石英砂支撑剂长期导流能力变化规律实验研究

利用石英砂代替陶粒支撑剂能有效降低施工成本，在致密油气藏压裂改造中广为应用。为探究石英砂支撑剂对裂缝长期导流能力的影响规律，选用20～40目、40～70目和70～140目石英砂，开展长期导流能力测试实验，探究有效应力、铺砂浓度、粒径组合、铺置模式等因素对石英砂长期导流能力的影响并拟合参数化经验模型。研究认为：长期导流能力随铺砂浓度的增加，先升高再降低，反映了从“支撑”到“封堵”的演化；在低铺砂浓度条件下，大粒径石英砂易破碎堵塞流道，因此可在高闭合压力储层优选细砂，在低闭合压力储层优选中砂或粗砂；在考虑混合铺置时，应先采用低黏度压裂液泵送大粒径石英砂，后采用高黏度压裂液泵送小粒径石英砂，文中给出的混合铺置导流能力预测模型适用于混合铺置支撑剂粒径及比例的优化设计。

Experimental Study on Variation Law of Long-term Conductivity of Quartz Sand

The use of quartz sand instead of ceramsite proppant can effectively reduce the construction costs and is widely used in fracturing reforming in tight oil and gas reservoirs. To explore the influence of quartz sand proppant on the long-term conductivity of fractures, choosing 20-40 mesh, 40-70 mesh and 70-140 mesh quartz sand to carry out long-term conductivity test experiments to explore the effects of effective stress, sand concentration, particle size combination, laying mode and other factors on the long-term conductivity of quartz sand and fit the parameterized empirical model. The results show that, the long-term conductivity increases first and then decreases with the increase of sand paving concentration, reflecting the evolution from "support" to "blocking". Under the condition of low sand paving concentration, large-diameter quartz sand is easy to break and block flow channel, therefore, fine sand can be preferred in high closure pressure reservoirs, and medium sand or coarse sand can be preferred in low closure pressure reservoirs. When considering mixed paving, low-viscosity fracturing fluid should be used to pump the large-particle quartz sand first, and then use high-viscosity fracturing fluid to pump small-sized quartz sand. The prediction model of mixed paving conductivity given in the paper is suitable for the optimal design of particle size and proportion of mixed paving proppant.