Key Technologies Practice on Re-entry Well Capping for Old Boreholes with Cement Plug

If there is an exposed side drilling borehole drilled to the cap layer or uncovered reservoir in the old wells in the reservoir area, it is a bottleneck in the construction of underground gas storage reservoirs to avoid oil and gas leakage and ensure the safety of gas injection and extraction production after effective plugging is implemented. There is no target magnetic field formed by the drilling tool “falling fish” in the “cement plug” type complex old borehole to be disposed of, and the inclination angle of the well reaches 52.63°, which makes it difficult to locate and navigate in the old borehole, and the cable measurement method of magnetic distance measuring instrument relying on gravity can not be lowered into the borehole. Expand the application scope of domestic magnetic ranging system, develop drilling and transmission related tools, explore the casing tracking and positioning, trajectory correction, plug finding and re-entry, punchdown identification and logging and logging auxiliary integrated technical solutions. It was successfully applied in NPXX well of Jidong Gas Storage Reservoir, and the effect of re-entering and sealing the complex old borehole reached the standard, creating a precedent of re-entering the left-over borehole of sidetracking drilling outside the casing. The application shows that: the domestic drilling tool conveying active magnetic ranging technology together with integrated auxiliary technologies such as rock crushing ratio work, rock chip comparison, gas logging anomaly and well diameter morphology change can accurately track the casing and realize the re-entry of cement plugged old borehole. This technology provides practical experience for effective plugging of complex old boreholes with multiple boreholes and large slopes in gas storage reservoirs, and has a wide application prospect.