【作者】 高长海；

【导师】 查明；

【作者基本信息】 中国石油大学 ， 地质资源与地质工程， 2009， 博士

【摘要】 近几年来随着我国东部断陷盆地勘探实践的不断深入,新发现的油气藏中不整合油气藏在储量和产量上占据着重要地位,已成为断陷盆地油气增储上产的重要目标。不整合油气藏形成机理研究的主要内容之一就是不整合对油气的输导作用问题,实际上就是油气能否以及如何沿不整合从“源”到“藏”的问题,也即不整合输导油气有效性的问题,它直接影响和控制了不整合油气藏的形成。目前,有关不整合输导油气有效性的研究还较少,甚至有些方面还未涉及,这极大限制了不整合油气藏的勘探和开发。因此,针对断陷盆地,对不整合输导油气有效性问题进行深入分析和研究,是油气勘探的迫切需要,对不整合油气藏形成机理、分布规律及相关理论的认识和研究具有十分重要的意义。论文以我国东部断陷盆地─渤海湾盆地的济阳坳陷和冀中坳陷为主要研究区,以不整合空间结构特征和不整合运移通道类型研究为基础,以不整合空间结构的非均质性、油气沿不整合运移的物理模拟实验及其有效性研究为重点,对不整合输导油气有效性进行了综合研究,在此基础上,预测了不整合油气藏的有利区带。通过对济阳坳陷和冀中坳陷不整合油气藏勘探实例的分析,认为断陷盆地不整合在空间上具明显的三层结构特征,即不整合面之上的底砾岩层、不整合面之下的风化粘土层和半风化岩石层,其中底砾岩层和半风化岩石层是油气运移的主要通道,且油气主要在半风化岩石层中聚集。理论上不整合可出现48种结构类型,当不整合不发育风化粘土层,且不整合面之上为砂岩时,不整合结构类型以出现“输导体”居多,不整合面之上为泥岩时,不整合结构类型以形成封堵或圈闭居多;当不整合发育风化粘土层,则以形成圈闭居多。在对不整合空间结构特征研究的基础上,提出了油气沿不整合运移的通道类型:宏观上,存在由不整合面之上底砾岩和不整合面之下半风化岩石两种高效运载层组合成的双运移通道型和单运移通道型两种通道类型;微观上,底砾岩“连通孔隙”和半风化岩石“孔-洞-缝”系统可作为油气运移的主要通道。它们可将砂体和断层等连接起来,组成区域性的运移输导网络,共同控制着油气的运移。通过对断陷盆地不整合各结构层的几何形态、连续性、厚度变化特征、岩性变化特征以及物性变化特征等的定性及定量研究结果表明,不整合无论是在平面、层内,还是层间均表现出强烈的非均质性,且半风化岩石层的非均质程度要强于底砾岩层。依据不整合各结构层渗透率变异系数、渗透率突进系数和渗透率级差的大小,建立了断陷盆地不整合非均质性的评价指标。在此基础上,尝试性的将油气沿不整合发生有效输导的非均质性参数Vk的下限值定为0.7,即Vk≥0.7时,油气可沿不整合面之下的半风化岩石层发生有效输导并聚集成藏。根据冀中坳陷不整合油气藏勘探实际,针对性地建立实验模型,对不整合油气运移过程进行了实验模拟,结果表明:①不整合可作为油气侧向运移的良好通道,且油气主要沿物性好的输导层运移;②半风化岩石层始终是油气运移的优势通道,大部分的油气均沿此通道运移;③油气沿不整合的运移普遍表现出明显的非均一性,这种非均一性既表现在层间,也表现在层内;④沟通底砾岩层和半风化岩石层的开启性断层不仅是油气运移的良好通道,而且大大提高了不整合输导油气的能力;⑤油气在不同结构层中的运移特征直接受其物性的控制,如在物性好的半风化岩石层中,油气的运移速度快、运移量大、运移距离远等;⑥在注油压力、注油量相同的条件下,半风化岩石层的含油饱和度最高(散失量也最大),其输导油气的有效空间体积明显大于底砾岩层,具有较强的油气输导能力。在之前相关研究及物理模拟实验的基础上,论文对不整合输导油气有效性进行了综合研究:①断陷盆地油气沿不整合发生侧向运移的距离最远可达50km,有利于成藏的距离在5～20km之间;②油气在不同坳陷中沿不整合运移的速度差异较大,在0.28～8.33km/Ma之间;③油气在平面上由“凹”向“凸”呈“线状”运移(即沿优势通道运移),而不是“面状”运移,在剖面上则沿着“梁”运移,而不会在“沟底”运移;④不整合的半风化岩石层和底砾岩层始终是输导油气的主要通道,且半风化岩石层的“孔-洞-缝”系统较底砾岩层的“连通孔隙”具更高的输导能力,油气主要在半风化岩石层中运移和聚集;⑤断陷盆地控制油气沿不整合发生有效运移的因素主要有油源、油气运移动力、不整合特征(包括区域分布、结构性、通道类型、非均质性等)、不整合与其它输导体(如断层)的配置关系等,其中油源和油气运移动力是前提条件,而不整合特征及不整合与其它输导体的配置关系是关键因素。论文还对断陷盆地不整合油气藏的有利区带进行了预测:①盆地或凹陷边缘的地层超剥带,是不整合油气藏发育的有利区带;②鼻状构造带与超剥带的组合区域,是不整合油气藏最为富集的区带;③盆地或凹陷内部隆起,是今后寻找不整合油气藏(尤其是潜山油气藏)的重要区带。更多还原

