Fracture Pressure Calculation Method in Transversely Isotropic Formation by Logging

Abstract

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.