PASSIVE RANGING TECHNIQUES IN BOREHOLE SURVEYING
First Claim
1. A method for determining the location of a target subterranean structure from within an adjacent borehole, said subterranean structure generating magnetic flux, the method comprising:
- (a) providing a downhole tool including first and second gravity measurement devices disposed at corresponding first and second positions in the borehole, at least one of the first and second positions selected to be within sensory range of magnetic flux from the subterranean structure, the tool further including a magnetic field measurement device disposed at one of the first and second positions and within sensory range of magnetic flux from the subterranean structure, the first and second gravity measurement devices constrained from rotating with respect to one another about a substantially cylindrical borehole axis;
(b) using the first and second gravity measurement devices to measure corresponding first and second gravity vector sets;
(c) processing the first and second gravity vector sets to determine a local borehole azimuth;
(d) measuring a total local magnetic field using the magnetic field measurement device;
(e) processing the total local magnetic field, the local azimuth and a reference magnetic field to determine a portion of the total magnetic field attributable to the target subterranean structure;
(f) re-positioning the tool at new locus for first and second positions in the borehole so that the magnetic field measurement device remains within sensory range of the magnetic flux from the subterranean structure;
(g) repeating (b), (c), (d), (e), and (f) for a predetermined number of cycles;
(h) generating an interference magnetic field vector for each locus for first and second positions, each of the interference magnetic field vectors corresponding to the portion of the total magnetic field determined in (e) at the corresponding locus; and
(j) extending the interference magnetic field vectors to determine a location of the target subterranean structure.
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Accused Products
Abstract
A method for determining the location of a target subterranean structure from within an adjacent borehole is disclosed which uses first and second gravity measurement devices disposed at corresponding first and second positions in the adjacent borehole and a magnetic field measurement device disposed one of the first and second positions. The method includes processing a total local magnetic field, a reference magnetic field, and a local azimuth determined using the gravity measurement devices to determine a portion of the total magnetic field attributable to the subterranean structure multiple points in the adjacent borehole. The location of the subterranean structure is determined using the portion of the total magnetic field attributable thereto. A system adapted to execute the disclosed method and a computer system including computer-readable logic configured to instruct a processor to execute the disclosed method are also provided.
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Citations
52 Claims
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1. A method for determining the location of a target subterranean structure from within an adjacent borehole, said subterranean structure generating magnetic flux, the method comprising:
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(a) providing a downhole tool including first and second gravity measurement devices disposed at corresponding first and second positions in the borehole, at least one of the first and second positions selected to be within sensory range of magnetic flux from the subterranean structure, the tool further including a magnetic field measurement device disposed at one of the first and second positions and within sensory range of magnetic flux from the subterranean structure, the first and second gravity measurement devices constrained from rotating with respect to one another about a substantially cylindrical borehole axis;
(b) using the first and second gravity measurement devices to measure corresponding first and second gravity vector sets;
(c) processing the first and second gravity vector sets to determine a local borehole azimuth;
(d) measuring a total local magnetic field using the magnetic field measurement device;
(e) processing the total local magnetic field, the local azimuth and a reference magnetic field to determine a portion of the total magnetic field attributable to the target subterranean structure;
(f) re-positioning the tool at new locus for first and second positions in the borehole so that the magnetic field measurement device remains within sensory range of the magnetic flux from the subterranean structure;
(g) repeating (b), (c), (d), (e), and (f) for a predetermined number of cycles;
(h) generating an interference magnetic field vector for each locus for first and second positions, each of the interference magnetic field vectors corresponding to the portion of the total magnetic field determined in (e) at the corresponding locus; and
(j) extending the interference magnetic field vectors to determine a location of the target subterranean structure. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41)
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42. A system for determining the location of a target subterranean structure from within an adjacent borehole, said subterranean structure generating magnetic flux, the system comprising:
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a down hole tool including first and second gravity measurement devices deployed thereon, the tool operable to be positioned in a borehole such that the first and second gravity measurement devices are located at a preselected series of corresponding first and second positions in the borehole, each first and second position in the series corresponding to a predetermined locus of the tool in the borehole, at least one of the first and second positions selected to be within sensory range of magnetic flux from the subterranean structure at each locus, the tool further including a magnetic field measurement device disposed at one of the first and second positions and within sensory range of magnetic flux from the subterranean structure at each locus, the first and second gravity measurement devices constrained from rotating with respect to one another about a substantially cylindrical borehole axis; and
a processor configured to determine;
(A) first and second sets of gravity vectors from measurements of the first and second gravity measurement devices, respectively, at the first and second positions, respectively, at each locus;
(B) a local borehole azimuth at each locus from the first and second gravity vector sets in (A);
(C) a total local magnetic field for each locus as measured by the magnetic field measurement device;
(D) a portion of the total magnetic field attributable to the subterranean structure at each locus, said portion determined from the total local magnetic field in (C), the local azimuth in (B), and a reference magnetic field made available to the processor;
(E) an interference magnetic field vector for each locus, each of the interference magnetic field vectors corresponding to the portion of the total magnetic field determined in (D) at the corresponding locus; and
(F) a location of the target subterranean structure based on extension of the interference magnetic field vectors determined in (E). - View Dependent Claims (43, 44, 45, 46)
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47. A computer system comprising:
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at least one processor; and
a storage device having computer-readable logic stored therein, the computer-readable logic accessible by and intelligible to the processor;
the processor further disposed to receive input from first and second gravity measurement devices when said first and second gravity measurement devices are deployed on a down hole tool at a preselected series of corresponding first and second positions in a borehole, each first and second position in the series corresponding to a predetermined locus of the tool in the borehole, at least one of the first and second positions selected to be within sensory range, at each locus, of magnetic flux generated by a target subterranean structure located outside the borehole, the first and second gravity measurement devices constrained, when deployed on the tool, from rotating with respect to one another about a substantially cylindrical borehole axis, the processor further disposed to receive input from a magnetic field when said magnetic field measurement device is deployed on the tool at one of the first and second positions and within sensory range at each locus of magnetic flux from the subterranean structure, the computer-readable logic further configured to instruct the processor to execute a method for determining the location of the target subterranean structure, the method comprising;
(a) determining first and second sets of gravity vectors based on input from the first and second gravity measurement devices, respectively, at the first and second positions, respectively, at each locus;
(b) calculating a local borehole azimuth at each locus from the first and second gravity vector sets determined in (a);
(c) determining a total local magnetic field for each locus based on input from the magnetic field measurement device;
(d) determining a portion of the total magnetic field attributable to the subterranean structure at each locus, said portion determined from the total local magnetic field in (c), the local azimuth in (b), and a reference magnetic field made available to the processor;
(e) calculating an interference magnetic field vector for each locus, each of the interference magnetic field vectors corresponding to the portion of the total magnetic field determined in (d) at the corresponding locus; and
(f) determining a location of the target subterranean structure based on extension of the interference magnetic field vectors determined in (e). - View Dependent Claims (48, 49, 50, 51, 52)
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Specification