LONDON, Feb. 16 -- GDF Suez is preparing a field development plan for the first phase of Cygnus gas field in the southern UK North Sea after testing 32 MMscfd of natural gas from the deeper Carboniferous reservoir with appraisal well 44/12a-3. The well is 6 km east-northeast of the previous Cygnus well 44/12a-2. The flow was constrained by equipment.
The well, drilled to 12,433 ft TD, is located 6 km east-northeast of the previous Cygnus well 44/12a-2. It confirmed the presence of gas in both primary and secondary reservoir intervals. The likely reserves of the secondary reservoir are believed to be more than 100 bcf of gas.
Jean-Marie Dauger, executive vice-president of GDF Suez in charge of global gas and LNG, said success of the appraisal well "confirms a sizeable northward extension for Cygnus. It also provides a very solid commercial foundation for what is likely to be one of the larger UK southern North Sea developments in recent years."
GDF hopes to sanction the development plan later this year with first gas for 2010-11 from estimated gross incremental reserves over 100 bcf. Subsequent development of Cygnus will depend on the results of the second appraisal well and field performance.
The company wanted to prove the presence of the Leman reservoir in the eastern part of the field, to assess reservoir quality and fluid content of the primary Leman reservoir, and to test the deeper Carboniferous reservoir as a secondary target.
"A well test was also performed on the Leman reservoir, which flowed at low rates in line with predrill expectations," said Venture Production PLC, a partner in the field.
The Noble Ronald Hoope jack up rig drilled appraisal well 44/12a-3, which encountered a gas water contact consistent with Fault Block 1 thereby confirming predrill estimates of gas in place volumes. The quality of the Leman reservoir was as per predrill expectations, while the Carboniferous reservoir interval substantially exceeded expectations.
The partners will drill another appraisal well 8 km northwest of 44/12a-3 to test another fault block in the northeastern part of the field once it has completed this one.
Cygnus is a large multifault block accumulation within UKCS Blocks 44/12a and 44/11a near the Caister Murdoch System (CMS) area.
Mike Wagstaff, chief executive of Venture Production, said that Venture believes Cygnus is one of the southern North Sea's largest undeveloped gas fields. "In 2009 we have a very active drilling campaign especially in the southern North Sea, and this is a great start to what should be an exciting year."
GDF Suez has a 38.75% interest with Venture Production holding 48.75% and Endeavour Energy UK Ltd. holding 12.5%.
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