Development Characteristics And Main Controlling Factors Of Multi-scale Fractures In Marine Shale In Eastern Chongqing

The distribution of fractures in shales is an important parameter that must be taken into account in the development of shale gas.Fractures can also serve as an important reservoir space,but there are few studies on shale fractures.By analyzing the image logging,core and lamella data,the fracture line density of the Longmaxi Formation read by the imaging logging in the study area is approximately 0.33⁰.48 bars/m;The fracture line density of the Longmaxi Formation in the study area obtained from the observation of the core is approximately from 40⁶5 bars/m,the line density of the fracture in the Niutitang Formation obtained from the observation of the core is about 62⁸3 bars/m;The areal density of fractures in the Longmaxi Formation is 1.91×10^-2mm^-1,the areal density of fracture surface in the Niutitang Formation is 2.39×10^-2mm^-1,and the fractures in Niutitang Formation in the study area is more developed than the Longmaxi Formation.It is found that the contents of TOC and brittle minerals in the Longmaxi Formation and Niutitang Formation are the main controlling factors for fracture development.The individual minerals do not determine the degree of fracture development and shale heterogeneity.is not the main controlling factor for the development of fractures.By establishing a shale fracture porosity calculation model,it is calculated that the fractured porosity range of the Longmaxi Formation in the study area is 0.09⁰.41%,the ratio of fracture porosity to total porosity is 2.56¹6.62%,and in the Niutitang Formation the fracture porosity is in the range of 0.11⁰.41%,and the ratio of fracture porosity to total porosity is 6.62¹7.05%.The pore space provided by the shale fracture is an important reservoir space,and the ratio of the fracture porosity and the fracture porosity of the Niutitang Formation is larger than that of the Longmaxi Formation.Fractures have a great influence on the seepage performance of shale.The permeability of samples with fractures may increase by tens to thousands of times compared with the permeability of samples without fractures in the same area.