Over the last decade productive capacity of both oil and gas from uneconomic North American unconventional shale resources has been dramatically enhanced due to advanced horizontal drilling technology combined with multi-stage hydraulic fracturing treatment maximizing access to productive zones. Currently two types of multi-stage fracturing completion systems are in common use:
• The conventional Plug-and-Perf (P-n-P) method in cased hole.
• Frac sleeves using open hole (OH) packers or cementing to isolate multiple stages.
To streamline the fracturing process, a new pressure-activated toe sleeve has been developed for both multi-stage fracturing methods, and is run in the hole on the bottom of the completion string and actuated after two pressure applications. This sleeve isn’t open after first pressure application, so casing integrity testing can be conducted and pressure can also be held indefinitely to satisfy regulatory requirements. As the second low pressure is applied, the sleeve can lock open, then composite plugs for P-n-P or balls for frac sleeves multi-stage system can be pumped down to begin subsequent stimulation operations. This toe sleeve is especially beneficial in P-n-P completions as an alternative to tubing conveyed perforating (TCP) to initiate pump-down operations, and is able to eliminate the initial perforation run to perforate the first stages at the toe of the wells for P-n-P operations.
This paper will present the operational mechanisms of this unique toe sleeve with two pressure applications to open this sleeve by adding significant operating efficiency and lowering the cost of multi-stage fracturing.