Instantaneous resistivity vector difference used to simulate the seepage of polymer flooding in an oilfield

摘要

The instantaneous resistivity vector difference provides a method for monitoring the predominant seepage path of oil in real time remaining in a reservoir by numerical simulation. The target stratum in Shahejie Formation, Bohai Bay Basin, eastern North China has a relatively high resistivity (15-25 Omega m), which is reduced to 3-10 Omega m with the in-pouring of viscous polymer-water solutions. The instantaneous resistivity (rho(t)) of each monitored well-point changes with the continuous injection of polymer. Mitchell's improved model calculates rho(t) for every well-point at time t, and its reliability is verified by the core-displacement and production-logging methods. Using first-order differences and a differential model to recognize anomalous changes in the target zone, we can effectively extract and highlight changes in the resistivity of the target layer caused by polymer injection, and determine the distribution of resistivity. The position of maximum change in instantaneous resistivity in each direction can be calculated using second-order differences, with the zero line reflecting the boundary position of the anomalous body. The rho(t) differential results is consistent with H-3 tracking results. This study aimed to determine the characteristics of the predominant seepage field in the study area, provide real-time technical support for the deployment and adjustment of polymer flooding schemes avoiding an inefficient polymer cycle, and improve the tertiary recovery factor of oilfields.