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Reservoir case studies |
1 NAM Netherlands, Schepersmaat 2, 9405 TA, Assen, The Netherlands (e-mail: m.dekeijzer{at}shell.com)
2 Shell International Exploration and Production, Kessler Park 1, 2288 GS, Rijswijk, The Netherlands
Reservoir-scale structural heterogeneity, especially in terms of mechanical layering and natural fracture systems, is often insufficiently constrained by subsurface data alone. In North Oman, a large dataset in Cretaceous carbonates comprises data from multiple subsurface reservoirs and analogue outcrops. This provides an ideal opportunity to integrate outcrop constraints into the subsurface, and to calibrate the resulting models dynamically. For this purpose, a reservoir-scale analogue outcrop fracture template was created for the Jebel Madmar anticline in the Oman Mountains foothills. The outcrop template provides improved conceptual and quantitative constraints on (i) fracture types and dimensions (e.g. of NE-trending fracture corridors), (ii) fracture heterogeneity, both aerially and stratigraphically, (iii) fracture properties (e.g. cementation evolution, variations due to preferential fault/fracture reactivation) and (iv) structural evolution and history of reactivation. Within a regionally consistent structural framework, the outcrop template has greatly assisted in the creation of geologically realistic models for one of the fractured carbonate reservoirs, complementing the subsurface dataset. Initial dynamic calibration indicates successful application of the outcrop template in that the spatial fracture heterogeneity was succesfuUy captured in the reservoir models and provides a history match to production data. The reduced range of possible fracture system geometries in turn has provided better constraints on the effective fracture properties.
