Numerical simulation of stress field of Fu-2 Member in Tongcheng fault zone and development suggestions

Key words:  fractured reservoir  stress field  numerical simulation  reservoir breakdown pressure  fracture open pressure  Tongcheng fault zone

Abstract:

Based on numerical simulations of the ancient stress field of the fracture formation, the fracture occurrence of Fu-2 Member in Tongcheng fault zone was predicted. Present-time in-situ stress orientations for wells were determined using the core velocity experiment and micro seismic monitoring technology. The size of present-time in-situ stress for wells was determined by the combination of the fracturing data. Numerical simulations of the present-time stress field were carried out by ascertaining the rock mechanical parameters and establishing the finite element model. The reservoir natural fracture opening pressure and the opening sequence were predicted on the basis of fracture occurrence and present-time stress field simulation state. The results are as follows:the present-time horizontal maximum stress is NEE. Fractures with the NEE maximum stress direction open first and fractures with the SEE direction open afterwards in the process of waterflooding. Fracture opening pressure increases when the angle between the fracture direction and the maximum horizontal stress direction increases. Fracture depth and opening pressure also have positive correlation. Fracture opening pressure is between 25-45 MPa in the structural high part(1850-2350 m) and 45-75 MPa in the low part (3300-4000 m). It is proposed that different blocks use different injection pressures by calculating the actual reservoir breakdown pressures to ensure the high and stable production of oil and gas wells.