Optimizing Marginal Subsea Well Developments Through Application Of Intelligent Completions
Authors: Lehle G. , Bilberry D. 
Published: October 2008

A Gulf of Mexico field development was considered marginal economically because additional wells over and above the single well drilled did not demonstrate the level of reserves originally expected. Consequently, a stand alone platform or dry tree structure could not be justified. After some consideration, the operator determined that a subsea completion with a tieback to a host platform could be economically feasible if development costs were minimized.

Completion requirements were complex. There were three producing zones, each requiring frac or gravel packs. The completion design provided for selective production from two intervals, with production from the lower two zones being commingled as one interval. The economics of the completion could be further improved with the use of an Intelligent Well System, which would minimize the need for intervention over the life of the well.

Drawbacks of using new subsea hardware issues were long delivery time and cost. As a result, it was decided to refurbish and modify existing subsea equipment. These modifications - at the tree and hanger interface - required changes to the completion equipment and installation procedures.

Completion costs were reduced significantly by minimizing the use of wireline or coiled tubing operations during installation.

Introduction

Developing a marginal Gulf of Mexico well in approximately 425 ft water depth presented several challenges. Typically, the application of intelligent completions to subsea wells is associated with large scale, high rate production in deepwater development fields. In this case a shallow water reservoir, unable to justify a platform development, would have to economically support a subsea tieback to enable development to proceed.

The economics of the project deemed the well marginal. Due to the high cost of intervention using a semi submersible to shut off water or switch zones, any future intervention would have rendered the project unecomonic.

Background

East Cameron (EC) 374 Well #1 was drilled and temporarily abandoned in May 2001. The well was drilled to 6755 ft MD and 5389 ft TVD and a total of three pay zones were encountered. To optimize the discovery, the production scenario required that all three zones be produced with the lower two being approved for commingled production. The upper zone was planned for future selective production, extending the overall life of the well. As a result, the ultimate production volume from all three zones could enter the completion via two remotely controlled sliding sleeves.

The completion consists of three separate gravel packed intervals. The 4000 ft sand and 3700 ft sand are frac packed and commingled as the primary production source within the well. The 3100 ft sand is gravel packed and isolated via the intelligent completion selective sliding sleeve.

As production from the lower zones declines/waters out, the ability to isolate without re-entry and commence production from the 3100 sand is possible. The well is subsea completed in 425 ft of water with a 14,000 ft tieback to the EC 373 platform.