纯化油田沙四段上亚段自然电位曲线异常影响因素

Influential factor of SP curve in upper Sha4 member,Chunhua oilfiel

纯化油田沙四段上亚段储层自然电位测井资料出现异常现象,因此,在储层识别和划分过程中,经常会漏失储层或出现储层厚度划分不准确的情况。从自然电位形成机理出发,对地层厚度、地层水矿化度和岩性变化等因素对自然电位的影响进行了分析。研究结果表明:储层自然电位曲线无明显异常是地层压力、储层厚度、储层流体性质和储层岩性等因素作用所致;储层自然电位曲线出现正异常,是由于钻井液滤液的矿化度高于地层水矿化度;泥岩段自然电位曲线出现负异常是由于地层碳酸盐含量较高以及异常高压产生微裂缝等。利用研究成果,使自然电位曲线异常井段储层识别精度由原来的80%提高到98.3%。

The abnormal phenomena of the data of SP log appeared in the upper Sha4 member in Chunhua oilfield. Some reservoirs have been missed easily and the thickness of some reservoir is inaccurate during the process of identifying reservoir. Based on the theory of SP curve occur, some reasons are analyzed such as formation thickness, formation water salinity and lithological change. The result shows that the abnormal pressure, reservoir thickness, lithology and fluid property caused salt concentration unequal of drilling fluid when the formation was drilled, and this resulted in the anomaly drop of SP curve. In some reservoir, the mud filtrate salinity is more than formation water salinity, this caused SP curve anomaly positive. High carbonate content and microfracture caused by abnormal pressure are the main reasons resulted in SP curve anomaly negative in mudstone. The research obtained good effect in the process of production and improved the accuracy of the logging data interpretation.