Abstract: NMR measurements and methods of analyzing those measurements are disclosed. A single NMR measurement is performed then that data is analyzed. Additional NMR measurements are performed and analyzed sequentially then the array of NMR analyzed data is analyzed again to get information about the system under study.

Abstract: Methods and systems are provided that enable logging while drilling NMR measurements to be made with magnets placed outside of the drill collar and magnetically permeable members to control the magnetic field gradient. A set of magnets can be disposed on and/or embedded on a drill collar, with an antenna disposed axially therebetween. Alternatively, a set of magnets and an antenna disposed therebetween can be disposed on a sleeve that is slid onto a recess in a drill collar. Additionally, a permeable member can be axially positioned between the set of magnets for affecting the depth of investigation.

Abstract: In some aspects of what is described here, a downhole nuclear magnetic resonance (NMR) logging tool can obtain NMR data from a subterranean region. The NMR logging tool includes a magnet assembly operable to produce a static magnetic field in the subterranean region. The NMR logging tool includes an antenna system having a first radio-frequency (RF) antenna, a second RF antenna, and a switching system. The switching system can switch the second antenna among operating modes while the NMR logging tool is disposed in a borehole in the subterranean region. The operating modes can include a booster mode, a spoiler mode, and an inactive mode.

Abstract: Circuits including a low noise amplifier (LNA) configured to receive a radio-frequency (RF) that include an input transistor to receive a waveform control signal at a gate terminal are provided. The circuits include a control transistor configured to receive a gate signal from a source terminal in the input transistor when the waveform control signal is high and to discharge the gate signal into a current sink coupled to ground when the waveform control signal is low at a controlled rate based on a resistor-capacitor (RC) network and a changing gain of the control transistor. The circuits include a buffer and a dump transistor to connect the critical resistor for optimal damping to the input of LNA when the dump transistor is ‘on’ and disconnect when the dump transistor if off. Systems and methods for use in an NMR sensor including a circuit as above are also provided.

Abstract: According to some aspects, a method of suppressing noise in an environment of a magnetic resonance imaging system is provided. The method comprising estimating a transfer function based on multiple calibration measurements obtained from the environment by at least one primary coil and at least one auxiliary sensor, respectively, estimating noise present in a magnetic resonance signal received by the at least one primary coil based at least in part on the transfer function, and suppressing noise in the magnetic resonance signal using the noise estimate.

Abstract: Apparatus and systems include a magnet assembly comprising a central magnet having a first axial end and a second, opposite axial end; a first end piece magnet having a proximal end and a distal end, the proximal end spaced apart from the first axial end of the central magnet; and a second end piece magnet spaced apart from the second axial end of the central magnet; at least one first shim magnet disposed adjacent to or at least partially surrounded by first magnetically permeable material, the at least one first shim magnet disposed next to an end of the first end piece magnet that is proximal to the central magnet, or next to an end of the first end piece magnet that is distal to the central magnet; and a downhole tool attached to the magnet assembly. Additional apparatus, systems, and methods are disclosed.

Abstract: In a method and a pulse sequence optimization device to determine a pulse sequence for a magnetic resonance system, a determination of a time interval in a pulse sequence that is to be optimized with regard to a gradient curve initially takes place, the pulse sequence including a number of radio-frequency pulses and a number of gradient pulses that are to be chronologically coordinated, under determination of the following boundary conditions for the gradient curve: length of the time interval, target integral of the gradient curve over the time interval, start value of the gradient curve at the beginning of the time interval, end value of the gradient curve at the end of the time interval.

Abstract: A nuclear magnetic resonance (NMR) measurement, at two or more depths of investigation, of a subsurface formation containing formation water and a mud filtrate from a water-base mud is obtained, and the mud filtrate is distinguished from the formation water. A NMR logging tool is disposed in a wellbore penetrating the formation containing the mud filtrate and the formation water and NMR measurements at different radial depths of investigation into the formation are made. The mud filtrate is distinguished from the formation water by determining the relative salinities of the mud filtrate and the formation water. The relative salinities are determined by comparing distribution relaxation times across different depths of investigation or by comparing logarithmic mean values across different depths of investigation.

Abstract: A downhole tool includes a cylindrical housing. A magnet and an antenna may be positioned within the housing. An excluder may be positioned around the housing, and a thickness of the excluder may vary around the housing.

