泥浆侵入地层双感应测井曲线正负差异特性分析

The Influential Factors on Electrolog Response of Formation with Mud Filtration Invasion

泥浆侵入地层径向电阻率发生不同的变化造成以电测井资料识别油气层困难。依据油水两相渗流理论、水的对流方程 ,结合电测井理论 ,进行泥浆侵入地层的双感应测井响应特性分析。研究表明 ,泥浆侵入地层的径向电阻率分布较为复杂 ,深中感应曲线的正、负差异不仅与储层含油性有关 ,同时受到泥浆滤液与地层水矿化度差异、束缚水饱和度、残余油气饱和度等因素影响。油层减阻侵入是有条件的 ,当泥浆滤液与地层水矿化度差异较大、束缚水饱和度、残余油气饱和度较高时 ,油层可表现为增阻侵入。不能简单根据深浅电阻率曲线幅度的差异性直接判断油气、水层 ,必须结合该研究区块地层水矿化度、泥浆性质、地层特性等因素进行综合判断。

The radial complex resistivity distribution of the formation enlarges the difficulty in evaluating reservoir with electrolog. In this paper, the influential factors on the dual induction logging response of reservoir with mud filtrate invasion are analyzed on the basis of the filtration theory of oil-water two-phase flow, the diffusion equation and the electrolog theory. As a result, the radial resistivity distribution of formation is very complex, and the difference of the deep and shallow resistivity logs not only rely on the oil-bearing degree, but the salinity difference between formation water and mud filtration, the saturation of bound water and the residual oil saturation of formation. The decreased resistance invasion in the hydrocarbon zone is not absolute. For reservoirs with high bound water saturation and high residual oil saturation, the increased resistance invasion can appear in oil layer if the salinity difference between formation water and mud filtration is large enough . Therefore, the water-oil bearing properties of the formation can not simply identified according to the difference characters of deep resistivity log and shallow one.