【作者】 王亚青；

【导师】 林承焰； 董春梅；

【作者基本信息】 中国石油大学 ， 地质资源与地质工程， 2008， 博士

【摘要】 随着油气田勘探和开发程度的不断提高,勘探对象由易于识别的构造油气藏逐渐转变为隐蔽油气藏,特别是勘探程度较高的盆地,隐蔽油气藏已成为重要的勘探开发目标。岩性油气藏是重要的隐蔽油气藏类型,其储量在隐蔽油气藏储量中占有重要地位。本文以典型的岩性隐蔽油气藏—车西洼陷东风港油田主力区块沙三上亚段油藏为例,通过储层地质的精细研究,发现了一批小型沉积扇体滚动勘探目标,为油田增储上产奠定了基础。本文是在完成储层精细地质研究所要求的“精雕细刻”的同时,另一个重要内容是,储层精细地质研究所建立的地质模型一定要具有“预测性”。储层精细地质研究的预测性要求主要表现在以下两个方面:一是对于沉积储层展布的预测性,二是对于油气分布的预测性。对于沉积储层的预测,关键的问题是建立适合研究区沉积规律的沉积相模式,分析其控制要素对沉积相形成与演化的控制和影响作用,在此基础上对沉积储层的展布进行预测;对于油气藏中油气分布的预测,是在对沉积相及储层分布预测的基础上,通过储层非均质性研究、储层综合评价以及油气成藏等系统研究,分析油气的分布规律,并用以指导勘探和开发。开展精细地层划分对比,建立高分辨率等时地层格架是沉积相和储层研究的主要基础。采用高分辨率层序地层学结合沉积旋回分析,对车西洼陷沙三上亚段和沙二段地层进行了精细划分和对比。沙三上亚段和沙二下亚段总体上是一个三级基准面旋回。沙三段与沙二段的界限,等同于三级基准面旋回内部两个四级基准面旋回界面。沙三上划分为两个四级基准面旋回,沙二下划分为一个四级基准面旋回,这三个四级基准面旋回都是基准面上升旋回,沙二上亚段也划分为一个四级基准面旋回,为基准面下降旋回。沙三上的两个四级基准面旋回包括四个五级基准面旋回,沙二下包括四个五级基准面旋回,沙二上也划分为四个五级基准面旋回,总共识别出了十二个五级基准面旋回。其中,沙三上和沙二下四级基准面旋回内部的五级基准面旋回是以基准面上升旋回和基准面上升与基准面下降复合旋回为主,沙二上内部的五级基准面旋回为典型的基准面下降旋回。在高分辨率地层对比的基础上,对砂体以及沉积相在垂向上和平面上的分布特征与演化规律进行了详细研究,研究区在断陷湖盆缓坡带上发育小型浊积扇体,规模小,内部结构简单,分布分散,扇体呈薄层状,垂向上多期扇体与泥岩层交互出现。通过大量实际工作,提出了研究区浊积扇沉积的“叠置扇”模式。叠置扇是指同一沉积环境的地层单元内,多期扇体在垂向上相互叠置,依次向前推进或向后退缩,同时多期扇体在平面上时常发生侧向迁移的展布形式。叠置扇相模式主要特征是“垂向叠置,扇上有扇;侧向迁移,扇外有扇”。叠置扇具有三个重要特点:一是多期扇体垂向上相互叠置,不同扇体在侧向上经常迁移;二是单个扇体规模小,内部结构简单;三是在多个方面与Walker的“叠覆扇”模式存在明显的差异。叠置扇模式不是单一相模式,而是一种复合模式。“叠置扇”与Walker的“叠覆扇”模式具有明显不同。“垂向叠置”表明在垂向上发育多期扇体叠置,预测在已发现扇体的上方或下方可能存在新的扇体;“侧向迁移”表明在已发现的扇体的两侧,可能会发育新的扇体。在分析了构造运动、湖平面变化、沉积物供给等控制沉积相形成与演化要素的基础上,认为“源—坡—洼配置”与“湖平面变化”综合控制了浊积扇的形成与演化。研究浊积扇,需要从“源”入手,在“坡”上追踪搬运路径,“洼”内寻找扇体,“源—坡—洼”之间不同的配置关系导致形成的扇体特征不同,特别是浊积扇沉积时沉积区“洼”的三维形态,直接控制和影响了浊积扇的规模与展布。湖平面变化控制了扇体的发育期次和演化特征。受“叠置扇”发育模式和储层非均质性的控制,研究区垂向上油层层多、但单层较薄,平均单层厚度为0.65-2.84m,具有油层分布不均一的特点,油气主要集中在沙三上1、2、3砂层组的中部;平面上发育多个油砂体,单个油砂体面积较小、分布零散,研究区沙三上共发育169个油砂体,7口井以上控制的油砂体只有8个,而2口井以下控制的油砂体有119个;多期油砂体叠合连片发育。在开展扇体展布规律、储层非均质性、储层综合评价等研究基础上,根据“叠置扇”垂向叠置特征,分析湖平面变化对扇体叠置的控制作用,寻找“扇上扇”;根据“叠置扇”侧向迁移特征和“源—坡—洼”配置关系,在古地貌低洼之处寻找“扇外扇”;在预测有利扇体的基础上,根据储层综合评价结果,明确有利勘探目标。依据储层地质精细研究成果,在车44区块东部车444井附近的古沟槽内寻找勘探目标,成功完钻车44-51、车44-49等9口井,均钻遇油层;同时进一步侧向迁移向古沟槽的西翼进行钻探,成功完钻井车44-521、车44-520等5口井,均有油层发育。在车40、44块分别向西部、中部和东部进行滚动扩边,其中在西部继承性古地貌低洼处车44-410井区成功完钻4排18口开发井,均发现油气,新增含油面积1.0Km2,新增探明地质储量70万吨。在“古沟槽、今高点”的车17井区成功完钻井车44-60、车44-59、车17-5、车17-7等9口井,均见油层,含油面积向东扩大。在车40区块的中部继承性古地貌低洼处完钻井车40-27-21、车40-29-X21、车40-31-19和车40-31-X21开发井4口,同样均钻遇油层。实践证明,叠置扇模式及其控制要素“源—坡—洼配置”与湖平面变化综合分析方法在研究区滚动勘探中发挥出重要作用,在实际应用中取得明显成效。更多还原

【Abstract】 With the continuous development of oil exploration and exploitation, subtle reservoirs, especially in basins with high degrees of exploration, have gradually become the significant prospecting targets instead of structural reservoirs that are easy to be identified. Turbidite subtle reservoir, whose reserves play an important role in subtle reservoir reserves, is one of the significant subtle reservoir types. Take a typical turbidite reservoir in the major blocks of Dongfenggang Oilfield as an example, this paper focuses on the detailed research on reservoir geology and finds a number of fans as the next prospecting targets.In accordance with its requirements, reservoir fine geologic research, must be carried out with“great care”, in addition, the geological model established by fine geologic research must be“predictable.”The requirements for predictability mainly include the following two aspects: one is the prediction of sedimentation and reservoir, and the other is the forecast of hosting gas.The prediction of sedimentation and reservoir lies in building a suitable sedimentary facies model of the studied area and analyzing its controlling factors’influences on the