Surveying a subterranean borehole using accelerometers
AssigneeHalliburton Energy Services, Inc.
InventorGraham McElhinney
Life of this patent
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Abstract
A method and apparatus for surveying a subterranean borehole is disclosed which uses two sets of accelerometers joined by a joining structure which prevents relative rotation between the two sets, the whole apparatus being arranged to permit movement along a borehole to one or more survey positions. Each set of accelerometers measures the gravity in at least two directions at its respective positions, and then from these measured values it is possible to calculate the borehole inclination and azimuth. The present invention is particularly suitable for use in areas with high magnetic interference, or for measuring boreholes with low inclinations. Tests of the present invention shows that an accuracy similar to that obtained by gyro surveys was achievable.
Claims17
A method for determining a tool inclination and azimuth in a borehole in an earth formation, said tool having a first and second gravity measurement devices mounted therein, comprising the steps of:
- (a) aligning at least one of said gravity measurement devices with a known reference azimuth;
- (b) positioning said tool in said borehole, said first device being positioned at a first position and second device at a second position in said borehole, said first and second devices being constrained from rotating with respect to each other;
- (c) measuring a first and a second set of gravity vectors using said first and second devices, respectively;
- (d) determining the inclination and azimuth of said tool at said first position in said borehole from said first and second sets of gravity vectors.
An apparatus for determining the inclination and azimuth of a tool in a borehole traversing an earth formation, comprising:
- (a) a first and second gravity measurement devices, said devices being axially positioned with respect to said tool and offset from each other and constrained from rotational movement with respect to each other, wherein said first and second devices each measure a set of gravity vectors at a first and second position in said borehole, respectively, each set comprising at least two perpendicular gravity vectors;
- and
- (b) a processor to determine the inclination and azimuth of said tool with respect to an azimuthal reference based on said sets of gravity vectors.
Dependencies are inferred from the claim text.