强水敏储层矿物高温变化对储层物性的影响——以金家油田沙一段为例

Influence of thermal alteration of minerals in strong water sensitive reservoir on physical properties:A case study from the first member of Shahejie Formation in Jinjia Oilfield

金家油田沙一段稠油油藏储层具有强水敏特征,在蒸汽吞吐开发及高温下储层矿物易发生变化,并改变储层的孔隙结构,影响储层物性。为此,在此次研究中开展了高压釜物理模拟实验。实验结果表明：高温下储层矿物发生变化主要体现在3个方面,即蒙脱石晶间距的改变引起的膨胀性变化、矿物溶蚀及转化、溶蚀孔隙等;当温度为200～300℃时,蒙脱石膨胀性减弱至接近消失,溶蚀作用进一步增强使得储层孔隙呈大中孔,孔径增大,连通性和储层物性进一步变好。因此,强水敏性稠油油藏在蒸汽吞吐过程中,要切实保证注入蒸汽的温度和干度,使储层温度高于200℃,以降低储层水敏性,从而改善储层物性,提高开发效率。

The heavy oil reservoir o f the first member of Shahejie Formation in Jinjia Oilfield has strong water sensitivity. In the process of steam stimulation, minerals are easy to change at high temperatures, which makes pore structure change and affects reservoir physical properties. In order to understand the characteristics of mineral changes and their effects on reservoir physical properties, an autoclave physics simulation was conducted. Experiment results show that the changes of minerals in the reservoir at high temperatures were reflected in the following three aspects：the expansion caused by the changes of crystal spacing of montmorillonite, mineral dissolution and transformation, as well as dissolved pores. From 200 ℃ to 300 ℃, the expansion of montmorillonite weakened and was gradually near to disappear, and the dissolution further strengthened, which makes the pores large and medium, and then reservoir connectivity and physical properties further changed better. In the steam stimulation process of strong water sensitivity heavy oil reservoirs, it need to ensure the temperature and dryness of injecting steam to make the reservoir temperature higher than 200 ℃, so as to reduce reservoir water sensitivity, and improve reservoir physical properties and enhance development effect.