Communications – electrical: acoustic wave systems and devices – Seismic prospecting – Well logging
Reexamination Certificate
1999-12-16
2003-04-22
Lefkowitz, Edward (Department: 2862)
Communications, electrical: acoustic wave systems and devices
Seismic prospecting
Well logging
C181S104000
Reexamination Certificate
active
06552962
ABSTRACT:
FIELD OF THE INVENTION
This invention relates generally to a method and apparatus utilized in hydrocarbon exploration. More specifically, the invention relates to the utilization of acoustic sources and receivers to determine acoustic properties of geologic formations as a logging tool traverses them, be it a wireline logging tool or a logging while drilling tool. More particularly, the present invention is directed to methods of and apparatus for determining certain acoustic velocities characteristic of the pertinent geologic formations.
BACKGROUND OF THE INVENTION
Geologists and geophysicists are interested in the characteristics of the formations encountered by a drill bit as it is drilling a well for the production of hydrocarbons from the earth. Such information is usefull in determining the correctness of the geophysical data used to choose the drilling location and in choosing subsequent drilling locations. In horizontal drilling, such information can be useful in determining the location of the drill bit and the direction that drilling should follow.
Such information can be derived in a number of ways. For example, cuttings from the mud returned from the drill bit location can be analyzed or a core can be bored along the entire length of the borehole. Alternatively, the drill bit can be withdrawn from the borehole and a “wireline logging tool” can be lowered into the borehole to take measurements. In still another approach, called “measurement while drilling” (“MWD”) or “logging while drilling” (“LWD”) tools make measurements in the borehole while the drill bit is working. There are a wide variety of logging tools, including resistivity tools, density tools, sonic or acoustic tools, and imaging tools.
An acoustic logging tool collects acoustic data regarding underground formations. The purpose of such a tool is to measure the “interval transit time” or the amount of time required for acoustic energy to travel a unit distance in a formation. In simple terms, this is accomplished by transmitting acoustic energy into the formation at one location and measuring the time that it takes for the acoustic energy to travel to a second location or past several locations. The measurement is complicated by the fact that the tool is roughly in the middle of a borehole of unknown diameter and is surrounded by mud. Further, the formation along the borehole may have been disturbed by the action of the drill bit and may no longer have the same acoustic characteristics as the undisturbed formation.
SUMMARY OF THE INVENTION
In general, in one aspect, the invention features a logging-while-drilling acoustic logging tool comprising one or more acoustic transmitters and one or more acoustic receivers. One or more elements of a set comprising the acoustic receivers and the acoustic transmitters are spaced radially apart from one or more of the remaining elements of the set.
Implementations of the invention may include one or more of the following. The tool may include a transmit module coupled to the acoustic transmitters, a data acquisition module coupled to the acoustic receivers, and a transmitter trigger signal coupled to the transmit module and to the data acquisition module. The transmit module may be configured to initiate transmission via the acoustic transmitters and the data acquisition module may be configured to initiate data acquisition via the acoustic receivers.
In general, in another aspect, the invention features a logging-while-drilling acoustic logging tool comprising a multipole-capable acoustic source.
Implementations of the invention may include one or more of the following. The multipole-capable acoustic source may comprise one or more acoustic transmitters.
In general, in another aspect, the invention features an acoustic logging tool comprising a multipole capable acoustic source. The source comprises one or more acoustic transmitters. Each acoustic transmitter is configured to have a transmission direction. An acoustic transmitter is paired with another acoustic transmitter having an azimuthally opposite transmission direction.
Implementations of the invention include one or more of the following. The acoustic logging tool may comprise a transmitter module coupled to the acoustic transmitters. The transmitter module may be configured to fire the acoustic transmitters. The transmitter module may be configured to fire each acoustic transmitter. One or more of the acoustic transmitters may be configured to transmit acoustic energy at one or more selectable frequencies. The transmitter module may be configured to control frequency content of the acoustic energy transmitted by one or more acoustic transmitters. The transmitter module may be configured to control timing of the acoustic energy transmitted by one or more acoustic transmitters. The transmitter module may be configured to cause one of the acoustic transmitters to transmit acoustic energy and at least one other acoustic transmitter to transmit acoustic energy with a controlled time delay or phase shift relative to the one acoustic transmitter. The transmitter module may be configured to control magnitude of the acoustic energy transmitted by one or more acoustic transmitters.
In general, in another aspect, the invention features a logging-while-drilling acoustic logging tool comprising a multipole-capable acoustic receiver. The logging-while-drilling acoustic logging tool may further comprise a multipole-capable acoustic source.
In general, in another aspect, the invention features an acoustic logging tool comprising a multipole capable acoustic receiver, the receiver comprising one or more acoustic receivers. Each acoustic receiver is configured to have a receive direction. An acoustic receiver is paired with another acoustic receiver having an azimuthally different receive direction.
Implementations of the invention include one or more of the following. The acoustic logging tool may comprise one or more sample-and-hold amplifiers, each sample-and-hold amplifier configured to sample and hold a signal originating in the acoustic receivers and conditioned by one or more conditioning components. The one or more sample-and-hold amplifiers may sample substantially simultaneously. The acoustic logging tool may comprise a processor. The conditioning components may comprise an adjustable high-pass filter having a cutoff frequency adjustable under control of the processor. The processor control of the cutoff frequency may be adaptive. The conditioning components may comprise an adjustable amplifier having a gain adjustable under control of the processor. The adjustable amplifier may be configured to be adjusted separately for one or more receiver channels. The processor control of the adjustable amplifier may be adaptive. The conditioning components may comprise a low pass filter. The conditioning components may comprise a pre-amplifier interfaced to the receivers. The conditioning components may comprise an amplifier. The acoustic logging tool may comprise an analog-to-digital converter for converting the analog signals held by the one or more sample-and-holds to a digital signal. The digital signal may be coupled to the processor. The acoustic logging tool may comprise a multiplexer for selecting, based on an address, one of the analog signals held by the one or more sample-and-holds to couple to the analog-to-digital converter. The acoustic logging tool may comprise a counter for producing the address and a clock. The clock may drive the counter and the analog-to-digital converter. The counter may have a sample-and-hold output configured to cause the sample-and-holds to sample. The counter may have a processor output configured to inform the processor that the counter had completed a counter cycle. The acoustic logging tool may comprise a multipole-capable acoustic source. The acoustic logging tool may comprise one or more analog to digital converters, each analog to digital converter configured to sample a signal originating in one of the acoustic receivers and conditioned by one or more conditioning components. T
Arian Abbas
Varsamis Georgios L.
Wisniewski Laurence T.
Dresser Industries Inc.
Lefkowitz Edward
Taylor Victor J.
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