Borehole tool, procedures, and interpretation for making permeability

Abstract

A borehole tool has a source probe in fluid contact with the borehole wall, a fluid flow line for bringing fluids to and from the source probe, two injection fluid chambers containing clean oil and clean water and in fluid contact with the fluid flow line, at least one sample chamber for receiving fluid from the formation, valves for selectively routing the formation fluids and the clean oil and water through the fluid flow line, at least one pressure controller for controlling whether fluid is to be injected or withdrawn from the formation via the source probe, and a pressure gauge for measuring the pressure seen at the source probe. Permeability measurements are made by sequentially injecting one clean fluid into the formation, followed by a cleaning of the line with the other fluid which was not injected, followed by the injection of the other fluid into the formation. The order in which the oil and water are injected is based on the type of mud used for drilling. Using the sequential injection preceded and separated by cleaning, end point effective and relative permeability determinations are made by measuring the pressure seen at the probe during steady-state injection conditions of known flow rate in order to calculate mobility of the fluid phase being injected; the mobility being related to the end point effective permeability via the viscosity of the liquid being injected.