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Use of Automated Mineralogical Scanning Techniques to Aid Permeability Predictions in Fine Grained Micro-Porous Reservoirs

Watson, Paul 1; Mathews, Anna 1; Hailwood, Ernie 1
1 Fugro Robertson Ltd, LLandudno, United Kingdom.

Silica in highly porous fine grained carbonate reservoirs is a current issue as it can affect wettability, porosity and permeability. Using conventional techniques surprisingly high levels of silica have been recorded in these lithologies, but when examined in detail it has been difficult to discern how the silica is manifesting itself at nµ scale within the rock fabric.

By using automated mineralogical scanning techniques with a combined SEM and EDS system (QEMSCANTM) it is possible to identify and quantify the silica content in chalk samples. The recorded quantitative mineralogical data has been used in conjunction with conventional petrological analysis, SEM analysis and magnetic susceptibility measurements (MagPoreTM) to increase understanding of the rock fabric and its relationship to porosity and permeability and in particular permeability anisotropy (Kmin direction vs. Kmax direction). Consequently the defined characteristics can be plotted in well sections to aid the identification and direction of any enhanced permeability horizons. Initial results suggest that bioturbartion may be a controlling factor on the distribution of silica in these lithologies.

The workflows and techniques developed for the study of fine grained carbonate reservoirs are illustrated and the conclusions discussed. This methodology has now been adapted and utilised for defining the mineralogical and pore fabric characteristics of other fine grained micro porous lithologies, such as shale gas reservoirs. Further examples of these are illustrated.

 

AAPG Search and Discovery Article #90090©2009 AAPG Annual Convention and Exhibition, Denver, Colorado, June 7-10, 2009