Numerical simulation on pressure response of formation testing while drilling in anisotropic formations
Dynamic intrusion of drilling fluid and formation anisotropy will lead to different pressure response characteristics during formation testing and directly affect the interpretation accuracy of formation pressure test results.Therefore,based on the seepage theory of anisotropic porous media,a mathematical model of pressure response of formation testing while drilling in transverse isotropic formation under drilling fluid intrusion was established.The finite element method was used to solve the model,and the model was verified by comparing with the classical analytical solution.The influence of permeability anisotropy,formation occurrence,suction interval time and suction probe radius on formation pressure response while drilling is analyzed.The results show that the degree of formation anisotropy and formation occurrence have great influence on the pressure increase around the well caused by drilling fluid invasion in the pre-pumping stage.After formation pressurization around the well,the initial response value of formation pressure tested while drilling is higher than the original formation pressure.During pressure recovery,the pressure first increases and then decreases.The smaller the anisotropy of permeability,formation dip and inclination are,the larger the initial pressure responsevalue and the pressure drop value are in the suction pressure drop stage,and the slower the pressure recovery rate is in the pressure recovery stage.The suction interval time and the suction probe radius also affect the pressure response behavior.The smaller the suction interval time is,the larger the initial pressure is.The larger the probe radius,the faster the pressure recovery rate.This paper reveals the influence of permeability anisotropy on the pressure response of formation testing while drilling,which can provide theoretical basis for interpretation of formation testing results and inversion of formation parameters.
formation testing while drillingdrilling fluid invasionanisotropypermeabilitypressure responsenumerical simulation
万方数据
维普
