Schlumberger Technology Corporation

David Brian White

Raj Banerjee

Peter Allan Goode

Jeffrey Spath

Raj Kumar Michael Thambynayagam

Leslie J Bradbury

A reservoir pressure in an underground formation surrounding a well is analyzed based on a direct measurement of the pressure at the wall of the well using the permeability of mud cake on the wall of the well in the region in which the pressure measurement is made; determining the thickness of mud cake on the well of the well; determining the hydrostatic pressure in the well in the region in which the pressure measurement is made; calculating a pressure decay index from the mud cake permeability and thickness, the hydrostatic pressure and the measured pressure; and using the pressure decay index to analyze the measured pressure to derive the reservoir pressure.

Method for analysis of pressure response in underground formations

In a drill stem test, a packer is set in the well bore to isolate a potential producing zone. A drill pipe with a down hole valve is fitted through the packer. The pipe is usually partially filled with a liquid column prior to commencement of the test, which essentially comprises opening the valve so that formation fluids can flow into the drill pipe and measuring various parameters associated with the fluid transfer. A method for estimating porosity and/or permeability includes the steps of setting up such a drill stem test wherein flow of formation fluid to a drill pipe may be controlled by a down hole valve, opening the valve to establish a flow, recording flow parameters, and analyzing oscillatory transients in the flow to compute therefrom estimates of porosity and permeability.

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Fen Ditton, United Kingdom

David Brian White