Meter for Measuring Distribution of Gas Flow in Well Bores

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Abstract A flowmeter has been developed at Gulf Research and Development Co. and testedin the field for measuring the flow of gas ill well bores. It has been used ina study of the injection capacity of different horizons in gas injection wellsin Oklahoma. The flow sensitive element of the meter is a semi-conductor having a very hightemperature coefficient of resistance. Advantages possessed by this meter arethe result of that property and the high specific resistance of the element.The instrument possesses a sensitivity considerably higher than any reportedpreviously. In the application described here the element is heated to a temperatureconsiderably above ambient by an electric current, which is supplied by avoltage source at the surface. When fluid flows through the meter the rate ofdissipation of heat is increased and the temperature of the element decreases.Because of the negative temperature characteristics of the resistance elementsuch a decrease of temperature will be accompanied by an increase of resistancewhich, under flow conditions ordinarily found in wells, is of such a magnitudethat it can be directly measured or recorded in terms of a change in voltage atthe surface. In practice, rate of flow is measured in terms of the drop in voltage in theresistance element. All the metering and control apparatus remains at thesurface while the thermal element is lowered into the well on a singleconductor cable, consisting of an insulated wire and sheath. The meter iscalibrated by passing known quantities of gas through it either at the surfaceor in the hole at a point immediately above the region in which gas is lost tothe formation. In case calibration is made at the surface, the ambienttemperature in the hole may readily be obtained by a second resistance elementwhich is operated at a current so low that effectively no heating occurs. The instrument has been adapted to continuous recording, but the velocity ofthe meter relative to that of the gas must be low unless corrections are made.Curves giving data obtained in actual field tests are shown. The meter can alsobe used to determine the distribution of flow capacity in a gas producingwell. A differential form of the meter has been designed and built in which the localflow or injection capacity of the formation is obtained directly. Introduction When fluid is injected into a well in a secondary recovery orpressure-maintenance operation the question of its most effective useinvariably arises. Although the core log, when available, will show the regionsof good permeability and oil saturation, there is normally no assurance thatthe fluid actually enters the formation in zones where injection is deemeddesirable. In view of the uncertainties involved in such programs, it isgenerally conceded that measurements of permeability for a formation in placeare more significant than those obtained by the core-sampling technique. A subsurface meter has been developed at the Gulf Research and Development Co.for measuring flow of fluids at different horizons in a well bore, and fieldtests have been made on the instrument in cooperation with the Tulsa Divisionof the Gulf Oil Corp. T.P.2276