Abstract: A method for obtaining a maximum horizontal stress at a depth of a geological formation, includes: setting an estimate SHmax of the maximum horizontal stress; conducting an elastoplastic modeling simulation of the geological formation around a wellbore with the estimate SHmax and obtaining a simulated value ?b,1 of a breakout angle, wherein the breakout angle is a half-width of a breakout region; and upon determining that the estimate ?b,1 is greater than or equal to a prescribed value and is different from a measured breakout angle ?b,m at the depth by more than a threshold value, repeatedly changing the estimate SHmax and conducting the elastoplastic modeling simulation.

Abstract: A method includes running a wired tubing having perforating arms, a packer, and a scanner into a casing string having an annulus. A portion of the annulus that is void of cement is determined using the scanner. The packer is activated to isolate a downhole section of the casing string from an up-hole section of the casing string. A plurality of holes are punched in the up-hole section of the casing string by ejecting the perforating arms from the wired tubing. The annulus of the casing string is cemented by pumping cement through the plurality of holes into the portion of the annulus void of cement.

Abstract: Images of subsurface formation walls adjacent well bores are obtained by the borehole imaging systems. The borehole images are processed to characterize the nature of fractures in the formation walls. The fractures are characterized as natural fractures or stress-induced tensile fractures based on the borehole image processing for geomechanical modeling in connection with reservoir characterization, fracture modeling, and stress analysis. A capability is provided to discriminate between the natural fractures and the stress induced tensile fractures and for performance of well activities.

Abstract: A method for predicting fracture treatment performance includes inducing tube waves in a well drilled through a formation to be fracture treated. A polarity of reflected tube waves in the well is determined, and using the reflected tube waves, hydraulic conductivity of at least one zone in the well hydraulically connected to the formation is estimated. The estimated hydraulic conductivity is compared to a selected threshold. The selected threshold is based on pumping parameters and pumping pressure behavior of at least one pumped hydraulic fracture treatment. A warning signal is generated when the hydraulic conductivity is below the selected threshold and/or the determined polarity indicates a closed boundary condition so that the treatment may be adjusted to avoid screenouts and other operational and treatment issues.

Abstract: There are described methods, systems, and techniques for performing automated drilling of a well bore. The well bore is drilled according to one or more drilling parameter targets associated with one or more corresponding drilling parameters. A controlling drilling parameter of the one or more drilling parameters is determined to be outside a threshold window. In response to determining that a stringer has been encountered, one or more controlled drilling parameter targets of the one or more drilling parameter targets are updated. The controlled drilling parameter targets comprise a revolutions per minute (RPM) target and weight-on-bit (WOB) target.

Abstract: A method for identifying a leak for dynamic logging may comprise estimating a Stoneley wave slowness, separating a Stoneley wave into an up-going Stoneley wave and a down-going Stoneley wave, estimating an amplitude of the up-going Stoneley wave and the down-going Stoneley wave, identifying a difference between the amplitude of the up-going Stoneley wave and the down-going Stoneley wave, forming an amplitude summation curve or an amplitude difference curve, and identifying a location of the leak.

Abstract: A system for monitoring borehole parameters and switching to millimeter wave drilling based on the borehole parameters is provided. The system can include a mechanical drilling apparatus for forming a first portion of a borehole of a well. The first portion of the borehole can be formed based on a permeability of the first portion of the borehole and a temperature within the first portion of the borehole. The system can also include a millimeter wave drilling apparatus configured to inject millimeter wave radiation energy into a second portion of the borehole of the well via a waveguide. The second portion of the borehole can be formed via the millimeter wave drilling apparatus in response to determining the permeability of the first portion of the borehole is below a permeability threshold value and the temperature within the first portion of the borehole exceeds a temperature threshold value.

Abstract: A distributed sensing apparatus based on Optical Time Domain Reflectometry, OTDR, including an optical source; an optical splitter in optical communication with the optical source, the optical splitter having first and second outputs; a sensing fibre in optical communication with the first output of the optical splitter; a combining unit arranged to combine a reference signal derived from the second output of the optical splitter with a backscattered signal derived from the sensing fibre, wherein the combining unit comprises one or more 3×3 fused fibre couplers; and a signal processing unit configured for processing information derived from the combining unit so as to provide distributed sensing data. The combining unit includes a polarization diversity arrangement including one or more polarization sensitive elements.

Abstract: A method and apparatus for determining the compressive strength of masonry units based on airborne sonic signals generated by stimulating the samples with short duration, mechanical impulses are described. The non-destructive testing apparatus consists of a specimen support unit which mechanically isolates the masonry unit from the environment and from the support, a mechanical stimulator, and an acoustic response detector. The signals recorded are analyzed to extract the pertinent features which are then used to compute the compressive strength of the sample. The pertinent signals are deduced through a calibration of the masonry type being analyzed (material and shape) based on physical analysis of the sample's normal modes of vibration, or through Finite Element Analysis of the vibrations, or through direct empirical calibration. This non-destructive testing method is low-cost, readily implemented and provides a reliable technique for compressive strength estimation.

