DETERMINING FLUID PROPERTIES FROM PRESSURE, VOLUME AND TEMPERATURE MEASUREMENTS MADE BY ELECTRIC WIRELINE FORMATION TESTING TOOLS

摘要

A method of determining an amount of dissolved gas in a fluid sample isdisclosed. The method includes hydraulically confining and expanding the samplewhile measuring pressure and volume. A first volume and pressure are determined atwhich the rate of change in pressure with respect to volume deviates from a linearrelationship. A second volume and pressure at which continued expansion of the fluidcauses substantially no change in pressure is determined The first pressure andvolume are extrapolated by the linear relationship to intersect an extrapolation from thesecond volume and pressure at no change in pressure, thereby determining a bubblepoint comprising a bubble point pressure and a bubble point volume. A third pressurecorresponding to measured pressure of the fluid sample at the bubble point volume isdetermined. An extrapolated sample volume is determined at the third pressure byextrapolating the linear relationship from the bubble point to a sample volume alongthe linear relationship corresponding to the third pressure. A volume of gas dissolvedin the fluid sample is determined by linearly scaling a difference between the bubblepoint volume and the extrapolated sample volume with respect to a difference betweenthe second volume and the bubble point volume.In a preferred embodiment of the invention, the sample is withdrawn into asample chamber in an electric wireline formation test tool having a means formeasuring pressure and volume of the sample chamber.