Abstract: Getting the Most from Data in the World's Longest Step-Out Wells, Wytch Farm, UK

EVANS, JONATHAN; CHRISTINE TELFORD; ANDREW HOGG; GRAHAME SMITH, and GILES WATTS

The extended reach development (ERD) wells in the Wytch Farm field have near horizontal reservoir sections of up to 2.5 km. It is important to understand which zones the wells have penetrated in order to build information from the wells into reservoir models and to optimize future development options.

The ERD wells penetrate three main pay sands which are separated by mudstone barriers. These sands do not have any unique log character or biostratigraphic signature which would allow unequivocal interpretation of the reservoir zones. The sands are not resolvable using seismic data. The objective of this study is to determine the zonation by integrating all available data, static and dynamic, to give a consistent interpretation.

During drilling, the reservoir zonation is determined by correlation with adjacent wells, by "counting down" through the stratigraphy and by using constraints from seismic data. When faults are encountered it is difficult to identify which sandstones or mudstones are juxtaposed; often several models are equally valid. After the well has been completed an integrated interpretation is made using all available static (cuttings, LWD, core, seismic) and dynamic (RFT's, mud losses and production log) data. Even at this stage several different interpretations are possible.

The result of this approach has been a better understanding of reservoir architecture and flow behavior which is essential to optimum location of wells, field management strategy and future investment decisions.

AAPG Search and Discovery Article #90942©1997 AAPG International Conference and Exhibition, Vienna, Austria