Pathway System of Large-Scale Petroleum System and Its Controls on Hydrocarbon Accumulation in the Bozhong Sub-Basin, Bohai Bay Basin
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摘要: 渤中坳陷东营组沉积期以来快速沉降和强烈断裂活动的地质背景导致其呈现出不同于渤海湾盆地其他地区的油气成藏特征.凹陷周缘凸起带成为油气聚集的主要场所, 输导体系的分布与演化控制了油气运移和成藏.在阐明渤中坳陷大型油气系统烃源岩和油气分布规律的基础上, 综合利用多种资料分析了各类潜在输导通道的发育特征及其空间配置, 识别出断裂主导型、砂体主导型和不整合主导型3类控藏输导体系.凸起边缘继承性的长期断层充当了垂向流体释放和油气运移的主输导通道, 控制了凸起带上新近系储集层中的油气聚集.特别是在构造活跃期, 开启的长期断层成为油气快速垂向运移的首选通道.古近系沙河街组和东营组的连通性砂体与活跃烃源岩直接接触, 不仅是早期油气运移和聚集的主要场所, 也是晚期油气运移和聚集的始发站.因此, 它们不仅控制了古近系圈闭的油气聚集, 同时在很大程度上直接控制了凸起带新近系圈闭的油气供给.不整合T8是中生代末区域构造变革的产物, 其渗透性因风化作用而得以提高, 充当了深部侧向油气运移的输导通道, 控制了潜山储集层中的油气成藏.3类输导体系对油气成藏的时间、部位、速率和规模等都具有不同程度的影响, 但断裂主导型输导体系的控制作用最为显著.Abstract: The geological evolution of the Bozhong sub-basin, characterized by rapid subsidence and strong fault activities since the initiation of the Dongying Formation, exerts important effect on the characteristics of hydrocarbon accumulation in this area, which is distinguished from those in other areas in the Bohai Bay Basin. Uplifts around depressions serve as predominant sites for hydrocarbon accumulation, and the distribution and evolution of pathway systems have obviously been controlling hydrocarbon migration and accumulation. Based on clarification of the distribution of hydrocarbon source rocks and petroleum resources in the large-scale Bozhong petroleum system, growing characteristics of all kinds of potential pathways and their spatial relevance are analyzed by means of multiple data, and then three pathway system types controlling hydrocarbon migration and accumulation: fault-dominant, carrier bed-dominant and unconformity-dominant types are identified. Long-term growth faults adjoining uplifts act as the predominant pathways for vertical fluid release and hydrocarbon migration, and control hydrocarbon accumulation in the Neogene reservoirs on uplifts. Especially in the active stage of tectonic movement, the open long-term growth faults must be preferential pathways for the rapid vertical hydrocarbon migration. The interconnected sandbodies in the Paleogene Shahejie and Dongying Formations, directly contacting with active hydrocarbon source rocks, serve as the primary sites and starting stations for the early and late hydrocarbon migration and accumulation, respectively. Therefore, they not only control hydrocarbon accumulation in the Paleogene traps, but also directly impact hydrocarbon supply to the Neogene trap on uplifts to some extent. Unconformity T8, resulted from regionally tectonic transformation in last Mesozoic, serve as pathway for deep lateral hydrocarbon migration and control hydrocarbon accumulation in the buried hill type reservoirs due to its improved permeability attributed to long-term weathering process. Three types of pathway systems all impact even control the times, locations, velocities and scales of hydrocarbon accumulation in various degrees. However, the fault-dominant type pathway system shows the most outstanding effect among them.
