Schlumberger

Case Study: Chevron Jack Well Subsea Test Tree Challenge

SenTREE HP high-pressure completion subsea test tree supports high flow rate and pressure

Challenge: Successfully deploy a subsea test tree (SSTT) system rated to 15,000 psi and a 1.2-million-lbf tensile load.

Solution: Design, manufacture, and deploy SenTREE HP high-pressure completion subsea test tree.

Result: Completed and tested well in 7,000 ft of water and more than 20,000 ft under the sea floor, breaking the Tahiti record as the deepest successful well test in the Gulf of Mexico.

Extreme water and well depth

Chevron announced discovery of the Jack prospect in September 2004. It is approximately 270 mi southwest of New Orleans and 175 mi offshore. Chevron needed to successfully deploy an SSTT that was rated to 103 MPa [15,000 psi]. A 1.2 million lbf tensile load rating was also necessary. The Schlumberger team was able to fully qualify all the required tools under the Jack well’s specific downhole conditions faster than the planned operation required.

Fail-safe operations in a difficult location

The SenTREE HP subsea test tree had been designed, manufactured, and used on the Tahiti well test for Chevron in 2004. It enables the installation of well completions for development subsea wells and high rate/high pressure well testing in challenging environments. Because of that prior positive experience, Chevron came to Schlumberger first for a solution for the Jack well. Based on the specific downhole conditions, the Schlumberger team was able to refine the SenTREE HP test tree to achieve the long-term functionality required for the Jack well testing. Chevron was an active part of the process in defining the specifications and scope of the project.

The system delivered large bore access (63⁄8-in ID), with a modular design for flexibility in blowout preventer interfacing, multiple electrical/hydraulic feeds for completion functions, and a secondary hydraulic unlatch system. In addition, a 15,000-psi [103-MPa] flowhead with tensile rating to 1.2 million lbf was used. It took approximately 9 months to fully test and qualify this equipment in preparation for the operation.

Past experience yields results

Past experience enabled Schlumberger to grow its existing technologies and meet the requirements. The Jack well was completed and tested in 7,000 ft [2,134 m] of water, more than 20,000 ft [6,096 m] under the sea floor, breaking the 2004 Tahiti discovery well record as the deepest successful well test in the Gulf of Mexico. All objectives were achieved. The well test gathered enough information for the appraisal team and partners (Statoil and Devon Energy) to support well and project plans going forward.

There were no service quality incidents during the entire operation. Developing and executing this solution has positioned Schlumberger as the leading provider of SSTT services in the industry.


Download: Chevron Jack Well Subsea Test Tree Challenge (1.14 MB PDF)

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"The results of the Jack test allow Chevron and its co-owners to better understand the deliverability of the emerging Lower Tertiary trend."
Gary Luquette
President
Chevron North America
Exploration and Production

Rigorous Qualification Testing

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