Deepwater oil field development
Shenandoah deepwater oil field lies at a water depth of approximately 1,700m in the Gulf of Mexico, offshore US.
The field is jointly owned by LLOG Exploration Offshore (30.95%, operator), Venari Resources (30%), Navitas Petroleum (23.1%), and Blackstone Group (15.95%). Its ownership has passed through different companies, including Cobalt International Energy, ConocoPhilips, Anadarko Petroleum and Marathon Oil Company.
First oil production from the Shenandoah deepwater oil field is expected in 2023.
The Shenandoah oil field lies offshore Shenandoah city in Louisiana, 322km south of New Orleans. It spans the Walker Ridge Blocks 51 and 52 and the north half of Block 53 in the Gulf of Mexico, across a leased area of 12,960 acres.
Shenandoah was originally discovered by the then operator Anadarko in February 2009 by an exploratory well named Shenandoah #1. The well was drilled into Inboard Lower Tertiary horizons to a depth of approximately 30,000ft in Walker Ridge block 52 and encountered 300ft of net oil pay.
The Shenandoah field is part of the Inboard Lower Tertiary trend. It is estimated to contain gross resources of 281 million metric barrels of oil-equivalent (Mmobe).
The Shenandoah #2 appraisal well was drilled to a depth of 31,400ft in Walker Ridge block 51, approximately 2.1km south-west of the exploratory well, in the third quarter of 2012. It encountered a net oil pay of more than 1,000ft in the Lower Tertiary-aged reservoirs, which established it as a commercial oil discovery.
A second appraisal well, Shenandoah #3, was completed in February 2015, 3.7km east of the Shenandoah #2 well. It encountered an extended reservoir section and confirmed the reservoir qualities of the field. Shenandoah #4 was the third appraisal well drilled in the fourth quarter of 2015 to prove the updip extent of the field. A sidetrack to the well was also drilled, which encountered more than 600ft of net oil pay.
Anadarko also drilled the Shenandoah #5 appraisal well to a total depth of 31,100ft on Walker Ridge Block 51 in 2016 to determine the reservoir boundaries of the field. The well discovered more than 1,000ft of net oil pay in the Lower Tertiary Wilcox sands and expanded the field reservoir boundary towards the east.
The Shenandoah #6 appraisal well and a sidetrack were drilled in April 2017, which did not encounter any oil-water contact in the eastern part of the field. Appraisal activities were suspended by Anadarko following the results of the appraisal well.
Development of the Shenandoah deepwater oil field was resumed when LLOG was appointed as the operator of the field in 2018 in place of Anadarko, when the latter relinquished its ownership interest.
The Shenandoah deepwater oil field development includes the drilling of eight production wells, out of which four production wells will be drilled initially. The development plan also includes the installation of a new floating production system (FPS), subsea facilities and associated pipelines.
The new FPS will have a production capacity of more than 70,000 barrels of oil-equivalent per day. Its design will be based on a regional-hub production model similar to those installed by LLOG at DeltaHouse and Who-Dat fields.
Subsea trees capable of handling pressures of up to 20,000 pounds per square inch (PSI) will be installed at the field.
LLOG Exploration contracted TechnipFMC to supply subsea trees for the Shenandoah oil field in October 2019.
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