Using Chemostratigraphy to Identify Reservoirs with Optimal Deliverability to Increase Gas Production from the Carboniferous (Pennsylvanian) of the United Kingdom Southern North Sea

Georgina Doughty¹, Tim Pearce², and Duncan McLean^3
1 ConocoPhillips (UK) Limited, Aberdeen, United Kingdom
² Chemostrat Limited, Llanfyllin, United Kingdom
³ Sheffield University, Sheffield, United Kingdom

The application of the latest chemostratigraphic techniques (Pearce et al 2006, this abstracts volume) has significantly advanced ConocoPhillips' understanding of the stratigraphic architecture of the UK Carboniferous Southern Gas Basin, in particular UK Quad 44- the heartland of the UK Carboniferous gas producing area. It has led to a focus on key reservoir intervals and ultimately contributed to exploration and development success.

Gas is currently produced from Westphalian A, B and C/D reservoirs, which span approximately a 10My period and encompass a wide range of fluvial & lacustrine depositional environments. The latter record shifts in climate and sediment supply in a variety of high and low accommodation space settings. The resultant stratigraphic architecture is complex and predicting high net-to-gross, high deliverability section away from well control is a major challenge.

Decades of exploration and standard subsurface analysis have improved significantly the understanding of these varied depositional environments and therefore the prime reservoir intervals within them. More recently however, the identification and differentiation of very similar sand units through the application of chemostratigraphy has proved invaluable when used in conjunction with conventional palynology, well and seismic correlation predictive techniques. This integrated approach to reservoir prediction has enabled optimal well placement of both exploration and development wells, resulting in higher deliverability wells and efficient reservoir drainage. A case study, ‘exploration to development of the Munro field Block 44/17b,' is used to illustrate the high impact of the new chemostratigraphic scheme, which has improved reservoir prediction and allowed exploration to focus on the highest deliverability reservoirs.