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井漏是制约安全、快速、高效钻井的技术瓶颈。为了提高防漏堵漏效率,基于断裂力学理论,采用理论分析和数值模拟方法,研究堵漏材料在裂缝内不同位置架桥及考虑不同封堵效率的裂缝尖端应力强度因子、井周有效切向应力及裂缝宽度大小。研究表明,井筒压力一定时,裂缝越长,裂缝宽度和裂缝尖端应力强度因子越大;堵漏材料在裂缝开口处架桥时,井周有效切向应力提高最多,裂缝尖端应力强度因子最小,承压堵漏效果越好;缝内压力越低,井周有效切向应力提高越多,裂缝尖端应力强度因子越小。钻井中应根据裂缝宽度变化范围,选择合理的颗粒尺寸,使架桥位置靠近井筒,并随钻加入防漏堵漏材料,及时封堵微裂缝,防止裂缝持续扩展;同时使用优化的粒度分布及高性能的堵漏材料,形成致密封堵层,可以提高地层承压能力,有效预防井漏。通过现场试验验证,研究结果对现场防漏堵漏工作具有很好的指导意义。
Lost circulation is a technical bottleneck that restricts safe, rapid and efficient drilling. In order to improve the efficiency of leakage prevention and plugging, based on the theory of fracture mechanics, the theoretical analysis and numerical simulation methods are used to study the stress intensity factor of crack tip at different locations of the plugging material in different positions and considering the different plugging efficiency. Stress and crack width size. The results show that when the wellbore pressure is constant, the longer the crack, the larger the crack width and the crack tip stress intensity factor. When the plugging material bridges the crack opening, the effective circumferential tangential stress increases most, the crack tip stress intensity factor is the smallest, The better the pressure and plugging effect; the lower the pressure in the seam, the more effective the tangential stress of the well is, the smaller the stress intensity factor of the crack tip is. Drilling should be based on the range of changes in the width of the cracks, the choice of a reasonable particle size, the bridging position close to the wellbore, and with the addition of leak-proof plugging materials, timely sealing of micro-cracks to prevent the continuous expansion of cracks; while using optimized particle size distribution and High-performance plugging material, forming a seal caused by sealing, can improve the bearing capacity of the formation, effectively prevent leakage. Through the field test, the research results have a good guiding significance on the work of site leakage prevention and plugging.