Rupture Disk Valve Improves Plug-and-Perf Applications

Abstract

Technology Update Plug-and-perf completions have proved to be the most flexible multistage well completion schemes. The main reason is that each stage can be perforated and treated optimally because options can be exercised right up to the moment the perforating gun is fired. This allows the engineer to apply knowledge from each previous stage to the stage under treatment. For example, using real-time microseismic fracture mapping techniques provides a view of where previous fractures have propagated, which enables adjustments to be made to perforating depth and pumping schedules for subsequent stages. Some people have argued that the plug-and-perf technique is too time consuming and that it is too slow at the start because of the need to run the first stage perforating guns in with coiled tubing, stick pipe, or a downhole tractor, thus adding an unnecessary expense. A new technique introduced by Schlumberger adds significant operating efficiency and lowers the cost of cemented, multistage fracturing by eliminating the initial perforating run. The technique uses the KickStart pressure-activated rupture disk valve to enable the first stage treatment to be combined with casing operations. In addition to reducing downtime, the technique has been shown to lower fracture initiation pressure, thereby eliminating the risk of closed perforation tunnels caused by shale swelling, and to increase the likelihood of fracturing the stage to completion. The extensive study of geomechanics has shown that rock formations fracture at their weakest point and that the weakest point aligns with the plane of maximum horizontal stress whenever the overburden (vertical) stress exceeds lateral stresses, which occurs most of the time. The pressure-activated rupture disk valve has a unique helical port design that exposes the formation outside the casing to fracture pressure, thereby ensuring that the fracture will align with the maximum horizontal stress plane and propagate at the weakest point in the formation. A major benefit of this alignment is the reduction of tortuosity at the fracture initiation point, which significantly reduces the probability of a premature screenout of the initial fracture treatment at the toe of the completion.