Shell Exploration & Production Co. announced in mid-September its plans to develope two more deepwater Gulf of Mexico discoveries, Oregano and Serrano (Fig. 1). The developments include the world's first flowlines used as electric conductors for heating, Shell said. A non-metallic composite insulation is used between the pipe-in-pipe flowlines.
Shell developed this application at its Westhollow Research Center, Houston.
Steve Sears, Shell's subsea development manager, said the electrically heated lines eliminate the need for two separate flowlines, required for pigging, and the need for injecting methanol for controlling hydrates. He estimated Shell will save about $17 million in capital and operating expenses because of this technology.
Sears said to control hydrates and wax, an AC current will heat the flow lines to about 85° during flow shut-in periods and to 130° F. during longer shut in periods.
Development plans
The fields, in 3,400-ft water, will be produced via a subsea production system tied back to the Auger tension leg platform, in 2,400-ft water
Shell said these were its 14th and 15th deepwater developments. Both are 100% owned by Shell.
Shell estimated that each field will recover about 50 million boe, primarily gas from Serrano and oil from Oregano. It said development costs for the two projects are $250 million, excluding lease costs, with production scheduled to begin at Serrano in September 2001 and at Oregano in December 2001. Peak daily production rates will reach 150 MMcfd and 20,000 bo/d, respectively.
Although Serrano and Oregano are separate fields, Shell said the development activities are being executed through a single integrated plan.
At each field, its plans include completing two wells initially, setting a flowline sled, and installing a single 6 in. x 10 in. pipe-in-pipe insulated, electrically heated flowline that will tie back to its Auger TLP.
Serrano
Serrano is in Garden Banks Blocks 516 and 472, about 220 miles southwest of New Orleans. Shell acquired the GB 516 lease in the 1985 OCS Sale 104 for $1,023,000 and the GB 472 lease in the 1989 OCS Lease Sale 123 for $162,000.
The discovery wells were drilled on GB 516 in 1996 and on GB 472 in 1999.
Shell said it is targeting reservoirs in the SE 40 and SE 55 sands at depths of about 12,000 and 18,000 ft subsea. It said the gas and associated gas condensate reservoirs have an average net pay of about 80 and 110 ft, respectively.
Shell indicated that the $120 million development project will begin producing in September 2001, with peak production rates increasing to 150 MMcfd by 2003, as gas-handling capacity at Auger becomes available
Oregano
Oregano is in Garden Banks Block 558 and 559, about 225 miles southwest of New Orleans.
Shell acquired both leases in the 1989 OCS Sale 123-GB 559 for $177,000 and GB 558 for $162,000. The discovery well was drilled on GB 559 in 1999.
In Oregano, it said its target is the oil and associated gas K sands reservoirs at about 19,000 ft subsea. The oil has 35-37° API gravity and contains about 1.08% sulfur.
Shell expected production from the $130-million project to begin in December 2001, with peak production rates to reach 20,000 bo/d by 2002.
