(中海石油有限公司天津分公司,天津300452)
摘 要:油气运移是当今世界石油地质学中研究最薄弱的环节,也是最前沿的学科,它是成藏动力学研究的核心。断裂是裂陷盆地内重要的油气运移通道,但是断面与烃源岩接触面积小,不能吸收大量油气,大断层下降盘的水下扇砂体与生烃岩大面积接触,能吸收烃源岩中生成的大量油气,当达到一定饱和度时,温—压升高,伴随着断层的“幕式”运动,油气从砂体——中转站中沿断层向上运移成藏。正、反两方面勘探实践验证了断裂—砂体的油气中转站运移模式的正确性,它将对今后油气运移的研究和勘探起到一定的指导作用。
关键词: 断裂;砂体;中转站;油气运移;模式中图分类号:TE112 文献标识码:A
油气运移是油气成藏的核心因素之一,而油气运移的研究又非常困难[1],它不同于烃源岩、储层、盖层、圈闭及保存的研究。伴随着计算机技术的迅速发展和油气勘探程度的日益提高,勘探家们拥有很多高质量的地震、探井资料,直接反映烃源岩、储层、盖层、圈闭及保存情况,只要投入一定的研究力量,不难搞清凹陷或预探目标的生、储、盖、圈、保条件。但是,油气运移的研究则不同,油气运移发生在数百万至数亿年之前的地下几百米至几千米,钻探井之前,没有直接资料反映是否发生过油气运移,目前发展较快的“包裹体”直接分析油气运移技术,也是在钻探井之后,局限性很大。
油气运移的研究因其重要性和复杂性而成为当今世界石油天然气地质学中最热门的研究课题,成藏动力学的核心就是油气运移的过程。断裂是油气运移的重要通道,尤其在裂谷盆地内更是如此,L.C.Price 曾撰文[2]指出,裂谷盆地内断层越多、活动时间越长,油气运移越充分,油气越富集。断裂是中国东部裂陷盆地内油气运移的重要通道,在渤海湾盆地内,上第三系已发现的储量约占总储量的30%,而上第三系为河流相
沉积,本身不能生油,其油气来自下第三系的沙河街组和东营组。上第三系能否成藏,运移是关键。笔者曾统计过,渤海海域近几年预探的失利构造,有30%是运移条件差。可见研究油气运移在勘探实践中的重要性。
前人对断裂的油气运移做了大量的研究工作,得出了很多有益的认识,如油气在上第三系大砂岩内的“网毯”式运移[3],等等。笔者从20世纪80年代起一直在渤海从事石油勘探的研究和技术管理工作,深感油气运移的重要性和复杂性,一直在关注国内外油气运移研究的进展,也一直在探索渤海油气运移的方式和途径[4]。本文意在通过大量的实例来论述此模式的理论基础、科学性及实用性,希望能对油气运移的研究、油气勘探有所帮助。
1“中转站”油气运移模式
通过对断层—砂体油气运移的大量研究,通常认为断至生油岩内的断层可以作为油气源的运移通道,形成下生上储的组合模式。但是笔者在渤海勘探工作的长期实践中发现,不少圈闭有断层(甚至是大断层)沟通了凹陷内的烃源层与储层,但钻探后未发现任何
作者简介:邓运华,男,高级工程师,1985年毕业于江汉石油学院,1988年毕业于石油勘探开发科学研究院,获硕士学位,一直从事勘探、开发、科研管理工作。
收稿日期:2005-06-13
中国石油勘探2005年第6期14油气显示。同一条大断层伴生了多个圈闭,有的富集成油田,有的没有油气聚集,而他们的储—盖、圈闭条件非常相似。这说明断层作为油气运移的通道,除了与断层本身特点有关之外,还与其他因素有关,这就是与它相配置的砂体。
单条断层只有一个断面,断面附近的裂缝可以改善岩层的渗透性,但它创造的储集空间很少。断至烃源岩内的断面与烃源岩接触的面积不大,既没有较大的储集空间,也缺乏足够的接触面积吸取烃源岩中生成的油气。因断层下部缺少足够的供给量,上部的断面也就没能运移大量油气,即使是由多条断层组成的断裂带也是如此。
断裂—砂体油气运移的“中转站”模式,特别强调了大断层下降盘砂体的作用(图1)。继承性发育的大断层在盆地的强烈扩张期、生油岩形成时,断层上升盘的隆起区提供了碎屑物源,在下降盘形成了近岸水下扇砂体。这些扇体的根部与大断层接触,而前缘与烃源岩呈“指状”大面积接触,当烃源岩成熟后生成的油气在温—压作用下向近岸水下扇砂体内发生初次运移;
[5]
砂体内的油气达到一定饱和度后(5%~10%),压力增高,伴随着断层的活动,油气沿断面从近岸水下扇砂体内向上部的圈闭中运移;随着砂体内油气向上运移,压力降低,断层活动停止,从烃源岩中初次运移来的油气再次在砂体内聚集,周而复始,这个近岸水下扇砂体就犹如一个“中转站”,没有这个砂体“中转站”,大断层就不能成为油气运移的良好通道。
从断裂—砂体油气运移的“中转站”模式可以看出,在裂陷盆地内,断层附近钻探下生上储式圈闭时,除了研究圈闭、储—盖、烃源岩、断层之外,还要研究断层根部的砂体。这个砂体不一定是钻探的目的层,而是油气运移的“中转站”。没有这类砂体,断层不能提供充足的油气源,圈闭内的储层很可能装的是水。从这个模式也可以看出,烃源岩沉积以后晚期形成的断层不是油气运移的良好通道,它可以起到再次分配油气的作用。
