骨架导电低阻油层人造岩样实验及导电规律与导电模型研究

Low resistivity reservoirs have become an important source for increase of oil reserves and oil production in oil field. The genetic types of low resistivity reservoirs are various, and matrix conduction is one of the major causes of low resistivity reservoirs. However, resistivity models for low resistivity reservoirs in current use are almost established on the basis of Archie equation, so they can't give a good description of conductive law of matrix-conducting low resistivity reservoirs. Therefore, the research project is on the low resistivity reservoirs in which rock matrix contains a certain amount of conductive minerals. First, matrix-conducting core samples with different shale distribution and shale content are designed and manufactured. Second, Matrix-conducting sample resistivity in different water salinity and oil saturation and corresponding experimental data are measured. Third, effects of shale distribution, shale content and conductive mineral content etc. on conductance mechanism of matrix-conducting core samples are studied with measured data. Forth, based on experimental research results of conductance mechanism of matrix-conducting low resistivity samples, a generalized resistivity model for matrix-conducting low resistivity reservoirs is proposed with effective medium pore combination conductance theory or symmetrical conductance theory. It considers that low resistivity in hydrocarbon bearing sands is caused by matrix grains with a certain amount of conductive minerals, high saline water, dispersed clay, high irreducible water saturation, and laminated shale. Finally, the accuracy of the model is evaluated to make it apply to matrix-conducting low resistivity reservoir interpretation and meet the needs of production for oil field.

低阻油层已成为油田增储上产的一个重要来源。由于低阻油层成因类型多样，而骨架导电又是低阻油层的主要成因之一，且现用的低阻油层电阻率模型均是在阿尔奇公式基础上建立的，尚不能描述骨架导电低阻油气层的导电规律。因此，本课题针对骨架含有导电矿物的低阻油层,人工压制的不同泥质分布形式及含量的骨架导电岩心样品,测量骨架导电岩样在不同含油饱和度下的电阻率及相关实验数据，从实验角度考察不同泥质分布形式和含量的骨架导电岩心的导电规律，研究泥质分布形式和泥质含量变化及骨架导电对泥质砂岩导电特性的影响。基于骨架导电低阻油层导电规律实验研究结果，利用有效介质孔隙结合导电理论或对称导电理论，考虑岩石骨架含有一定量的导电矿物、高矿化度地层水、黏土附加导电性、高束缚水及砂泥岩薄互层引起油层低阻的因素，建立适用于骨架导电低阻油层的通用电阻率模型，并评价模型精度，以适用于骨架导电低阻油层解释，使之满足油田生产需要。

通过本项目研究，取得了如下主要成果：.（1）形成了一套骨架导电混合泥质岩石人造岩样压制与成型技术。.固定石英砂质量，根据实验设计的人造岩样的黄铁矿和粘土体积含量，提出了一种黄铁矿和粘土质量的计算方法；采用该方法，按照设计的黄铁矿和粘土体积含量压制了骨架导电分散泥质长方体岩石，再在其上方压制一层粘土，制成了骨架导电混合泥质长方体岩石；在长方体岩石上钻取圆柱形岩心，经过封装成型制成了骨架导电混合泥质岩石人造岩样实验样品。.（2）建立了一套研究骨架导电低阻油层导电规律的实验方案。.对于骨架导电纯岩心和泥质岩心，分别取两块和三块并行样完成岩样的岩电和配套实验数据测量。原样、并行样1、并行样2的实验项目及顺序分别为孔渗、岩电测量，孔渗、核磁特性、压汞实验、阳离子交换能力测量，孔渗测量、全岩分析、粒度分析。.（3）分析总结了骨架导电岩石的导电规律。.实验研究表明，饱含水骨架导电纯岩样电导率随地层水电导率的增大而呈非线性增大，其电阻增大系数与含水饱和度关系在双对数坐标上为非线性关系。混合泥质岩样电导率随层状泥质含量、分散泥质含量、黄铁矿含量增大而增大，其电阻增大系数随层状泥质含量、分散泥质含量、黄铁矿含量增加而降低。骨架导电泥质岩样电导率随温度增大而增大。.（4）证明了有效介质对称导电理论和孔隙结合导电理论能够描述骨架完全由导电矿物组成的纯岩石以及分散泥质砂岩的导电规律。.（5）建立了可适用于五种成因类型同时存在的骨架导电低阻油层通用电阻率模型。.利用有效介质对称导电理论、电导率差分方程、连通导电方程与HB方程结合建立了3种能描述骨架导电、分散泥质导电、微孔隙水导电、可动水导电、层状泥质导电的通用电阻率模型。理论和实验证明了建立的电阻率模型能够描述骨架导电低阻油层的导电规律。.研究成果对人造岩样压制和实验有指导意义，对提高骨架导电低阻油层评价精度有很好的应用前景。