煤储层水力压裂破裂压力影响因素数值模拟研究

Numerical simulation study on influence factors of hydraulic fracturing pressure in coal reservoir

为提高煤层气井的压裂效率,通过利用ANSYS有限元软件,模拟了煤层气井压裂过程中的降低煤层破裂压力的各种途径和方法,研究建立了套管射孔完井的应力计算模型,并计算了模拟煤岩破裂压力,分析了射孔长度、孔径、煤岩的泊松比与杨氏模量、地层深度等对煤岩破裂压力的影响。模拟结果表明,当射孔长度和射孔孔径分别控制在1 m左右和15 mm左右的情况下,有利于降低煤岩的破裂压力;较低的煤岩泊松比在一定程度上有利于减小破裂压力;煤岩杨氏模量对破裂压力的影响不大;而煤层的深度越大,其破裂压力受水平主应力差的影响越小。

In order to improve the fracturing efficiency of the coalbed methane well,an ANSYS finite element software was applied to simulate the different path and method to reduce the seam fracturing pressure during the coalbed methane well fracturing process. A stress calculation model of the perforation completion was researched and established. Thus a simulated coal / rock fracturing pressure was calculated and the perforation borehole length,diameter,coal / rock Poisson's Ratio and Young's Modulus,strata depth and others affected to the coal / rock fracturing pressure were analyzed. The simulation results showed that when the perforation borehole length and diameter were individually controlled about 1 m and 15 mm,the coal / rock fracturing pressure would be favorably reduced. A low coal / rock Poisson's ratio would be favorable to reduce the fracturing pressure in a certain degree. The coal / rock Young's Modulus would not have high influence to fracturing pressure. While more deep depth of seam,the fracturing pressure would have a less influence by horizontal main stress difference.