关键词: 构造裂缝, 低孔低渗, 有限元数值模拟, 定量预测, 库车坳陷

Abstract: The Jurassic low-porosity and low-permeability sandstone is an important reservoir of Yinan-Tuzi area in Kuche Depression. Well-developed tectonic fractures serve as important migration pathways and accumulation spaces, and their nature and distribution are the key to guiding further exploitation. Most fractures without filling veins are supposed to develop after the Miocene, on the base of the analysis of fossil stress field evolution and the nature of filling. On the basis of previous acoustic emission studies and rock mechanical tests, a 3-D finite elemental simulation on the tectonic stress field of Kuche depression was made to predict the distribution of tectonic fractures in Yinan-Tuzi area, considering several factors such as geologic setting, geometry of strata, and faults etc. With the constraints of 14 segments of wells, the modeling result showed that the distribution of tectonic fractures is controlled by several aspects such as different rock fracture mechanics for each layers, the shape of fault, and the curvatures of strata. Among all layers, the formation of Lower Jurassic has the highest density of fractures, within which the density in the southwest area towards Well Yinan 2 reaches more than 1.5 m-1on average and decreases gradually eastward.

Key words: tectonic fractures, low porosity and low permeability, finite element, quantitative prediction, Kuche depression