Current completion targets are individual reservoir flow units, often comprising a single depositional unit such as an upper shoreface sandbody or a tidal channel which has remained undrained from previous development campaigns.

Identification, location, and accurate description of these targets requires detailed models of reservoir stratigraphy and architecture, based upon good-quality core and well data sets, together with accurate structural and stratigraphic mapping using high-resolution 3D seismic so that the connected oil in place and transmissivity can be estimated accurately for individual flow units.

The method of ichnofabric analysis, combined with routine sedimentology, provides unequivocal interpretation of shallow marine and estuarine depositional environments allowing the interpreter to recognize and determine the relative importance of the various stratal surfaces seen in cores. The tectonic tilt of the stratal surfaces as interpreted from dip-logs such as the FMI, FMS, or even the SHDT, assists in determining the relative importance of these stratal surfaces.

The key stratal surfaces concept provides the main correlation surfaces (erosional sequence boundaries and flooding surfaces) for delineating individual parasequences, parasequence sets and sequences and for constructing a new high-resolution sequence stratigraphy (HRSS). Once calibrated, these surfaces can be recognized in, and correlated between, uncored wells by the shapes of the natural gamma-ray and density logs. By careful integration of all well data with the high-resolution seismic within the HRSS framework, an accurate description of the geometries and architecture of all the reservoir sediment bodies is obtained.

The final product is a robust and accurate description of the reservoir architecture and facies contents down to the bedset (decimeter) scale. This is a sound basis from which to construct computer-based 3D reservoir models and assign petrophysical properties for reservoir simulation studies.

Shell’s proprietary reservoir modelling software (GEOCAP-MoReS) has been used to provide detailed static 3D reservoir models for reservoir simulation. Results of this work have allowed engineers to optimize field development plans in the mature development phase of field life.