井底围压对高压水射流的影响规律研究

随着油气资源开发的不断深入,井底围压对高压水射流的影响问题越来越突出。为了对比研究井下围压及地面模拟围压条件下高压水射流破岩性能,通过试验研究了高压水射流在井下真实围压条件与3种地面模拟条件下的破岩能力,并研究了锥形喷嘴、直旋混合喷嘴和空化射流喷嘴的破岩效率。研究结果表明:在650 m深的井底,围压约6.45 MPa,喷嘴压降仅17.08 MPa条件下,高压水射流仍能有效破岩;与井下情况相比,在地面无围压淹没条件下,破岩深度和破岩体积较大,而直径较小;在定压降模拟围压条件下,仅破岩直径与井底围压条件下相似,而破岩深度和破岩体积较小;在定排量模拟围压条件下,高压水射流很难有效破岩。分析认为,目前地面模拟围压的方法并不适合研究井下高压水射流性能,井底围压对高压水射流没有影响,无围压淹没条件可满足试验要求。通过对比不同类型喷嘴的破岩能力,推荐使用空化射流喷嘴。研究成果可为高压水射流技术在钻井、压裂和冲砂洗井等领域的应用与研究提供有益指导。

Study on the Influence of Bottom Hole Confining Pressure on High-Pressure Jetting Techniques

As the development of oil and gas resources continues to deepen,the impact of bottom hole confining pressure on high-pressure water jetting has become more and more prominent.To compare the rock-breaking performance of high-pressure water jet under the conditions of downhole confining pressure and ground simulated confining pressure,the rock-breaking ability of high-pressure water jet under real downhole confining pressure conditions and three ground simulation conditions are studied through experiments.Rock breaking efficiency of cone nozzle,direct swirl mixing nozzle and cavitation nozzle are studied.The research results show that,at the bottom of the well at a depth of 650 m,with the confining pressure about 6.45 MPa and the nozzle pressure drop of only 17.08 MPa,the high-pressure water jet can still effectively break the rock.Compared with the downhole situation,under the condition of no confining pressure submerged on the ground,the broken rock depth and volume are larger,but the diameter is smaller.Under the constant pressure drop and simulated confining pressure condition,only the broken rock diameter is similar to that of the bottom hole confining pressure condition,while the broken rock depth and volume are smaller.Under the condition of constant displacement and simulated confining pressure,high-pressure water jet is difficult to effectively break the rock.It is concluded that the current method of ground simulation of confining pressure is not suitable for studying the performance of downhole high-pressure water jet.The bottom hole confining pressure has no effect on the high-pressure water jet,and the submergence condition without confining pressure can meet the test requirements.By comparing the rock breaking ability of different types of nozzles,cavitation jet nozzle is recommended.The research results can provide guidance for the application and research of high-pressure water jet technology in the fields of drilling,fracturing and sand washing.