RESERVOIR DEVELOPMENT, SEQUENCE STRATIGRAPHY AND GEOLOGICAL MODELING OF WESTPHALIAN FLUVIAL RESERVOIRS OF THE CAISTER-C FIELD, UK SOUTHERN NORTH-SEA

The earliest Westphalian B reservoir of the Caister C Field (informall y named the Caister Sandstone Unit) consists of erosive conglomeratic sandstones deposited in stacked low sinuosity fluvial channels. Channe l types and architectural elements demonstrate an upward change to mor e sinuous forms. The Caister Sandstone Unit is believed to contain. in cised valley-fill sediments deposited as late lowstand and transgressi ve systems tracts when rising base level generated accommodation space . The dominant control on reservoir quality is primary depositional te xture with the best permeability found in higher energy coarse sandsto ne and pebbly intervals associated with basal channel-fill units; crev asse channel and splay sandstones offer poor reservoir properties. The robust correlation framework, which is based upon laterally extensive coal seams, enables a sequence stratigraphic model of the field to be developed, thereby allowing a better understanding of reservoir exten t and sandbody continuity. A 3D geocellular geological model is built with reservoir architecture elements controlled by the sedimentologica l model. This is used for volumetrics calculations, input to a reservo ir simulator and in the locating and planning of in-fill wells.