裂缝性特低渗储层油水渗流特征研究

Study on oil-water seepage characteristics of fractured ultra-low permeability reservoir

裂缝性特低渗储层进行常规注水时,存在水窜水淹、水驱波及体积小等问题,水驱采收率低。为增强注水受效,针对裂缝性特低渗储层渗流机理不清的问题,以宝塔采油厂姚280区块储层天然岩心为研究对象,运用室内动、静态物理模拟实验的方法,揭示了裂缝性特低渗储层渗吸、驱替双重作用下的采油效率主控因素及影响规律。实验结果表明①岩心与水接触面积越大渗吸效果越好,全裸露岩心样品的渗吸采出程度为仅裸露上下两端样品的2.5倍;②实验岩心渗透率在(0.506~0.721)×10^(-3)μm^(2)时,静态自发渗吸主要在前100 min,渗透率越高,渗吸采出程度越高、渗吸速率衰竭越快;③渗吸围压升高,渗吸采油效果先增强后下降,最佳值约为4 MPa,采出程度可达12.56%;④对于渗透率为(0.506~0.721)×10^(-3)μm^(2)的岩心样品,驱替采出程度小于自发渗吸采出程度,且发生有效驱替需压力梯度大于0.3 MPa/cm。

Conventional water injection in fractured ultra-low permeability reservoirs has the problems of water channeling,it would lead to low recovery factor.In order to enhance the effect of water injection,aiming at the problem of unclear seepage mechanism in fractured ultra-low permeability reservoirs,the main control factors and influencing rules of oil production efficiency under the double effects of imbibition and displacement in fractured ultra-low permeability reservoirs are revealed by using indoor dynamic and static physical simulation experiments.The natural cores of Yao 280 block in Baota Oil Production Plant would be the research objects.The experimental results show that:①The larger the contact area between the core and the water,the better the imbibition effect would be,the imbibition recovery factor of fully exposed core sample is 2.5 times of that of exposed both ends core samples;②When the permeability of core samples are in the range of(0.506~0.721)×10^(-3)μm^(2),the imbibition effect of the core samples is mainly in the first 100 min,and the higher the permeability,the higher the imbibition recovery factor and the faster the rate of imbibition depletion;③The confining pressure increases,the imbibition effect first rises and then decreases,and the optimal value is about 4 MPa which the recovery factor is 12.56%;④When the permeability is in the range of(0.506~0.721)×10^(-3)μm^(2),the spontaneous imbibition is better than displacement effect.The pressure gradient required for effective displacement is higher than 0.3 MPa/cm.