Deep High-Pressure Completions: A Case History Offshore Gulf of Mexico

Abstract

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 181557, “Pushing the Completion Design Envelope in Ultradeepwater: Design, Installation, and Performance of Deep High-Pressure Completions—A Case History of the Gunflint Development, Offshore Gulf of Mexico,” by Jack Sanford, SPE, John Healy, SPE, Tim Hopper, SPE, Josh Fink, SPE, Ladd Grammer, SPE, James Koy, SPE, Jocelyn Perroux, SPE, Ian Magin, SPE, Kevin Williams, and Tom Seeley, Noble Energy, prepared for the 2016 SPE Annual Technical Conference and Exhibition, Dubai, 26–28 September. The paper has not been peer reviewed. A Gulf of Mexico case history is presented describing the successful delivery of two deep high-pressure high-rate-designed oil wells in an ultradeepwater environment. Well conditions, coupled with challenging production requirements (depletion of 10,000 psi), posed an arduous design challenge. More than two dozen firsts for the operator, and indeed for the industry, were required to deliver the final completion designs. Introduction The Gunflint field is located in five Mississippi Canyon blocks in approximately 6,100 ft of water. The discovery well (MC948 2) was drilled in 2008. The field contains stacked Middle Miocene age reservoirs between depths of 23,800 and 27,000 ft true vertical depth subsea. A mixture of black oil, rich gas condensate, and dry gas has been penetrated in seven reservoirs. Only three oil reservoirs, Green B, Green C, and Blue E, are considered commercially viable for development. Reservoir pressures and temperatures range from 17,000 to 19,000 psi and from 210 to 240°F, respectively. Petrophysical analysis determined that the primary reservoir sands are high-quality sandstones with good permeability. The development plan consists of two subsea wells tied back to the Gulf Star I platform. The first well (G4, the “Blue” well) is a twin to the original discovery well in the top of the structure and targets the Blue E horizon as a single completion. The second well (G2, the “Green” well) is a sidetrack of the original discovery well targeting the Green B and C reservoirs in a dual commingled smart completion. Initial well productivity was designed for 15,000 BOPD for the Blue well and 20,000 BOPD from the commingled Green well. Instantaneous initial total oil potential is expected to be between 30,000 and 35,000 BOPD, and each well will have a dedicated 6-in. pipeline for flowback to the host facility. However, the expected total field plateau rate is 25,000 BOPD owing to capacity limits at the remote host. Specifically, the project’s statement of requirements stipulated that G4 was to deliver a production capacity of 15,000 BOPD at a skin (production efficiency) of less than 3, while G2 was to deliver a production capacity of 20,000 BOPD (combined) at a skin (production efficiency) of less than 3.