formation and evolution of sedimentary facies, while on the basis of the above work, the forecast of oil and gas bearing in the reservoir is to analyze the distribution regularity of oil and gas through reservoir heterogeneity research, providing guidance for oil exploration and exploitation.The detailed stratigraphic division and comparison as well as the establishment of high-resolution isochronous stratigraphic framework are one of the foundations and key factors in oilfield exploration and exploitation. High-resolution sequence stratigraphy combined with sedimentary cycle analysis is used to perform fine correlation and division of Sha-3 upper sub-member and Sha-2 member.On the whole, Sha-3 upper sub-member and Sha-2 member constitute a three basal level cycle. The boundary of Sha-3 member and Sha-2 member are equal to two four basal level cycle boundaries inside the three basal level cycle. There are two four basal level cycles in Sha-3 upper sub-member and one in Sha-2 lower member, all of the three cycles are ascending ones, meanwhile in Sha-2 upper member, the only cycle is a descending one. In total, 12 five basal level cycles are identified, among which 4 are in Sha-3 upper sub-member, 4 are in Sha-2 lower member and 4 are in Sha-2 upper member. The five basal level cycles in both Sha-3 upper sub-member and Sha-2 lower member are mainly characterized by ascending cycles as well as compounding cycles formed by ascending and descending ones, whereas in Sha-2 upper member, they are typical descending cycles.Following the correlation, a detailed research on the characteristics of distribution and evolution of sand bodies and sedimentary facies both in vertical and planar direction has shown that, a turbidite fan with a small scale and simple inner structure is developed on the gentle slope of fault trough lake basin in this area. It scatters randomly with a shape of thin layer and in vertical direction, multi-stage fan bodies and mud layers appear mutually.A“superimposed fan”model of turbidite fan deposition in the studied area is put forward in this paper through lots of practice. Superimposed fan refers to a distribution pattern of fan bodies, through which different-phase fan bodies superimpose on each other in vertical direction, and fan bodies take turns to move forward or backward, while fan bodies move far away from the center on the horizontal level. Superimposed fan model is featured by“fan bodies superimpose vertically, overlaying on each other; fan bodies move laterally, standing side by side”with the following three important characteristics: firstly, multi-stage fan bodies superimpose on each other in vertical direction, and different fan bodies may move away in the lateral direction; secondly, individual fan body in superimposed fan bodies is very small with simple internal structure; thirdly, superimposed fan model differs distinctively from Walker’s“suprafan”model. Superimposed fan model is not a single-phase model but a complex one.The reservoir prediction direction of superimposed fan model is obviously different from that of Walker’s“suprafan”.