天然水驱油藏水淹层微观变化特征:以文昌油田珠江组为例

Micro-Variation Characteristics of Water Flooded Layer in Natural Water Flooded Reservoir:A Case Study from Zhujiang Formation in Wenchang Oilfield

以文昌油田不同开发时期密闭取心井的岩心为例,依据物性、薄片分析、压汞测试等分析化验方法,研究了其珠江组天然水驱油藏不同开发阶段的储层微观变化特征及机理。研究结果表明,储层孔隙度在水淹过程中变化不大,而渗透率在水淹前期以减小为主,水淹中后期以增大为主;水淹后储层泥质含量增加,喉道平均值和微喉道体积都是先减小后增大,退汞效率在前期水淹平均降低30%,水淹中后期约降低8%。储层特征发生变化的主要机理是:储层内颗粒和填隙物在水侵作用下发生溶蚀、破碎和迁移,导致储层非均质性增强,到水淹中后期阶段黏土矿物类型发生明显的变化,部分地层微粒被生产带走,储层内可流动喉道的体积分数增多,导致渗透率变大。因此认为泥质含量、细孔喉堵塞环境及可流通喉道体积的发育程度是影响水淹后储层参数变化的主要因素。

Based on the cores of sealed coring wells in different development periods,the cores were analyzed by various methods including thin section analysis,mercury and physical properties test,the microvariation characteristics,and physical-mechanical test for Zhujiang Formation of Wenchang Oilfield in different development stages of natural water flooded reservoir.The results show that the porosity change is not evident in water flooded stage,however,the change of permeability is complex,which decreased in the main part in the early stage,then increased in the mid-late stage of water flooding.Shale content increased in the reservoir after water flooding,while the mean value of the throat and the volume of the micro throat both decreased and then increased.The mercury withdrawal efficiency was reduced by 30% in the early stage,then the value decreased to 8%in the mid-late stage.The mechanism is that the clay particles and interstitial material in reservoir dissolved,crushed and moved by the action of water erosion,and pore structure and heterogeneity in sandstone reservoirs can change remarkably.During the mid-late stage of water flooding,the clay mineral type changed obviously,then was taken away,with the minimum increase of flowing pore-throat,leading to the permeability increase.It is thus agreed that shale content,fine pore throat blocking environment and the volume of the minimum flowing pore-throat are the main factors for the reservoir physical change after water flooding.