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输导体系是含油气系统中连接烃源岩和圈闭的纽带,约束着油气的运移路径和聚集场所.因此,它不仅是油气运移研究的重要内容,更是成藏动力学研究的基础.所谓输导体就是具有相互连通且渗透性较强的可供流体流动和油气运移的通道空间的地质体.断裂(Hooper,1991;Aydin,2000;Boles et al., 2004)、连通性砂体(Nie et al., 2001)、不整合(潘钟祥,1983)、古老风化带和底辟构造(Xie et al., 1999)都可作为输导体.它们在三维空间的组合和配置构成了约束流体活动和油气运移的输导体系(Hindle,1997;谢泰俊等,1997).不同学者根据输导体系的构成及其配置关系(Galeazzi,1998),输导体系的成因与形成时间(梁书义等,2005)以及输导体系的有效性及其识别的难易程度(卓勤功等,2005)将其划分为各种类型.实际上,输导体系的类型、形成与演化也因沉积盆地的类型及其演化的差异而明显不同.不同类型的盆地甚至同一个盆地的不同构造部位往往具有不同的输导体系,单个体系的输导性能也随盆地演化阶段的差异而改变(赵忠新等,2002;邹华耀等,2005;杨德彬等,2012).所以,在含油气系统中,只有在关键时刻及其之后发生的输导体系演化对油气成藏和分布才具有控制作用.
渤中坳陷是渤海湾盆地东营组沉积期以来沉降速率最高.晚期断裂活动最强烈的地区(龚再升和王国纯,2001;郝芳等,2004;Xie et al., 2007).独特的地质背景造就了其不同于渤海湾盆地其他地区的油气成藏特征.凹陷周缘凸起带成为油气聚集的主要场所,远离古近系烃源岩的新近系储集层成为油气成藏的主要层系(邓运华,1999;龚再升等,2000;朱伟林等,2000;姜福杰和庞雄奇,2011).前人从不同角度开展了大量的研究来揭示渤中坳陷复杂的油气成藏机理,取得了一系列创新性成果和认识(龚再升和王国纯,2001;Yang and Xu, 2004;邓运华,2005;Zhang et al., 2006;Hao et al., 2007, 2009, 2010, 2011;Gong et al., 2010;Zou et al., 2011),但对输导体系及其与成藏关系的研究依然很薄弱.鉴于渤中坳陷的这种油气远源成藏特征,本文试图在阐明输导体系形成和演化的基础上,讨论其与油气成藏过程的时空配置和成因联系,为该地区的成藏动力学研究及油气勘探提供参考.
1. 地质背景
渤中坳陷是渤海湾盆地唯一完全位于渤海海域的一级构造单元,包括渤中、渤东和秦南等3个凹陷以及渤南、渤东、石臼坨和庙西等4个凸起(图 1),沉积了古近系孔店组、沙河街组和东营组,新近系馆陶组和明化镇组以及第四系平原组等地层(图 2).渤中坳陷的构造演化总体分为裂陷和裂后两个时期(何仕斌等,2001;图 2),其最重要的特征是裂陷Ⅳ幕(东营组沉积期)以来保持的渤海湾盆地最高的沉降速率以及裂后Ⅱ幕(明化镇组上段-第四系沉积期)发育的异常构造沉降和强断裂活动(图 2;龚再升和王国纯,2001;郝芳等,2004;Xie et al., 2007),结果导致地层中发育较强的超压现象,成为含烃流体释放和油气运移、充注的一个动力源(刘晓峰等,2008).
图 1 渤中坳陷区域位置、构造单元以及烃源岩和油气藏分布油气藏分布据张功成等(2001),Yang and Xu(2004),Gong et al.(2010),姜福杰和庞雄奇(2011)等资料编绘;现今Ro等值线据Zou et al.(2011),用来表示沙河街组三段和东营组三段两套烃源岩的大致分布范围Fig. 1. Regional location, structural units and distribution of source rocks and petroleum pools of the Bozhong sub-basin渤中坳陷主要发育沙河街组三段、沙河街组一段和东营组三段等3套烃源岩,孔店组中段也具有一定供烃潜力;勘探证实的油气藏主要分布在凸起带和凹陷边缘断背斜带,明化镇组下段、馆陶组和沙河街组二段为主要的储集层;沙河街组一段和明化镇组下段上亚段为区域性盖层(图 1和图 2;Yang and Xu, 2004).渤中坳陷多套源岩供烃,多套层系储油,多期充注晚期成藏的复杂背景导致以某一烃源岩为中心的含油气系统识别与划分非常困难,因而李思田(2004)以渤中富生烃凹陷为中心,加上与之相关的油气藏群整体称为大型油气系统.Cao et al.(2005)提出的准噶尔盆地北缘混杂油气系统(hybrid petroleum system)也具有类似的成藏特征.
