Gregoire Jacob

Dissolvable Plug and Perf System Eliminates Mill-Outs in Multistage Stimulations

38 JPT • JUNE 2015 Of all the technologies that have propelled the unconventional boom in the United States over the past 15 years, plug and perf (P&P) remains the No. 1 method for stimulating multistage wells, enabling operators to achieve significant economic gains in previously inaccessible reservoirs. Unconventional wells have become longer, with laterals extending as far as 10,000 ft and beyond. When combined with tighter spacing between stages, this growing lateral length has dramatically increased stage counts. In North American land activity, stages per lateral have nearly doubled in most basins since 2008, thanks in part to increased efficiencies in P&P operations. P&P relies on the use of a wireline or electric line to convey perforating guns and plugs to isolate sections of a reservoir for hydraulic fracturing. After the well is stimulated, the plugs are milled out with some type of mechanical intervention, such as the use of coiled tubing (CT). Over the years, P&P has been improved with the development of composite plugs, as opposed to permanentstyle plugs, that can be milled out in a continuous operation, pump-down operations to replace mechanical conveyance, and toe-initiator valves, which eliminate the need to mechanically convey perforations for the initial stage of the P&P operation. Despite these advances, mechanical intervention remains costly and risky, and in some instances may damage the recently placed fractures. In cases of low reservoir pressure or extended-reach laterals, milling can be especially problematic. Returns do not easily reach the surface, and friction and helical buckling effects can often result in CT lockup, preventing the CT from reaching the required depth to remove plugs in the toe section of the well. Debris left behind from milled-out plugs in the wellbore can result in the CT becoming stuck, thus driving up costs and further delaying production. These limitations signaled the need for the industry to move a step beyond conventional P&P technology. A new, dissolvable P&P system eliminates the need for mechanical intervention to remove plugs, enabling an unlimited number of stages to be stimulated. Launched in February, the dissolvable P&P completions system has been successfully implemented in many of the major unconventional plays in North America.