New Deepwater, High-Pressure GOM Tubular Maximizes Capability, Reduces Cost
Authors: Carpenter Chris 
Published: January 2017

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 173034, “New Deepwater, High-Pressure Completion Tubular for Gulf of Mexico Maximizes Combined-Load Capability While Incorporating Proven Cost- Saving Features,” by T. Anderson, C. Fontenot, and R. Davey, Chevron; J. Dugas and B. White, Quail Tools; K.A. Hamilton, C-FER Technologies; and P.S. Beauchamp, L.C. Karlapalem, A. Muradov, and J. N. Brock, NOV Grant Prideco, prepared for the 2015 SPE/IADC Drilling Conference and Exhibition, London, 17–19 March. The paper has not been peer reviewed.
A 2-year comprehensive effort to design, test, manufacture, and deploy a new high-pressure completion tubular (CT) for Chevron’s deepwater Gulf of Mexico (GOM) operations is presented. The completion application expected harsh, aggressive loading modes and high pressures to be encountered. The major challenge was to design, test, and manufacture a subsea-completion string that would provide efficient hydraulics during fracturing operations while ensuring mechanical and pressure integrity.
Introduction
In 2004, the first built-for-purpose CT incorporating a gas-tight, rotary-shouldered connection was developed and deployed in the GOM. Since that time, rotary-shouldered connections have evolved (this evolution is described in detail in the complete paper). Present-day connections offer improved performance, increased torsional capacity, and improved hydraulics, and have created slimmer profiles. Additionally, running and handling characteristics have been improved, providing faster makeup, reduced trip time, and decreased repair cost because of reduced connection damage. However, the need remained to incorporate these technological advancements and benefits into a second-generation CT.
CT Requirements
In March 2002, the operator drilled the Tahiti 1 well in 4,017 ft of water to a total depth of 28,411 ft. The GOM well was located approximately 190 miles southwest of New Orleans in Green Canyon Block 640. Results from the exploratory well indicated the presence of high- quality reservoir sand with a total net pay of more than 400 ft. Following the results of the exploratory well, two appraisal wells were drilled simultaneously in Green Canyon Blocks 596 and 640. The appraisal program verified the operator’s initial estimates of 400 to 500 million bbl of ultimate recoverable oil reserves, one of the most significant net-pay accumulations recorded in the GOM.
Because of the extreme depth and bottomhole pressure of the Tahiti reservoir, the completion and well test required the design of new equipment to successfully perforate, frac pack, and flow test the Tahiti 1 discovery well, including the design and qualification of a perforating and frac-pack CT.
The CT requirements included
Fishable within the 9?-in. tieback, limiting the connection outer diameter (OD) to 7 in.
An inner diameter (ID) of no less than 4¼ in. to provide the desired treating rate during fracturing operations
An absolute-internal-working-pressure rating of approximately 29,000 psi to sustain internal pressure and not leak, potentially jeopardizing the frac-pack results
An absolute-external-working-pressure rating of approximately 24,500 psi to sustain elevated annulus pressures and not collapse or leak
The ability to withstand multiple makeup and breakout cycles while maintaining sealability at pressure to enable multiple trips into the well for cleanout, displacement, perforation, and fracture operations
A high-performance metal-to-metal seal that possessed integrity against fluid leak