2. 油-源地球化学与烃源岩演化
渤中坳陷3套烃源岩具有很多相似的地球化学特征,如有机质丰度较高,属于好烃源岩;有机质类型比较接近,总体以Ⅱ型为主,Ⅲ型次之;呈现明显的姥鲛烷优势,Pr/Ph值为0.93~2.28等.但它们的伽马蜡烷和4-甲基甾烷分布却存在明显差别,沙河街组三段烃源岩以贫伽马蜡烷和富4-甲基甾烷为特征,沙河街组一段烃源岩以高伽马蜡烷含量和低4-甲基甾烷含量为特征,东营组三段烃源岩伽马蜡烷与4-甲基甾烷含量均较低,因而成为区分3套烃源岩的一个重要指标(王培荣等,2004;Hao et al., 2007, 2009).相比之下,原油的地球化学特征复杂得多,以伽马蜡烷和4-甲基甾烷指标为例,除贫4-甲基甾烷、贫伽马蜡烷的原油可能主要来源于东营组三段烃源岩外,其他类型原油均呈现明显的混源特点(Hao et al., 2009).
图 3是基于Easy%Ro模型(Sweeney and Burnham, 1990)通过数值模拟得到的渤中坳陷3套烃源岩的热演化结果.模拟边界条件的设置参考了何仕斌等(2001)、Hu et al.(2001)、Wang et al.(2002)以及He and Wang(2003)的研究成果.如图 3所示,渤中凹陷中心沙河街组三段烃源岩在30Ma开始生油,21~13Ma处于生油高峰,13Ma开始生气,现今已过成熟;沙河街组一段烃源岩在27Ma开始生油,12~8Ma处于生油高峰,随后进入主生气阶段,现今已过成熟;东营组三段烃源岩在24Ma开始生油,8~5Ma处于生油高峰,5Ma开始生气至今.渤中凹陷边缘斜坡带沙河街组三段烃源岩在17Ma开始生油,3Ma至今处于生油高峰;沙河街组一段烃源岩在14Ma开始生油,2Ma至今处于生油高峰;东营组三段烃源岩在12Ma开始生油,现今处于生油高峰.Zou et al.(2011)也指出,渤中坳陷新构造期(裂后Ⅱ幕)多生烃凹陷和多层段广泛发育活跃生油岩(0.5%≤Ro≤1.3%),为大型油田(如PL19-3油田)的晚期快速成藏提供了充足的油源(图 1).
图 3 渤中坳陷3套烃源岩Ro演化剖面(剖面位置见图 1)Fig. 3. Evolution of vitrinite reflectance in three source rock intervals of the Bozhong sub-basin可见,渤中坳陷3套烃源岩在东营组沉积期以来的陆续成熟、持续生烃和多源供烃为凸起带油气田的发育奠定了坚实的物质基础;则这个时期输导体系的发育和演化必然成为控制油气的运移、聚集和油气藏定位的另一个关键因素.
