高效脉冲式加砂压裂技术研究与实践

随着致密砂岩气藏的深入开发,压后气井稳产时间短、产量递减快的问题日益凸显。因此,对人工裂缝有效穿透率及导流能力要求也就越来越高。脉冲式加砂压裂技术引入缝内非连续多层铺砂理念,通过可高频切换的脉冲混砂车、密集多簇射孔技术及特殊纤维材料,确保支撑剂段塞的流动稳定性并最终在裂缝内部形成非均匀铺置砂柱与沟槽,从而使得裂缝导流能力相对常规均匀铺砂提升几个数量级。室内工程模拟评价及现场试验结果表明:压前储层评价、脉冲时间设计、可降解纤维及配套设备的优化是脉冲式加砂压裂工艺成功的关键;与常规压裂相比,其压后产量得以大幅提升,同时还可降低支撑剂用量和减少砂堵风险。在鄂尔多斯盆地苏里格气田桃7区块首次完成了3井6层次自主化脉冲式加砂压裂技术先导性试验,其平均支撑剂用量降低了28.3%,平均加砂强度降低了21.88%,压后平均日产气量提高了26.8%。结论认为:该项技术为我国致密砂岩气藏提供了一种高效、环保的储层改造工艺选择。

Research and practice of the impulse sand fracturing technology

With the deep development of tight sand gas reservoirs, problems such as short stable production period and quick production decline of gas wells after fracturing has become increasingly prominent. Consequently, there is an increasing demand of the effective penetration and conductivity of artificial fractures. Impulse sand fracturing technology introduces a concept of discrete multilayer sanding inside fractures; joint application of pulse blender which can be switched at high frequency, intensive multi-cluster perforation and special fibrous material made it possible to ensure the flow stability of proppant slug, and placement of nonuniformly-laid sand pinnacles and grooves, which markedly upgraded the capacity of the fracture conductivity to several orders of magnitude more than the conventional method. Laboratory engineering simulation evaluation and field test show that pre-fracturing reservoir evaluation, pulse time design and the optimization of degradable fiber and support equipment are the keys to the success of impulse type sand fracturing. Compared with the conventional fracturing, this technique can effectively increase well production, decrease the volume of fracturing proppant, and lower sand plugging risks. An independent sand fracturing pilot test has been conducted in 6 layers of 3 wells for the first time in Tao Block 7 of the Sulige Gasfield Ordos Basin, the average volume of fracturing proppant dropped by 28.3%, the average sand intensity dropped by 21.88%, and the post-fracturing average daily gas output increased by 26.8%. This technology provides an efficient and environmentally friendly reservoir stimulation option for tight sand gas reservoirs in China.