Seal predictability

Fault seal prediction in hydrocarbon reservoirs requires an understanding of fault seal mechanisms, fault rock petrophysical properties, the spatial distribution of seals, and seal stability. The properties and evolution of seals within fault zones can be evaluated using the combined results of structural core logging, microstmctural and physical property characterisation, together with information on fault populations from seismic and outcrop studies and well test data. 

Complexity in fault zone structure and implications for fault seal prediction... 

Due to seismically irresolvable complexities of fault zone structure, the juxtapositions of footwall and hangingwall rocks predicted from seismic data will in most cases be different from those actually present. The importance of such differences to the prediction of across-fault connectivity, of both hydraulically passive and hydraulically active fault zones, is strongly dependent on the reservoir sequence. Connectivities are calculated for hydraulically passive and active faults offsetting an Upper Brent Reservoir sequence. Shaley fault rocks within brittle fault zones often represent a spatially persistent, although variable thickness, component of the zones and provide a basis for the application of empirical methods of fault seal prediction to brittle faults. 

The distribution of fault rocks cannot be characterised from well data, raising the question of whether purely deterministic methods for fault seal prediction can ever be successful. The way forward is refinement of current empirical methods by achieving a more detailed characterisation of sub-surface faults, allowing more quantitative comparisons of target faults with those of known sealing behaviour. 

A model for the development of the complex internal structures of fault zones has recently been proposed (Childs et al., 1996). Although this model does not increase the predictability of sub-surface fault zone structure, it demonstrates how complexity can arise from the operation of simple processes and provides a framework for consideration of the uncertainties inherent in prediction. The purpose of this paper is to describe and develop this model in terms relevant to the problems of fault seal prediction. While... 

Fristad, T., Groth, A., Yielding, G. and Freeman, B. 1997. Quantitative fault seal prediction a case study from Oseberg Syd. In P. Mpller-Pedersen and A.G. Koestler (Editors), Hydrocarbon Seals ... 

Quantitative fault seal prediction a case study from Oseberg Syd... 

Yielding, G., Freeman, B. and Needham, D.T. 1997. Quantitative fault seal prediction. Am. Assoc. Pet. Geol. Bull., 81 897-917. 

K.A. Foxford, J.J. Walsh, J. Watterson, I.R. Garden, S.C. Guscott, and S.D. Burley (1998) Structure and content of the Moab fault zone, Utah, USA, and its implications for fault seal prediction. Faulting, Fault Sealing and Fluid Flow in Hydrocarbon Reservoirs, G. Jones, Q.J. Fisher, and R.J. Knipe (eds.). Geological Society Special Publications, vol. 147, 87-103. 

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