水力喷砂射孔与起裂大型物理模拟试验

Physical simulating experiments of hydrajet perforating and fracture initiation process

采用油田现场使用的施工参数、喷射工具和施工设备,用与长庆油田长6地层对应的露头岩样制作靶件,模拟水力喷砂射孔与起裂的过程,进行大型物理模拟试验,并用专用工具解剖试验靶件。结果表明:喷砂射孔的完整孔形呈泪滴形,分为套管穿孔段、入口反溅段、水泥环缩径段和主体段4部分;起裂后的孔道末端还有一狭长的剑形通道;试验条件下,射流速度超过一定限度后会导致靶件起裂,表明射流速度提高可使孔内局部增压显著;起裂后射流顺裂缝方向冲刷形成剑形通道,使喷砂射孔通道成倍增长,有利于改善穿透效果;多个喷嘴射出的孔道保持各自独立的孔形,起裂后的裂缝可连通各个孔道,在试验条件下多个射流通道共同作用可引导近井地带裂缝的形成与扩展。

Experimental researches were introduced by selected samples from Chang 6 formation of Changqing Oilfield, and the process of hydrajet perforating and fracture initiation process was simulated by using field parameters, jetting tools and e- quipments. The tested samples were all cut by special tools. The experimental results show that the whole jetting hole is of tear-drop shape, and it includes four parts of casing perforation, entrance spOttering section, cement reduction and main sec- tion. When fracture initiated, a slim channel with gladiate shape is added in the end of the hole. The sample will fracture when jetting velocity is high enough in test condition, which indicates that the pressure in jetting hole increases obviously with the jetting velocity increase. The jetting flow erodes out a slim channel along crack propagate direction when fractures initi- ate, which makes the jetting hole length increase doubly, and is beneficial to enhance penetration efficiency. Individual channels are connected by crack when fractures initiate, which indicates that jetting hole can guide the fracture initiation and extension near the well bore in test condition.