纯砂岩油层水淹高电阻率现象分析

Analysis on High Resistivity of Water-Flooding in Pure Sandstone Reservoir

当油田进入高含水开发期之后,中水淹、强水淹层电阻率高,岩心水驱实验过程中电阻率增大。为提高水淹层解释符合率,以纯砂岩储层为研究对象,利用阿尔奇模型表征孔隙式储层电学性质,通过理论模拟计算结果分析不同水淹阶段油层电阻率变化规律、电阻率增大现象及其存在条件。模拟结果表明,纯砂岩油层淡水驱电阻率增大现象仅出现在理论与岩心实验之中,实际地层中尤其在污水回注驱状况下不存在。实际中强水淹油层高电阻率不是水淹升高的结果,而是电阻率高的油层由于水淹作用减阻到较高电阻率状态。水淹层解释过程中需考虑原始油层电阻率,通过水淹前、后对比来获得正确的水淹结论。

When the oilfield enters the high water-flooded development period,the medium water-flooded layers and strong water-flooded layers have high resistivity,the resistivity increases during the core water-flooded experiment.In order to improve the interpretation coincidence rate of water-flooded layers,the Archie model is used to characterize the electrical properties of pure sandstone reservoirs.Theoretical simulation results are used to analyze the changes of resistivity and the existence conditions.Results show that the increase of the resistivity in pure sandstone reservoirs only exist in theory and core experiments,but not in actual formations especially under the condition of sewage injection.The high resistivity of strong water-flooded layers is not the result of increased water-flooded,but the oil layers with higher resistivity decrease to a high resistivity state by water-flooded.The resistivity of the original oil layer should be considered during the interpretation of the water-flooded layer,and the conclusion should be compared with the condition of unflooded and water-flooded.