Abstract: Anisotropic elastic properties and subsequently in situ stress properties for a rock formation surrounding a wellbore are computed from rock physics and geomechanical models. Mineralogy data measured from DRIFTS on cuttings from the wellbore and rock physics and geomechanical models that have been log-calibrated in another wellbore are used in the computation. The method includes: (1) Defining and calibrating rock physics and geomechanical models using data from the first wellbore; (2) using DRIFTS analysis to measure mineralogy data on rock cuttings obtained through drilling operation in the second wellbore; and (3) using previously calibrated models to estimate in situ stress properties, including a stress index and the minimum principal stress magnitude.

Abstract: A method of processing geological data comprising a plurality of geological surfaces within a geological volume is provided. The method includes the steps of: (i) specifying a well trajectory which extends through the geological volume; (ii) identifying the geological surfaces within the volume which are intersected by the trajectory; (iii) determining, for each intersected surface, the depth, the dip angle and the dip direction of the surface at the point of intersection with the trajectory; and (iv) predicting a well log for the trajectory, the log specifying the depths, dip angles and dip directions of the intersected geological surfaces.

Abstract: Embodiments of the present invention address aliasing problems by providing a plurality of discrete acoustic sensors along a cable whereby acoustic signals may be measured in situations where the fiber optic cable has not been secured to a structure or area by a series of clamps. Acoustic sampling points are achieved by selectively enhancing the acoustic coupling between the outer layer and the at least one optical fiber arrangement, such that acoustic energy may be transmitted selectively from the outer layer to the at least one optical fiber arrangement. The resulting regions of acoustic coupling along the cable allow the optical fiber to detect acoustic signals. Regions between the outer layer and the at least one optical fiber arrangement that contain material which is acoustically insulating further this enhancement since acoustic waves are unable to travel through such mediums, or at least travel through such mediums at a reduced rate.

Abstract: The light source unit generates probe light. The splitting unit splits Brillouin backscattered light, which arise in the optical fiber under test owing to the probe light, into two branches of a first light path and a second light path. The delay unit gives a delay between light propagating through the first light path and the second light path. The multiplexer unit multiplexes light propagating through the first light path and the second light path to generate multiplexed light. The coherent detection unit performs heterodyne detection on the multiplexed light to output a difference frequency as a first electrical signal. The frequency shift amount obtaining unit performs homodyne detection on one of the two branches split from the first electrical signal and the second electrical signal having the same frequency as the frequency of the first electrical signal to obtain a frequency shift amount.

Abstract: A passive acoustic system and a method of utilizing the passive acoustic system in a subsurface borehole are discussed. The method includes disposing the passive acoustic system in the borehole, the passive acoustic system including at least one passive acoustic resonator, and monitoring a frequency of an acoustic signal at the at least one passive acoustic resonator. The passive acoustic system includes a protective tubing, a fiber optic cable disposed within the protective tubing, a fluid layer between the fiber optic cable and the protective tubing, and at least one passive acoustic resonator, the at least one passive acoustic resonator representing an area within the protective tubing having a known geometry, wherein the fluid layer affects a frequency of an acoustic signal obtained from the at least one passive acoustic resonator.

Abstract: A method for thermoelastic logging in a borehole of a subterranean formation. The method includes generating, by a computer processor, a reference dispersion based on a borehole wave dispersion measurement of the borehole, wherein the reference dispersion represents far-field elastic properties in the subterranean formation, analyzing, by the computer processor, a difference between the reference dispersion and the borehole wave dispersion measurement based on a thermoelastic model of the subterranean formation to generate an analysis result, and determining, by the computer processor and based on the analysis result, a temperature dependent parameter of the subterranean formation.

Abstract: Disclosed is a formation testing tool for extracting formation fluid from an earth formation penetrated by a borehole having a drilling fluid. The tool includes: a sample flow element configured to extract formation fluid from the formation in a sample zone; a sample zone seal forming a perimeter defining the sample zone; a contamination removal flow element configured to extract formation fluid contaminated with the drilling fluid from a contamination removal zone in the formation; a contamination removal zone seal forming a perimeter defining the contamination removal zone, which surrounds and excludes the sample zone; and a controller configured to control a sample flow rate in the sample flow element and a contamination removal flow rate in the contamination flow removal element in order to decrease an amount of time required to acquire a sample of the formation fluid having an acceptable amount of contamination.

