Falkland fields to yield waxy crude, gas-condensate

By OGJ editors

The subsurface and well characteristics of the Sea Lion main complex, including the 450-m water depth and remote location 200 km north of the Falkland Islands, lend themselves to an FPSO development concept with subsea wells, said Rockhopper Exploration PLC.

The company noted that it has several more exploratory wells to drill in the North Falkland basin. It estimated that it will have spent about $2.5 billion exploring the area by the time it starts oil production from Sea Lion in 2016 (OGJ Online, Sept. 14, 2011). Ultimate recovery is estimated at 350 million bbl of oil.

The Sea Lion main complex covers 68 sq km with little faulting. Large, continuous sand layers vary in thickness from 25 to 90 m with 21% porosity and 200 md permeability. The reservoir is undersaturated at 100 bar pressure with a low gas-oil ratio of 280 at about 2,400 m true vertical depth subsea.

The complex has a water leg that provides ease of application of pressure support through water injection.

Flow rates of 9,000 b/d are achievable from vertical wells in thicker sections.

The company has the ability to drill the reservoir sections with horizontal wells or wells deviated 70-85° from vertical.

The as yet unsubmitted development plan calls for 24 production wells on four subsea manifolds producing a combined 108,000-120,000 b/d of oil. Water would be injected at 135,000-150,000 b/d through 12 wells and produced at 120,000 b/d and gas injected at 25-30 MMscfd.

Electric submersible pumps would be used to lift the waxy crude from the normally pressured reservoir.

Sea Lion crude is 29.2° gravity, .21% sulfur, and has a pour point of 30° C. Wax content is around 20% with a low total acid number of .25%. Rockhopper believes Sea Lion crude to be attractive to refiners in several locations and lists typical time to market by tanker of 20 days to the US Gulf Coast, 25 days to Northwest Europe, and 35 days to the Far East.

The crude would likely sell in a range of 10% discount to a 5% premium to Brent Blend, Rockhopper estimated.

The company estimates 1.086 billion bbl of oil in place in the Sea Lion main fan and lists a total expenditure through June 30, 2011, of $0.26/bbl.

Rockhopper has also assessed potential development of the Shell 14/5-1 Johnson gas-condensate discovery in 500 m of water with recovery potential of 3 to 30 tcf of gas, although it used 5-10 tcf in scoping studies. The studied scenarios include floating and onshore liquefied natural gas. Condensate volumes range from 125 million to 1 billion bbl.

Well capacities would range to 50-60 MMscfd and average 20 MMscfd over a 20-year field life. The onshore scenario includes a 30-in. gas pipeline.

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