中文摘要：

摘要天然裂缝是致密油储层重要的储集空间和主要的渗透通道，影响致密油气成藏、富集规律、单井产能及其开发效果。本文利用野外相似露头、岩心、薄片及成像测井资料，在研究四川盆地中部下侏罗统致密灰岩储层裂缝类型和发育特征的基础上，阐明了其裂缝分布的主控因素与发育规律。四川盆地中部下侏罗统致密灰岩储层普遍发育构造裂缝和成岩裂缝，其中以高角度构造剪切裂缝为主，大部分裂缝为有效裂缝。在同一区域应力场作用下，构造裂缝的分布主要受岩性、层厚及构造的控制。其中灰岩中裂缝最发育，随着泥质含量的增加，泥质灰岩、灰质泥岩和泥岩的裂缝密度依次降低。总体上，随着灰岩层厚的增加，裂缝间距增大，裂缝发育程度降低。大安寨致密灰岩储层可以分为4种组合模式，不同组合模式的裂缝发育程度存在明显的差异，其中单层厚度为4～8m的介壳灰岩与单层厚度小于5m的泥页岩互层是形成裂缝的有利条件。不同构造部位的裂缝分布亦存在差异，其中断裂带附近与背斜轴部和转折端等构造高部位是裂缝发育的有利区域。

英文摘要：

Natural fractures are important storage space and fluid-flow channels for tight oil reservoirs. They have an influence on the petroleum accumulation, enrichment, single well production and development effect of tight oil reservoirs. Analogous outcrops, cores, thin sections and image logs are used to illuminate the main controlling factors and distribution laws of fractures based on the study of fracture types and characteristics in the Lower Jurassic tight limestones in central Sichuan Basin. The results show that tectonic and diagenetic fractures are widely developed in the study area. The tectonic-shear fractures with high-dip angles are the most abundant. Most fractures are effective without entirely filled. The fracture distribution is mainly controlled by lithology, bed thickness and structure in the same tectonic stress field. Fractures are the most abundant in limestones. Then with the increasing shale content, fracture intensities gradually decrease in argillaceous limestones, lime mudstones and mudstones. In general, fracture spaces increase with the increasing bed thickness of limestones, thus resulting in the decreasing fracture intensities. Tight limestone reservoir of the Da＇anzhai Formation can be divided into four combined models. Different combined models of the tight limestone reservoir present different fracture abundance. The interbeds of shell limestone with a thickness of 4- 8 m and mudstone with a thickness of generally less than 5 m are the most favorable for fracture development. Fracture development degree varies in different structures. Structural high parts, such as the axis and hinge zone of anticlines, and around fault zones are the favorable areas for fracture development.