Abstract: Disclosed are methods and systems for producing bipole source modeling with reduced computational loads. A method may comprise receiving first electromagnetic data and second electromagnetic data from a first shotpoint and a second of a marine electromagnetic survey, modelling a first electromagnetic field and second electromagnetic field for one or more dipole sources of a bipole source and combining a plurality of data points to provide an approximation of an electromagnetic field for the bipole source. A system may comprise electromagnetic sensors, a bipole source, wherein the bipole source comprise a pair of electrodes that are separated by a distance, wherein the bipole source is configured to generate an electromagnetic field, and a data processing system configured to receive electromagnetic data from a plurality of shotpoints of the bipole source and model electromagnetic fields for one or more dipole sources of the bipole source from the electromagnetic data.

Abstract: Electromagnetic (EM) inversion includes determining an electric field associated with EM data within a predetermined sensitivity area around each of a plurality of source positions, iteratively inverting the electric field for a subsurface resistivity EM model indicative of a subterranean formation for each of a plurality of EM electrical resistivity data cells within each of the predetermined sensitivity areas, and storing results of the iterative inversion. A linear system of equations comprising a Jacobian matrix is generated based on the iterative inversion, the linear system of equations is stored, and the linear system of equations is solved at each iteration of the iterative inversion to update the subsurface resistivity EM model until a convergence criterion is met. A resistivity map based on the updated subsurface resistivity EM model can be produced.

Abstract: Methods of geophysical modeling and inversion are disclosed. A sparse domain is defined for a geophysical model, over which a sparse model result is computed. A full model result is then resolved by interpolation over the sparse domain. The full model result may be used as the forward modeling result in a geophysical inversion process. Reconstruction error, or model error, or both may be used to adjust the sparse domain, the model, or the geophysical basis of the model.

Abstract: Methods of geophysical prospecting and surveying are disclosed herein. The methods include obtaining a raw data set representing energy signatures recorded over an area of the earth and using a computer to form a final data set representing the physical properties of the area of the earth, the process including combining physical property data subsets into a final data set using a quality statistic for each physical property data subset or each datum of each physical property data subset as a weighting factor to compute a weighted average.

Abstract: A method for jointly inverting subsurface resistivities and noise parameters that may comprise the steps of identifying electromagnetic data acquired from one or more electromagnetic sensors, wherein the electromagnetic data includes a source-generated signal and noise, and jointly inverting at least subsurface resistivities and noise parameters based on the electromagnetic data. A marine electromagnetic survey system, that may comprise a data processing system configured to identify electromagnetic data acquired from one or more electromagnetic sensors, wherein the electromagnetic data includes a source-generated signal and noise and jointly invert subsurface resistivities and noise based on the electromagnetic data.

Abstract: Electromagnetic (EM) inversion includes determining an electric field associated with EM data within a predetermined sensitivity area around each of a plurality of source positions, iteratively inverting the electric field for a subsurface resistivity EM model indicative of a subterranean formation for each of a plurality of EM electrical resistivity data cells within each of the predetermined sensitivity areas, and storing results of the iterative inversion. A linear system of equations comprising a Jacobian matrix is generated based on the iterative inversion, the linear system of equations is stored, and the linear system of equations is solved at each iteration of the iterative inversion to update the subsurface resistivity EM model until a convergence criterion is met. A resistivity map based on the updated subsurface resistivity EM model can be produced.

Abstract: Disclosed are methods and systems for producing bipole source modeling with reduced computational loads. A method may comprise receiving first electromagnetic data and second electromagnetic data from a first shotpoint and a second of a marine electromagnetic survey, modelling a first electromagnetic field and second electromagnetic field for one or more dipole sources of a bipole source and combining a plurality of data points to provide an approximation of an electromagnetic field for the bipole source. A system may comprise electromagnetic sensors, a bipole source, wherein the bipole source comprise a pair of electrodes that are separated by a distance, wherein the bipole source is configured to generate an electromagnetic field, and a data processing system configured to receive electromagnetic data from a plurality of shotpoints of the bipole source and model electromagnetic fields for one or more dipole sources of the bipole source from the electromagnetic data.

Abstract: Methods of geophysical modeling and inversion are disclosed. A sparse domain is defined for a geophysical model, over which a sparse model result is computed. A full model result is then resolved by interpolation over the sparse domain. The full model result may be used as the forward modeling result in a geophysical inversion process. Reconstruction error, or model error, or both may be used to adjust the sparse domain, the model, or the geophysical basis of the model.

Abstract: Methods of geophysical modeling and inversion are disclosed. A sparse domain is defined for a geophysical model, over which a sparse model result is computed. A full model result is then resolved by interpolation over the sparse domain. The full model result may be used as the forward modeling result in a geophysical inversion process. Reconstruction error, or model error, or both may be used to adjust the sparse domain, the model, or the geophysical basis of the model.

Abstract: Methods of geophysical prospecting and surveying are disclosed herein. The methods include obtaining a raw data set representing energy signatures recorded over an area of the earth and using a computer to form a final data set representing the physical properties of the area of the earth, the process including combining physical property data subsets into a final data set using a quality statistic for each physical property data subset or each datum of each physical property data subset as a weighting factor to compute a weighted average.