3. 输导体系构成及其组合特征
3.1 输导体系要素
3.1.1 断裂
渤中坳陷新生代断裂系统在空间上总体呈NE、NNE、近EW及NW等走向(图 1);在时间上分为早期断层、长期断层和晚期断层(图 4).早期断层主要切割古近系地层,且多在晚渐新世,即沙河街组三段烃源岩成熟前已经消亡,所以对油气运移的影响较弱,但因其活动改变的两盘岩性对接方式可能影响古近系油气聚集.晚期断层多发育于裂后Ⅱ幕,切割深度较浅,未能直接沟通烃源岩与储集层,对大规模油气运移的作用较弱,可能影响油气在新近系储集层中的分布.而长期断层不仅发育时间长、规模大,而且直接沟通了烃源岩与储集层,可充当垂向流体释放和油气运移的主输导通道,进而控制油气在新近系圈闭中成藏.图 4是基于浮力驱动原理利用PetroMod软件模拟的现今油气运移状态,很好地反映了长期断层对油气垂向穿层运移的输导作用.新近系少量保存的传递超压也是深部超压流体沿长期断层快速充注的证据(Zhang et al., 2006;刘晓峰等,2008).
图 4 渤中坳陷构造-地层格架及油气运移剖面图(剖面位置见图 1)Fig. 4. Section showing structural and stratigraphic framework and hydrocarbon migration of the Bozhong sub-basin对长期断层而言,一方面,断层周期性幕式活动的活动期比间歇期具有更强的输导能力,会在其附近形成同层混源或异层同源的复式油气聚集带(于翠玲和曾溅辉,2005);另一方面,断层活动期的输导能力在很大程度上又受其总体走向与区域主压应力方向关系的影响.渤中坳陷3套烃源岩自晚渐新世陆续成熟、生烃以来,渤海海域区域构造应力场发生了多次改变,晚渐新世东营组一段沉积期(27.4~24.6Ma)的区域主压应力方向为SE102°,晚中新世-上新世明化镇组沉积期(12~2Ma)的区域主压应力方向为SE178°,第四纪(2~0Ma)的区域主压应力方向为NE70°(万天丰等, 2004, 图 5a).近EW和NW走向断层因其总体走向与区域主压应力方向在晚渐新世和第四纪近平行或交角较小,呈张性或张扭性而具有较好的输导能力;但在上新世则近于垂直或交角较大,呈压性或压扭性而导致输导能力明显减弱,但侧向封闭性增强.同理,NE走向断层的输导能力在第四纪最强,晚渐新世和上新世相对较弱;NNE走向断层的输导能力在上新世最强,晚渐新世近于封闭(图 5).总之,断层输导能力强,有利于深部烃源岩生成的油气向浅部储集层快速运移;输导能力弱或封闭能力强,则有利于赋存在输导层或储集层中的油气成藏.长期断层的幕式活动及其活动期输导和封闭能力的变化,导致渤中坳陷绝大多数已发现油气藏均位于长期断层附近,且多表现为多期充注—耗散和晚期聚集成藏的特点(图 5b).
图 5 渤中坳陷油气成藏期区域应力场对主要活动断层输导能力及油气藏分布的影响E型油气藏指最早在晚渐新世已发生油气聚集的油气藏,N型油气藏指最早在晚中新世出现油气聚集的油气藏,Q型油气藏指第四纪才发生油气聚集的油气藏.区域应力场据万天丰等(2004)编绘,断层系统据徐杰等(2011)编绘Fig. 5. Effects of regional stress field on transporting capabilities of major active faults and the distribution of petroleum pools during the hydrocarbon migration and accumulation periods in the Bozhong sub-basin3.1.2 砂体输导层
渤中坳陷砂体输导层主要以馆陶组粗碎屑辫状河沉积和东营组大型远源三角洲为代表.馆陶组辫状河平原砂体具有分布广,连通性好及单层厚度大等特点(图 6a),且埋藏较浅,胶结疏松,是浅层油气侧向运移的重要输导通道.东营组三角洲体系物源供给充足,砂体规模较大,以多期推进的方式进入凹陷内部并与东营组烃源岩直接接触(图 6b),构成了深层油气大规模侧向运移的有利通道.沙河街组短物源扇体,尽管规模和连通性均不如前者,但直接被烃源岩包围,具有近源优势(图 6c),是油气沿凸起边缘长期断层垂向运移的“中转站”(图 4;邓运华,2005).明化镇组曲流河砂体规模小,单层厚度薄,输导能力有限,可能控制了局部构造的油气分布.
