New Completion Techniques Applied to a Deepwater Gulf of Mexico TLP Completion Successfully Gravel Pack an Openhole Horizontal Interval of 2400 Feet
Authors: Duhon Pete , Holley Alan , Gardiner Nick , Grigsby Tommy 
Published: October 2008

As the scope of development continues to expand, more instances are being noted in which traditional technologies cannot satisfy job parameters. In deepwater projects, for example, high-rate production and completion reliability present major challenges to operators, and traditional methods of sand control often have not been able to address the changing conditions. In this paper, a solution that combines gravel packing, enhanced downhole tool capability, and advanced fluid technology is used in an offshore environment in which the completion was performed in a horizontal openhole extended-interval wellbore from a deepwater tension leg platform (TLP). New gravel pack tools and procedures were developed to meet the stringent requirements of the proposed scenario and will be discussed. The successful application of the first extended horizontal openhole gravel packs in the Northern Gulf of Mexico has proven that gravel packing can be successfully applied to extended horizontal wellbores.

Introduction

Conventional openhole horizontal completions have been widely used in the Gulf of Mexico since the early 1990's. However, the number of failures experienced by some operators has raised questions on the reliability of this type completion. Alternate completion methods such as frac packing have been evolving techniques since the late 1980's' and have provided increased completion reliability and production rate capability. Openhole gravel packing for extended horizontal interval lengths has remained an unproven technique. A major operator in the east south-east region of the Gulf of Mexico was planning a development in an offshore location with water depths of approximately 3200 feet. The structure had 22 slots (2 for pipeline export risers) allocated, and depending on the final tubular and production riser sizes, could accommodate about 18 wells. The first four wells were to be predrilled from a floating drilling rig prior to TLP installation. Objective zones were located approximately 12500- to 13500-ft TVD. Measured depths would depend on the specific directional plans and would range from 16000- to 22000 ft. The following sections will review the areas of concern and how the resulting challenges were met.

Project challenges

Two main completion challenges were primary in planning this project. First, high initial rate (&gt;15000 BOPD oil wells or &gt;70 mmeflD gas wells) completions are required. This is a typical economic requirement of most high cost deepwater offshore development projects. In order to achieve these rates from the pay sands in this field, long (2000 to 2500-ft) horizontal well completion technology is selected for most of the wells. Fig. 1 provides a representative schematic of the first two installations. The second challenge is well reliability. The desired well life is about 15 years, and well reliability is dependent upon the type of completion technique used and metallurgy of the downhole tubulars and accessory equipment. Since a typical open hole horizontal completion with a pre-packed screen or metal filter is prone to plug and/or produce excessive sand before reservoir depletion, openhole gravel packing was selected to enhance sand control, reduce plugging, and provide hole stability for this project. A custom prepacked screen was selected, and specifications and quality plans were prepared to assure manufacturing quality.