Abstract: A method for jointly inverting subsurface resistivities and noise parameters that may comprise the steps of identifying electromagnetic data acquired from one or more electromagnetic sensors, wherein the electromagnetic data includes a source-generated signal and noise, and jointly inverting at least subsurface resistivities and noise parameters based on the electromagnetic data. A marine electromagnetic survey system, that may comprise a data processing system configured to identify electromagnetic data acquired from one or more electromagnetic sensors, wherein the electromagnetic data includes a source-generated signal and noise and jointly invert subsurface resistivities and noise based on the electromagnetic data.

Abstract: Disclosed are methods and systems for using electromagnetic sources that are substantially stationary in a body of water while electromagnetic field signals are detected with electromagnetic sensors towed through the body of water. An embodiment discloses an apparatus comprising: a vessel; a first electromagnetic source coupled to the vessel and configured to have a dipole moment oriented in a first direction; and a second electromagnetic source coupled to the vessel and configured to have a dipole moment oriented in a second direction, wherein the second direction is generally orthogonal to the first direction. Another embodiment discloses a system comprising: a sensor streamer configured for towing in a body of water, wherein the sensor streamer comprises a plurality of electromagnetic sensors disposed at spaced apart positions; and an electromagnetic source assembly configured for deployment at a substantially stationary position in the body of water.

Abstract: Disclosed is an electromagnetic receiver assembly for marine electromagnetic surveying, the electromagnetic receiver assembly comprising an elongated housing and receiver electrodes mounted at separate points along the elongated housing. An embodiment may include an electromagnetic receive assembly that includes an elongated housing, wherein the elongated housing defines an interior chamber. The electromagnetic receiver assembly may further include receiver electrodes configured to be in contact with water when in operation, wherein the receiver electrodes are mounted at separate points along the elongated housing. The electromagnetic receiver assembly may further include sensor electronics disposed in the interior chamber and electrically coupled to the receiver electrodes. The electromagnetic receiver assembly may be configured for deployment on or near a bottom of a body of water.

Abstract: A disclosed electromagnetic survey system includes one or more streamer(s) having multiple electromagnetic sensors and motion sensing units. Each motion sensing unit has one or more accelerometer(s) to measure motion perpendicular to an axis of the streamer, and a rotation sensor to measure rotation about the axis. The measurements of the accelerometer are adjusted based on measurements from the rotation sensor. The survey system also includes one or more processor(s) that determine, for each electromagnetic sensor, a motion signal based on the adjusted measurements. A described electromagnetic survey method includes processing acceleration and rotational motion measurements to obtain an orientation of motion sensing units as a function of time. The measured acceleration is manipulated based on the orientation to obtain one or more velocity signal(s) for each motion sensing unit. Interpolation is performed on the velocity signals to determine at least one velocity signal for each electromagnetic sensor.

Abstract: Disclosed is an electromagnetic receiver assembly for marine electromagnetic surveying, the electromagnetic receiver assembly comprising an elongated housing and receiver electrodes mounted at separate points along the elongated housing. An embodiment may include an electromagnetic receive assembly that includes an elongated housing, wherein the elongated housing defines an interior chamber. The electromagnetic receiver assembly may further include receiver electrodes configured to be in contact with water when in operation, wherein the receiver electrodes are mounted at separate points along the elongated housing. The electromagnetic receiver assembly may further include sensor electronics disposed in the interior chamber and electrically coupled to the receiver electrodes. The electromagnetic receiver assembly may be configured for deployment on or near a bottom of a body of water.

Abstract: Disclosed are methods and systems for using electromagnetic sources that are substantially stationary in a body of water while electromagnetic field signals are detected with electromagnetic sensors towed through the body of water. An embodiment discloses an apparatus comprising: a vessel; a first electromagnetic source coupled to the vessel and configured to have a dipole moment oriented in a first direction; and a second electromagnetic source coupled to the vessel and configured to have a dipole moment oriented in a second direction, wherein the second direction is generally orthogonal to the first direction. Another embodiment discloses a system comprising: a sensor streamer configured for towing in a body of water, wherein the sensor streamer comprises a plurality of electromagnetic sensors disposed at spaced apart positions; and an electromagnetic source assembly configured for deployment at a substantially stationary position in the body of water.

Abstract: A method for electromagnetic surveying below the bottom of a body of water includes deploying a plurality of nodal recording devices in a selected pattern on the water bottom. An electromagnetic transmitter is towed in the water. At least one electromagnetic sensor streamer is concurrently towed in the water. The electromagnetic transmitter is actuated at selected times and signals detected by sensors in the nodal recording devices and in the at least one streamer are recorded.

Abstract: A disclosed electromagnetic survey system includes one or more streamer(s) having multiple electromagnetic sensors and motion sensing units. Each motion sensing unit has one or more accelerometer(s) to measure motion perpendicular to an axis of the streamer, and a rotation sensor to measure rotation about the axis. The measurements of the accelerometer are adjusted based on measurements from the rotation sensor. The survey system also includes one or more processor(s) that determine, for each electromagnetic sensor, a motion signal based on the adjusted measurements. A described electromagnetic survey method includes processing acceleration and rotational motion measurements to obtain an orientation of motion sensing units as a function of time. The measured acceleration is manipulated based on the orientation to obtain one or more velocity signal(s) for each motion sensing unit. Interpolation is performed on the velocity signals to determine at least one velocity signal for each electromagnetic sensor.