Badley Ashton’s integrated petrographic and imaging workflow delivered a quantifiable reduction in subsurface uncertainty, directly mitigating the primary reservoir quality risk in the low net-to-gross Sele Formation. By precisely defining reservoir Architectural Elements at the well scale, the project successfully differentiated high-quality channel-fill sandstones (up to 445 mD mean permeability) from low-permeability terminal lobe deposits (1.2 mD). This work provided a de-risked geological model necessary for accurate volumetric and dynamic simulation, thereby optimising field development and tieback planning.
The Capercaillie field, situated down-dip in the mature Central North Sea, presents a significant commercial challenge: identifying and accurately modelling small, lower net-to-gross hydrocarbon accumulations within the deepwater Palaeocene-Eocene Sele Formation. The core risk lay in the high uncertainty associated with rock quality heterogeneity; average sandstone permeabilities were known to be low (a few 10s mD), but the geological controls on reservoir grade were poorly understood.
The primary objective (Aims) was to use an integrated, multi-scale dataset to accurately define the sedimentological architecture and petrophysical controls on reservoir quality. This systematic de-risking would enable the commercial viability of a potential tie-back to existing infrastructure by providing a reliable basis for volumetric estimation and sweep efficiency modelling.
The study focused on the appraisal effort in Quad 29, centred around Well 29/04e-5 and its sidetrack, Well 29/04e-5z. The core database consisted of a comprehensive suite of wireline logs, pressure data, and key high-resolution inputs:
The initial step involved the observation-based definition of Core-based Lithotypes (from RSWC) and BHI Image Facies. Applying the Badley Ashton deepwater scheme hierarchically across the RSWC, bed, and bed-stack scales established a fundamental link between:
Our workflow focused on:
Figure 2 Schematic diagram showing the depositional model proposed by Davis et al. (2009) for the Sele Formation sediment-gravity flows in the Everest, Lomond and Pierce fields, Central North Sea. Using the bed type distribution proposed by Davis et al. (2009), this model has been overlaid with its equivalent depositional package distribution; and gross depositional maps for the S1 and S2/S3 units of the Sele Formation, Central North Sea, indicating the location of the Capercaillie Field. Source: modified from Eldrett et al. (2015
The systematic correlation of Depositional Packages was then translated into a 3D geological architecture. The process detailed the extent of these Packages to create quantifiable, dimensioned Architectural Elements, which are the fundamental building blocks for static reservoir modelling:
The key scientific discovery was that this architectural contrast is the fundamental control on rock quality via texture, mineralogy, and diagenesis.
The study translated the technical geological insights directly into actionable, quantified reductions in reservoir uncertainty:
This integrated study successfully characterised the geological architecture and petrophysical controls of the challenging Sele Formation, mitigating the key risk of reservoir quality heterogeneity in this mature basin. The high-value outcome is a fully de-risked set of Architectural Elements precisely dimensioned and petrophysically calibrated.
The derived, calibrated Architectural Elements and their associated petrophysical properties are now ready for population into the dynamic reservoir simulator to refine sweep efficiency estimates, optimise well placement, and provide the final commercial assurance for the proposed tie-back development.
