横观各向同性地层破裂压力测井计算方法

Fracture Pressure Calculation Method in Transversely Isotropic Formation by Logging

破裂压力是钻井工程、完井工程和水力压裂改造技术的关键参数之一, 利用测井资料计算连续的地层破裂压力是最常用的方法, 但常规计算方法忽略了地层各向异性的影响。为此, 将地层视为横向各向同性介质, 通过计算弹性刚度矩阵得到垂向和横向的杨氏模量及泊松比;考虑垂向应力与水平应变的关系了, 推导出基于深度— 应变关系计算地层破裂压力的新公式;最后, 将其优化编程并应用于L区块地层破裂压力的计算。地层破裂压力的现场实测结果和测井预测结果对比表明, L1井4266m处水力压裂实测地层破裂压力为90. 5MPa, 传统方法计算的破裂压力为93. 5MPa (与实测结果相对误差为5. 4%) 、横观各向同性方法计算的破裂压力为95. 4MPa (与实测结果相对误差为3. 3%) , 新方法计算的地层破裂压力精度优于传统方法计算的地层破裂压力精度, 有良好的适用性和可比性。

Fracture pressure is one of the key parameters in drilling engineering, completion engineering and hydraulic fracturing technology. Using logging data to calculate continuous formation fracture pressure is the most commonly used method, but the effect of formation anisotropy is usually ignored by the conventional method. To this end, the formation is considered as the transversely isotropic medium, and the Young' s modulus and Poisson's ratio in the vertical and horizontal directions are obtained by calculating the elastic stiffness matrix. By considering the relationship between vertical stress and horizontal strain, a novel formula is derived to calculate the formation fracture pressure based on the relationship between depth and strain. Finally, this novel formation fracture pressure formula is optimally programmed and applied to the calculation of the formation fracture pressure in Block L. The comparison between the field measurement results of formation fracture pressure and the logging prediction results shows that the measured formation fracture pressure of hydraulic fracturing at 4, 266m in Well L1 is 90. 5MPa, while the fracture pressure calculated by the traditional method is 93. 5MPa (with a relative error of 5. 4% compared with the measured results) , and the fracture pressure calculated by the transversely isotropic method is 95. 4MPa (with a relative error of 3. 3% compared with the measured results) . The accuracy of the formation fracture pressure calculated by the new method is better than that of the formation fracture pressure calculated by the traditional method, which is applicable and comparable.