运用断裂理论确定地层破裂压力(P_F)值

Determination of the Fracturing Pressure of Formation with Fracture Mechanics Theory

本文综合应用断裂理论、岩体力学等知识,对油气层压裂机理进行了有益的探讨。通过对油气井井底的地应力静应力场,和动应力场的分析,考虑地层岩石存在天然微裂隙这一客现事实。建立了地应力与压裂液共同作用时,地层裂隙的应力强度因子表达式;根据断裂判据,推得了地层破裂压力计算模型;并对四川油田川中矿区几口井进行了实算与电算对比,验证了模型的可靠性。

This paper discusses fracture mechanism of oil/gas bearing formation with both linear elastic mechanics of fracture and rock mechanics. By analysing the formation stress at the bottom of a wellbore (with the effect of both static stress field and kinetic stress field of the earth taken into consideration) this paper establishes the stress intensity factors formulas under the action of both formation stress and fluid stress, which is based on the fact that natural micro-crack exists in the formation rock. On the basis of fracturing criterion, models for computing the formation fracturing pressure have been obtained and the reliability of those models have been proved through actural computation and comparison of several wells in central Sichuan Oil Field.