“Vertical superimposition”is in the forecast of multi-stage fan bodies overlaying in the vertical direction, and“lateral movement”indicates that new fan bodies may appear on the two sides of individual fan bodies on the plane. Adhering to“superimposed fan”model, multi-phase fan bodies superimposition may be found on the upper or lower parts of the fan bodies which have been discovered, and new fan bodies may also be found on the two sides of the fan bodies which have been discovered.On the basis of analyzing the factors intriguing the formation and evolution of sedimentary facies, such as tectonic movement, lake level changes, sediment supply, it is concluded that“source -slope– depression”collocation and“lake level changes”both dominate the formation and evolution of turbidite fan. Concerning the study of turbidite fan,we first need to center on the“source”, then trace the transportation path along the“slope”and look for the fan bodies in the“depression”. Various“source - slope– depression”arrangements may lead to fan bodies with different characteristics. In particular, the paleogeomorphology of deposition zone caused by the deposition of turbidite fan directly controls and influences the scale and distribution of turbidite fan. The lake level change in the vertical direction controls the developmental phases and evolution features of fan bodies.Dominating by the“superimposed fan”model and reservoir heterogeneity, the oil and water distribution in studied area in the vertical direction is characterized by thin oil layer with an average thickness of 0.65-2.84m, multi oil layers and uneven distribution mainly focusing on the middle part of 1, 2 and 3 sand bed sets in the upper Sha 3, meanwhile, on the plane, single oil sand body has a small area, and scatters randomly, there are 169 sand bodies in total, among which, only 8 are controlled by more than seven wells and 119 by less than two wells. While, multi-stage oil sand bodies grow congruently in a large scale.Through researching on fan distribution regularity, reservoir heterogeneity and reservoir comprehensive evaluation, on one hand, fans overlaying on each other become the prospecting targets by analyzing the control of lake level changes on fan superimposition referring to its vertical characteristics; meanwhile,on the other hand,“lateral movement”and“source-slope-depression arrangements”provide guidance for finding fans developed in the paleogeomorphic low part on the two sides of individual fan bodies. Finally, favorable targets are confirmed by predicting favorable fans according to the results of reservoir comprehensive evaluation.Referring to the results of detailed research on reservoir geology, continue eastwardly drilling in the ancient groove occurred around Che 444 hole in the east of 44 block. Nine wells including Che 44-51, Che 44-49 and so on are all successfully completed with oil. Meanwhile, continue drilling in the west of the ancient groove, five holes including Che 44-521, Che 44-520 hole and so on are also successfully completed with oil. Expanding reserves exploitation in Che 40 and 44 blocks, successfully completed 18 holes in Che 44-410 well field of the west inherited ancient groove and all find hydrocarbon, new oil area is 1.0Km2, new reserves are 700000 t. In Che 17 well field of the east ancient groove which is high now, nine holes are successfully completed with oil, including Che 44-60 hole and so on, oil area expand eastwardly. In the middle of Che 40 block, four holes is complete in inherited ancient groove, including Che 40-27-21 hole and so on, and also all penetrate oil layers.The results show that, superimposed fan model with its controlling factor-the“source-slope-depression arrangements”as well as the synthetic analysis of lake level changes have played an important role in this area and also received good results in practice.更多还原