Abstract: A conditioning system includes a sample chamber capable of receiving a specimen as well as first and second specimen-holding fixtures positioned within the sample chamber and configured to apply mechanical stimulation to a specimen held by the fixtures. The system has at least one port capable of providing a fluid to the sample chamber. The chamber is sized and shaped so that it can be inserted into an imaging device which can record images of a specimen held by the fixtures.

Abstract: Disclosed embodiments include well ranging apparatus, systems, and methods which operate to receive normal components of electromagnetic field strength azimuthal measurements within a first well at different tool azimuth angles in the first well. Further activities include determining an approximate range from the sensors to a second well that serves as a source of an electromagnetic field, via direct transmission or backscatter transmission, using the normal components of the electromagnetic field strength azimuthal measurements. In some embodiments, the approximate range can be determined without introducing sensor azimuthal separation into range calculations. Additional apparatus, systems, and methods are disclosed.

Abstract: Methods and apparatuses are provided for analyzing a composition of a hydrocarbon-containing fluid. The methods include using a nuclear magnetic resonance (NMR) tool to conduct NMR measurements on the hydrocarbon-containing fluid to obtain NMR data. A non-NMR tool, such as an optical tool, is used to conduct additional measurements and to obtain non-NMR data on the fluid. The methods further include determining an indication of the composition of the fluid by using the NMR data and normalizing the indication of the composition of the fluid using the non-NMR data.

Abstract: An apparatus and method which produce a magnetic field gradient by physically rotating one or more permanent magnets near an object in order to obtain images of the object.

Abstract: A logging tool electronics system is disclosed with noise minimization features and pulse compression signal processing techniques to improve the signal-to-noise ratio of array induction logging tools. The borehole is radiated with a magnetic field produced by a configurable multi-frequency and/or multi-amplitude sine wave signal stimulus section driving a fully differential single transmitter coil. Received signals from multiple mutually balanced fully differential receiver arrays are processed by receiver signal chains using adaptive algorithms under firmware control. The received signals are used to determine the conductivity and resistivity of the formation surrounding the borehole.

Abstract: Systems and methods that provide relaxivity-insensitive permeability logs. At least some logging system embodiments include a logging tool assembly that measures spin-spin relaxation time distributions of formation fluid nuclei at different positions along a borehole. A processor operates on the measurements to provide a permeability log that is relatively insensitive to relaxivity coefficient changes and hence insensitive to changes in formation fluids. Thus, permeability logs will be relatively unaffected by invasion of the borehole fluids into the formation, even if surfactants in the borehole fluid cause large changes in formation wettability. For each position logged within a borehole, the processor may process the measured relaxation time distribution to determine a Swanson parameter value; adjust the Swanson parameter value to reduce dependence on relaxivity; and convert the adjusted value to a permeability measurement.

Abstract: In a method and a pulse sequence optimization device to determine a pulse sequence for a magnetic resonance system, a pulse sequence is selected for optimization that includes a number of radio-frequency pulses and a number of gradient pulses chronologically coordinated therewith. An automatic analysis of the pulse sequence takes place to identify fixed point/time periods in the pulse sequence that are to be left unmodified, and modifiable time intervals in the pulse sequence that may be optimized. An automatic optimization of gradient pulses in the modifiable time intervals takes place according to a predetermined optimization criterion, while keeping the length of modifiable time intervals constant.

Abstract: A system for use in downhole detection comprises a downhole arrangement defining a throughbore and a tool deployable through the throughbore of the downhole arrangement. The system further comprises a primary electromagnetic element provided on one of the downhole arrangement and the deployable tool and a secondary electromagnetic element provided on the other of the downhole arrangement and the deployable tool, wherein the primary and secondary electromagnetic elements are configurable for electromagnetic coupling therebetween. Such a system may be used for determining a status and/or an identity of a downhole tool in an oil or gas well from a determined degree of electromagnetic coupling between the primary and secondary electromagnetic elements.

Abstract: A method for processing nuclear magnetic resonance (NMR) measurement data includes: receiving, with a processor, NMR measurement data obtained from an NMR tool, the NMR measurement data being affected by a motion artifact and having a first echo train obtained with a long polarization time TWET and a second echo train obtained with a short polarization time TWTL that is shorter than TWET; and at least one of (i) reducing, with a processor, an effect on the NMR measurement data of the motion artifact using the first echo train and the second echo train and (ii) identifying, with a processor, the motion artifact using the first echo train and the second echo train; wherein the motion artifact is related to a magnetic field magnitude that varies in a volume of interest due to a motion of the NMR tool.

