Abstract: An assembly for drilling and logging includes a device for electro pulse drilling (EPD device), at least one device to receive acoustic signals generated by the EPD device, distinguished in that the assembly further includes at least one device to receive electromagnetic signals generated by the EPD device. A method for drilling and logging, and device for electro pulse drilling.

Abstract: Assembly for drilling and logging, comprising a device for electro pulse drilling (EPD device), at least one device to receive acoustic signals generated by the EPD device, distinguished in that the assembly further comprises at least one device to receive electromagnetic signals generated by the EPD device. Method for drilling and logging, and device for electro pulse drilling.

Abstract: A method of determining a vertical component of particle velocity from seismic data acquired using at least one receiver disposed within a water column includes determining the vertical component of particle velocity from the pressure at a first location and a second location. The first location is the location of a first receiver, and is vertically beneath the second location. The method uses an operator accurate for seismic data acquired at a vertical separation between the first and second locations of up to at least 0.4 times the minimum wavelength of seismic energy used to acquire the seismic data. The second location may be at or above the surface of the water column. Alternatively, the method may be applied to a twin streamer seismic surveying arrangement in which the second location is below the surface of the water column and is the location of a second receiver.

Abstract: A method of analyzing an electromagnetic wavefield includes the steps of measuring the electric and magnetic fields at at least one receiver, formulating a respective spatial domain filter in respect of each of mutually orthogonal components of each of the electric and magnetic fields, and applying the filters to the measured acquired data to decompose the wavefield into upgoing and downgoing components.

Abstract: A method of deriving a calibration filter for electromagnetic data is provided. The method comprises providing a source (21, 22) of electromagnetic radiation and subsequently measuring components of the source electromagnetic field (23, 24, 25) at a receiver when the source is sufficiently close to the receiver that the down-going signal dominates over the up-going signal reflected from features below the receiver. Such a measurement can be used in frequency domain analysis (26, 28, 29) to extract the down-going signal component and derive a calibration filter for the receiver. The method is repeated (27, 30) for each receiver used in an electromagnetic sounding survey.

Abstract: A method of deriving a calibration filter for electromagnetic data is provided. The method comprises providing a source (21, 22) of electromagnetic radiation and subsequently measuring components of the source electromagnetic field (23, 24, 25) at a receiver when the source is sufficiently close to the receiver that the down-going signal dominates over the up-going signal reflected from features below the receiver. Such a measurement can be used in frequency domain analysis (26, 28, 29) to extract the down-going signal component and derive a calibration filter for the receiver. The method is repeated (27, 30) for each receiver used in an electromagnetic sounding survey.

Abstract: A method of determining a vertical component of particle velocity from seismic data acquired using at least one receiver disposed within a water column comprises determining the vertical component of particle velocity from the pressure at a first location and a second location. The first location is the location of a first receiver, and is vertically beneath the second location. The method uses an operator accurate for seismic data acquired at a vertical separation between the first and second locations of up to at least 0.4 times the minimum wavelength of seismic energy used to acquire the seismic data. The second location may be at or above the surface of the water column. Alternatively, the method may be applied to a twin streamer seismic surveying arrangement in which the second location is below the surface of the water column and is the location of a second receiver.

Abstract: A method of determining a vertical component of particle velocity from seismic data acquired using at least one receiver disposed within a water column comprises determining the vertical component of particle velocity from the pressure at a first location and a second location. The first location is the location of a first receiver, and is vertically beneath the second location. The method uses an operator accurate for seismic data acquired at a vertical separation between the first and second locations of up to at least 0.4 times the minimum wavelength of seismic energy used to acquire the seismic data. The second location may be at or above the surface of the water column. Alternatively, the method be applied to a twin streamer seismic surveying arrangement in which the second location is below the surface of the water column and is the location of a second receiver.

Abstract: A method of determining the source radiation pattern of at least one source (2) of electromagnetic radiation is provided. The method comprises the steps of at at least one sensor (3), measuring the electric and magnetic fields due to the at least one source; formulating a surface integral over the measured data, the measured data weighted by a Green's function and its spatial derivatives; and evaluating the surface integral at at least one location to determine the source radiation pattern at that location due to the at least one source.

Abstract: A method of analysing an electromagnetic wavefield. The method comprises the steps of measuring the electric and magnetic fields at least one receiver; formulating a respective filter in respect of each of mutually orthogonal components of each of the electric and magnetic fields; and applying the filters to the measured data to decompose the wavefield into upgoing and downgoing components.

Abstract: A method of determining a vertical component of particle velocity from seismic data acquired using at least one receiver disposed within a water column comprises determining the vertical component of particle velocity from the pressure at a first location and a second location. The first location is the location of a first receiver, and is vertically beneath the second location. The method uses an operator accurate for seismic data acquired at a vertical separation between the first and second locations of up to at least 0.4 times the minimum wavelength of seismic energy used to acquire the seismic data. The second location may be at or above the surface of the water column. Alternatively, the method be applied to a twin streamer seismic surveying arrangement in which the second location is below the surface of the water column and is the location of a second receiver.