泥浆侵入致密气层双侧向电阻率变化模拟研究

Changes of simulation of dual lateral resistivity in wake of mud invading tight gas

井眼压力高于地层压力会导致泥浆侵入,电阻率测井响应受到泥浆侵入的影响而不能真正反映地层的电阻率特性。笔者依据双侧向电阻率测井的基本机理,气-水两相渗流方程及传导对流方程,进行仿真模拟,得到泥浆侵入高矿化度致密气层的二维轴对称模型。研究含水饱和度、地层电阻率以及深浅侧向井壁电场分布随侵入时间的变化规律。研究发现:随着侵入时间的增加,含水饱和度增大,地层电阻率减小;泥浆侵入对致密气层深浅侧向测井响应都产生一定的影响,导致致密气层深浅侧向电阻率幅度差比常规储层深浅侧向电阻率幅度差大,幅度差峰值出现较早。

The fact that borehole pressure is higher than formation pressure will lead to mud invasion,and resistivity logging cannot truly reflect the formation resistivity. According to the basic mechanism of dual lateral resistivity log and gas-water two phase percolation equation and conduction equation,this study carried on the simulation and got two-dimensional axisymmetric model of high salinity tight gas reservoir which is invaded by mud. In this paper,the variation of water saturation,formation resistivity and electric field distribution of deep / shallow lateral wall over time were studied. It found that water saturation increases and formation resistivity decreases as the time increases. Mud invasion influences both deep laterolog and shallow laterolog response,which lead to resistivity difference of tight gas of deep laterolog and shallow laterolog is higher than that of conventional one,and the resistivity difference peak of tight gas appear earlier.