从断裂—砂体油气运移的“中转站”模式还可以看出,大断层上部的上储式圈闭内若已发现了油气层,断层根部很可能有水下扇砂体,若晚期断层活动停止,断层封闭,水下扇砂体内可能有油气富集,成为深部勘探的目的层。
从断裂—砂体油气运移的“中转站”模式来看,不整合面的运移能力较强,在中国东部裂陷盆地内的不整合面是油气运移的重要通道。凸起上形成的披覆背斜油气藏充满度一般很高(如孤岛、孤东、埕岛、港东、蓬莱19-3、曹妃甸11-1、秦皇岛32-6、南堡35-2、绥中36-1、锦州25-1南等),因为不整合面曾经是一个长期的风化剥蚀面,其上砂体发育,与烃源岩广泛接触,它是长期继承性的运移通道。但是不同岩性的基岩形成的砂体大小、孔—渗性不同,油气运移能力不同。混合花岗岩风化后能提供大量的石英、长石颗粒,最利于形成高质量的“中转站”砂体。而灰岩、中—基性火山岩不能提供质量好、数量大的陆源碎屑,形成良好的“中转站”,其运移能力相对较差。
2勘探实践对“中转站”模式的检验
断裂—砂体油气运移的“中转站”模式是根据油气运移的理论在勘探实践中总结出来的,同时又被后来的大量勘探实践所验证。渤海湾盆地是一个新生代的陆相裂陷盆地,断裂是重要的油气运移通道,下第三系沙河街组是主要烃源岩,东营组下段是重要的烃源岩。上第三系为河流相沉积,不能生烃,上第三系储—盖层与下第三系烃源岩之间地层厚度1000~2000m,发育最典型的下生上储式油气藏。渤海湾盆地内的渤中25-1、渤中34-1、歧口17-3、港东油田以及锦州20-2、锦州20-1、歧口18-7等构造的钻探,验证了断裂—砂体油气运移“中转站”模式的科学性。
渤中25-1是渤海湾盆地凹陷内最大的上第三系油田,地质储量超过1.5×108m3,它位于黄河口凹陷北
15No.6 2005China Petroleum Exploration图1 断裂—砂体油气运移“中转站”模式图
Fig.1 Pattern map showing "transfer station" of fault-
sandstone body oil-gas migration
石油地质 部,是凹陷边界大断层下降盘的逆牵引背斜圈闭,油层为明化镇组河流相储层,大断层沟通了黄河口凹陷沙河街组生油层与圈闭内明化镇组储层(图2),生油层与明化镇组油层垂直距离1300~2000m。渤中25-1-5井证实在运移断层附近,沙三—沙四段发育巨厚的砂体(40~260m),沙河街组砂体起到了吸收生油岩中生成的分散油气后运移到明化镇组的“中转站”作用。由于晚期断层活动弱,深部断层封闭,沙河街组砂体内有油气富集,形成沙河街组油田。
图4 港东油田上、下第三系油藏模式图
Fig.4 Pattern map showing Eogene and Neogene oil
reservoirs in Gangdong oilfield
图2 渤中25-1油田上、下第三系油藏模式图Fig.2 Pattern map showing Eogene and Neogene oil
reservoirs in Bozhong 25-1 oilfield
类似于渤中25-1油田的实例还有渤中34-1、歧口17-3(图3)、港东(图4)油田等。它们都是凹陷内
上第三系油田,靠断层运移油气,在运移断层的根部都
有沙河街组的水下扇,扇三角洲砂体发育,这已被钻井所证实,一些深层砂体有油气富集成为油田。
上述的构造是断层根部有砂体、上部有油层的实例。下面列举的锦州20-1、歧口18-7是下面无砂体、上部无油层的例证。锦州20-1构造在辽西凹陷东面控凹大断层下降盘,东营组上段储—盖组合配置好,逆牵引背斜圈闭很完整,深部沙河街组的生烃条件已被附近的锦州14-2-1井所证实。但是,1987年钻探的锦州20-2-8井在圈闭内无油气显示,说明没有油气运移到圈闭内。2002年以深部沙河街组断鼻为目的层,又钻探了锦州20-1-1井,钻前分析认为沙河街组近岸水下扇储层发育,自生自储式成藏条件优越。但钻后发现沙河街组近岸水下扇不存在,只有很薄的粉砂岩(图5)。断
图3 歧口17-3油田上、下第三系油藏模式图Fig.3 Pattern map showing Eogene and Neogene oil
reservoirs in Qikou 17-3 oilfield
中国石油勘探2005年第6期图5 锦州20-1—锦州20-2地质剖面图
Fig.5 Geological section of Jinzhou 20-1-Jinzhou 20-2
16层上部无油气富集是因根部生油层附近无砂体发育,缺乏“中转站”。
