Different from hydraulic jetting fracturing technique and plug-and-perf fracturing technique, it is not necessary to perforate for fracturing using reclosable casing sliding sleeves, the wellbore is connected with reservoir through sleeves, and the opening and closing are controllable. The reclosable casing sleeve technique provides the possibility to enrich the fracturing mode in horizontal wells and also provides a technical means to solve the development contradiction such as water breakthrough.

The demand for reclosable casing sleeves is increasing in unconventional reservoir development. A new idea is to change the conventional fracturing sequence from toe to heel to skip fracturing to strengthen the stress interference between different stages, so as to create more complex three-dimensional fracture network and larger SRV. For waterflood development zone, especially the infill area with small well spacing, sleeves can be directly closed to save the well in case of fracturing fluid breakthrough and to realize water-out treatment during the production stage. In terms of production management, alternate production of the stimulated stages can be achieved.

In recent years, field tests of reclosable casing sleeves have been carried out in more than 10 horizontal wells in Ordos Basin unconventional reservoirs. This paper focuses on some typical application cases. Case 1 introduces a successful case of skip fracturing. According to the principle of complex fracture generated by stress interference, skip fracturing test is carried out, and successful experience is obtained in the process. Case 2 introduces a fracturing fluid breakthrough treatment with reclosable casing sleeves in a waterflood infill area. Breakthrough occurs during fracturing, resulting the connection between the fracturing stage and an injection well. The problem is solved by adjusting fracturing string and closing the sleeve, the subsequent stages are normally fractured, and an infill horizontal well is saved. Case 3 introduces a successful application of closing sleeves to treat high water-cut in a horizontal well after six months of production, which provides experience for treating water-out wells. Case 4 introduces the first successful case of the 28 reclosable casing sleeves + 3611.5m permanent optical fiber monitoring test outside casing in China. The success rate of sleeves is 89.3%, the real-time optical fiber monitoring signal is stable, and the operation is successfully completed.

The reclosable casing sleeve has a wide application prospect in enriching reservoir stimulation mode and well production management, but there are still many problems to be solved related to the sleeve and its application. There are both successful experiences and lessons in tests. This paper will share these with the peers, and promote the improvement and application of reclosable casing sleeve technique.

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