小洼油田W38块东三段储层伤害因素分析及保护技术

Reservoir Damage Factors Analysis and Protection Techniques for Third Member of Dongying Formation in Block W38 of Xiaowa Oilfield

小洼油田W38块东营组油藏属稠油油藏,长期热采使储层伤害严重。为深入研究储层伤害因素,寻求储层保护有效方法,利用储层常规物性和微观结构、成分等数据对储层性质进行分析;通过模拟流动实验,分析储层伤害的过程及机理。研究结果表明,研究区储层为高孔、高渗型砂岩储层,泥质含量高,黏土矿物中蒙皂石含量较高,为强水敏性储层。热采流体与地层水不配伍,使黏土水敏膨胀、微粒运移及地层岩石矿物溶解、转化等,导致地层骨架坍塌,出砂严重,降低渗透性,造成储层伤害。通过伤害机理分析,采用了注入黏土稳定剂的保护措施,结果表明高温黏土稳定剂可很好地保护储层,防止黏土膨胀及控制出砂,在多个井组试验均效果良好,可进一步推广。

The oil reservoir in Dongying Formation in Block W38,Xiaowa Oilfield was a heavy oil one,and it has been damaged severely because of long-term thermal recovery. To make in-depth study on reservoir damage factors and seek effective ways for reservoir protecction,we analyzed reservoir quality by means of conventional reservoir properties and such data as microstructure and composition. We analyzed the process and mechanism of reservoir damage via flow simulation test. Results showed that the reservoir in the study area was high-porosity and high-permeability sandstone reservoir,with high shale content and higher smectite content in clay minerals. It was also of strong water sensitivity. Thermal fluid was not compatible with formation water,which led to water sensitivity and swelling of clay,migration of particles,and dissolution and transformation of rocks and minerals,etc. This resulted in stratigraphic frame collapse,severe sanding,decrease in permeability,and damage to reservoir. Through the analysis on damage mechanism,we adopted the protection measures like injecting clay stabilizer. It was revealed that high-temperature clay stabilizer could protect oil reservoir better,prevent clay from swelling and control sanding of oil reservoir. The results were proved good after testing in many well groups. The techniques could be popularized further.