Patent ID: 6216532
Filing Date: 2001-04-17
Classification: E21B,G01F

Abstract:
A method of determining downhole in nearly-horizontal sections of a well borehole the flow rate of gas within a multiphase fluid containing a mixture of gas and liquid, the method comprising the steps of;positioning within a length of a borehole of interest a logging tool carrying thereon a pair of local sensors spaced apart a known distance axially along the tool and thus along the borehole, each sensor being able to detect the difference between gas and liquid, and being mounted on arms extendible from a main body of the tool such that, with the tool positioned within the borehole, the sensors are disposed to be actually in a path of any gas bubbles likely to be in the fluid;correlating the output of the pair of sensors to allow an identification of individual gas bubbles passing from one sensor to the other;measuring the time taken for gas bubbles to pass from one sensor to the other;determining from a distance-over-time calculation a gas bubble velocity;determining a time-averaged hold-up of the gas within the multiphase fluid; anddetermining by a hold-up-times-borehole area-times-gas bubble velocity calculation the gas flow rate within the length of the borehole.