Integration of Horizontal Well Geological Data into Reservoir Descriptions: Rotliegendes Sandstones, Lancelot Area, Southern North Sea

William C. Fisher and David J. Went

The Lancelot area contains three significant gas accumulations, Lancelot, Guinevere and Excalibur. The fields are operated by Mobil North Sea Limited and have been developed by drilling a series of horizontal wells.

In six of the wells drilled through aeolian and related sedimentary deposits imaging logs have been run and facies and fracture characteristics analysed. Internal bedding characteristics of aeolian sandstones have been interpreted from the image logs to provide a detailed picture of the scale and orientation of the sets of cross bedding. All data have been linked to stratigraphic variations in facies determined from cored vertical wells to provide better lateral control to the reservoir description.

Variations in reservoir quality within aeolian sandstones have been investigated at the small scale by using core and mini-permeameter data and at a medium scale by comparison of cross-bedding characteristics and porosity from logs. Data from all scales have been integrated to provide an improved, more 3-dimensional reservoir description focusing on the frequencies and scales of variation (heterogeneity) present within the formation.

It is planned to use this work as a basis for developing more accurate and detailed well and full field simulation models, of use in long term field management. We believe this style of analysis to have wider applicability in appraisal, development and production phases for fields in similar settings.

AAPG Search and Discover Article #91019©1996 AAPG Convention and Exhibition 19-22 May 1996, San Diego, California