Conoco (U.K.) Ltd. and Total Oil Marine plc have begun work on the Caister Murdoch System (CMS), a gas production, gathering, and transportation network, in the southern U.K. North Sea.
The 400 million ($777 million) project is scheduled to begin handling production in the fourth quarter of 1993.
The development involves two usually unmanned platforms controlled from Conoco's Theddlethorpe gas terminal in Lincolnshire, linked to the terminal by 16 in. and 26 in. pipelines. Peak production from CMS, expected in 1994, will be about 280 MMcfd of gas.
Conoco and Total are discussing development of other nearby fields, using the Murdoch platform and Theddlethorpe terminal.
Caister and Murdoch fields lie in Quadrant 44, some 112 miles northeast of Theddlethorpe. They include the first Carboniferous reservoirs to be developed in the U.K. sector. Caister also includes a Triassic Bunter reservoir.
The fields hold about 620 bcf of recoverable gas and 5.7 million bbl of condensate.
Gas from Caister, in Block 44/23a, will be carried by a 16 in. line 7 miles to Murdoch in Block 44/22a. There it will join Murdoch's output for transmission to shore in the 26 in. pipeline. A 4 in. line will supply corrosion inhibitor and methanol (to prevent hydrate formation) from the terminal. All pipelines will be trenched.
THE FIELDS
The Caister Bunter formation was discovered in 1967, while the Carboniferous reservoir was found with the field's fourth well in 1985.
The field lies in 135 ft of water. Bunter pay occurs at about 4,600 ft, the Carboniferous at about 11,200 ft. Together they hold about 300 bcf of gas and 3.5 million bbl of condensate.
Gas production will peak at about 140 MMcfd. Field life is estimated at 15 years.
Appraisal of the formation was completed in April 1989, after three exploration and four appraisal wells had been drilled, Seven development wells are being drilled through a 10 slot, 42 metric ton template installed last March. The Santa Fe Drilling Co. (North Sea) Ltd. Galveston Key jack up spudded the first development well in April. The rig will complete the drilling program by March next year.
The four leg, steel Caister platform, to be installed in April 1993, will carry 10 well production/test manifolds, a test separator, wet gas metering equipment and utilities.
It sits on a 200 ft high jacket weighing 1,200 tons and fixed by a skirt pile at each leg. The deck weighs 1,400 tons.
Total became operator in 1988 when it acquired CSX. Current field partners are Total 49%, CanadianOxy North Sea Petroleum Ltd. 30%, and Lasmo plc 21%.
Murdoch field's Carboniferous pay was discovered in 1984 at a depth of 11,700 ft.
One exploration and six appraisal wells were drilled.
The reservoir is thought to hold 320 bcf of gas and 2.2 million bbl of condensate. Water depth is 98 ft.
Peak production will be 140 MMcfd of gas. Field life is estimated at 25 years.
The Rowan Drilling (U.K.) Ltd. Arch Rowan jack up recently was drilling the third of seven development wells to be drilled through a 13 slot, 42 ton template installed last December.
The four leg, steel Murdoch platform will be installed next April. The unit will hold nine well production/test manifolds, a test separator, wet gas metering equipment, an automatic sphere launcher, and utilities.
It will be capable of producing from 13 wells.
The jacket is 170 ft high and weighs 1,300 tons.
It is fixed by two skirt piles at each leg, to carry a deck weighing 1,640 tons.
Operator Conoco holds 54.5% interest in the field.
ARCO British Ltd. holds 34%, Total Oil Marine 11.5%.
GAS SALES, EXPLORATION
All production from Murdoch field is to be bought by Kinetica, the joint venture independent gas supplier formed by Conoco and the U.K. electric utility Powergen.
The gas will help supply about 1,000 U.K. schools, hospitals, and industrial sites.
Powergen's competitor, National Power, has bought Caister gas for its planned 600 megawatt combined cycle, gas turbine power station at Killingholme on South Humberside, which is due to come on stream later this year. The gas will be delivered via a new 100 mile pipeline.
Quadrant 44 gas is said to contain high levels of carbon dioxide and nitrogen.
The direct sales for generation remove the need for processing.
Conoco sees Quadrant 44 as the last major undeveloped gas province in the southern gas basin. The first tranche of exploration blocks in the 14th round of U.K. licensing includes Blocks 44/23b, 44/26b and c, 44/27c, 44/28c, and 44/29c. Bidding closes Dec. 16.
Conoco estimates it holds interests in reserves totaling 1.5-2 tcf of gas in the southern part of the quadrant, including CMS and its Blocks 44/17 and 44/21 discoveries.
Altogether, Conoco has interests in five blocks in Quadrant 44 besides the CMS blocks.
THREE PHASES
"Caister Murdoch is just the start of a three phase operation by Conoco to develop its own reserves in the area," said John Willis, the Quadrant 44 asset manager.
Following the CMS project, the second phase will involve introduction of offshore compression and possibly accommodation facilities on the Murdoch platform to bring in gas from other reservoirs, he said. This will be followed by development of satellite fields.
The project will give Quadrant 44 its first gas transportation network. Because further pipeline construction is unlikely, Conoco says, CMS could become the sole transporter of the 5 tcf of potential gas reserves estimated for the area.
Conoco operates the terminal where the gas will come ashore. Theddlethorpe's 750 MMcfd gas capacity will enable 470 MMcfd of processing throughput to be made available to third parties.
Conoco and Total are discussing potential tie-ins to CMS with other operators having gas discoveries nearby.
These include Shell U.K. Exploration & Production, which has the Schooner prospect in Block 44/26a and Ketch in Block 44/28b, as well as Lasmo North Sea plc, ARCO British Ltd., and Sovereign Oil & Gas plc, which has been acquired by Finnish state oil company Neste Corp.
Beyond 1995, when developments via Murdoch are likely to happen, separate compression and accommodation platforms could be installed, bridge-linked to the original production platform.
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