考虑黏土连续性影响的低孔隙度低渗透率砂岩储层导电模型研究

On Conductivity Model with Continuous Clay Distribution in Low Porosity and Low Permeability Shaly Sand Reservoirs

针对高含泥低孔隙度低渗透率储层具有连续产状的黏土和高束缚水等特征,基于有效介质对称导电理论,考虑黏土连续性对于岩石导电规律的影响,建立了低孔隙度低渗透率泥质砂岩储层电导率模型。理论分析黏土连续性对岩石导电规律的影响,发现当黏土产状从断续到连续时地层导电性增强、地层电阻增大系数降低;针对黏土包裹的球形颗粒立方体模型和斜方体模型,估算出了形成单层和双层黏土颗粒包裹所需的黏土含量界限值。通过岩电实验数据验证,说明黏土颗粒的连续性随黏土含量变化而变化。实际应用表明,该导电模型能描述高含泥低孔隙度低渗透率储层的导电规律。

Research on conductance law in low porosity and low permeability shaly sand reservoirs is one of the key methods to improve the accuracy to calculate saturation. In this paper, based on symmetrical effective medium conductance theory, a new conductivity model is proposed for low porosity and low permeability shaly sand reservoirs with continuous clay distribution and high capillary bound water in pores. In the model the effect of continuity of clay distribution on shaly sand conductivity is considered. By theoretical analysis, it is found that the conductivity of formation increases and resistivity index reduces as clay distribution in pores occurs from discontinuity to continuity. Clay content cutoffs can be estimated for cubic clay-covered grain arrangement model and rhomboidal clay-covered grain arrangement model while the single-layer clay or double layer clay occurs around the grains. Also, validation of experimental data of Group 2 from Wax man and Smits shows that the continuity of clay distribution changes with the clay content. The interpretation result for log data proves that the proposed model can describe the conductance law in low porosity and low permeability shaly sand reservoirs.