提高水力喷枪喷嘴施工效率方法探讨

Discussion about efficiency increasing for hydraulic jet nozzle

通过分析水力喷射压裂施工过程中38套喷枪喷嘴损坏的原因，得出了喷嘴的损坏主要是由于第1次喷砂射孔过程中选择了高排量和高压力导致喷嘴憋掉、扩径和射流液的回压冲击等造成喷枪在第2次喷射时达不到设计要求的喷射压力。利用能量守恒定律和地面模拟矿场水力喷射实验数据，计算了地面加压后喷枪射开套管与储层之间的阻挡层所需的喷射速度、喷嘴处的速度损失、克服静液柱压力产生的速度损失、回流液的阻挡造成的速度损失，得出了射开阻挡层所需的地面临界喷射排量和对应的喷射深度。采用略高于临界喷射排量的施工排量对3口井21段水平井第一段进行喷砂射孔和喷射压裂施工、后续几段保护性使用喷嘴的方法进行喷射施工试验。通过成功实施的19段，验证了该方法的可靠性，提高了喷嘴的使用频次。在2012年长庆区域底水油藏等小砂量水平井的水力喷射压裂施工应用中，单井减少了1～2趟更换喷射压裂管柱作业，提高了生产时效和降低了水平井施工成本。

Through analyzing 38 sets of nozzle failure during hydraulic jet fracturing, it is found that the main reason of nozzle failure is nozzle drop and inner diameter enlarging caused by high flowrate and high pressure in the first jetting, as well as back pressure impact caused by the jetting fluid. The nozzle needs to be changed for the second jetting. By using law of energy conservation and data of surface jetting simulation, it is calculated that the needed jetting speed for the blockage between casing and formation, speed loss at the nozzle, speed loss to resist hydrostatic column pressure, and speed loss caused by flow back fluid, and the surface critical discharge rate and corresponding depth are obtained. When performing the jetting and fracturing tests on 3 horizontal wells with 21 sections, the discharge rate for the first section is higher than the critical discharge rate, and the following sections are using nozzle protective method. The success on 19 sections proved the method a reliable way to increasing the nozzle lifetime. In 2012, hydraulic jetting fracturing was performed with small proppant volume in reservoirs like bottom water driven reservoir in ChangQing area, and 1 to 2 times of fracturing BHA changing were decreased, which increased the production efficiency and decreased the operation cost.