Abstract: Optical spectral data associated with a formation fluid flowing through a downhole formation fluid sampling apparatus is obtained. Based on the obtained optical spectra data, a plurality of measures each relating the formation fluid to a corresponding one of a plurality of different fluid types are estimated. Blending coefficients each corresponding to a different one of the different fluid types are determined and utilized with the predetermined mapping matrices, each corresponding to a different one of the different fluid types, to obtain a blended mapping matrix. A parameter of the formation fluid is then predicted based on a projection of the obtained spectral data onto the blended mapping matrix.

Abstract: A method for estimating a property of subsurface material includes extracting a sample of the material using a downhole formation tester and performing a plurality of nuclear magnetic resonance (NMR) measurements on a sensitive volume in the sample where each measurement in the plurality is performed in a static homogeneous magnetic field with a pulsed magnetic field gradient that is different in magnitude from other NMR measurements to provide a waveform signal. The method further includes transforming each received waveform signal from a time domain into a frequency domain and comparing the frequency domain signal to a reference to provide proton chemical-shift information related to a chemical property of one or more molecules in the sample and transforming the frequency domain signals into a complex number domain that quantifies waveform signal amplitude changes to provide one or more diffusion rates with each diffusion rate being associated with a corresponding frequency.

Abstract: An equipment and method for forecasting tunnel water inrush using a magnetic resonance differential, where a computer is connected to a transmitting bridge circuit through a high voltage power supply, to a control unit, a first and second signal modulating circuits and a multi-channel collecting circuit; the control unit is connected to a transmitting driver circuit, a first and second protection switches, and the transmitting bridge circuit through the transmitting driver circuit; two ends of a transceiving multi-turn coil are connected to the multi-channel collecting circuit through the first and second protection switches; two ends of a receiving multi-turn coil are connected to the multi-channel collecting circuit through the second protection switch and the second signal modulating circuit; one end of the transceiving multi-turn coil is connected to the transmitting bridge circuit, and the other end is connected to the transmitting bridge circuit through a resonant capacitor.

Abstract: The present invention relates to a constant gradient field nuclear magnetic resonance (NMR) rock sample analysis method and instrument.

Abstract: Technologies applicable to detection and characterization of subsurface contaminants by NMR and dielectric measurements are disclosed. The disclosed technologies include methods for obtaining and combining data from NMR and dielectric measurements to detect, quantify, and characterize non-native non-aqueous phase liquid (NAPL) contaminants located in geologic materials.

Abstract: method of comparing a secondary oil recovery process with a tertiary oil recovery process, the secondary oil recovery process and the tertiary oil recovery process being applied to a substantially fluid-saturated porous medium containing an oil phase and an aqueous phase. The method comprising using relaxation time measurements in the calculation of a wettability index modification factor for the oil phase or the aqueous phase, thereby comparing the tertiary oil recovery process with the secondary oil recovery process.

Abstract: Various disclosed nuclear magnetic resonance (NMR) logging systems and methods employ a plurality of NMR sensors, including atomic magnetometers, mounted on pads. Certain method embodiments include: utilizing the Earth magnetic field to pre-polarize the protons in a formation; utilizing a plurality of atomic magnetometers to obtain NMR measurements; and determining at least one characteristic relaxation time of the formation. The NMR sensor may optionally include a permanent magnet assembly.

Abstract: Described herein is a method and system for characterizing in-ground rock types from measurement-while-drilling data in a mining environment. The method includes the steps of drilling holes at a plurality of selected locations within a region of interest; collecting measurements while drilling to obtain an array of data samples (162) indicative of rock hardness at various drilling depths in the drill hole locations; obtaining a characteristic measure (163) of the array of data samples; performing Gaussian Process regression (164) on the characteristic measure; and applying boundary detection (166) to the rock hardness output data obtained from the Gaussian process model to identify the distribution (280) of at least one cluster of rock type within the region of interest.

Abstract: The magnet and antenna assemblies of a logging tool can be arranged according to geometries optimal for concentric or eccentric well logging operations. In an example configuration, a logging tool can include a magnet, a magnetic core made of a magnetically permeable material, and an antenna. The outward path of the antenna can be positioned along a surface of the magnetically permeable magnetic core that faces away from the magnet, and the return path of the antenna can also be positioned along a surface that faces away from the magnet.

