Fracture intensity from geomechanical models: application to the Blue Forest 3D survey, Green River Basin, Wyoming, USA
Published:January 01, 2007
S. J. Wilkins, 2007. "Fracture intensity from geomechanical models: application to the Blue Forest 3D survey, Green River Basin, Wyoming, USA", Structurally Complex Reservoirs, S. J. Jolley, D. Barr, J. J. Walsh, R. J. Knipe
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A geomechanical method is presented for the prediction of subseismic fracture intensity associated with faulting using a boundary element model conditioned from 3D seismic interpretation within the Green River Basin, Wyoming, USA. Seismic data indicate two major phases of deformation: (1) an early phase of approximately ESE-verging contraction accommodated along a NNE–SSW striking system of basement-involved reverse faults and associated drape folds; and (2) a later phase of transtension accommodated by ENE–WSW-trending normal faults that are preferentially located in the hanging wall, above the crest of the drape fold.
The models predict different spatial patterns of fracture intensity for each phase of deformation. For D1, enhanced probability for shear failure develops in the upper quadrant of the footwalls along the reverse faults (i.e. forelimb) and the greatest magnitudes occur adjacent to regions with the largest component of observable dip-slip displacement along the faults. During D2, enhanced probability for joint and fault formation occurs along-strike of the normal faults and in a general NE trend. Seismic velocity anisotropy data support the geomechanical predictions for both phases of deformation in that the location and azimuth of large anisotropies correlate with regions of predicted enhancement in joint and fault intensity.
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Structurally Complex Reservoirs
Structurally complex reservoirs form a distinct class of reservoir in which fault arrays and fracture networks, in particular, exert an overriding control on petroleum trapping and production behaviour. With modern exploration and production portfolios now commonly held in geologically complex settings, there is an increasing technical challenge to find new prospects and to extract remaining hydrocarbons from these reservoirs. This volume reviews our current understanding and ability to model the complex distribution and behaviour of fault and fracture networks, highlighting their fluid compartmentalizing effects and storage-transmissivity characteristics, and outlining approaches for predicting the dynamic fluid flow and geomechanical behaviour of these reservoirs. This collection of 25 papers provides an overview of recent progress and outstanding issues in the areas of (i) structural complexity and fault geometry, (ii) detection and prediction of faults and fractures, (iii) compartmentalizing effects of fault systems and complex siliciclastic reservoirs and (iv) critical controls affecting fractured reservoirs.