Abstract:

The lower Jurassic lowporosity and lowpermeability tight sandstone is a major reservoir of Dibei gas field in the Kuqa depression, Tarim Basin. As a migration channel and reservoir space, the development features and distribution of tectonic fractures is the key to oil and gas exploration and development. This study adopts the latest 3D structural map of the Dibei area, taking geological setting, geometry of strata, and faults into consideration, and divides the Ahe Formation into three sections. Based on the measured rock mechanics parameters, a three dimensional elastic finite element numerical simulation method is used to calculate the maximum principal stress of Pliocene structural stress field in the Kuqa depression. The calculated results matched the observed results. Under the restraints of 11 wells, the two factor method is proposed to simulate the development of tectonic fractures by means of rock failure value and strain energy density together to predict tectonic fracture density of the three sections of the Ahe Formation. The results show that the Yinan2Dixi1Dibei104 area and the area to the south of Dibei101Yinan5 as well as the area to the west of Tuzi1 and to the north of Tuzi3 have the highest density of fractures; in addition，the J1a23 formation is easier to be cracked than the J1a1 formation. The prediction results of tectonic fractures in the Ahe Formation provide a new geological reference for the exploration and development of Dibei gasfield.

Key words: tectonic fractures, tight sandstone, Ahe Formation, finite element, two factor method