Abstract: Illustrative permanent electromagnetic (EM) monitoring systems and methods have a casing string positioned inside a borehole and equipped with one or more EM transducer modules having a layer of soft magnetic material that substantially encircles the casing string to amplify a signal response of a magnetic field transmitting and/or sensing element. The layer preferably has an axial dimension at least twice an axial dimension of the magnetic field sensing element, with a relative permeability at least twice that of the casing material. The magnetic field transmitting element can be a coil. The magnetic field sensing element can be a coil or a piezoelectric or magnetostrictive element that applies stress to an optical fiber. A well interface system communicates with the one or more EM transducer modules to transmit and/or collect EM signals over time. Additional casing strings may be provided in other nearby boreholes to enable tomographic mapping and monitoring of fluid interfaces in the reservoir.

Abstract: A driving circuit for a fluid conductivity sensor includes a pulse width modulation unit, an H-bridge, first and second differential amplifiers, and an analog-to-digital converter (ADC). The pulse width modulation unit generates two opposing driving signals. The H-bridge receives the two opposing driving signals and generates two H-bridge outputs. The first differential amplifier includes first inputs connected in parallel to a shunt resistor. One of the first inputs is coupled to the two generated H-bridge outputs. The second differential amplifier includes second inputs connected in parallel with a pair of terminals having a sensor attached thereto. One of the second inputs and the pair of terminals receive a signal from the other of the two generated H-bridge outputs. The ADC receives a first output representative of a first current from the first differential amplifier; and a second output representative of a second current from the second differential amplifier.

Abstract: NMR properties of earth formations are determined using a logging device movable in a borehole. The logging device includes a magnet assembly to generate a static magnetic field and an antenna expandable from the surface of the magnet assembly into the borehole toward the borehole wall to increase the magnetic dipole moment of the antenna. The logging device can be lowered or raised through a drill pipe with the magnet assembly being configured to generate no magnetic field while the device is conveyed within the drill pipe. The logging device may also include a side-looking sensor to acquire fast relaxation component of the NMR signals.

Abstract: A nuclear magnetic resonance (NMR) measurement system for high pressure and temperature measurements on fluids is disclosed. The system has a sensor assembly that includes a sample holder having a body formed from a non-magnetic metal and defining an interior cavity for receiving a fluid sample, a frame member disposed in the interior cavity of the sample holder, an antenna coil disposed in the interior cavity about the frame member, an inlet that allows the fluid sample to enter the interior cavity, an outlet that allows for the fluid sample to be flushed from the interior cavity, and a magnet assembly having a central bore in which the sample holder is disposed. Adjacent to the sample holder are pulsed field gradient coils for performing diffusion measurements. The system further includes pulse sequencer circuitry that supplies signals to the antenna coil.

Abstract: A nuclear magnetic resonance relaxation dispersion method to determine the wettability and other parameters of a fluid in a porous medium such as in an earth formation is provided. The method includes the steps of measuring the spin-lattice relaxation time T1 of the fluid in the porous medium at varying polarizing magnetic field strengths or nuclear Larmor frequencies; and determining whether the values of T1 at varying Larmor frequencies follow a dispersion curve that is characteristic of the parameter of the fluid in the porous medium to be determined.

Abstract: A method of determining rheological properties of a fluid. The method includes: providing an open-bore tube and defining within the bore a three dimensional grid (3DG) of voxels; defining at least an inlet cross section (ICS) and an outlet cross section (OCS); defining a volume of interest within the bore between the ICS and the OCS; obtaining rheological properties of the fluid; applying a pressure gradient to the bore between the ICS and the OCS; and nuclear magnetic resonance imaging the fluid within the volume of interest to determine various aspects of the fluid.

Abstract: Technologies applicable to surface-based NMR measurement are disclosed. A surface probe is positionable at or above a surface of the Earth and adapted to make NMR measurements of shallow or very shallow subsurface volumes. NMR spectrometer components connected to the surface probe are configured to control electromagnetic pulses produced by the surface probe and to record resulting detected NMR signals from the subsurface volume.

