东濮凹陷三叠系致密砂岩储层裂缝与油气成藏

Relationship Between Fractures and Hydrocarbon Accumulation of Triassic Tight Sandstones in the North of Dongpu Depression

根据露头、岩心、薄片观察、成像测井、声发射实验、包裹体测温、原油族组成、原油组分碳同位素分析等技术,在分析裂缝分布特征和成藏特征的基础上,探讨了东濮凹陷北部三叠系裂缝形成期次与油气成藏的匹配关系。研究认为,研究区以构造裂缝为主。裂缝及其溶蚀孔洞的孔隙度平均为2.25%,渗透率为40×10-3μm2左右,是主要的储集空间和渗流通道。三叠系致密砂岩储层裂缝主要分两期形成,分别为燕山运动期和喜马拉雅运动期。三叠系储层油源为古近系沙三段和沙四段烃源岩,其生烃高峰期主要为东营组沉积末期—馆陶组沉积时期(晚期裂缝形成时期),而造成三叠系砂岩致密的压实、胶结等成岩作用主要在新生代以前完成。油气生成时期与喜马拉雅期有效裂缝的形成时间匹配良好,而与基质孔隙的发育匹配关系较差,从而造成研究区裂缝含油,砂岩的基质孔隙基本不含油。

The distribution of the natural fractures controls the distribution and the accumulation of the hydrocarbon reservoir in the Triassic of Wenmingzhai area, Dongpu depression. The formation time of the fractures and the relationship between the effective evolution law and the hydrocarbon generation peak determine the behavior of the hydrocarbon reservoir. Based on the data of outcrops, cores, thin sections, logs, sound emission experiments, fluid inclusion analyses, oil component analyses and carbon isotope analyses, the distribution characteristics of the fractures, the fracture sequence and the relationship between the fractures and the hydrocarbon accumulation are discussed. The results show that the structural fracture is the dominant fracture type in the reservoirs of Triassic tight sandstone in the north of Dongpu Depression. The average porosity of the fractures and the related dissolved pores is 2.25%, and the average permeability is about 40x10^-3 μm2. The fractures and the related dissolved pores are important storage spaces and seepage channels. The fractures of the light sandstone reservoir of Triassic are formed in two stages. The oil sources of Triassic arethe source rocks of Sha3 and Sha4 Member of Palaeogene whose peak period of the hydrocarbon generation is lhe period when the Dongying-Guantao Formation is fimned. But the diagenesis was completed betore Cenozoic. The distribution of oil reservoirs is controlled by the development of fractures and high part of the structure.