最新的勘探资料,对合肥盆地的地质构造与演化及油气地质条件进行了较系统的研究与论述。印支运动造就了盆地的统一基底和基本形态,其基本构造格架为“三坳围一隆”;盆地经历了4个演化阶段,其动力在早期主要源自大别山构造带,后期主要源自郯庐断裂带,其间为二者的联合控制作用;区内石炭—二叠纪煤系具有良好的煤型气及一定的煤层气潜力,中、下侏罗统和下白垩统暗色泥岩类是最具生油潜力的烃源岩系。印支期古风化壳层和中央隆起构造则是最有利的区域性油气储集场所。      

渤海湾盆地垦东凸起构造特征与油气聚集

渤海湾盆地中南部地区垦东凸起是一个新的油气勘探领域。为了深入研究垦东凸起的构造特征与油气聚集规律,寻找有利的油气圈闭,就下列问题进行探讨:渤海湾盆地中、南部的区域构造特征,垦东凸起的构造演化和构造样式和油气圈闭类型和油气富集特征。通过对本区地质、地球物理和地球化学的综合研究认为,渤海湾盆地中南部区域由于成带状的伸展断陷-断凸和连接它们的横向调节带的存在,构造上呈现出南北分带、东西分段的断块构造格局。构造发展史表明,垦东凸起及北部斜坡带经历了裂谷期前、裂谷期和裂谷期后3大发育阶段,纵向上呈3层结构分布。垦东凸起可分为西段高凸起、东段低凸起,分别与北部斜坡带西段和东段相连。其中北部斜坡带的构造样式主要为同向的阶梯状正断层。凸起内部主要为背向正断层组合形成的地垒和面向正断层组合形成的地堑。垦东凸起圈闭可分为5种类型,其中构造圈闭主要有牵引背斜、逆牵引背斜、屋脊断块以及披覆背斜等。油气主要来自古近纪黄河口伸展断陷生油中心,自北向南沿砂体、不整合面和正断层呈阶梯状侧向和垂向运移至北部斜坡带和凸起,在新近纪和古近纪地层组成的有利圈闭处聚集。     

渤海湾盆地东濮凹陷不同区带油气成藏期差异性及主控因素

东濮凹陷是渤海湾盆地典型富油气凹陷,利用烃源岩生排烃史模拟和储层流体包裹体分析,对凹陷内不同区带、不同层系油气藏的形成时期及差异性进行了系统研究。结果表明,研究区存在两期成藏:第一期为古近纪东营组沉积后期至抬升初期,第二期为新近纪明化镇组沉积末期,其中第一期为主成藏期。不同区带、不同层系油气充注成藏时期存在明显差异:第一期成藏范围广泛,在全区均有分布,第二期成藏则主要分布于近生烃凹陷区;中浅部层系多为第一期单期成藏,深部层系多为两期成藏,第二成藏期主要分布于深部主力生烃层系中。不同区带及不同层系成藏的差异性主要受控于烃源岩主生排烃期断层活动性和高成熟烃源岩的分布。     

渤中坳陷超压-构造活动联控型流体流动与油气快速成藏

渤中坳陷是东营组沉积期及其之后渤海湾盆地沉降-沉积速率最高的地区, 亦是晚期断裂活动最强烈的地区.较高的沉降-沉积速率产生了重要的成藏物质效应: (1) 持续的较快速沉降-沉积使东营组发育较深湖-深湖相泥岩并成熟, 从而使渤中坳陷发育沙河街组和东营组2套有效源岩; (2) 较高的沉降-沉积速率引起的压实不均衡及伴生的源岩快速生烃引起较强的超压, 超压对有机质热演化的抑制作用使沙河街组源岩生、排烃滞后, 从而使沙河街组和东营组在晚期同时保持在较有利的生、排油阶段, 这是渤中坳陷油气资源丰富和油气晚期快速成藏的物质基础.较强的超压和强烈的断裂活动决定了超压-构造活动联控型流体流动, 进而决定了油气幕式快速成藏过程和油气分布: 油气主要富集于新近系, 新构造运动控制油气分布      

Wide rift model in Bohai Bay Basin: insight into the destruction of the North China Craton

The Bohai Bay Basin is a Cenozoic extensional basin along the eastern aspect of Asia. Whether the Bohai Bay Basin is a pull-apart or rift basin is controversial. The Bohai Bay Basin exhibits a high density of extensional faults and records destruction of the North China Craton. Many structural analyses have been performed on the Bohai Bay Basin, especially the Tan-L and Taihang Mountain fault systems which control its boundary. The initial deposition of Kongdian Formation was mainly distributed along the boundary of Bohai Bay Basin during the Palaeocene–early Eocene. Subsequently, tectonic activity migrated toward the interior of the basin during deposition of Shahejie Formation in the middle Eocene–early Oligocene. Bohai Bay Basin crust was thickened in early Mesozoic time and has thinned since late Mesozoic time. The crustal strength profile of Bohai Bay Basin is characterized by very weak lower crust, which differs from that of adjacent crust. In regard to the crustal structure, lithospheric thickness, and extensional style, an alternative rift model is proposed. Initial Bohai Bay Basin rifts were characterized by metamorphic core complexes affecting the North China Craton, which reflects collapse of parts of the early Mesozoic intra-plate orogen. Furthermore, westward subduction of the Palaeo-Pacific Plate led to upwelling of asthenosphere mantle. Persistent upwelling of mantle decreased the strength of lower crust and led to the warm heat-flow regime and generation of a lower crustal fluid layer and wide rifting. Outward flow of ductile lower crust following late Cretaceous extension thinned the lower crust and generated the overall sag appearance of the basin in early Cenozoic time. The model supports a model whereby a wide rift narrows with time. For the Bohai Bay Basin, extension and strike-slip faulting were two independent deformation systems superimposed on each other.