Abstract: Inverting nuclear log data for a geological formation surrounding a borehole involves acquiring nuclear log data for a borehole portion using a moveable nuclear logging tool and acquiring additional log data for the borehole portion using another logging device with superior resolution. Boundaries between adjacent zones are identified that exhibit an attribute of the geological formation to a detectably contrasting degree. From pre-acquired data describing one or more characteristics of the nuclear logging tool, a modeled log of the attributes is generated over the borehole portion, and a zone response is calculated from the pre-acquired data for each zone by using the boundaries to define an initial measure of the depth of each zone and ascribing a value of the attribute in dependence on the depth of each zone.

Abstract: A Nuclear Magnetic Resonance (NMR) apparatus and method for measuring the water content of samples has a device to produce a main magnetic field; a sample receiving space within a main magnetic field; a device to excite a measurable RF magnetization to a sample placed into the sample receiving space at an operating frequency defined by the main magnetic field; a device to measure the RF signal produced by the excited sample; and a device to determine the water content in the sample based on the RF signal. The sample receiving space is capable of accommodating a sample having a volume of at least 0.5 dm3, and the device to produce a main magnetic field has a resistive electromagnet which is adapted to produce a main magnetic field corresponding to an operating frequency of 400-2000 kHz.

Abstract: In some aspects, a downhole nuclear magnetic resonance (NMR) tool includes a magnet assembly and an antenna assembly. The NMR tool can operate in a wellbore in a subterranean region to obtain NMR data from the subterranean region. The magnet assembly produces a magnetic field in a volume about the wellbore. The antenna assembly produces excitation in the volume and acquires an azimuthally-selective response from the volume based on the excitation. The antenna assembly can include a transversal-dipole antenna and a monopole antenna.

Abstract: A method of hydrocarbon resource recovery from a subterranean formation may include forming a plurality of spaced apart injector/producer well pairs in the subterranean formation. Each injector/producer well pair may include a laterally extending producer well and a laterally extending injector well spaced thereabove. The method may include forming an intermediate well adjacent a given injector/producer well pair, and operating a positioning actuator to position a radio frequency (RF) sensor coupled to the positioning actuator to at least one predetermined location within the intermediate well. The method may further include operating the RF sensor at the at least one predetermined location within the intermediate well to selectively sense at least one corresponding portion of the subterranean formation adjacent the given injector/producer well pair. The method may also include recovering hydrocarbon resources from the plurality of injector/producer well pairs including the given injector/producer well pair.

Abstract: Nuclear Magnetic Resonance (NMR) measurement apparatus, NMR sensors, NMR measurement methods are disclosed to determine NMR properties of engineered flow management structures, and to estimate engineering properties using determined NMR properties. Example engineered flow management structures include engineered water storage, water management, water production, water sampling structures, and/or structures that serve as conduits or barriers to water movement. Technologies disclosed herein are also applicable to measuring properties relating to other fluid and/or gas flow in engineered flow management structures.

Abstract: In a method for frequency calibration in a magnetic resonance system in a volume section containing an unknown number of determined substances, the predetermined volume section is excited with RF pulses and subsequent echo signals are recorded at different times and spectral information is determined for each of the echo signals, from which a peak value in the spectral information and an associated relaxation time are determined. Dependent on the relaxation time, a substance is determined for each peak value. A frequency adjustment substance dependent of the magnetic resonance system is then implemented. Multiple peak values in the spectral information of the echo signals can be determined.

Abstract: An ultrasonic wave transceiving device is provided. The device includes a transmitter for transmitting at least one kind of first detection data ultrasonic signal and a plurality of kinds of second detection data ultrasonic signals, a receiver for receiving echo signals of the first and second detection data ultrasonic signals, and first and second information generators for generating first and second information based on the echo signal of the first and second detection data ultrasonic signals, respectively. The transmitter transmits the first and second detection data ultrasonic signals which transmission period of the first detection data ultrasonic signal intervenes between transmission periods of the second detection data ultrasonic signals in time axis. The second information generator generates the second information by using the echo signals of the second detection data ultrasonic signals.

Abstract: A system and method estimate a property of an earth formation comprising hydrocarbon and non-hydrocarbon components. The method includes conveying a carrier down a borehole penetrating the earth formation, and performing a nuclear magnetic resonance (NMR) measurement on fluid in the earth formation with an NMR instrument disposed at the carrier to provide total NMR measurement data. The method also includes separating the total NMR measurement data into hydrocarbon-resultant NMR measurement data and non-hydrocarbon-resultant NMR measurement data, scaling a portion of the non-hydrocarbon-resultant NMR measurement data based on a correction factor to obtain scaled non-hydrocarbon-resultant NMR measurement data, and estimating the property based on the hydrocarbon-resultant NMR measurement data and the scaled non-hydrocarbon-resultant NMR measurement data.

