Abstract

The connectivity of reservoir bodies has been tested in unfaulted and variably faulted, high resolution 3D geocellular stratigraphic models (16 million cells in a 20 km × 20 km × c. 600 m volume) from the East Pennine Coalfield, UK. These deterministic stratigraphic–structural models are underpinned by high density borehole and mineplan data. The stratigraphy extends from mid-Westphalian A to base Westphalian C and represents a low net:gross (0.03–0.27) coal-bearing, delta top/fluvial reservoir analogue. The models contain up to 1467 post-depositional normal faults with maximum displacements ranging from 1 m to 140 m. Using two sets of facies as net, the effect of fault size on inferred reservoir connectivity has been assessed for stratal intervals with different sedimentary architecture, interval net:gross and thickness.

Faults often disconnect reservoirs in thinner, lower net:gross intervals containing only laterally discontinuous, channelized bodies. By contrast, faults generally increase reservoir connectivity in thick, relatively high net:gross intervals containing laterally extensive, tabular reservoir bodies. The most significant factor for fault-related reservoir connectivity is the dimensionality and scale of reservoir bodies in relation to the displacement distribution along faults. Populations of small, sub-seismic, faults (<5 m throw) can reconnect reservoir bodies that are dissected by larger displacement, seismic resolvable, faults (>20 m throw).

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