过套管电阻率测井仪器刻度及井下测量数值模拟

为提高过套管电阻率测井的准确性,对刻度装置建模并数值模拟刻度过程,提出套管电流近似算法,数值模拟薄、厚两种地层模型的近似电流、地层视电阻率和二阶电位差。结果表明:仪器刻度数值模拟结果能够确定刻度装置参数,提供理论刻度曲线,辅助计算电极系系数;井下测量数值模拟所提出的电流近似算法具有较强的地层分层能力,且低阻薄地层的视电阻率逼近程度明显下降,高阻厚地层的二阶电位差值极小,对测井仪分辨率要求较高。

Numerical simulation of resistivity logging through casing on instrument calibration and down-hole measurement

In order to improve the accuracy of resistivity logging through casing, numerical simulation research on instrument calibration and down-hole measurement was constructed. In the aspect of instrument calibration, the calibration device was modeled and the numerical simulation on instrument calibration was executed. In the aspect of down-hole measurement, the approximate method for current calculation was proposed, and the approximate current, the apparent formation resistivity and the second order potential difference of the thin layer and the thick layer were simulated numerically. The simulation results of instrument calibration help to select the parameter for the calibration device, provide the theoretical calibration curve and assist to calculate the coefficient of the electrode array. The simulation results of down-hole measurement show that the approximate method for current calculation has strong ability to distinguish layer boundaries, and the approximate degree of apparent formation resistivity for the thin layer with low resistivity drops obviously. The thick layer with high resistivity requires high instrument resolution because its second order potential difference is extremely small.