低渗透砂砾岩油藏水敏伤害机理及注入水水源优选

Water-sensitive damage mechanism and the injection water source optimization of low permeability sandy conglomerate reservoirs

利用全流度理论评价不同矿化度注入水驱油实验效果,并结合驱替前后的扫描电镜、黏土矿物X衍射、非线性渗流与核磁共振实验对比分析结果和微粒运移抑制实验结果,分析北部湾盆地乌石区低渗透砂砾岩油藏水敏伤害和改善水驱机理。建立考虑流体低速非达西渗流与储集层应力敏感的油水两相流井产油量方程,定量评价水敏伤害导致的储集层物性和油水两相渗流能力变化对油藏产能的影响,并且根据不同种类注入水对应的岩心动态配伍性实验结果选择适合乌石区低渗透砂砾岩油藏的注入水水源。研究表明,注入水为2倍矿化度地层水时储集层渗流能力最强;乌石区储集层水敏伤害机理包括黏土矿物水化作用和微粒运移,通过增加注入水中阳离子(特别是K^+、Mg^2+)含量能够有效抑制储集层水敏伤害;浅层涠洲组地层水可作为乌石区低渗透砂砾岩油藏的注入水水源。

The global mobility theory was used to evaluate the experimental results of oil displacement with water of different salinities.The results of scanning electron microscopy,X diffraction of clay minerals,nonlinear seepage and nuclear magnetic resonance experiments and particle migration inhibition experiments before and after water flooding were compared to determine the mechanisms of water sensitive damage and enhanced water flooding mechanism of low permeability sandy conglomerate reservoirs in Wushi region of Beibuwan Basin,China.A production equation of the oil-water two phase flow well considering low-speed non-Darcy seepage and reservoir stress sensitivity was established to evaluate the effect of changes in reservoir properties and oil-water two-phase seepage capacity on reservoir productivity quantitatively,and injection water source suitable for the low permeability sandy conglomerate reservoirs in Wushi region was selected according to dynamic compatibility experimental results of different types of injected water.The seepage capacity of reservoir is the strongest when the injected water is formation water of 2 times salinity.The water-sensitive damage mechanisms of the reservoirs in Wushi region include hydration of clay minerals and particle migration.By increasing the content of cations(especially K^+and Mg^2+)in the injected water,the water-sensitive damage of the reservoir can be effectively inhibited.The formation water of Weizhou Formation can be used as the injection water source of low permeability sandy conglomerate reservoirs in the Wushi region.