Influence Of Shaliness Upon Conductivity In Shaly Sandstones In The Northern North Sea Area. Available to Purchase

A cross-plotting technique, based on Waxman-Smits' concept applied to openhole logging data, has been utilised to investigate the influence of shaliness upon conductivity in shaly sandstones in the northern North Sea area. Two significant dangers were highlighted in this study. The investigation shows that the more classical shaly sand model developed for other parts of the world must be used with care in this area. These models could be looked upon as Archie equation with an extra empirical term to correct, or worse, overcorrect for shale conductivity. The presented cross-plots show that the predominant oil-bearing formations seem to have no or very little conductivity contribution from the shale fraction. An apparently similar effect resulting in overestimation of the shale conductivity can be obtained by indiscriminate application of Cation Exchange Capacity (CEC) from crushed cores wet chemistry techniques as input to the Waxman-Smits' model. The consequence of using too high shale conductivities in the area is to calculate unrealistically high oil saturations.