US 2003/0155121 A1 · Logging-while-drilling apparatus and methods for measuring density

Abstract

Logging-while-drilling gamma ray back scatter density system with elements configured to minimize material between sensor and the borehole environs, maximize shielding and collimation efficiency, and increase operational reliability and ruggedness. The system comprises a drill collar with a cavity in the outer wall, and an instrument package containing a sensor. The instrument package is disposed in the cavity and protrudes from the outer wall of the collar. Embodied as a density LWD system, the sensor consists of a gamma ray source and two detectors mounted within an instrument package framework made of high Z shielding material. A stabilized containing an alignment channel in the inner surface is disposed around the collar and receives the protrusion. The source and detectors are preferably positioned within the instrument package so that they fall within a radius defined by the outer surface of the collar. The source is threaded directly into the high Z material framework of the instrument package.

Claims30

Dependent claims

An LWD logging system comprising:

(a) a drill collar comprising
(i) a collar wall defined by an inner collar surface and an outer collar surface, and
(ii) a cavity within said collar wall and opening at said outer collar surface;
(b) an instrument package comprising a sensor, wherein said instrument package is disposed within said cavity and forms a radial protrusion from said outer collar surface;
and
(c) a stabilizer disposed circumferentially around said outer collar surface, wherein said stabilizer comprises
(i) a stabilizer wall defined by an inner stabilizer surface and an outer stabilizer surface, and
(ii) an axial alignment channel within said stabilizer wall and opening to said inner stabilizer surface, and wherein
(iii) said axial alignment channel receives said radial protrusion.

6 more elements

An LWD density logging system comprising:

(a) a drill collar comprising
(i) a collar wall defined by an inner collar surface and an outer collar surface, and
(ii) a cavity within said collar wall and opening at said outer collar surface;
(b) an instrument package with a radial center and comprising a high Z framework and which is removably disposed within said cavity and which forms a radial protrusion from said outer collar surface, wherein said instrument package further comprises
(i) a cesium-137 gamma ray source threaded into said framework,
(ii) a short spaced gamma ray detector spaced axially at a first distance from said gamma ray source,
(iii) a long spaced gamma ray detector spaced axially at a second distance from said gamma ray source, wherein said second distance is greater than said first distance,
(iv) a first pathway in said high Z material extending radially outward from said source to said inner stabilizer surface thereby forming a source collimator window, wherein the axis of said source collimator window is in a plane defined by the major axis of said collar and said radial center of said instrument package, and wherein said source collimator window is filled with low Z material,
(v) a second pathway in said high Z material extending radially outward from said short spaced detector to said inner stabilizer surface thereby forming a short spaced detector collimator window, wherein the axis of said short spaced detector collimator window is in a plane defined by said major axis of said collar and said radial center of said instrument package, and wherein said short spaced detector collimator window is filled with said low Z material, and
(vi) a third pathway in said high Z material extending radially outward from said long spaced detector to said inner stabilizer surface thereby forming a long spaced detector collimator window, wherein the axis of said long spaced detector collimator window is in a plane defined by said major axis of said collar and said radial center of said instrument package, and wherein said long spaced detector collimator window is filled with said low Z material, and wherein
(vii) said source and said short spaced detector and said long spaced detector are disposed in said instrument package within a radius defined by said outer collar surface;
and
(c) a stabilizer disposed circumferentially around said outer collar surface, wherein said stabilizer comprises
(i) a stabilizer wall defined by an inner stabilizer surface and an outer stabilizer surface,
(ii) an axial alignment channel within said stabilizer wall and opening to said inner stabilizer surface,
(iii) a first low Z insert that is disposed within said stabilizer wall and extends radially from said inner stabilizer surface to said outer stabilizer surface and terminates said first pathway,
(iv) a second low Z insert that is disposed within said stabilizer wall and extends radially from said inner stabilizer surface to said outer stabilizer surface and terminates said second pathway, and
(v) a third low Z insert that is disposed within said stabilizer wall and extends radially from said inner stabilizer surface to said outer stabilizer surface and terminates said third pathway, and wherein
(vi) said axis of said source collimator window forms an acute angle with said major axis of said collar,
(vii) said axis of said first detector collimator window forms an acute angle with said major axis of said collar, and
(viii) said axial alignment channel receives said radial protrusion.

18 more elements

Dependencies are inferred from the claim text.

Logging-while-drilling apparatus and methods for measuring density

Life of this patent

Logging-while-drilling apparatus and methods for measuring density

Life of this patent

Abstract

Claims30