Abstract: A method for measuring the resistivity of geologic formations is described. An electromagnetic field may be generated using at least one stationary long-range transmitter. The frequency of the electromagnetic field may be between and/or including the ULF/ELF range. At least one component of the electromagnetic field may be measured by land, marine, submarine, and/or airborne receiver. A conductivity distribution may be determined based on the at least one measured component. The determined conductivity distribution may be correlated with geological formations and/or hydrocarbon deposits.

Abstract: A method for 3D modeling and inversion of potential field geophysical survey data measured above a geological formation having density and/or magnetization and/or susceptibility is described, using potential field data including but not limited to gravity and/or magnetic scalar and/or vector and/or tensor data. The 3D earth model is parameterized in terms of spatially variable contrast surfaces between different geological formations which are characterized by physical properties such as density and/or magnetization and/or susceptibility values and/or functions. The properties of the 3D earth model may be constrained from a priori information. The potential field responses and/or Frechet derivatives (sensitivities) of the spatially variable contrast surfaces between different geological formations and/or physical properties are analytically evaluated using Cauchy-type integral representations of the potential fields for each of the contrast surfaces.

Abstract: A method for measuring the resistivity of sea-bed formations is described. An electromagnetic field is generated using at least one stationary long-range transmitter. The frequency of the electromagnetic field is between and/or including the ULF/ELF range. At least one component of the electromagnetic field is measured. A conductivity distribution is determined based on the at least one measured component. The determined conductivity distribution is correlated with geological formations and/or hydrocarbon deposits.