Combining production from multiple intervals within a well during completion has been used for many years. Many of these reservoirs required hydraulic-fracture stimulation, and a number of promising fracturing methods have been developed where several stages can be performed sequentially, provided there is some method used to isolate previously stimulated intervals.

One method claims high efficiency by using high-rate treatments and limited-entry perforating concepts. However, the promises proved to be elusive. Contingencies for early screenout, perforating gun missfires, and other equipment failures have often dramatically impacted completion efficiency. To guard against these failures, the proppant schedules were underdesigned or purposely overflushed, thus reducing the resulting fracture conductivity.

To achieve limited-entry diversion, high-treatment rates were used, which required a large amount of hydraulic horsepower onsite. Yet, even when efficiencies were achievable, production logging often showed that, at best, only 50% of the intended fracturing targets would actually produce at fracture-stimulated rates. Discovery of an important phenomenon was recently explained using computational fluid dynamics (CFD) simulation. It was found that the difference in the physical qualities of proppant and the carrying fluid cause the upper intervals to receive mostly proppant-free fluid.

Pinpoint-stimulation fracturing methods can allow all of the multiple intervals completed to be stimulated efficiently, such that all intervals received the designed proppant volumes one interval at a time. For the most effective of these methods, coiled tubing (CT) is used to hydrajet perforate intervals for individual fracturing treatments, and proppant plugs are used to isolate stimulated intervals while maximizing near-wellbore (NWB) conductivity. These methods do not require removing the CT from the well between treatments, so early screenouts can be remediated immediately with minimal impact.

A new entry in this class of fracturing that allows real-time, on-demand downhole proppant-schedule control can be combined with real-time fracture-mapping diagnostics to optimize stimulated reservoir volume (SRV) on-the-fly, when needed. A 15-stage completion in the Marcellus is used to demonstrate the process.

You can access this article if you purchase or spend a download.