歧口18-7构造在歧口凹陷南部海1大断层下降盘,其上第三系圈闭、储—盖条件、断层活动强度与歧口17-2非常相似,两者都是在海1大断层下降盘,相距仅9km,但歧口17-2上第三系内有油气富集,地质储量约1900×104m3,而歧口18-7构造上第三系无油气聚集(图6)。主要原因可能还是断层根部砂体发育程度不同。钻井证实,与歧口17-2构造只一条断层相隔的歧口17-1-1井在沙河街组有厚砂体存在,经地震及钻井资料分析认为,歧口17-2构造深部有较大砂体发育。而歧口18-7构造南部的歧口18-1油田位于扇三角洲前缘-远端前缘,歧口18-7位于沙河街组的三角洲远端前缘相带上,砂层不发育,缺少“中转站”。
高点不富集的原因。2004年在中高点与生烃凹陷间的
斜坡上,以岩性地层圈闭为目的层钻探了CFD23-3-1井,该井在基岩面之上的目的层段没有发现砂岩,也没有发现油气层。1989年BP公司在CFD23-3-1井附近曾钻探了CFD23-1-1井,该井也因为在下第三系缺乏储层而没有发现油气层。从埕北低凸起北、中、南三个高点的含油气状况和斜坡部位已钻井揭示的砂体分布来看,南、北高点油气富集,其斜坡部位砂体发育(SH8、CFD21-2-1),而中高点油气不富集,对应斜坡上砂体亦不发育(CFD23-1、CFD23-3-1)。渤海一些勘探工作者认为,南、北高点油气富集是因为凸起斜坡上砂体发育,砂体作为油气运移的“中转站”起到了吸收油气的作用,而中高点对应斜坡上砂体不发育,缺乏油气运移的“中转站”。可见,砂体作为油气运移的“中转站”,在以不整合面为运移通道的凸起上也起着重要的作用。分析凸起上聚烃条件同样应分析毗邻的生烃凹陷内“中转站”砂体的发育程度。
断裂—砂体油气运移的“中转站”模式是1995年提出来的,经过渤海湾盆地10年的勘探实践证明了它的科学性,本文结合大量实际资料系统论述了其原理及应用情况。笔者坚信,随着中国东部裂陷盆地勘探的深入,尤其是岩性地层油气藏勘探的发展,必将进一步证明其科学性,并对油气运移的研究和勘探实践有一定的指导作用。
参考文献
[1]胡见义.石油地质学前沿和勘探新领域[J].中国石油勘
图6 歧口18-7地质剖面图
Fig.6 Geological section of Qikou 18-7
探,2004,9(1):8~14
[2]Price L C. Basin richness and source rock disruption:
a fundamental relationship? Journal of Prtroleum Geology[3]李丕龙.济阳成熟区非构造油气藏深化勘探[J].石油学报,
在埕北低凸起上的北、中、南三个高点上,南、北
高点都发现了油田(埕岛油田、埕北油田),而中高点上已钻两口井(H8、H20)油气不富集。从基本石油地质条件来看,三个高点的圈闭、储—盖条件相似,离渤中生烃凹陷的距离也相似,地质家一直没能解释中
2003(5)
[4]邓运华.歧南断阶带油气聚集因素探讨[J].中国海上油气,
1995
[5]Elise B Bekele.Modeling secondary oil migration with
core-scale data: Viking formation Alberta Basin. AAPG,86(1)
17No.6 2005China Petroleum ExplorationABSTRACT ABSTRACTFeatures and Exploration Potential of Lithologic Oil Reservoirs in Southern Songliao Basin // Mao Chaolin1,2,Zhao Zhanyin1,2 ,MaYutian1,2 ,Song Lizhong1 and Liu Ke1/ 1 China University of Geosciences, Beijing 100083;2 PetroChina Jilin Oilfield Company, SongyuanCity, Jinlin Province138001
Abstract:On the basis of analyzing the forming conditions of lithologic oil reservoirs in the south of Songliao Basin,the types anddistributing features of lithologic oil reservoirs have been summarized. There are 6 types of lithologic oil reservoirs such as updipsandstone pinchout oil reservoir, lenticular sandstone oil reservoir,structural-lithologic oil