Abstract: A measurement system in one embodiment includes an acquisition module and a determination module. The acquisition module is configured to acquire resonant frequency information corresponding to a sensor disposed in a remote location from the acquisition module. The resonant frequency information includes first resonant frequency information for a first resonant frequency of the sensor corresponding to environmental conditions of the remote location, and also includes second resonant frequency information for a different, second resonant frequency of the sensor corresponding to the environmental conditions of the remote location. The determination module is configured to use the first resonant frequency information and the second resonant frequency information to determine the temperature and the pressure at the remote location.

Abstract: A method of verifying a substance interface location during a cementing operation can include optically measuring vibrations caused by substances flowing across structures distributed along a wellbore, the vibrations being caused at each structure, and the vibrations changing at each structure as the interface displaces across the structure. A method of determining a property of at least one substance flowed in a wellbore can include optically measuring vibrations caused by the substance flowing across structures distributed along a wellbore, the vibrations being caused at each structure, and the structures having different shapes, thereby causing the vibrations at the structures to be different from each other when the substance flows across the differently shaped structures.

Abstract: A pressure response to low frequency harmonic pressure oscillations generated in a borehole by at least one oscillation source is registered by at least one acoustic sensor. A phase shift of stationary pressure oscillations registered by the acoustic sensor relatively to the low frequency harmonic pressure oscillations of the oscillation source and a ratio between an amplitude of the stationary pressure oscillations registered by the acoustic sensor and an amplitude of the low frequency harmonic pressure oscillations of the oscillation source are determined. A thickness of a mudcake is determined and based on the results a cake piezoconductivity or a fluid mobility or both are determined.

Abstract: In some embodiments, an apparatus and a system, as well as a method an article, may operate to move a borehole seal in space with respect to the wall of a borehole while monitoring borehole seal contact quality data, which may comprise borehole seal contact pressure data and acoustic data. Operations may further include adjusting the movement of the borehole seal based on the borehole seal contact quality data. Additional apparatus, systems, and methods are disclosed.

Abstract: A method and apparatus for determining the location of a material located behind an obstruction. A plurality of acoustic resonators (6) having a known resonant frequency are dispersed in the material (3), the material to be located on a first side of the obstruction (2). An instrument (5) is provided at an opposite side of the obstruction to the material. The instrument emits an acoustic signal and measures a response. If the resonant frequency is detected, it is determined that the material is located substantially adjacent to the instrument. The apparatus may be used for determining the height of cement slurry located between a well casing wall and a borehole.

Abstract: A method for monitoring fluid flow through a downhole device, comprises a) providing an acoustic tube wave in fluid in the device; b) measuring the acoustic tube wave after it has passed through the fluid in the device; and c) assessing the permeability of the device by measuring the attenuation of the acoustic signal. Changes in velocity of the acoustic signal may also be measured. The device may be a permeable downhole device such as a sand screen the measurements in step b) are made using a plurality of sensors deployed in the hole. The method may further including the step of cross-correlating a signal received at a first receiver with signals received at additional sensors so as to obtain an effective response as if the signal had been emitted from a source at the position of said first receiver.

Abstract: A method for determining properties of a formation is described herein. The method includes disposing a well-logging tool in a borehole. The well-logging tool includes a device for varying temperature of the formation and two acoustic logging probes located symmetrically along the well-logging tool length relative to the device for varying temperature of the formation. During the logging tool movement in the borehole, continuous varying of the formation temperature, continuous acoustic logging, and continuous measurement of formation temperature are performed. Dependencies of the measured velocity and attenuation of the Stoneley waves as functions of the measured temperature of the formation are obtained. Based on the obtained dependencies, properties of the formation are determined.

Abstract: A sensor apparatus includes a first elongated housing to at least partially enclose a sensor device and a second elongated housing coupled longitudinally to the first elongated housing. The second elongated housing includes at least one radial port extending from an inner surface to an outer surface of the second elongated housing to allow a first material received through an opening of the second elongated housing to flow through the second elongated housing and out the radial port in the vicinity of the sensor apparatus.

Abstract: Acoustic waves from a controllable downhole acoustic source in a cased borehole are focused into a region of an earth formation. A hydrophone is used to monitor acoustic signals for onset of cavitation. The estimated pressure from the source in the focus region provides an estimate of formation pore pressure.

Abstract: In some embodiments, an apparatus and a system, as well as a method an article, may operate to move a borehole seal in space with respect to the wall of a borehole while monitoring borehole seal contact quality data, which may comprise borehole seal contact pressure data and acoustic data. Operations may further include adjusting the movement of the borehole seal based on the borehole seal contact quality data. Additional apparatus, systems, and methods are disclosed.

Abstract: Various embodiments include apparatus and methods of providing a sensor, in a transducer subassembly, having a backing (1) coupled to a housing (7) without bonding the sensor to the housing such that the sensor is effectively mechanically decoupled from the housing except for longitudinal waves traveling through the front face of the transducer subassembly. Additional apparatus, systems, and methods are disclosed.

