Abstract

Relative permeability in a reservoir can be changed by damage induced by drilling, completion, and production operations. Hydrocarbons and water reside in different pore networks in a hydrocarbon reservoir. Selectively blocking off the hydrocarbon pore network at the wellbore by depositing hydrocarbon components, drill fines, or water block greatly reduces the relative permeability to hydrocarbons. Additionally, this reduces the cross-sectional area of the reservoir and increases the hydraulic gradient across the water pore network. This in turn can overcome the capillary forces that are holding the water in place and allow water production out of a hydrocarbon reservoir that would have produced 100% hydrocarbons before the damage. Once this damage has been done, volumes of water or water compositions are of no help in evaluating the productive nature of the reservoir had it not been damaged. There are large numbers of hydrocarbon reservoirs that have damaged and deemed water bearing when in fact they would be commercial hydrocarbon reservoirs if not damaged.