reservoir,fault-lithologic oil reservoir,hydrodynamic trap oil reservoir and mud fractured oil reservoir. By researching and summarizing, it is thought that there would be 5forming regularities of lithologic oil reservoirs and approximately 1 billon tons oil resources potential in the southern Songliao Basin.Meanwhile, it is put forward that next target areas should be the frontal zones of the western, westsouth and eastsouth deposition systems.Key words: southern Songliao Basin, lithologic oil reservoir, distribution regularity, exploration potential, depositional system Exploration Thinking and Mapping Suggestion for Lithologic-stratigraphic Oil Traps // Yao Chao1, Jiao Guihao2, Lu Yousheng3and Zheng Lianghe3 /1 PetroChina Exploration & Production Company, Beijing 100011;2 Langfang Branch, PetroChina ResearchInstitute of Petroleum Exploration and Development, Langfang City, Hebei Province 065000;3 CNPC BGP Inc., Zhuozhou City, HebeiProvince 072751
Abstract:The formation and distribution of lithologic-stratigraphic traps are dependent on the geological structural background, spacedistribution of strata, special deposition environment of the basin, and the effect of later structure events. With the theory of sequencestratigraphy and seismic stratigraphy, it analyses the various types of lithologic-stratigraphic traps, their occurrence conditions and theexploration difficulty, and also proposes the exploration thinking that builds in the basement of finding out \"three surfaces and one line\"(i.e. maximum flooding surface, initial flooding surface, unconformable surface and pinchout line) in oil-rich sags and the suggestionsthat include mapping for lithologic-stratigraphic traps and checking the interpretation quality in the term of lithologic-stratigraphic traps.The suggestion is not only helpful for mapping standardization of lithologic-stratigraphic trap, but also to promote deepening theinterpretation of lithologic-stratigraphic traps and discover more promising lithologic-stratigraphic oil reservoirs.
