Improved Efficiency of Multi-Stage Fracturing Operations:An Innovative Pressure Activated Toe Sleeve

摘要

Over the last decade productive capacity of both oil and gas from previously 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 methods which is run in the hole on the bottom of the completion string and actuated after two pressure applications.This sleeve isn’t immediately open after the first pressure application,so casing integrity pressure testing can be conducted and pressure can also be held indefinitely to satisfy a range of regulatory requirements.As the second application of pressure is bled down,the sleeve locks open and then composite plugs for P-n-P or balls for frac sleeves 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,eliminating the initial perforation run. As a result the following features and benefits can be realized: This toe sleeve is is hydraulically actuated after two separate pressure cycles applications Each pressure cycle application can be held indefinitely for casing integrity pressure testing to satisfy all expected regulatory requirements There is no restriction on the time between two pressure applications It eliminates the need for TCP perforating in the first stage of a cemented P-n-P completion at the toe of well Multiple sleeves can be installed and activated open simultaneously at the toe of the completion string The toe sleeve design incorporates port areas sufficient to pump the first stimulation operation, adding an additional zone to any fracturing completion The toe sleeve is fully cement compatibleThis paper will present the operational mechanisms and a case study of the use of this unique toe sleeve which adds significant operating efficiency and lowers the cost of multi-stage fracturing with valid casing integrity pressure test.