Abstract:

The casing damage of horizontal wells for shale gas, especially for deep shale gas, has always been a problem that troubles the staged fracturing development of shale gas. The conventional methods, such as casing patching and chemical plugging, cannot simultaneously meet the demands of high pressure, high flow rate and small bridge plug passing during fracturing, resulting in the difficult implementation of the staged fracturing technology through pumping of bridge plugs. Besides, the staged fracturing technology with multi-packer is difficult to meet the requirements of pumping rate and scale due to the limited number of segments and limited displacement, resulting from the limited range of the ball-drop sliding sleeve. Taking Well-WY9-2HF as an example, by conducting the researches such as risk demonstration, pipe string mechanical analysis and structural optimization, tool development and improvement, and wellbore simulation test, the following conclusions are drawn: the string with suspension packer is suitable for isolating the casing-damaged sections; the combination of the upper casing and the lower tubing for injection can raise the pump rate; the full bore infinite sliding sleeve can increase the number of segments and the pump rate; together with multi-packer, well control safety measures and high-rate segmented fracturing technique, the full bore infinite sliding sleeve is used to realize a large-scale and high-rate fracturing with 31 stages in Well-WY9-2HF, which achieves the expected targets and obtains a commissioning production of 8.75×10⁴ m³/d. This technology can be used as a reference for the fracturing and commissioning of such wells.

Key words: shale gas, casing damage, full bore, infinite sliding sleeve, suspension packer