Key words:lithologic-stratigraphic trap, exploration difficulty, exploration thinking, three surfaces and one line, interpretation technique,industry mapping, quality checking
ÒTransfer StationÓ Model of Oil-gas Migration Formed by Fault-sandbody // Deng Yunhua /CNOOC Tianjin Company, Tianjin 300452Abstract: Oil-gas migration is regarded as the weakest link in petroleum geology research in the world and is the most frontier scienceas well, and is the core of the dynamic research of oil-gas accumulation and migration. Although fault is the important pathway for oil-gas migration in the faulted-depression basin, the contact plane of the hydrocarbon source rock is small, which cannot absorb a mass ofoil and gas. However,in the downthrow block of the major fault, the subsea fan sandbody has large contact plane with the hydrocarbonsource rock, which could absorb the most of oil and gas produced in the hydrocarbon rock. While reaching the certain saturation of oiland gas, the temperature and pressure will rise and along with the episodic movement of the fault, oil and gas will migrate upwards in thetransfer station of the sandbody along the fault, accumulate, and the reservoir will then be formed. Both the success and the failurepractice in exploration proved that the way of model\"Oil-gas Transfer Station \"of the fault-sandbody is correct, furthermore, it will guidethe research and exploration for the oil-gas migration in the future.Key words:fault, sanbody, transfer station, oil and gas migration, model
Application of Chemical Kinetic Theory in Resource Evaluation of Immature to Low-mature Oil in Huanghua Depression // LuShuangfang1, Guo Chunping1, Shen Jianian1, Wang Feng1, Liao Qianjin2 and Yu Junli2/1 Daqing Petroleum Institute, Daqing City,Heilongjiang Province 163318; 2 Research Institute of Exploration and Development ,PetroChina Dagang Oilfield Company, Tianjin 300280Abstract: The application of chemical kinetic models in Huanghua Depression indicates that the botryococcus, organic mater (OM) reworkedby microbe and soluble OM (non-hydrocarbon and asphatene) in the research region do begin to generate hydrocarbons in large amount atshallower buried depth relative to the normal threshold of oil generation. Combined with the distribution, thickness, and buried history ofsource rocks as well as their geochemical characteristics and feature of residue hydrocarbon, the quantitative evaluation shows that theamounts of hydrocarbon generation and expulsion for the 2nd member of Kongdian Formation are 3.45 billion tons and 3.19 billion tonsrespectively in the south region of Kondian,and that for the 1st member of Shahejie Formation are 1.34 and 0.94 billion tons respectively,theamounts of oil resource (including mature oil) of the 2nd member are 0.71 and 0.28 billion tons respectively. This means that the 2ndmember of Kongdian Formation in south Kongdian will results the enrichment of oil accumulation of immature to low-mature oil, and theexploration potential related to the 1st member of Shahejie Formation is not negligible. These also suggest that it is both reliable and workableto evaluate the amount of generation and expulsion as well as the resource of immature to low-mature oil from the chemical kinetic theory.Key words: Huanghua Depression, immature oil, low-mature oil, resource evaluation, chemical kinetics
Karstification Study on Gas-oil Reservoirs // Liu Shanhua, Dai Zongyang and Wu Changjiang / Southwest Petroleum Institute,ChengduCity, Sichuan Province 610500
No.6 2005China Petroleum Exploration
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