关于侧向稳定输导层中的油气运移,尽管还存在最小阻力控制(Rhea et al., 1994)和最大动力控制(Hindle,1997)之争,但高孔渗带无疑是流体活动和油气运移的首选通道.图 7a和7b显示了渤中坳陷碎屑岩现今孔隙度和渗透率的垂向变化.值得注意的是,在2200m~3800m深度段出现了孔隙度和渗透率相对增大的现象,说明沉积物在埋藏过程中遭受了溶蚀作用,产生了次生孔隙.长石颗粒在溶于地层水的CO2和有机酸作用下发生高岭石化被认为是该深度(中成岩A期)次生孔隙发育的主要机制(图 7c).从矿物颗粒中析出的Na+、K+和Ca2+等碱性金属离子被及时带走以及CO2和有机酸源源不断的补给是次生孔隙产生并得以维持的重要基础,而活跃的流体活动和油气运移恰恰满足了其物质输运和能量传递的需求(Gouze and Coudrain-Ribstein, 2002).该阶段因CO2补给可能也产生了大量的碳酸盐胶结物(图 7d),但似乎并未影响次生孔隙的发育.所以,次生孔隙发育带恰恰说明砂体输导层中曾经或正在发生流体活动和油气运移,也在一定程度上证明了砂体的有效输导.
3.1.3 不整合
渤中坳陷T8、T5和T2这3个不整合对油气运移影响明显.邓运华等(2011)认为,渤中坳陷凸起带大油田的发育与不整合的输导作用具有密不可分的成因联系.T8界面形成于中生代末至古新世的区域构造抬升阶段(图 2),基岩风化壳发育,是油气向潜山储集层运移的重要通道.T5界面形成于喜山运动Ⅲ幕的构造抬升阶段,与上覆沙河街组二段砂体输导层配合,构成了深层油气侧向运移的重要输导通道.T2界面形成于喜山运动Ⅳ幕,与其上发育的馆陶组辫状河砂体输导层匹配,构成了浅层油气侧向运移的重要输导通道.
3.2 输导体系类型
综合考虑各类输导要素的发育、演化与空间配置,并结合对已知油气藏分布规律的认识(图 1),本次研究将渤中坳陷输导体系划分为断裂主导型、砂体主导型和不整合主导型3种类型.
断裂主导型输导体系由长期和晚期断层组成的断层网络、新近系砂体输导层及T2不整合等要素组成,主要分布在凹陷周缘陡坡带、断阶带等部位(图 4).该类输导体系组合于上新世以来的新构造活动期,属源岩生烃后发育的后生输导体系.在这类输导体系中,长期断层不仅是连接烃源岩和其他输导要素的枢纽,也是油气进入新近系储集层成藏的主要通道.因而,它在整个输导体系中起主导作用,在一定程度上决定了新近系油气聚集带的分布,并与其他要素共同控制聚集带内油气的再分配.
砂体主导型输导体系主要包括古近系砂体输导层、长期和早期断层组成的断层网络及T5不整合等要素,在凹陷周缘的缓坡带和陡坡带均有分布(图 4).该类输导体系组合于晚渐新世东营组沉积期,略早于烃源岩生烃期,属先存输导体系,但其有效性保持至今.砂体输导层是该类输导体系形成和生效的基础,它伸入凹陷内部与烃源岩直接接触,不仅是油气二次运移的起点,也是油气储集的主要场所,因而在很大程度上决定了古近系油气聚集带的分布.断层和不整合对油气运移和聚集具有调整和改善作用.
