长垣地区低孔隙度低渗透率砂岩储层中连通导电模型的应用

Study on Connectivity Model for Low Porosity and Permeability Sand Reservoirs in Daqing Placanticline

研究了长垣地区F油层储层特征,该区F油层为低孔隙度特低渗透率储层,泥质含量高,微孔隙发育,孔隙结构复杂,束缚水饱和度高。基于该区F油层具有泥质附加导电、束缚水导电和可动水导电的特征,结合连通导电理论,将地层划分为骨架相、自由流体相和黏土相。考虑了黏土水、束缚水、可动水导电路径不同对岩石导电性的影响,认为3个导电相有不同的导电指数,并对其分别应用连通方程,得出各相电导率。用混合导电理论将各相电导率与地层总电导率联系起来,建立适用于长垣地区F油层的连通导电模型。讨论了连通导电模型中水连通校正系数对岩石导电规律的影响,从理论上分析了各导电相导电指数间的相互关系,得出该地区F油层的骨架相和黏土相导电指数均小于等于自由流体相导电指数。利用岩电实验数据,采用最优化方法确定了模型中的各导电相导电指数。密闭取心井含水饱和度对比和试油结果验证表明,该模型可很好地应用于该区F油层的低孔隙度低渗透率泥质砂岩储层定量评价。

Studied are the reservoir characters in F formation of Daqing placanticline, where the reservoir is characterized by low porosity, low permeability, high shale content, more microscopic capillary pore, complex pore structure and high irreducible water saturation. Based on three conducting components of shale, irreducible water and free water in F formation, and the features of connectivity theory, the reservoirs in F formation are divided into matrix phase, free fluid phase and clay phase. After analyzing the effect of the conductance paths of clay water, free water and irreducible water on rock conductivity, it is found that the three conducting phases have different conductivity exponents, and the conductivity of each phase may be calculated using connectivity equation. Finally, total rock conductivity can be related with the conductivities of three phases by mixing conductivity law, and the connectivity model in F formation of Daqing placanticline is established. After that, the influence of water connectivity correction index on the conductivity of the rock is discussed, and the relationship of conductivity exponent of each phase is analyzed theoretically. Therefore, it is concluded that the conductivity exponents of matrix phase and clay phase are either less than or equal to that of the free fluid phase. Also, the conductivity exponent of each phase is determined from core experimental data with an optimization technology. Comparison of core-analyzed water saturation in sealed coring well with well test results shows that the connectivity model can be used in quantitative evaluation of low porosity and permeability shaly sand reservoirs in F formation.