Effects of diagenesis (cement precipitation) during fracture opening on fracture aperture-size scaling in carbonate rocks
J. N. Hooker, L. A. Gomez, S. E. Laubach, J. F. W. Gale, R. Marrett, 2012. "Effects of diagenesis (cement precipitation) during fracture opening on fracture aperture-size scaling in carbonate rocks", Advances in Carbonate Exploration and Reservoir Analysis, J. Garland, J. E. Neilson, S. E. Laubach, K. J. Whidden
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A correlation is demonstrated between the presence of crack-seal texture and power-law kinematic aperture-size (width) distributions among opening-mode fractures in rocks of dominantly carbonate mineralogy. Crack-seal opening increments (opening-displacement increment sizes or ‘gaps’) within individual fractures follow narrow normal or log-normal size distributions, suggesting that fracture widening accumulates in characteristic (usually micrometre-scale) size increments. The scale invariance in overall fracture width distributions present in some fracture sets most likely arises from grouping of these increments (localization) to form larger fractures (millimetre- to centimetre-scale widths). Such localization could be a consequence of the tendency for larger, less cemented fractures to break preferentially during subsequent deformation. Cement accumulation patterns thus provide a mechanism for positive feedback whereby large-fracture growth exceeds small-fracture growth. Using characteristically sized growth increments, a fracture growth model accurately simulates fracture arrays having power-law fracture-width distributions. Model parameters can be altered to produce characteristic-width fracture size distributions. The results have implications for how fracture porosity and permeability evolve in carbonate reservoirs.
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Carbonate reservoirs contain an increasingly important percentage of the world's hydrocarbon reserves. This volume presents key recent advances in carbonate exploration and reservoir analysis. As well as a comprehensive overview of the trends in carbonate over the years, the volume focuses on four key areas:
emerging plays and techniques – with special reference to lacustrine plays in syn-rift basins and development of super-giant heavy oil plays
improved reservoir characterization – with examples from the Middle East and Europe and case studies of how outcrop analogues can provide key data for input to geological models
impact of fractures and faults in carbonates –contributors highlight the need for integrated structural and diagenetic approaches in order to understand how fractures evolve as fluid-flow conduits
advances in geomodelling of carbonate reservoirs –several papers discuss the application of new and innovative geomodelling and geostatistical techniques to carbonate reservoirs.