Numerical Simulation Study of Focused Borehole to Surface Electric Imaging

Hu, Haitao (CNPC Logging Co. Ltd. Research Institute of Logging Technology) | Xiao, Zhanshan (CNPC Logging Co. Ltd. Research Institute of Logging Technology) | Zhao, Baocheng (CNPC Logging Co. Ltd. Research Institute of Logging Technology) | Yu, Zhennan (CNPC Logging Co. Ltd. Research Institute of Logging Technology) | Zhu, Ruiming (CNPC Logging Co. Ltd. Research Institute of Logging Technology) | Liu, Jianguo (CNPC Logging Co. Ltd. Research Institute of Logging Technology)

OnePetro 

Abstract

Focused borehole to surface electric imaging is researched through numerical simulation in this study, this method makes downhole electrical logging synchronize with three dimensional space electrical exploration near the well, and combines borehole electrical logging with surface electrical prospecting, which can expand spatial scale of well logging evaluation technology and increase vertical resolution of borehole to surface electric imaging evaluation technology. This method can be used for detecting the geological information around well and between wells and wells. It provides a new means for exploration of residual oil distribution and evaluation of unconventional reservoirs fracturing effect. In this method, a new electrode structure, multi frequency focused high power transmission mode and surface reception modes are adopted. Based on the three dimensional finite element numerical simulation method, the instrument response characteristics in homogeneous formation and in homogeneous formation are analyzed. The influences of electrode depth, electrode length, and current return electrode orientation on surface potential distribution are analyzed. The results indicate that borehole to surface electric imaging system can effectively identify formation resistivity anomalies. The larger the spatial scale of resistivity anomaly, the better the recognition effect. Under certain conditions, downhole emission electrode depth is inversely proportional to surface potential distribution distortion, and downhole emission electrode length is proportional to it. When current return electrode B is placed far enough from the wellhead, the influence of electrode B orientation on surface potential distribution is negligible.