【Abstract】 In recent years, hydrocarbon exploration demonstrates that unconformity reservoirs play an important role in newly found reservoirs and become primary exploration targets in faulted basins, eastern China. As the main hydrocarbon pathway, one of the objectives for unconformity study is to prove how hydrocarbon to migrate through unconformity from source rocks to reservoirs, i.e., the efficiency of hydrocarbon migration through unconformity which directly control the formation of unconformity reservoirs. However, few studies have been done on migration efficiency through unconformity, which restricts the exploration and development of unconformity reservoirs. Therefore, further studies should be carried on, which is significant for the formation and occurrence of unconformity reservoirs.This dissertation focuses on Jiyang and Jizhong Depressions, Bohai Bay basin. Based on the unconformity structure and the types of migration passages, it discusses the heterogeneity and physical modeling experiments of unconformity. Moreover, the efficiency of hydrocarbon migration through unconformity is intensively studied and prospects of unconformity reservoirs are predicted.Study shows that the vertical structure of unconformity in faulted basin includes three parts: basal conglomerate, weathered clay and semi-weathered rock, among which basal conglomerate and semi-weathered rock are major passages for hydrocarbon migration, and semi-weathered rocks are the main reservoirs for petroleum accumulation. The structure of unconformity can be subdivided into 48 types. If weathered clay is absent and the overlying layer is sandstone, the unconformity mainly becomes carrier bed, and the sealing or trap is formed if the overlying is mudstone. When weathered clay develops, the unconformity tends to trap oil and gas.Two kinds of unconformity migration passages are presented, which are dual migration passage consisting of two types of highly effective transport passages and single migration passage, repectively. The dual migration passage occurs between semi-weathered rock and basal conglomerate. The cavern-fracture system of semi-weathered rock and the connected pores of basal conglomerate can be regarded as the major passages for hydrocarbon migration. They connected faults and sand bodies formed in different periods to construct the regional migrating network which controlled the hydrocarbon migration.The unconformity structure displays obvious heterogeneity because of the differences in geometry, continuity, thickness, lithology and physical property. The unconformity shows strong interformational, intraformational and plane heterogeneity. The semi-weathered layer is more heterogeneous than the basal conglomerate layer. With the consideration of permeability mutation coefficient, permeability dash coefficient and permeability graded differences, the evaluation criterion of unconformity heterogeneity has been established and hydrocarbon can migrate and accumulate through semi-weathered layer when Vk≥0.7.Modeling experiments are designed to simulate the process of hydrocarbon migration through unconformity. The experiment results can be summarized as follows:①Unconformity can be a good migration passage, and hydrocarbon migrates mainly along carrier beds with better physical property.②Most hydrocarbon migrates along the semi-weathered layer.③Hydrocarbon migration through unconformity is characterized by an obvious interformational, intraformational and plane heterogeneity.④Opened faults, which connect the semi-weathered layer and basal conglomerate layer, not only can be a good passage, but also improve the transportation capability of unconformity.⑤The physical properties of unconformity control the hydrocarbon migration. Hydrocarbon has faster migration velocity, larger volume and longer migration distance in semi-weathered layer than in basal conglomerate layer.⑥Under the same experimental conditions, the semi-weathered layer has the highest oil saturation and the largest loss. Moreover, the semi-weathered layer has broader effective passage volume than the basal conglomerate layer and shows stronger transportation capability.Based on the preceding research and physical modeling experiments, this paper discusses the efficiency of hydrocarbon migration through unconformity in faulted basins:①The lateral distance of hydrocarbon migration through unconformity can reach 50km, and favourable range is from 5km to 20km.②Different depressions have different migration rates, from 0.28km/Ma to 8.33km/Ma.③Hydrocarbon migrates from sag to uplift laterally, and migrates along ridges not gullies vertically.④Semi-weathered layer and basal conglomerate layer are always the migration passages in geological time, and cavern-fracture system of semi-weathered layer has a stronger transportation capability than the connected pores of basal conglomerate layer. Therefore, hydrocarbon migration and accumulation occurred mainly in semi-weathered rocks.⑤A lot of factors influence hydrocarbon migration through unconformity, including oil-source, migration drive force, unconformity features (such as regional distribution, structural nature, migration passages and heterogeneity) and the collocation of unconformity and other migration pathways. Among these, oil-source and migration drive force are prerequisite, and unconformity features and the collocation of unconformity and other migration pathways are key factors.In the end, favourable regions of unconformity reservoirs in faulted basins are predicted:①The stratigraphic onlap and denudation zones in basins or depressions are the favorable belt to discover unconformity reservoirs.②The stratigraphic onlap and denudation areas combine with nose structure belts to form a prolific zone of unconformity reservoirs.③The inner uplifts in basins or depressions will be the important targets for unconformity reservoirs (especially buried hill reservoirs) in the future.更多还原