Imaging of Formation Structure Ahead of the Drill-Bit
AssigneeBaker Hughes Incorporated
InventorsTheodorus W. Geerits, Thomas Bohlen, Olaf Hellwig
Life of this patent
Estimating the term…
Abstract
The present disclosure is related to apparatuses and methods for downhole acoustic logging. The tool may be used for generating a guided borehole wave that propagates into the formation as a body wave, reflects from an interface, and is converted back into a a guided borehole wave. Guided borehole waves resulting from reflection of the body wave are used to image a reflector. Methods may include processing of acoustic logging signals including: wavefield separation, auto-correlation of wavefield components, filtering using a dip filter, and estimating a distance to the reflective interface.
Claims20
A method of determining a distance to an interface in an earth formation, the method comprising:
- conveying a logging instrument into a borehole;
- activating at least one transmitter on the logging instrument to produce a guided acoustic wave which propagates downward to the bottom of the borehole and produces an acoustic wave in the earth formation;
- using at least one receiver on the logging instrument to:
- receive a first signal responsive to the downward propagating guided acoustic wave, and
- receive a second signal responsive to an upward propagating guided acoustic wave resulting from reflection of the acoustic wave in the formation at an interface therein;
- filtering the first signal and the second signal using a dip filter;
- and
- estimating from the filtered first signal and the filtered second signal a distance to the interface.
An apparatus configured to estimate a distance to an interface in an earth formation, the apparatus comprising:
- a logging instrument configured to be conveyed into a borehole;
- at least one transmitter on the logging instrument configured to produce a guided acoustic wave which propagates downward to the bottom of the borehole and produces an acoustic wave in the earth formation;
- at least one receiver on the logging instrument configured to:
- receive a first signal responsive to the downward propagating guided acoustic wave, and
- receive a second signal responsive to an upward propagating guided acoustic wave resulting from reflection of the acoustic wave at the borehole bottom and in the formation at an interface therein;
- and
- at least one processor configured to:
- filter the first signal and the second signals using a dip filter, and
- estimate from the first signal and the second signal a distance from the bottom of the borehole to the interface,
A computer-readable medium product having stored thereon instructions that when read by a processor enable the processor to execute a method, the method comprising:
- filtering a first signal and a second signal using a dip filter and estimating a distance from a bottom of a borehole to an interface in an earth formation wherein:
- the first signal is produced by a receiver on a logging instrument conveyed in a borehole responsive to a downward propagating guided acoustic wave in the borehole;
- and
- the second signal is produced by the receiver responsive to an upward propagating guided seismic wave in the borehole, the upward propagating wave resulting from reflection of an acoustic wave produced at the bottom of the borehole by the downward propagating guided acoustic wave and reflected at the interface.
Dependencies are inferred from the claim text.