Acoustic logging while drilling tool to determine bed boundaries
First Claim
1. A logging while drilling acoustic tool for a bottomhole drilling assembly, comprising:
- a transmitter assembly in said bottom hole assembly for generating an acoustic wave signal that is transmitted into the formation;
a receiver assembly in said bottomhole assembly for receiving acoustic wave reflections from a bed boundary, and generating an electrical signal indicative of the received acoustic reflections;
a processor receiving said electrical signal from said receiver, and correlating said received electrical signal to the signal transmitted by said transmitter to determine distance to a bed boundary and the orientation angle of the bed boundary; and
wherein said processor generates a transmission signal that is applied to said transmitter assembly.
4 Assignments
0 Petitions
Accused Products
Abstract
A LWD tool is disclosed for detecting the existence of and distance to adjacent bed boundaries. A transmitter assembly generates either a short acoustic pulse or a swept frequency signal that is detected by an associated receiver assembly. The received signal(s) are conditioned and converted to high precision digital signals by an A/D converter. The digitized signals are accumulated and transferred to a digital signal processor via a high speed data bus. The digital signal processor also receives a digital signal representing the transmission signal and compares the transmission signal and the received signals together to enable a downhole microprocessor to derive a time lag for the received signals. The microprocessor can transmit the time lag signal to the surface via a mud pulse for real-time control, or can operate as part of a closed loop drilling system to automatically control inclination of the drilling assembly to stay within, or to enter, a pay zone based upon the time lag associated with the received signals, and the measured speed of sound of the formation. In one embodiment, the receivers in the receiver array are steered to investigate various volume cells in the formation. A time delay is determined based on the volume cell, which is used to align and sum the received signals. The maximum sum value then is used as indicative of a bed boundary in that particular volume call.
219 Citations
75 Claims
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1. A logging while drilling acoustic tool for a bottomhole drilling assembly, comprising:
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a transmitter assembly in said bottom hole assembly for generating an acoustic wave signal that is transmitted into the formation; a receiver assembly in said bottomhole assembly for receiving acoustic wave reflections from a bed boundary, and generating an electrical signal indicative of the received acoustic reflections; a processor receiving said electrical signal from said receiver, and correlating said received electrical signal to the signal transmitted by said transmitter to determine distance to a bed boundary and the orientation angle of the bed boundary; and wherein said processor generates a transmission signal that is applied to said transmitter assembly. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19)
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20. A logging while drilling system, as part of a bottomhole assembly which drills through downhole formations, for providing an indication of the distance to bed boundaries, comprising:
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a transmitter assembly for generating acoustic signals into the formation; a receiver assembly detecting reflected acoustic signals from bed boundaries; a downhole processing unit for correlating the reflected signals received by said receiver assembly with the acoustic signals generated by said transmitter to remove extraneous noise and to determine a time lag for the reflected signals, said downhole processing unit using said time lag and speed of sound of the formation to determine the distance to bed boundaries. - View Dependent Claims (21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38)
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39. A method for geosteering a bottomhole assembly, comprising the steps of:
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transmitting acoustic signals into the formation; receiving reflected acoustic signals; generating an electrical signal representative of the received signals; correlating the transmitted and received reflected acoustic signals; determining the time lag for the received reflected acoustic signals; determining the formation speed of sound; identifying bed boundaries based upon the time lag determination and the speed of sound determination; and steering the bottomhole assembly based upon the identification of bed boundaries. - View Dependent Claims (40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54)
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55. A method for automatically steering a drill bit which is drilling through a downhole formation, comprising the steps of:
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transmitting an acoustic signal into the formation; receiving reflected acoustic signals; cross-correlating said received reflected signals with the transmitted acoustic signals; determining a time lag for a bed boundary based upon the time difference between transmitting the acoustic signal and receiving the reflected acoustic signal; changing the direction in which said drill bit drills based upon the time lag signal.
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56. A system for a bottomhole drilling assembly, comprising:
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a transmitter assembly for transmitting acoustic signals into a formation; a receiver assembly for detecting reflected acoustic signals; a digital signal processor receiving signals indicative of the transmitted acoustic signals and the received acoustic signals, said digital signal processor cross-correlating the received signal to obtain a cross-correlated product; and a microprocessor connected to said digital signal processor, said microprocessor analyzing said cross-correlated product to determine time lag for the received signals. - View Dependent Claims (57)
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58. An acoustic logging while drilling system for determining bed boundaries ahead of the drill bit, comprising:
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a section of tubing; an acoustic transmitter assembly located in said tubing section for transmitting a relatively low frequency signal into the formation ahead of the drill bit, said relatively low frequency signal have a wavelength (λ
);an acoustic receiver array located in said tubing section for receiving reflections of said relatively low frequency signal, said receiver assembly including a first receiver and a second receiver, and said first and second receivers are separated a distance equal to or greater than the wavelength (λ
) of the transmitted wave. - View Dependent Claims (59, 60, 61, 62, 63)
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64. An acoustic logging while drilling system for determining bed boundaries in the vicinity of a borehole, comprising:
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a section of tubing; an acoustic transmitter assembly located in said tubing section for transmitting an acoustic signal into the formation ahead of the drill bit, said transmitter assembly including a first transmitter located on one face of the tubing section, and a second transmitter assembly located on an opposite face of said tubing section for acoustic steering in the plane perpendicular to the tubing axis; an acoustic receiver array located in said tubing section for receiving reflections of the acoustic signal, said receiver assembly including a first receiver and a second receiver and said first and second receivers are separated a predetermined distance; and a processor for performing geometric corrections on the reflections received by the acoustic receiver array based upon a time delay that is selected to investigate a particular volume cell external to the borehole. - View Dependent Claims (65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75)
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Specification