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提出近油源低渗透砂岩油藏中的油层和水层地层水电阻率(Rw)选值及饱和度计算方法.选取东营凹陷南斜坡沙河街组沙三段(ES3)、沙四段(ES4)不同含油级别岩样,利用离子色谱技术对其进行氯盐含量测试,发现不同含油级别样品氯离子质量浓度存在明显的差异,进一步将氯离子质量浓度折算成矿化度,明确了油层、水层地层水矿化度取值规律及差异成因.研究结果表明:东营凹陷南坡沙河街组低渗透砂岩油藏中油层地层水矿化度约是水层的1.2~1.7倍,从油气成藏角度分析认为,油层地层水主要为伴随烃运聚的高矿化度水赋存于岩石微孔隙中,且与水层或围岩隔离,不宜扩散交换,得以保持成藏流体高矿化度特征(平均大于30g/L),而水层中基本保留了原始沉积的低矿化度水,导致即使同一套油水系统中,油、水层具有不同的矿化度,这一认识对近油源的低渗透砂岩油藏应当具有普遍意义.进而在反算典型水层地层水电阻率的基础上,利用实验获得的水层和油层地层水电阻率比例(水层R_w≈1.45×油层R_w),优化了油层R_w选值方法,为有效提高研究区低渗透砂岩油藏的饱和度解释精度提供了依据.
(Rw) selection and saturation calculation method of formation oil layer and water layer in the oil-bearing low-permeability sandstone reservoir are proposed.The ES3 and ES4 of the Shahejie Formation in the south slope of Dongying Sag are selected, ) Different oil level rock samples, the use of ion chromatography for chloride content test found that samples of different oil levels of chloride ion concentration there is a clear difference, and further chloride ion mass concentration converted to salinity, clear the reservoir, water The results show that the salinity of formation water in the low permeability sandstone reservoirs of Shahejie Formation in the southern slope of Dongying Depression is about 1.2-1.7 times that of the aquifer, From the angle analysis, it is considered that the formation water in the reservoir mainly contains high salinity water accompanying the hydrocarbon migration and accumulation in the micro-pores of the rock and is isolated from the water layer or the surrounding rock. Therefore, it is not suitable for diffusion exchange to maintain the high salinity of the reservoir fluid (Average greater than 30g / L), while the water layer basically retained the original deposit of low salinity of water, resulting in even if the same set of oil and water systems, oil and water layers have different degrees of salinity, the understanding of near oil source Low permeability sandstone reservoir should have Based on the calculation of the formation water resistivity of the typical aquifer, the optimal method for the R_w selection of the reservoir is optimized by using the ratio of the water resistivity of the aquifer and the formation obtained from the experiment (water layer R_w≈1.45 × reservoir R_w) It provided the basis for effectively improving the saturation interpretation accuracy of low permeability sandstone reservoirs in the study area.