可动水饱和度作为低渗砂岩气藏储层评价参数的论证

Demonstration of Mobile Water Saturation as Evaluation Parameter of Low Permeability Sandstone Gas Reservoir

由于低渗砂岩气藏高含水饱和度、易产水且产水量对于气藏的开发效果影响很大,使得采用常规储层评价方法评价低渗砂岩气藏时出现较大偏差,因此寻求能表征储层产水特征的新评价参数是低渗砂岩气藏储层评价的前提。通过室内大量岩心核磁共振测试的可动水饱和度及其与对应储层物性孔隙度、渗透率及含水饱和度之间的关系对比分析表明,低渗砂岩储层的可动水饱和度与储层孔隙度、渗透率及原始含水饱和度之间都没有很好的对应关系,可动水饱和度是由储层的微观孔隙结构决定的,与孔、渗同属一个层次的储层固有属性;而可动水饱和度测试结果与对应储层的气井产水特征分析表明,储层可动水饱和度与对应气井产水特征具有很好的对应关系,可动水饱和度可以有效表征低渗砂岩储层的产水特征。因而,可动水饱和度作为低渗砂岩气藏储层的评价参数是可行而且有效的。

Conventional reservoir evaluation method was unavailable for low permeability sandstone gas reservoirs,as they were easy to produce water and the influence of water production to development effect was great.So,determining a new reservoir evaluation parameter which could characterize water production of low permeability reservoirs was the first step for reservoir evaluation.Mobile water saturation of great number of core samples was measured by nuclear magnetic resonance (NMR),and the relationship between mobile water saturation and physical property of cores and water production of the corresponding gas wells was analyzed.The results show that there is no good relationship between mobile water saturation and porosity,permeability and original water saturation.Mobile water saturation is an intrinsic property of the reservoirs controlled by the micro-pore structure of reservoirs,which is on the same level with porosity and permeability;movable water saturation and the water production of corresponding gas wells have a good relationship.This indicates that mobile water saturation can effectively characterize the water production of low permeability sandstone gas reservoirs.Thus,mobile water saturation used as the evaluation parameters in low permeability sandstone gas reservoirs is feasible and effective.