Achieving High Rate Completions with Innovative Thru-Tubing Sand Control

Abstract

An improved through-tubing sand control technique was utilized recently to enhance reservoir recovery and improve life-cycle economics. This coiled tubing-conveyed method uses several technical innovations that improve the reliability of the vent screen sand control completion. The innovations can be shown to:improve the rate at which reserves can be recovered;improve completion efficiency;reduce mechanical risk;reduce completion costs;extend the economic life of the well; andcontrol fines migration. Introduction Ewing Bank 305 Field is located approximately 100 miles southwest of New Orleans, Louisiana. The current development 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 water drive 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 using 3–1/2 in. production tubing was adopted to increase production rates from new wells. The current program continues to employ gravel-packed completions with large, 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 completions can be performed without rig intervention. These future completions can be executed with or without gravel packs to deliver the best economic value. If no screens are installed, production rates may be limited to delay the onset of sand production. Much time and effort is spent 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. For the proposed rigless completion method to be considered at Ewing Bank 305, it was critical that the process remain economical in comparison with current rig rates, minimize mechanical risk, and not sacrifice the best practices developed for sand control completions in that area. This paper presents a case history of a single-trip, coiled tubing deployed rigless completion installed at Ewing Bank 305 in the Gulf of Mexico. Vent Screen Completion Method The vent screen, or dual screen, sand control method has been used for many years in situations requiring remedial sand control. The vent screen method uses two screen assemblies separated by blank pipes placed and packed in casing. Production enters the lower screen section and exits the upper screen section. The screen and blank assembly are run in the hole through the production tubing on electric line, slickline, or coiled tubing and set on the bottom. The sand control treatment, consisting of a gravel pack or high-rate water pack is placed at the desired rate. At the end of the treatment, gravel is allowed to pack in the screen and the blank annulus (Figure 1). This method is generally applied only to low-reserve, cost-sensitive reservoirs or as a last-ditch effort to control sand production in old wells. However, recent innovations in coiled tubing and sand control technologies now allow rigless through-tubing vent screen sand control completions to be considered for both initial and alternative remedial completions. Typical through-tubing completion candidates are identified as wells with 3–5 bcf of reserves, stacked pays, high rig costs, and intervals with a 6–12-month productive life in each zone.