Abstract: A method and system for estimation of electromagnetic earth responses in a marine electromagnetic survey. A method may comprise estimating initial values of the electromagnetic earth responses and ambient noise applicable to the marine electromagnetic survey; and processing electromagnetic data based on the initial values of the electromagnetic earth responses and the ambient noise to obtain a joint estimation of updated values of the electromagnetic earth responses and the ambient noise, wherein the electromagnetic data was acquired with one or more electromagnetic sensors, wherein the electromagnetic data contains measurements of an electromagnetic field.

Abstract: A method and system for estimation of electromagnetic earth responses in a marine electromagnetic survey. A method may comprise estimating initial values of the electromagnetic earth responses and ambient noise applicable to the marine electromagnetic survey; and processing electromagnetic data based on the initial values of the electromagnetic earth responses and the ambient noise to obtain a joint estimation of updated values of the electromagnetic earth responses and the ambient noise, wherein the electromagnetic data was acquired with one or more electromagnetic sensors, wherein the electromagnetic data contains measurements of an electromagnetic field.

Abstract: Disclosed are methods and apparatus using frequency-selected electromagnetic inversion to obtain sub-surface geophysical characteristics. One embodiment relates to a computer-implemented method for inverting an electromagnetic geophysical data signal to obtain an earth response. The method involves computing uncertainties associated with an electromagnetic geophysical data signal and selecting subset of frequencies based on the uncertainties. The electromagnetic geophysical data signal may then be inverted for the subset of the frequencies to determine the earth response. Other embodiments, aspects, and features are also disclosed.

Abstract: The current application is directed to methods and systems for processing EM-survey data in order to extract accurate earth-response curves from the raw EM-survey data. The more accurate earth-response curves are obtained as a result of a generally non-linear decimation, or parameterization, of the earth-response curves, the non-linear parameterization generally applied to extraction of earth responses from raw EM-survey data collected by multiple EM sensors. Parameterization of the earth-response curves and data allows for greater accuracy in estimating the earth-response curves from raw EM-survey data due to use of estimation methods based on processing over-determined raw EM-survey data. In addition, parameterization of earth-response curves may lead to a decrease in computational complexity and an increase in computational efficiency in subsequent intermediate-stage and final-stage processing operations.

Abstract: Systems and methods for measuring water properties during a marine survey are disclosed. While electromagnetic-field (“EM-field”) receivers located along streamers towed by a survey vessel measure surrounding EM fields, horizontal conductivity profiles of a body of water located above a subterranean formation are also measured. By inputting a substantially continuous, conductivity profile of the body of water along with EM-field data into an EM inversion process, estimates of the subterranean formation properties, such as resistivities, can be generated with a higher degree of confidence than estimates of properties based on a speculated or sparse conductivities of the body of water.

Abstract: The current application is directed to methods and systems for processing EM-survey data in order to extract accurate earth-response curves from the raw EM-survey data. The more accurate earth-response curves are obtained as a result of a generally non-linear decimation, or parameterization, of the earth-response curves, the non-linear parameterization generally applied to extraction of earth responses from raw EM-survey data collected by multiple EM sensors. Parameterization of the earth-response curves and data allows for greater accuracy in estimating the earth-response curves from raw EM-survey data due to use of estimation methods based on processing over-determined raw EM-survey data. In addition, parameterization of earth-response curves may lead to a decrease in computational complexity and an increase in computational efficiency in subsequent intermediate-stage and final-stage processing operations.