Patent application number | Description | Published |
20090309599 | Method for subsurface electromagnetic surveying using two or more simultaneously actuated electromagnetic sources - A method for electromagnetic exploration includes imparting a first electromagnetic signal into subsurface formations from a first location and imparting a second electromagnetic signal into the formations from a second location substantially contemporaneously with imparting the first electromagnetic signal. The first and second electromagnetic signals are substantially uncorrelated with each other. A combined electromagnetic response of the formations to the first and second imparted electromagnetic signals is detected at a third location. A response of the formations to each of the first and the second imparted signals is determined from the detected response. | 12-17-2009 |
20100013486 | Method for attenuating air wave response in marine electromagnetic surveying - A method for measuring the electromagnetic response of formations below the bottom of a body of water includes positioning at least one electromagnetic transmitter and at least one electromagnetic receiver in the body of water each at a selected depth below the water surface. A transient electric current is passed through the at least one transmitter. An electromagnetic signal is detected at the at least one electromagnetic receiver. The depths are selected so that substantially all electromagnetic response to the current passed through the transmitter from the air above the body of water in the detected electromagnetic signal occurs before the beginning of a response originating in the formations below the water bottom. | 01-21-2010 |
20100017133 | Method for reducing induction noise in towed marine electromagnetic survey signals - A method for reducing effect of motion on electromagnetic signals detected while moving an electromagnetic receiver through a body of water includes measuring a parameter related to an amount of current passed through an electromagnetic transmitter to induce an electromagnetic field in subsurface formations. A magnetic field proximate the electromagnetic receiver is measured. A transmitter portion of the measured magnetic field is estimated from the measured parameter. A motion portion of the measured magnetic field is estimated from the measured magnetic field and the estimated transmitter portion. A voltage induced in the receiver is estimated from the estimated motion portion. Signals detected by the receiver are corrected using the estimated voltage. | 01-21-2010 |
20100057366 | Method for attenuating correlated noise in controlled source electromagnetic survey data - A method for attenuating correlated noise in transient electromagnetic survey signals includes producing, from a transient electromagnetic signal measured by a first receiver, an estimate of the Earth response and an estimate of the correlated noise from a portion of the signal occurring before onset of an Earth response, and/or after the Earth response has substantially decayed. An estimate of the correlated noise is determined over the entire measured signal from the first receiver using the estimate of the Earth response. The noise estimate from the entire signal and the portion estimate are used to estimate correlated noise in transient signals from at least a second receiver. | 03-04-2010 |
20100188090 | Method for subsurface electromagnetic surveying using two or more simultaneously actuated electromagnetic sources - A method for electromagnetic exploration includes imparting a first electromagnetic signal into subsurface formations and imparting a second electromagnetic signal into the formations substantially contemporaneously with imparting the first electromagnetic signal. The first and second electromagnetic signals are substantially uncorrelated with each other. A combined electromagnetic response of the formations to the first and second imparted electromagnetic signals is detected. A response of the formations to each of the first and the second imparted signals is determined from the detected response. | 07-29-2010 |
20100201367 | Short-offset transient electromagnetic geophysical surveying - A method for electromagnetic surveying subsurface formations includes inducing an electromagnetic field in the subsurface formations by passing electric current through a transmitter. Response of the subsurface formations to the induced electromagnetic field is detected at a first plurality of spaced apart positions disposed longitudinally within a bipole length of the transmitter. A direct induction response is removed from the detected response. | 08-12-2010 |
20100315088 | Multi-Transient DC Resistivity Measurements - A method for measuring resistivity variations in the earth comprising passing a transient current between two source electrodes; measuring the transient current at the source electrodes; measuring the resultant transient voltage between at least one pair of receiver electrodes; estimating one or more processing functions for applying to the measured input current to provide a step current profile, and applying the same one or more processing functions to the measured voltage to provide an estimate of the step response voltage between the receivers, using both the step current and the estimated step response voltage between voltage to determine the resulting apparent earth resistance, and using the apparent earth resistance to determine the resistivity of the earth. | 12-16-2010 |
20100327885 | Method for estimating and removing air wave response in marine electromagnetic surveying - A method for determining resistivity distribution of formations below a bottom of a body of water from transient electromagnetic signals acquired by imparting a transient electromagnetic field into the water and detecting an electromagnetic response thereto at a plurality of spaced apart positions from a place of the imparting includes simulating an air wave response at each of the plurality of spaced apart positions. The simulated air wave response is subtracted from the detected response to produce a subsurface impulse response at each of the plurality of positions. The subsurface impulse responses are used to determine the resistivity distribution. | 12-30-2010 |
20110149683 | Combined impulsive and non-impulsive seismic sources - A method for seismic exploration of subsurface rock formations includes actuating an impulsive seismic energy source proximate the rock formations. A non-impulsive seismic energy source is actuated. A near field waveform of each of the impulsive and non-impulsive seismic energy sources is detected. A far field waveform of the combined output of the impulsive and non-impulsive seismic energy sources is determined from the near field waveforms. An impulse response of the subsurface rock formations is determined by deconvolving the far field waveform with detected seismic signals. | 06-23-2011 |