Abstract:

High pressure water jet technology has been widely used in oil and gas well descaling and unblocking because of its advantages of high efficiency, cleanliness and low cost. With the gradual development of oil and gas exploration and development to deep and ultra-deep depths, the application depth of water jet technology has increased significantly, and the unblocking effect of jet tools becomes worse under the condition of high confining pressure in deep wells. Although researchers have conducted extensive studies on jet flow fields and jet performance under confining pressure, the research methods remain relatively limited. Furthermore, as experimental confining pressures are typically confined to below 30 MPa, the mechanism by which high confining pressure affects jet application efficacy remains unclear. Aiming at the key problem of poor application effect of jet descaling and unblocking under high confining pressure, this paper uses the self-developed confining pressure jet comprehensive test system to carry out rock-breaking and axial dynamic pressure experiments under constant flow rate condition of confining pressure 0~100 MPa, analyzes the influence law of high confining pressure on jet rock-breaking effect and impact force. The influence mechanism of high confining pressure on the unblocking effect of water jet is revealed by combining the basic theory of water jet. Application recommendations are proposed for the jet unblocking under high confining pressure conditions in deep wells. Results: Keep the flow rate and jet distance constant, the rock-breaking depth, rock-breaking volume and jet impact force all decrease with the increase of confining pressure, and the decreasing trend decelerates with increasing confining pressure. From normal pressure to 100 MPa, the rock-breaking depth decreases by about 72%, the rock-breaking volume decreases by about 90%, and the jet impact force decreases by about 50%~60%. The decrease of jet axis dynamic pressure is due to the joint action of nozzle cavitation and the “damping effect” caused by high confining pressure environment. The main reason for the poor application effect of high confining pressure water jet is the decrease of jet impact force under confining pressure. To achieve high-efficiency jet unblocking under high confining pressure in deep wells, it is recommended to enhance jet performance under such downhole conditions and to implement a combined unblocking approach that integrates jetting with mechanical or chemical methods. This research is expected to provide a fundamental theoretical support for enhancing the application effect of water jet technology in descaling and unblocking under high confining pressure conditions in deep wells.

Key words: high confining pressure, water jet, jet rock-breaking, jet dynamic pressure

摘要：

高压水射流技术具有高效、清洁、低成本等优势，广泛应用于油气井除垢解堵作业。随着油气勘探开发进程逐步向深层、超深层发展，水射流技术应用井深显著增加，射流解堵工具在深井高围压条件下解堵效果变差。尽管研究学者对围压下射流流场和射流性能进行了大量的研究，但研究方法相对单一，且实验围压低于30 MPa，高围压对射流应用效果的影响机理尚不清楚。本文针对高围压下射流除垢解堵应用效果变差这一关键问题，利用自行研制的围压射流综合试验系统，开展了定排量条件下围压0~100 MPa射流破岩与轴线动压力测量实验，分析了高围压对射流破岩效果和冲击力的影响规律，并结合水射流基础理论，揭示了高围压对水射流解堵效果的影响机理，提出了深井高围压下射流解堵的应用建议。结果表明：保持排量和喷距一定，随着围压增大，射流破岩深度、破岩体积及射流冲击力均呈降低趋势，降低趋势随围压增大逐渐变缓；从常压到100 MPa围压，射流破岩深度降低约72%，射流破岩体积降低约90%，射流冲击力降低约50%~60%；射流轴线动压力降低是喷嘴空化和高围压环境所产生的“阻尼效应”共同作用的结果；高围压下水射流解堵除垢应用效果不佳主要是因为高围压下射流冲击力降低；为实现深井高围压下射流高效解堵，建议提升深井条件下射流性能和实现射流与机械或化学的复合解堵。该研究有望为提升水射流技术在深井高围压条件下除垢解堵的应用效果提供基础理论支撑。

关键词: 高围压, 水射流, 射流破岩, 射流动压力

CLC Number: 

• TE357

• O358