Downhole tomographic imaging
AssigneeHalliburton Energy Services, Inc.
InventorsDongwon Lee, Weijun Guo, Sriram Srinivasan
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Abstract
A tomographic imaging apparatus utilizes Compton backscattering to evaluate cement behind the casing. The imaging apparatus includes a slant-hole or pin-hole collimator coupled to a series of detectors in order to count the number of photons that backscatter off from the cement. The number of backscattered photons is proportional to the density of the cement behind the casing. Using the photon count, an image processing unit of the imaging apparatus generates a 2D or 3D tomographic image of the borehole.
Claims18
An apparatus for downhole photon imaging, comprising:
- a photon source that emits photons;
- a first detector module positioned above the photon source, the first detector module comprising a plurality of photon detectors to detect photons and produce a signal in response to the received photons, wherein each detector is positioned to correspond to a different depth of investigation;
- a first detector collimator coupled to the detectors to allow backscattered photons at a pre-determined angle to be detected by the detectors of the first detector module;
- a second detector module positioned below the photon source, the second detector module comprising a plurality of photon detectors to detect photons and produce a signal in response to the received photons, wherein each detector of the second detector module is positioned to correspond to a different depth of investigation;
- a second detector collimator coupled to the detectors of the second detector module to allow backscattered photons at a pre-determined angle to be detected by the second detector module;
- and
- an image processing unit that generates an image of a wellbore surrounding the apparatus based upon the signal produced by the detectors of at least one of the first detector module or the second detector module.
A method for downhole photon imaging, comprising:
- (i) emitting photons from a photon source, wherein the photons are backscattered from a region of interest surrounding a wellbore;
- (ii) receiving the backscattered photons within a first detector collimator positioned at a pre-determined angle;
- (iii) directing the backscattered photons through the first detector collimator and onto a first detector module, the first detector module comprising a plurality of photon detectors to detect the backscattered photons and generate a first signal;
- (iv) receiving the backscattered photons within a second detector collimator positioned at a pre-determined angle;
- (v) directing the backscattered photons through the second detector collimator and onto a second detector module, the second detector module comprising a plurality of photon detectors to detect the backscattered photons and generate a second signal;
- and
- (vi) utilizing at least one of first signal or the second signal to generate an image of the region of interest.
Dependencies are inferred from the claim text.