oa Derivation of Relative Permeability & Fractional Flow Behaviour from the Inversion of Saturation Logs in Horizontal Wells with Application to Water Shut-off and Predicting Volumetric Sweep Efficiency

An inversion method is presented that uses saturation log profi les recorded in horizontal wells to derive relative permeability and fractional<br>fl ow properties for a waterfl ooded carbonate reservoir. Observed water saturation profi les decreasing horizontally away from<br>hydraulically conductive faults suggest a line-drive type encroachment of water into the fault-bound matrix blocks. The waterfronts<br>have produced saturation profi les analogous to that predicted by Buckley-Leverett displacement theory, including the characteristic<br>shock front. These profi les record parameters such as irreducible water saturation, the shock-front saturation, average saturation behind<br>the front, and the residual oil saturation. These parameters are used to defi ne boundary conditions on a fractional fl ow plot using Welges<br>method. A fractional fl ow curve which meets the boundary conditions is then derived by changing the shape of the controlling relative<br>permeability curves. The observed saturation profi les also show a correlation with porosity, allowing a suite of scanning curves to be<br>derived for each porosity class. The reliability of the method is demonstrated by plotting the average pulsed-neutron-capture log saturations<br>at the perforations against the producing watercut at the time of logging on the fractional fl ow graph.