不整合主导型输导体系由T8不整合、古近系砂体输导层以及由长期和早期断层组成的断层网络等要素组成,主要分布在凹陷边缘的凸起倾末端.该类输导体系的形成大致始于古近系沙河街组沉积期,明显早于烃源岩生烃期,属典型的先存输导体系,现今仍保持有效性.在这类输导体系中,基底不整合是与潜山圈闭连接的直接通道,汇聚了沿砂体输导层和断层网络运移的油气,并控制了油气在潜山圈闭的聚集.
总之,各类输导要素在盆地发育演化过程中对油气成藏的影响不尽相同,具有层次性;输导体系类型可能因其所处部位和层段的差异而有所不同;不同类型输导体系间还可能存在相互作用.砂体主导型输导体系可能成为另外两类输导体系油气运移的起点,在一定程度上影响它们的油气运移量;而后者也可能影响和改变前者的油气聚集特征.
4. 输导体系对油气成藏的控制
毋庸置疑,渤中坳陷的油气成藏是盆地演化过程中生烃凹陷、输导体系和能量场及其演化共同控制的结果(图 8).前人分别从地质背景、物质基础和动力条件等角度探讨了其对油气成藏的影响和贡献(郝芳等,2004;李思田,2004;邓运华,2005;Hao et al., 2007, 2009, 2011;薛永安等,2007;Gong et al., 2010).新构造运动控制下的油气晚期成藏(龚再升和王国纯,2001)似乎已成为被广泛接受的认识.这里主要从输导体系角度探讨其对油气成藏的影响和控制(图 9).
4.1 输导体系控制油气成藏时间
渤中坳陷绝大多数已知油气田为晚期成藏(Gong et al., 2010),这固然与圈闭的形成时间较晚有关,但更重要的是输导体系,尤其是断裂主导型输导体系控制的结果.上新世以来,长期断层的开启和活化沟通了深部源岩(也可能是古油气藏)和浅部圈闭(图 4和5),为油气运移和充注提供了通道空间,使浅层油气聚集成为可能.而古油藏的破坏可能导致深部储层压力释放,扩大了其与烃源岩的压差,促进烃源岩进一步向其排烃,从而保证了浅层油藏充足的油源补给.可见,断裂主导型与砂体主导型输导体系共同控制了浅层圈闭的成藏时间,但前者强于后者(图 9).
4.2 输导体系控制油气成藏部位
古近系砂体输导层具有近源优势,这决定了其必然成为源岩直接排烃和油气就近聚集的首选场所,因而直接控制古近系油气成藏的部位(图 4).基底T8不整合风化壳结构发育,是潜山圈闭油气聚集的主要场所,但不与烃源岩直接接触,因而对油气成藏部位的控制受其他输导要素影响(图 9).对长期断层而言,尽管其不是油气聚集的场所,但它是油气向浅部垂向运移的主要通道,决定了浅层圈闭能否发生油气聚集,因而在宏观尺度上决定了新近系油气聚集带的分布(图 9).
4.3 输导体系控制油气成藏速率
稳态流动和瞬态流动是沉积盆地中油气运移的两种方式,前者速度缓慢但持续时间长,后者速度快但持续时间短暂.在构造平静期,断裂活动微弱或基本不活动,其输导能力很弱,油气主要以在砂体输导层和不整合输导体内的稳态流动方式缓慢运移,速率较低;但在构造活动期或超压导致水力压裂的情况下,断层输导能力显著增强,油气在断裂及各类与之相通的输导体中以瞬态流动方式快速运移,速率较高.因而,断裂主导型输导体系控制的油气田往往具有较高成藏速率,如PL19-3油田(Hao et al., 2007;Gong et al., 2010;Zou et al., 2011);砂体主导型和不整合主导型输导体系控制的油气田的成藏速率可能较低(图 9).
