储层敏感性机理及防治对策研究

王庄油田郑408块沙三段属于敏感性储层,现场采用冷采、蒸汽吞吐、注入CO2、HDCS等多种开采方式,效果均不理想。在对该区块储层特征、敏感性机理深入研究的基础上,得出黏土矿物含量相对较高,其中蒙脱石含量平均高达41%,致使储层具有强~极强水敏性,因此认为黏土矿物是影响储层渗透率、制约开发效果的主要因素。蒙脱石在富钙环境中会产生钙基蒙脱石,在富钠环境中会产生钠基蒙脱石。蒙脱石具有三层水结构:表层水、层间水和晶格水,失水由易到难,当温度达到300℃时,蒙脱石失去膨胀性能;长期在高温(800~1000℃)下,蒙脱石晶格破坏,产生相变,转化为莫来石和方石英。因此,实施注汽热采需把蒸汽温度提高到250~300℃,干度保持在70%。室内防膨静态和防膨流动实验表明,当SLAS-3防膨剂浓度为1.5%,黏土膨胀率为0,可以很好地起到抑制黏土膨胀的作用。该项成果的取得对指导王庄油田郑408块的开发具有重要的实用价值,同时也为同类油藏的开发提供了一定的借鉴。

Mechanism and Countermeasures for Prevention of Reservoir Sensitivity

The Sha3 member of Zheng 408 block in Wangzhuang oilfield belongs to the sensitive reservoir.It is developed through cold production,steam stimulation,CO2 injection,HDCS and other ways,but the effect is not ideal.Based on in-depth study of the reservoir characteristics and sensitivity mechanism of this block ,it is concluded that clay minerals are the main factors influencing reservoir permeability and restricting the development for its high content （about 41% of montmorillonite including） and strong-extreme strong water-sensitive. The montmorillonite may form calcium base one in the calcium rich environment and sodium base one in the sodium rich environment.It has three layers of water structures ：surface water,interstratum water and lattice water with water loss from easily to difficultly,and it will lose dilatability at the temperature of 300~C.Under high temperature of more than 800 to 1000℃ for long time,the montmorillonite will change into mullite and cristobalite for its lattice is destroyed.So the temperature of the steam should be up to 250 to 300℃ and dryness fraction should be 70% for thermal recovery through steam injection.Lab static and flowing anti-swelling experi- ments show that SLAS-3 anti-swelling agent can play a good role in inhibiting clay swelling for 0 of swelling rate of the clay at 1.5% of SLAS-3 content.The achievements have important practical value in guiding the development of Zheng 408 block in Wangzhuang oilfield and also provide some references and guidance for the development of similar reservoirs.