Abstract: A system for self-tuning sonic transmitters which transmits a plurality of frequencies into a downhole formation, then identifies which of the transmitted frequencies generates the best response from the formation. The system then uses the best frequency identified for subsequent logging of formation data until a subsequent tuning sequence is initiated.

Abstract: The shape and size of a borehole may be characterized downhole, using measurements of the borehole shape in conjunction with a catalog of shapes against which the measured shape is matched. A unique identifier for the measured borehole shape, and optionally a size parameter, may be transmitted to a surface facility, generally saving bandwidth compared with the transmission of the raw measured borehole-shape data. Alternatively or additionally, downhole measurements may be adjusted based on the measured shape.

Abstract: An electromagnetic (EM) telemetry system with telluric referencing for use with downhole equipment is described. Embodiments of an EM telemetry system with telluric referencing include a downhole transceiver comprising an encoded signal transmitter, a downhole sensor disposed to monitor the downhole equipment, the downhole sensor coupled to the transceiver, an encoded signal receiver, a reference receiver spaced apart from the encoded signal receiver and communicatively coupled to the encoded signal receiver, and a telluric voltage module coupled to one of the encoded signal receiver and the reference receiver. The telluric voltage module is communicatively coupled to the encoded signal receiver and the reference receiver to receive an encoded signal and a reference signal, respectively, which may include telluric noise. The telluric voltage module synchronizes the encoded signal and the reference signal, subtracts the reference signal from the encoded signal, and outputs a signal free from telluric noise.

Abstract: An electromagnetic (EM) telemetry system with capacitive electrodes for use with downhole equipment is described. Embodiments of the EM telemetry system with capacitive electrodes include a downhole transceiver comprising an encoded signal transmitter, a downhole sensor disposed to monitor the downhole equipment, and an encoded signal receiver comprising one or more capacitive counter electrodes. The one or more capacitive counter electrodes receives a first encoded signal from the downhole transceiver, the encoded signal corresponding to a voltage measured between the counter electrode and a wellhead. A decoder and demodulator of the encoded signal receiver recovers information in the first encoded signal. A second encoded signal, which may include instructions for the downhole equipment, may be similarly encoded, modulated, and transmitted from the encoded signal receiver to the downhole transceiver.

Abstract: In some embodiments, an apparatus and a system, as well as a method and an article, may operate to receive a derived clock signal downhole, the derived clock signal being derived from a surface clock signal (associated with a surface clock), such that the frequency of the derived clock signal is less than the frequency of the surface clock signal. Further activity may include measuring the frequency of the derived clock signal in terms of an uncorrected downhole clock frequency (associated with a downhole clock) to provide a measured frequency equivalent, and correcting time measurements made using the downhole clock, based on the measured frequency equivalent, or based on an actual frequency of the downhole clock determined according to the measured frequency equivalent. Additional apparatus, systems, and methods are described.

Abstract: A first set of radiation detectors may be disposable on the a drill string, wherein the first set of radiation detectors are capable of detecting gamma radiation and neutron radiation; and a combined chemical source spaced from the first set of radiation detectors, wherein the combined chemical source comprises a gamma radiation emitting material and a neutron radiation emitting material. The first set of radiation detectors and combined chemical source may be used in methods for logging a wellbore.

Abstract: An electromagnetic telemetry system can be used for determining a resistivity of a portion of a wellbore drilled through a subterranean formation. For example, the electromagnetic telemetry system can include a computing device and a downhole transceiver positioned on a well tool in the wellbore. The computing device can receive, from the downhole transceiver, a signal indicating a load impedance across an electrically insulating segment of the downhole transceiver. The computing device can determine a resistivity associated with a portion of the wellbore based on the load impedance. The computing device can determine a corrected resistivity by modifying the resistivity associated with the portion of the wellbore using a correction factor.

