应用断裂力学理论建立油气井压裂时岩石破裂压力计算模型

Establishing the models for calculating the fracturing pressure of formation rock during oil/gas wells fracturing by using fracture mechanics theory

考虑地层岩石存在天然微裂隙这一客观事实,运用断裂力学理论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;并对某油田几口井进行了实算与电算对比.结果表明,运用断裂理论建立的破裂压力计算模型由于考虑了裂隙的存在,与地层的实际更为吻合,因而准确性更高,适用范围更广.其计算结果与现场实测值更为接近,从而也验证了模型的可靠性.

According to the fact that there are natural micro cracks in formation rock, the stress intensity factor formulas of the cracks under the common action of formation stress and fracturing fluid are established based on fracture mechanics theory. The models for calculating formation fracturing pressure are obtained on the basis of fracturing criterion, and the reliability of these models is proved by the comparison of the calculated formation fracturing pressures of several wells in an oilfield with the actually measured ones.