Method and apparatus for locating stratification in production fluid in a well
AssigneeHalliburton Logging Services, Inc.
InventorsMichael L. Gartner, Larry L. Gadeken
Life of this patent
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Abstract
Apparatus for measuring the volume of gas present in a multiphase flow regime in a cased oil or gas well borehole and the amount, if any, of stratification thereof at a particular borehole depth. The apparatus includes a low energy gamma ray source and a sodium iodide detector located a very short distance from the source and separated by shielding material. Low energy gamma rays, unable to leave the well casing and return, are emitted from the source and scattered back from the multiphase production fluid to a detector comprising a sodium iodide crystal and photomultiplier tube. Both the source and detector are surrounded by rotatable slit collimators to provide sensitivity to azimuthal variations in gas volume percentage in the flow.
Claims18
A system for determining the existence of stratified flow in the gas phase of well fluids produced in a cased well borehole and flowing upwardly through a metal casing comprising:
- (a) a source of relatively low energy gamma rays, the energy of said gamma rays being chosen such that there is a small probability that a gamma ray from said source could penetrate a metal casing in the borehole and be scattered back through the metal casing by material outside the casing;
- (b) means for collimating gamma rays from said source of low energy gamma rays selectively along an azimuthal direction with respect to the axis of the well casing and for generating a signal indicative of said azimuthal direction;
- (c) a scintillation detector of gamma radiation and cooperative shielding means for preventing direct irradiation of said detector by said source while allowing the placement of said detector in as close proximity to said source as allowed by said cooperative shielding means to allow detection of gamma rays emitted by said source and scattered by materials inside said metal casing;
- (d) means for counting gamma rays detected by said detector and storing count rate signals indicative thereof;
- (e) means for processing said count rate signals according to a predetermined relationship to derive a measurement signal indicative of the gas holdup phase of well fluid in the vicinity of said source;
- and
- (f) means for displaying said gas holdup signal as a function of said azimuthal signal to provide an indication of stratified fluid flow.
A system for measuring the gas holdup of well fluids produced in a metal cased well borehole, the system comprising:
- (a) a sealed logging tool housing or sonde sized and adopted to pass through a cased well borehole;
- (b) a source in said housing of relatively low energy gamma rays having an energy selected so that there is a very small probability that a gamma ray from said source will penetrate the casing in the well borehole and be scattered back through the casing by formation material outside the casing;
- (c) a closely spaced detector in said housing responsive to gamma radiation;
- (d) cooperative shielding means interposed between said source and said detector, said shielding means determining the proximity of spacing between said source and said detector;
- (e) means for counting gamma rays detected by said detector and storing count rate signals indicative thereof;
- (f) means for processing said count rate signals according to a predetermined relationship to derive a measurement signal indicative of a gas holdup phase of well fluids in the vicinity of said housing;
- and
- (g) means for recording said gas holdup phase measurement signal as a function of well borehole depth.
Dependencies are inferred from the claim text.