Abstract: An electromagnetic (EM) telemetry system with telluric referencing for use with downhole equipment is described. Embodiments of an EM telemetry system with telluric referencing include a downhole transceiver comprising an encoded signal transmitter, a downhole sensor disposed to monitor the downhole equipment, the downhole sensor coupled to the transceiver, an encoded signal receiver, a reference receiver spaced apart from the encoded signal receiver and communicatively coupled to the encoded signal receiver, and a telluric voltage module coupled to one of the encoded signal receiver and the reference receiver. The telluric voltage module is communicatively coupled to the encoded signal receiver and the reference receiver to receive an encoded signal and a reference signal, respectively, which may include telluric noise. The telluric voltage module synchronizes the encoded signal and the reference signal, subtracts the reference signal from the encoded signal, and outputs a signal free from telluric noise.

Abstract: An electromagnetic telemetry system can be used for determining a resistivity of a portion of a wellbore drilled through a subterranean formation. For example, the electromagnetic telemetry system can include a computing device and a downhole transceiver positioned on a well tool in the wellbore. The computing device can receive, from the downhole transceiver, a signal indicating a load impedance across an electrically insulating segment of the downhole transceiver. The computing device can determine a resistivity associated with a portion of the wellbore based on the load impedance. The computing device can determine a corrected resistivity by modifying the resistivity associated with the portion of the wellbore using a correction factor.

Abstract: A system for self-tuning sonic transmitters which transmits a plurality of frequencies into a downhole formation, then identifies which of the transmitted frequencies generates the best response from the formation. The system then uses the best frequency identified for subsequent logging of formation data until a subsequent tuning sequence is initiated.

Abstract: A first set of radiation detectors may be disposable on the a drill string, wherein the first set of radiation detectors are capable of detecting gamma radiation and neutron radiation; and a combined chemical source spaced from the first set of radiation detectors, wherein the combined chemical source comprises a gamma radiation emitting material and a neutron radiation emitting material. The first set of radiation detectors and combined chemical source may be used in methods for logging a wellbore.

Abstract: The shape and size of a borehole may be characterized downhole, using measurements of the borehole shape in conjunction with a catalog of shapes against which the measured shape is matched. A unique identifier for the measured borehole shape, and optionally a size parameter, may be transmitted to a surface facility, generally saving bandwidth compared with the transmission of the raw measured borehole-shape data. Alternatively or additionally, downhole measurements may be adjusted based on the measured shape. Additional methods, apparatus, and systems are disclosed.

Abstract: In some embodiments, an apparatus and a system, as well as a method and an article, may operate to receive a derived clock signal downhole, the derived clock signal being derived from a surface clock signal (associated with a surface clock), such that the frequency of the derived clock signal is less than the frequency of the surface clock signal. Further activity may include measuring the frequency of the derived clock signal in terms of an uncorrected downhole clock frequency (associated with a downhole clock) to provide a measured frequency equivalent, and correcting time measurements made using the downhole clock, based on the measured frequency equivalent, or based on an actual frequency of the downhole clock determined according to the measured frequency equivalent. Additional apparatus, systems, and methods are described.

Abstract: A histogram includes a plurality of channels Ch1, Ch2, . . . ChN, which have respective channel numbers C1, C2, . . . CN. ChA with channel number CA, 1<A<N, representing a first peak, is associated with a known first-peak energy (EA). ChB with channel number CB, 1<B<N, A?B, representing a second peak, is associated with a known second-peak energy (EB). A system of equations, including a first equation that is a function of EA and CA and a second equation that is a function of EB and CB, is solved for an energy scale, ?, and a zero offset, E0. A function of EM, CM, ?, and E0 is used to identify features in the histogram, wherein EM is an energy associated with the Mth channel in the histogram, and CM is the channel number of the Mth channel (ChM) in the histogram.

Abstract: A histogram includes a plurality of channels Ch1, Ch2, . . . ChN, which have respective channel numbers C1, C2, . . . CN. ChA with channel number CA, 1<A<N, representing a first peak, is associated with a known first-peak energy (EA). ChB with channel number CB, 1<B<N, A?B, representing a second peak, is associated with a known second-peak energy (EB). A system of equations, including a first equation that is a function of EA and CA and a second equation that is a function of EB and CB, is solved for an energy scale, ?, and a zero offset, E0. A function of EM, CM, ?, and E0 is used to identify features in the histogram, wherein EM is an energy associated with the Mth channel in the histogram, and CM is the channel number of the Mth channel (ChM) in the histogram.