Chiswick Field: Long Horizontal Wells and Innovative Fracturing Solutions in a Low-Permeability-Sandstone Gas Reservoir in the North Sea
- Dennis Denney (JPT Senior Technology Editor)
- Document ID
- Society of Petroleum Engineers
- Journal of Petroleum Technology
- Publication Date
- March 2010
- Document Type
- Journal Paper
- 46 - 49
- 2010. Society of Petroleum Engineers
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- 60 since 2007
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This article, written by Senior Technology Editor Dennis Denney, contains highlights of paper SPE 124067, “The Chiswick Field: Long Horizontal Wells and Innovative Fracturing Solutions in a Low-Permeability-Sandstone Gas Reservoir in the North Sea,” by G. Coghlan, SPE, and B. Holland, SPE, Venture Production, prepared for the 2009 SPE Annual Technical Conference and Exhibition, New Orleans, 4–7 October. The paper has not been peer reviewed.
To obtain commercial flow rates from the Chiswick field, a low-permeability gas reservoir in the UK Southern Gas basin, field development would require horizontal wells with multiple propped hydraulic fractures. Only a few such completions have been attempted in sandstone reservoirs of the North Sea. The initial field-development plan entailed two horizontal wells with 2-km-long reservoir sections, stimulated with several massive propped fractures.
Chiswick is in a water depth of 42 m, approximately 160 km northeast of Great Yarmouth. A field-development plan was approved in 2006. The first-phase wells were completed on a minimum-facilities platform, and first gas was produced in September 2007. The field underwent a prolonged appraisal period following its discovery in 1984, directly reflecting the challenges posed by the low-quality Carboniferous sandstones that contain the majority of the gas.
The structure shown in Fig. 1 is a broad, northwest/southeast-trending, faulted anticline that is dip and fault closed with an almost square periphery. While a gas/water contact has never been drilled, a fieldwide contact at 3450 m true vertical depth subsea (TVDSS) can be inferred with fair accuracy. The area of closure is approximately 0.37 km2. The crestal part is at a depth of approximately 3250-m TVDSS. Crossfaults subdivide the field into five compartments: Alpha, Beta, Gamma, Delta, and Epsilon. Initial reservoir conditions were 3.92 MPa and 115°C at 3450 m TVDSS.
Porosity ranges from 3 to 14% and water saturation from 25 to 70%. Total gas initially in place for the Carboniferous reservoirs was estimated at 11.3×106 m2.
Chiswick Development Wells Initial development was two wells with 2- to 2.5-km-long horizontal sections, completed with five or six massive propped hydraulic fractures of 400,000 to 500,000 lbm each, spaced approximately 500 m apart. The formation dip allows a horizontal well to penetrate a succession of channels and connect several layered reservoirs. Within each channel, a propped fracture stimulates deliverability by exposing a large volume of rock to the wellbore.
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