Permeability, a major reservoir property that reservoirengineers strive to measure as accurately as possible, isnevertheless always measured indirectly, by estimation, eitherthrough well-testing or specific logging tools and techniques.Permeability measurement utilizing reservoir rock samplesdoes not necessarily guarantee accurate results, as fluidsaturation of rock samples may change dramatically due tostresses and pore pressure changes take place during coringand transportation of samples to the laboratory for testing. Inattempting to extrapolate fluid flow behavior in the reservoirfrom such samples, tremendous efforts have been directed upto now towards producing useful meanings of horizontal,vertical and directional permeabilities.This paper introduces a new permeability measurementapproach that brings fresh understanding to reservoirpermeability and a truer reflection of fluid flow behavioraround producing wells. The traditional use of horizontal,vertical and directional permeabilities to reflect theconductivity of a formation to fluid flow is often misleading.Actually, the flow comes from everywhere in the reservoir andreduces to the wellbore, and in many cases ended at theperforations. The flow pattern takes a shape of a cone wherethe base is at the boundary and the head is at the wellbore orthe perforation opening. This flow pattern produces a conicalor “tapering” permeability. This new 3-D permeability termshould enhance the accuracy of the models used to representfluid flow in porous media.A three-dimensional permeability term is newly introducedhere. A three-dimensional spot gas permeameter device andtechniques for measuring this term have been constructed inthe laboratory. This device is intended to enable directmeasurement of gas permeability at any spot on the surface ofthe sample, regardless of sample shape or size.The issues of probe sealing and gas slippage have beenresolved by introduction of a rubber baker at the tip of theprobe, and by allowing low-pressure injection. A newmathematical model has been derived to describe the flowpattern associated with measuring gas permeability using theproposed device. The proposed mathematical model alongwith numerical solution presented is expected to findapplication beyond the gas permeameter case, as its usefulnessis proven more relevant to reservoir behavior.
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