Achieving High-Rate Completions With Innovative Through-Tubing Sand Control
Authors: Bell Thomas A. , Morrison Dan W. , Martch William E. 
Published: December 2007

Recently, an improved through-tubing sand-control technique was used to enhance reservoir recovery and improve the life-cycle economics of an offshore well in the Gulf of Mexico. This coiled-tubing-conveyed method used several technical innovations to improve the reliability of the vent-screen sand-control completion. The two most important technologies in the system are a coiled-tubing wireless depth-correlation device and a new surface modification agent (SMA) for the proppant/sand. These innovations can improve reserve recovery rate and completion efficiency, reduce mechanical risk and completion costs, extend the economic life of the well, and control fines migration.

The Ewing Bank 305 field is located approximately 100 miles south-west of New Orleans. The current strategy for this field is to develop deep oil reserves and exploit shallow gas reservoirs. The hydrocarbons located in fault-trap reservoirs are normally pressured and produced by a waterdrive mechanism.

In the past, the wells were completed conventionally with circulating gravel packs, generally with a dual-completion configuration. In the mid-1990s, a single-completion strategy with 3½-in. production tubing was adopted to increase production rates from new wells. The current program continues to employ gravel-packed completions with larger, 3½-in., single-production strings. In addition, because many of the new wells cut multiple pays, a completion configuration is used to provide an initial conventional gravel-packed completion and through-tubing access so that future recompletions can be performed without rig intervention. For example, the packer and tubing do not need to be pulled from the well with a rig to perform the recompletion on the next zone of interest. Rather, coiled tubing and/or electric line can be used to perform the next zone change by means of a platform or jackup boat. Future recompletions can be executed with or without gravel packs, depending on the best economic value. If no screens are installed, production rates may be limited to prevent the onset of sand production by controlling the amount of pressure drop across the perforations. In the past, through-tubing screens were deployed in the tailpipe below the packer with a packoff or lock to suspend the screen assemblies. These methods, however, do not permit uphole recompletions because they are expensive and risky to recover from the well. The vent-screen method is effective for rigless sand control while providing future recompletion options for shallower zones without the need for a rig.

Extensive time and effort are devoted to optimizing each completion in the reservoir. Because of the rapid depletion of these faulted reservoirs, control of completion costs is critical to the economic success of each well. In considering which rigless completion method to use at Ewing Bank 305, it was critical that the process be economical compared to current rig rates, afford minimal mechanical risk, and not sacrifice the best practices developed for sand-control completions in the area.