自然电位测井技术在隐蔽油气层识别中的应用

南堡凹陷部分油层电阻率较低,分布面积广泛,纵向上与高电阻率油气层、高电阻率水层间互发育,在测井特征上具有复杂和隐蔽特性,电阻率测井反映出较大的局限性.以自然电位形成机理和岩石物理试验为基础,开展了薄膜电位与阳离子交换量和岩心含水饱和度等物理量之间的关系研究,明确了自然电位极性和异常幅度与地层水矿化度、含油饱和度、阳离子交换量之间的对应关系,提出了基于合理设计钻井液电阻率为前提、利用自然电位极性和异常幅度为定性解释基础、以双视地层水电阻率比值为定量解释指标的隐蔽油气层识别方法.实例表明,在电阻率-孔隙度测井油气层识别体系中,自然电位信息的应用大大增强了对低电阻率、低电阻增大率等油气层的识别能力,在隐蔽油气层识别技术中发挥了重要作用.

Application of spontaneous potential logging in recognition of blind zone

.Some of oil layers in Nanpu depression have low resistivity and distribute widely in the region, alternatively with high resistivity oil and water layer. Complexity and concealment are the characteristics of this kind of layer during logging. It is difficult to describe them only by resistivity. Based on formation mechanism of spontaneous potential and rock physical experi-ments, the relations between membrane potential and physical properties were studied, such as cation exchange capacity and water saturation, etc. The relations among spontaneous potential polarity, abnormal amplitude, reservoir water salinity, oil saturation, cation exchange capacity have been understood. Recognition method for blind zone was proposed, which is based on reasonable design of mud resistivity, taking spontaneous potential-abnormal amplitude as qualitative explanation base, and double apparent resistivity ratio of reservoir water as interoperation index. A lot of application cases show that, the application of spontaneous potential information improved the recognition of low resistivity layer in resistivity-porosity logging system, and has an important effect on recognition of blind zone.