用Mohr-Coulomb破坏准则预测最小水平主应力的实验方法

通过岩石力学实验，测定岩样的内聚力、摩擦系数和单轴抗压强度等岩石力学参数，可以用常规的Mohr-Coulomb破坏准则确定最小主应力。采用长庆油田、二连油田、吉林油田和四川盆地、塔里木盆地以及委内瑞拉将要进行水力压裂施工的砂岩地层的岩样，用该方法测定最小主应力，将测定结果与长源距声波测井和微压裂测定结果对比，误差一般为2～3MPa，证实这是一种经济可靠的方法。图1表1参12

Determination of minimum in-situ stress from normalized Mohr-Coulomb failure criteria

Minimum in-situ stress could be obtained from normalized Mohr-Coulomb failure criteria through rock mechanical property testing. These properties include cohesion, frictional angle and uniaxial strength along failure plane. Tested samples were taken from different sandstone formations of Changqing, Erlian, Jilin Oilfield, Sichuan and Tarim Basin and Venezuela and hydraulic fracturing treatments would be performed in these formations. By comparing experimental results with those obtained from long distance sonic logging and mini-frac, it showed that the differences were within 2-3MPa. So it is an economic and reliable method to determine minimum in-situ stress from normalized Mohr-Coulomb failure criteria.