基于COMSOL的井地电阻率正演研究

Study on borehole-to-ground resistivity forward modeling based on COMSOL

随着我国石油开发的不断深入,大部分油田已经进入高含水开发期。井地电阻率方法作为一种新型的电法勘探方法,具有地层影响小、测量成本低等优点,逐渐成为剩余油分布研究的关键技术之一,因此,开展井地电阻率测量正演以及相关反演解释算法研究具有十分重要的意义。首先,利用有限元算法建立井地电阻率测量模型,进行了数学分析,并选取了合适的边界条件;其次,通过改变高阻异常体和低阻异常体在模型的分布位置,分析了异常体的方位对地表电位分布的影响;最后,根据所处理问题的模型,设置合理的边界条件,并利用COMSOL软件进行数值模拟,得到求解区域电位的分布情况。试验结果表明,依据COMSOL软件并利用混合边界条件所建立的井地电位数值模拟模型求解精度高,且收敛速度快。由此可见,COMSOL应用于井地电阻率正演研究是有效可行的。

With the deepening of petroleum development in our country, most of oilfields have entered high water cut development period. The borehole-to-ground resistivity method is a new electrical prospecting method, which has less influence on the formation and low cost of measurement, and becomes gradually one of key technologies for researehing the distribution of remaining oil. Therefore, it has very important significance to study the borehole-to-ground resistivity tbrward modeling and inversion interpretation algorithm. Firstly, this paper established a forward modeling by using finite element method （FEM）, conducted mathematical analysis and selecled reasonable boundary conditions. Secondly, through changing the distribution of high resistivity anomaly and low resistivity anomaly in model, it analyzed lhe effeet of anomaly position on the surfaee potential distribution. Finally, aceording to the model to deal wilh problems, it set up reasonable boundary conditions, made the numerical simulation by COMSOL and got the potential distribution. The resuhs of numerical experiments show that the numerical simulation model of borehole-to-ground resistivity established based on COMSOL and using the mixed boundary condition can get a high precision and thst convergence speed. Therefore, the application of COMSOL in borehole-to-ground resistivity forward research is effective and feasible.