Abstract: A nuclear magnetic resonance relaxation time cutoff between results for a bound-water index of rock and a free-fluid index of the rock is determined. The determination is made based on measured and predicted values for permeability and/or wettability over a set of core plugs. The determination does not require a nuclear magnetic resonance operation performed on the core plugs under irreducible water saturation.

Abstract: This invention relates to a superconducting electrical machine, comprising: a superconducting winding at least partially surrounded by a magnetic flux guide, wherein the magnetic flux guide includes a binder loaded with a magnetic material.

Abstract: An apparatus and method to detect a fluid flow. The apparatus includes a nuclear magnetic resonance (NMR) tool to perform an NMR measurement on the fluid in a sensitive volume by establishing a magnetic field in the sensitive volume that exhibits a change in magnitude in a direction of the fluid flow when the fluid flow is radial with respect to the NMR tool and by transmitting refocus pulses, without any tipping pulse, to obtain the NMR measurement comprising spin echo signals. The system also includes a processor to receive the NMR measurement from the NMR tool and determine whether the fluid flow exists based on an amplitude of the NMR measurement.

Abstract: Various disclosed nuclear magnetic resonance (NMR) logging systems and methods employ an array of antennas to provide increased resolution without sacrificing signal-to-noise ratio. Certain method embodiments include: establishing a static magnetic field (B0) with a tool moving along a borehole through a formation; concurrently driving a multiple antenna cells to produce a radio frequency field (B1) in said formation; measuring an individual response from each antenna cell as nuclear spins undergo precession in the formation; and determining at least one characteristic relaxation time of the formation based at least in part on the individual response. The individual responses can be associated with positions where the individual responses were measured, and the relaxation time can be determined from a combination of those responses associated with a given position. Certain responses may be excluded due to tool motion that degrades the measured response.

Abstract: Estimating and displaying information about the size of molecules within a substance from nuclear magnetic resonance (NMR) maps and/or logs. Methods include utilizing a relationship between the molecular size (e.g., mean chain length), and either a moment of diffusion or a relaxation distribution, to create a scale on a two-dimensional map. In one case, applying the relationship between the molecular size, and either a moment of diffusion or a relaxation distribution, to one-dimensional diffusion or relaxation distributions for the purpose of estimating the mean chain length of molecules within the substance. In another case, a method includes determining mean chain lengths of molecules within a substance and providing a one-dimensional NMR log showing the mean chain lengths at a plurality of depths. In some cases, the NMR log includes actuatable regions for examining two-dimensional NMR maps or chain length distributions of the substance corresponding with distinct depths of the substance.

Abstract: The present invention provides a method of determining a physiochemical property of a drilling fluid at a drilling site during a drilling phase, said method comprising detecting a nuclear magnetic resonance signal from out-of-hole drilling fluid at said site and calculating therefrom a value indicative of said property.

Abstract: An apparatus for performing nuclear magnetic resonance (NMR) measurements of a material of interest includes an NMR tool and a processor. The NMR tool includes a transmitter antenna; a transmitter coupled to the transmitter antenna; and a receiver antenna configured to receive NMR signals in response to transmitted pulses of electromagnetic energy transmitted by the transmitter antenna. The NMR signals include at least a first signal and a second signal of a phase-alternated group of signals. The processor is configured to receive the NMR signals; receive a first system gain related to the first signal and a second system gain related to the second signal, each system gain being related to a system comprising the NMR tool and the material of interest; and calibrate the NMR signals using the first system gain and the second system gain.

Abstract: Source-receiver compression is used to help design surveys and mitigate the computational costs of data set inversion. The source-receiver compression is based on data redundancy and sensitivity. More particularly, a compressed source array is produced for minimum redundancy and maximum sensitivity to reservoir model parameters. The synthesized transmitter array has a reduced number of sources, thereby reducing the number of forward model simulations needed to carry out the inversion. Furthermore, the data collected at the receivers employed in the survey can be compressed. This has the implication of reducing the computational cost of constructing the Jacobian matrix and inverting the corresponding Hessian matrix.