DTEM With Short Spacing for Deep, Ahead of the Drill Bit Measurements
AssigneeBaker Hughes Incorporated
InventorsGregory B. Itskovich, Arcady Reiderman, Michael B. Rabinovich, Sergey Martakov, Emma Iomdina
Life of this patent
Estimating the term…
Abstract
A transmitter on a bottomhole assembly (BHA) is used for generating a transient electromagnetic signal in an earth formation. A processor estimates the distance to a resistivity interface using a signal produced by a receiver on the BHA. The transmitter-receiver distance may be less than 1 m. The estimation of the distance is done in real time using a thin conductive sheet approximation.
Claims33
An apparatus for evaluating an earth formation comprising:
- a carrier configured to be conveyed in a borehole;
- a transmitter on the carrier configured to produce a transient electromagnetic field in the earth formation;
- a receiver on the carrier positioned at a first distance from the transmitter configured to produce a first signal responsive to an interaction of the electromagnetic field with the earth formation, the first signal being affected by a resistivity interface at a second distance at least five times the first distance from the transmitter;
- and
- a processor configured to estimate from the first signal a value of the second distance.
A method of evaluating an earth formation comprising:
- using a transmitter on a carrier in a borehole for producing a transient electromagnetic field in the earth formation;
- using a receiver on the carrier positioned at a first distance from the transmitter for producing a first signal responsive to an interaction of the electromagnetic field with the earth formation, the first signal being affected by a resistivity interface at a second distance at least five times the first distance from the transmitter;
- and
- using a processor for estimating from the first signal a value of the second distance.
A non-transitory computer-readable medium product having stored thereon instructions that when read by a processor cause the processor to execute a method, the method comprising:
- estimating a distance of a resistivity interface from a bottomhole assembly (BHA) in an earth formation using a transient electromagnetic (TEM) signal produced by a receiver on the BHA responsive to a TEM field produced by a transmitter spaced less than 5 m from the receiver on a carrier in a borehole.
An apparatus for evaluating an earth formation comprising:
- a carrier configured to be conveyed in a borehole;
- a transmitter on the carrier configured to produce a transient electromagnetic field in the earth formation;
- a receiver on the carrier configured to produce a signal responsive to an interaction of the electromagnetic field with the earth formation, the produced signal being affected by at least one layer in the earth formation;
- and
- a processor configured to estimate from the produced signal a value of a distance to an upper surface of the at least one layer and a conductivity of the at least one layer using a thin conductive sheet approximation.
A method of evaluating an earth formation comprising:
- using a transmitter on a carrier conveyed in a wellbore for producing a transient electromagnetic field in the earth formation;
- using a receiver on the carrier for producing a signal responsive to an interaction of the electromagnetic field with the earth formation, the produced signal being affected by at least one layer in the earth formation;
- and
- estimating from the produced signal a value of a distance to an upper surface of the at least one layer and a conductivity of the at least one layer using a thin conducting sheet approximation.
A non-transitory computer-readable medium product having stored thereon instructions that when read by a processor cause the processor to execute a method, the method comprising:
- estimating a distance of a resistivity interface from a bottomhole assembly (BHA) in an earth formation using a transient electromagnetic (TEM) signal produced by a receiver on the BHA responsive to a TEM field produced by a transmitter on a carrier in a borehole;
- wherein a thin conducting sheet approximation is used in the estimation.
Dependencies are inferred from the claim text.