基于BF-PSO算法的水平井电阻率各向异性数值模拟与校正

Numerical Simulation and Correction of Resistivity Anisotropy in Horizontal Wells Based on BF-PSO Algorithm

水平井井眼轨迹与地层的相对位置发生变化,使得常规电测井仪器响应机理发生改变,电阻率测井表现出各向异性特征。为准确求取储层含油饱和度,必须对水平井的井斜角进行校正。运用有限元方法模拟在地层中双侧向测井仪器的电场分布,结合监督电极电势得到不同地层倾角条件下双侧向测井电阻率;利用数值模拟结果建立电阻率正演模型;结合基于粒子群算法的细菌觅食全局优化算法反演地层真实的电阻率。结果表明,电阻率受地层倾角的影响随着井斜角的增大而逐渐增大。利用拟合出的正反演模型,配合基于粒子群算法的细菌觅食全局优化算法,对准葛尔盆地玛湖地区水平井A和B测得的视电阻率进行了井斜角校正,得到了真实反映地层特性的电阻率值,并结合试油资料验证校正后的电阻率更能反映真实的含油饱和度。

Resistivity is an important parameter for identifying the properties of reservoir fluids.The trajectory of a horizontal well changing relative to formation causes the response mechanism of a conventional electrical logging tool to change,and the resistivity logging data are anisotropic.To get accurate oil saturation,it is necessary to correct the inclination of the trajectory.First the finite-element method is used to simulate the electric field distribution of the emitter electrodes of a downhole dual-lateral logging tool,and the dual-lateral logging apparent resistivity at different formation dips is obtained by considering the potential of the monitoring electrode;then a forward resistivity model is established;and finally,true formation resistivity is inverted by the bacterial foraging algorithm based on particle swarm optimization.The results show that resistivity is influenced by formation dip and increases with the deviation of trajectory.Taking horizontal wells A and B in the Mahu block in the Junggar Basin as cases,using fitted forward and inversion models and the bacterial foraging algorithm,trajectory deviation was corrected to the apparent resistivity recorded in the two wells.After further corrected by production test data,the final formation resistivity is more effective to reflect underground oil saturation.