4.4 输导体系控制油气成藏规模
输导体系可能通过改变油气成藏速率,破坏先存油气藏和改变油气运移路径等3种方式控制油气成藏规模.在断裂、砂体输导层和不整合3类输导体中,断层因其活动性而具有最强的输导能力可变性,因而对油气成藏规模的控制最强(图 9).渤中坳陷浅层大型油气田的发育,除与充足的烃源供给和良好的圈闭条件有关外,上新世以来断裂主导型输导体系控制下的油气快速穿层运移应该是主要原因.而深部古近系油气藏规模较小,既可能是先存油气藏因断层的垂向贯通而遭到破坏的结果;也可能是上新世断层活动期油气在地震泵吸作用下垂向运移趋势大于侧向运移,而导致油气主要在浅部聚集的结果.
5. 结论
(1) 渤中坳陷发育断裂、砂体输导层和不整合3类输导体.断裂的输导能力受其活动性以及其总体走向与区域主压应力方向关系的影响;砂体和不整合的输导能力取决于其渗透性,受沉积和成岩作用双重控制,次生孔隙带往往可作为流体活动或油气运移的示踪标志.
(2) 根据各类输导要素的发育、演化与空间配置,渤中坳陷输导体系可划分为断裂主导型、砂体主导型和不整合主导型3种类型.其中,断裂主导型输导体系的形成晚于烃源岩生烃,属后生输导体系;砂体输导层主导型和不整合主导型输导体系早于烃源岩成熟,属先存输导体系.
(3) 断裂主导型输导体系中,长期断层直接沟通源岩与储集层,决定了新近系油气聚集带的分布;砂体主导型输导体系中,古近系砂体直接与烃源岩接触,决定了古近系油气聚集带的分布;不整合主导型输导体系中,T8不整合控制了潜山圈闭的油气聚集.各类输导要素在对油气成藏的影响不尽相同,具有层次性,不同类型输导体系间还可能存在相互作用.
(4) 输导体系对油气成藏时间、成藏部位、成藏速率和成藏规模都具有不同程度的控制作用,比较而言,断裂主导型输导体系因长期断层的继承性活动对油气成藏的控制最为明显.
致谢: 本文研究得到了中海石油研究总院张功成及中海石油天津分公司周士科、于水和李建平等的支持与帮助,文中原始资料来自中海石油天津分公司研究院,在此表示衷心感谢! -
图 1 渤中坳陷区域位置、构造单元以及烃源岩和油气藏分布
油气藏分布据张功成等(2001),Yang and Xu(2004),Gong et al.(2010),姜福杰和庞雄奇(2011)等资料编绘;现今Ro等值线据Zou et al.(2011),用来表示沙河街组三段和东营组三段两套烃源岩的大致分布范围
Fig. 1. Regional location, structural units and distribution of source rocks and petroleum pools of the Bozhong sub-basin
图 2 渤中坳陷综合地层序列、构造-环境演化及生储盖组合(据Gong et al., 2010;何仕斌等,2001)
Fig. 2. Integrated stratigraphic column, tectonic and environmental evolution and source-reservoir-cap assemblages of the Bozhong sub-basin, Bohai bay basin
图 3 渤中坳陷3套烃源岩Ro演化剖面(剖面位置见图 1)
Fig. 3. Evolution of vitrinite reflectance in three source rock intervals of the Bozhong sub-basin
图 4 渤中坳陷构造-地层格架及油气运移剖面图(剖面位置见图 1)
Fig. 4. Section showing structural and stratigraphic framework and hydrocarbon migration of the Bozhong sub-basin
图 5 渤中坳陷油气成藏期区域应力场对主要活动断层输导能力及油气藏分布的影响
E型油气藏指最早在晚渐新世已发生油气聚集的油气藏,N型油气藏指最早在晚中新世出现油气聚集的油气藏,Q型油气藏指第四纪才发生油气聚集的油气藏.区域应力场据万天丰等(2004)编绘,断层系统据徐杰等(2011)编绘
Fig. 5. Effects of regional stress field on transporting capabilities of major active faults and the distribution of petroleum pools during the hydrocarbon migration and accumulation periods in the Bozhong sub-basin
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