Assessing and Advancing a CBM Resource Play towards Commerciality — A Case Study from the UK; PEDL 159 Solway Basin
Aldrich, Jeffrey B.¹; Hower, Tim²; Sipeki, Julianna²
¹Exploration, Dart Energy, Singapore, Singapore.
²Consultant, MHA, Denver, CO.
The Canonbie Coal Field lies in the Solway Basin, a late Devonian graben. During Westphalian deposition basin sediments were dominated by fluvial-deltaic cyclic similar to those that have been documented both in the Pennine Basin to the South and to the Midland Valley to the North. The Westphalian coals are subdivided into an Upper, Middle and Lower Coal Measures and overall thickness ranges from 400m to over 100m in the basin.
Greenpark Energy, now Dart Energy International, acquired the 300 km² PEDL 159 CBM license (PEDL) on the border of England and Scotland in 2006. There were no coal mines but 32 borehole penetrations of the Carboniferous Middle Coal Measures in the PEDL area, 14 of the boreholes being cored by the English Coal Board for testing. Based on original subsurface borehole and 2D seismic mapping, 6 seams of coal were mapped over a 75 sq km area. The Six Foot, Nine Foot, Three Foot, Five Foot, Black Top and Seven Foot Seams are regionally correlateble and lay between 200m and 1400m beneath the surface. Each seam ranges from just under 1 meter to over 2 meters in gross thickness. Net coal ranges from zero at the unconformity truncation to over 20m. Using original gas content data (265 106m3) 935BCF of OGIIP was calculated as a potential resource play.
Greenpark drilled three test coring wells at structurally shallow, moderate and deeper depths within the CBM basin and analyzed the cores for gas content and saturation. Additional permeability testing was done, using various techniques, at each of these wells. A further exploration well was drilled to define the limits of the basin and two sites were selected for pilot production test wells. At both sites horizontal wells were drilled in-seam and put on extended production tests.
As a result of the test coring holes 1C and 2C Potential Resources were able to be certified. With production tests and numerical simulation models, some of the Potential Resources were high-graded to Reserves. By using a managed testing program costs were contained and sufficient Potential Resources were able to be upgraded to Reserves to advance the field toward a commercial decision point.
[N.B. to the reviewers - this paper was accepted by the AAPG ICE for Milan but had to be withdrawn due to the Greenpark Management decisions during a sale process. Dart Energy has allowed the paper to be re-submitted for the Singapore ICE]
AAPG Search and Discovery Article #90155©2012 AAPG International Conference & Exhibition, Singapore, 16-19 September 2012