|
Aeolian Reservoirs |
British Gas Exploration and Production, 100 Thames Valley Park Drive, Reading, Berkshire RG6 1PT, UK
Mobil North Sea Ltd, Mobil Court, 3 Clements Inn. Holborn, London WC2A 2EB, UK
The Rough Gas Field lies in United Kingdom Continental Shelf Blocks 47/3d and 48/8b in the Southern North Sea and is operated in a gas storage mode by BGE&P involving the annual injection and production of large volumes of gas. To achieve full efficiency in this designated role it was necessary to carry out a detailed evaluation of the main producing reservoir, the Permian Rotliegendes Sandstone, after early development drilling demonstrated a need to re-evaluate the initial geological model. The present geological model is based on the detailed analysis of nine fully cored new development wells and well productivity surveys following an original six well conventional depletion. This resulted in the successful targeting of later development wells into specific geographic areas of the field for optimal field development.
Reservoir facies development can be described in terms of complex fluvial processes associated with the basin margin and aeolian influences associated with the basin as a whole. Within the Rough Field the Rotliegendes can be subdivided vertically into three reservoir units or layers (Units A, B, and C) and laterally into regions characterized by differing degrees of aeolian or non-aeolian influence. It is observed that the highest reservoir permeabilities are associated with aeolian or reworked aeolian sands while flow profile studies indicate close correspondence between injectivity/productivity and sedimentary facies. Aeolian facies or reworked aeolian sands of the lowermost ‘A’ unit facilitate the bulk of gas injection and production while fluviatile sands in all three units show reduced or even zero flow.
