页岩储层压裂减阻剂减阻机理研究

选择6种不同类型的减阻剂,通过研究不同浓度减阻剂的黏度和减阻效果,分析了减阻剂类型、分子量、分子结构、离子性能和浓度对其减阻性能的影响,并对减阻剂减阻机理进行了探索性研究。结果表明,减阻剂水溶液属于幂率流体,在一定流量范围内减阻率随着浓度的提高而提高;其水溶液黏度、离子特征和减阻率没有明显的联系,分子量在100万以上的减阻率在相同浓度下,减阻率趋于一致;影响减阻剂减阻性能的主要因素是减阻剂的分子结构。得出低分子量的长链结构的减阻剂和具有支链的长链结构的减阻剂以及具有柔顺、螺旋型分子链结构的减阻剂减阻性能更稳定;带支链的长链结构的减阻剂,在水中速溶,在较广泛的雷诺数范围内可得到理想的减阻率,具有较小的分子量,容易分解,对储层伤害小,此类减阻剂适合作页岩气储层大规模滑溜水压裂液的添加剂。

Functioning Mechanism of Drag Reducer Used in Shale Reservoir Fracturing

Six types of drag reducers were studied for their solution viscosities and drag reducing effects at different concentrations and in pipeline flow. The study shows that the water solutions of these drag reducers have power law flow patterns, and the drag reducing ratios increases with the increase of the concentrations of these drag reducers, if the concentrations are in certain ranges. Viscosity of the solution and ion characteristics have no obvious effect on the drag reducing ratios of these drag reducers. At the same concentrations, drag reducers having molecular weight (MW) greater than 1000,000 have almost the same drag reducing ratios. The main factor affecting the drag reducing performance is the molecular structures of the reducers. Drag reducers with low MW and long molecular chains, those with branched and long molecular chains, and those with flexible, helical molecular structures have drag reducing performances that are much more stable. Long chain drag reducers with branched chains dissolve quickly in water and have good drag reducing performance in a wide range of Reynolds numbers. Drag reducers with low MW are easy to degrade and hence impose very slight damage to the reservoirs. These drag reducers are suitable for use in large scale shale reservoir fracturing with slippery water fracturing fluids.