摘要:
A geophysical data acquisition system includes at least one geophysical sensor. The at least one geophysical sensor has associated therewith a signal generator configured to generate a signal corresponding to a type of the at least one geophysical sensor. The system includes at least one signal acquisition unit having a plurality of input channels. The at least one geophysical sensor is in signal communication with one of the plurality of input channels. The plurality of input channels each includes a detector for receiving and identifying the signal generated by the signal generator. The at least one signal acquisition unit includes amplification, filtering and digitizing circuits automatically configurable in response to the type of sensor identified by the detected signal.
摘要:
A method for determining a component of electric field response to a time varying electromagnetic field induced in the Earth's subsurface involves measuring magnetic field gradient in at least two orthogonal directions in response to the induced electromagnetic field and determining an electric field response in a direction normal to the magnetic field gradient measurements. A method for determining a component of electric field response of the Earth's subsurface to a time varying electromagnetic field induced in the Earth's subsurface involves measuring electric field response along a substantially closed pattern on at least one of the Earth's surface and the bottom of a body of water and determining an electric field response in a direction normal to the measured electric field response using electric field response measurements made at opposed positions along the closed pattern.
摘要:
A method for determining a component of electric field response of the Earth's subsurface to a time-varying electromagnetic field induced in the Earth's subsurface is provided. The method includes measuring electric field response along a nonlinear pattern on at least one of the Earth's surface and the bottom of a body of water. The method includes measuring magnetic field response in three directions along the nonlinear pattern on at least one of the Earth's surface and the bottom of the body of water. The method further includes determining an electric field response in a direction normal to the measured electric field response using the electric field response and magnetic field response measurements.
摘要:
An instrument is disclosed for measuring resistivity of Earth formations from within a conductive pipe inside a wellbore drilled through the formations. The instrument includes a plurality of housings connected end to end and adapted to traverse the wellbore. At least one electrode is disposed on each housing. Each electrode is adapted to be placed in electrical contact with the inside of the pipe. The instrument includes a source of electrical current, a digital voltage measuring circuit and a switch. The switch is arranged to connect the source of electrical current between one of the electrodes and a current return at a selectable one of the top of the pipe and a location near the Earth's surface at a selected distance from the top of the pipe, and to connect selected pairs of the electrodes to the digital voltage measuring circuit. The pairs are selected to make voltage measurements corresponding to selected axial distances and selected lateral depths in the Earth formations.
摘要:
A method for controlled source electromagnetic Earth surveying includes deploying a plurality of electromagnetic sensors in a selected pattern at the top of an area of the Earth's subsurface to be surveyed. At least one of a transient electric field and a transient magnetic field is applied to the Earth in the vicinity of the sensors at a plurality of different positions. At least one of electric field amplitude and magnetic field amplitude at each of the sensors is recorded each time the transient electric field and/or magnetic field is applied. Each recording is adjusted for acquisition geometry. An image is generated corresponding to at least one sensor position using at least two stacked, adjusted recordings.
摘要:
A method of determining resistivity of an earth formation penetrated by a wellbore having conductive casing. The preferred embodiment includes inserting a sonde into the wellbore, the sonde having a plurality of electrodes at axially spaced apart locations adapted to electrically contact the casing, applying electrical current between a first and a second one of the electrodes and measuring the current, measuring a first voltage between a first pair of electrodes axially disposed between the first and second electrodes and measuring a second voltage between a second pair of electrodes also axially disposed between the first and second electrodes and disposed externally to the first pair to determine casing resistance in between the pairs of electrodes. A second difference between the first and second voltages is also measured. Current is applied between other electrodes axially disposed to exclude a third pair of electrodes therebetween, and a third voltage is measured between the third pair to determine characteristic impedance. Current is applied between the first electrode and a surface return electrode, a fourth voltage is measured between the first pair of electrodes, a fifth voltage is measured between the second pair of electrodes, an additional second difference of voltages between the fourth voltage and the fifth voltage is measured, and formation resistivity is determined by combining the first voltage, the second voltage, the third voltage, the fourth voltage, the fifth voltage, the current measurements, the second difference and the additional second difference of the voltages.
摘要:
A method for determining a component of electric field response to a time varying electromagnetic field induced in the Earth's subsurface involves measuring magnetic field gradient in at least two orthogonal directions in response to the induced electromagnetic field and determining an electric field response in a direction normal to the magnetic field gradient measurements. A method for determining a component of electric field response of the Earth's subsurface to a time varying electromagnetic field induced in the Earth's subsurface involves measuring electric field response along a substantially closed pattern on at least one of the Earth's surface and the bottom of a body of water and determining an electric field response in a direction normal to the measured electric field response using electric field response measurements made at opposed positions along the closed pattern.
摘要:
A method for processing marine electromagnetic signal measurements includes acquiring magnetotelluric (MT) measurements from below a bottom of a body of water at a plurality of positions along the water bottom at substantially the same times at each position. Controlled source electromagnetic (CSEM) measurements are acquired from below the water bottom at substantially the same positions at substantially the same time at each position. The MT measurements and the CSEM measurements are jointly processed to obtain a model of conductivity distribution in the formations below the water bottom.
摘要:
A method for interpreting electromagnetic survey data includes acquiring electromagnetic survey data near a top of a portion of the Earth's subsurface. An initial model of the portion of the Earth's subsurface is generated. The model includes at least spatial distribution of formation resistivity within the portion. The initial model is applied to an artificial neural network trained to generate expected electromagnetic survey instrument response to the initial model. The acquired electromagnetic survey data are compared to an output of the artificial neural network. The initial model is adjusted, and the applying the model to the artificial neural network and the comparing are repeated until differences between the output of the network and the acquired survey data fall below a selected threshold.
摘要:
A method for subsurface Earth surveying includes acquiring seismic data over a selected region of the Earth's subsurface. Seismoelectric data are acquired over a selected region of the Earth's subsurface. Electroseismic data are also acquired over a selected region of the Earth's subsurface. At least one type of electromagnetic survey data is acquired over a selected region of the Earth's subsurface. Survey volumes of the seismic data, the seismoelectric data, the electroseismic data and the electromagnetic data are matched, and a model of the Earth's subsurface is generated that accounts for all of the seismic data, the seismoelectric data, the electroseismic data and the electromagnetic data.