Abstract: This invention describes an apparatus and a method for integrity monitoring of a borehole and the seal integrity of a caprock suitable for sequestration of greenhouse gases. The apparatus includes plural neutrally buoyant sensors for placement outside of a casing, placement including distribution within at least mud filter cake, cement, and proppant. This invention also includes a method for monitoring integrity of a borehole suitable for sequestration of greenhouse gases or other types of well using the described apparatus.

Abstract: An exemplary system for managing the deployment of a seismic data acquisition system uses a module configured to execute a plurality of task in the field by receiving one or more seismic devices. The module may include a power source that provides electrical power to the seismic devices. The module may also include a processor programmed to retrieve data stored in the seismic devices, perform diagnostics, facilitate inventory and logistics control, configure seismic devices and update data or pre-programmed instructions in the seismic device.

Abstract: Apparatus and methods for operating the apparatus provide a modular unit of hardware to make measurements in a well. The modular unit may include a housing arranged for placement in a drill-string element, where the housing includes a sensor and is structured such that the housing is transferable to another drill-string element without a calibration during or after the transfer. The drill-string elements associated with the transfer may be of different sizes.

Abstract: A resonator in the fluid for displacing the fluid has a sensing section and a non-sensing section. A compression contact member coupled to the mounting body compressively secures the resonator non-sensing section in a mounting body. The apparatus may further include a pressure feed through module received in the mounting body that is in signal communication with the resonator.

Abstract: The present disclosure relates to an apparatus and method for estimating a parameter of interest in a downhole fluid using a fluid analysis module. The fluid analysis module may include: a first transducer configured to generate a surface wave in a fluid. The first transducer may include one or more of: a piezoelectric crystal, a electromagnetic transducer, and a surface acoustic wave crystal. The apparatus may use the first transducer or a second transducer to generate a signal indicative of the dissipation of the surface wave in the fluid. The apparatus may include a compensator configured to reduce mechanical pressure on the transducer. The method may include estimating a parameter of interest of the fluid using a signal indicative of the dissipation of the surface wave.

Abstract: A method of passive surveying comprises generating one or more detected signals by passively detecting a signal generated within a subsurface earth formation due to a seismoelectric response or an electroseismic response in at least one porous subsurface earth formation containing at least one fluid, and processing the one or more detected signals to determine at least one property of the subsurface earth formation.

Abstract: Apparatus for making measurements in boreholes comprising a sonde having a radial array of arms provided thereon; wherein the sonde is connectable to a cartridge containing electronic circuitry specific to a predetermined measurement to be made in the borehole, each arm is connectable to a sensor pad specific to the predetermined measurement; and the sonde provides electrical connectivity between the sensor pads and the cartridge that is substantially independent of the predetermined measurement.

Abstract: A logging tool having a plurality of different sensor types having close spacings mounted on an articulated or extendible pad, a sleeve, a mandrel, a stabilizer, or some combination of those is provided and used to make measurements in a wellbore in a single logging run. Those measurements are used to create images of the wellbore and the images are used to deduce the local geology, optimize well placement, perform geomechanical investigation, optimize drilling operations, and perform formation evaluation. The logging tool includes a processor capable of making those measurements, creating those images, performing those operations, and making those determinations. The plurality of different sensors may be one or more resistivity sensors, dielectric sensors, acoustic sensors, ultrasonic sensors, caliper sensors, nuclear magnetic resonance sensors, natural spectral gamma ray sensors, spectroscopic sensors, cross-section capture sensors, and nuclear sensors, and they may be “plug-and-play” sensors.

Abstract: Methods and apparatus for performing Distributed Acoustic Sensing (DAS) using fiber optics with increased acoustic sensitivity are provided. Acoustic sensing of a wellbore, pipeline, or other conduit/tube based on DAS may have increased acoustic sensitivity through fiber optic cable design and/or increasing the Rayleigh backscatter property of a fiber's optical core. Some embodiments may utilize a resonant sensor mechanism with a high Q coupled to the DAS device for increased acoustic sensitivity.

Abstract: A fiber optic sensor system includes an optical source to output a first optical signal to launch into an optical fiber, and a coherent detector to mix a coherent Rayleigh backscatter signal generated by the optical fiber in response to the first optical signal with a second optical signal output by the optical source and to generate a mixed output signal. A phase detection and acquisition system determines a phase difference between first and second locations along the optical fiber based on phase information extracted from the mixed output signal and combines the phase information extracted from multiple acquisitions to detect strain on the optical fiber sensor.

Abstract: A method for obtaining seismic information about a subsurface formation using at least one fiber optic cable having its proximal end coupled to a light source and a photodetector comprises: transmitting into the cable at least one light pulse; receiving at the photodetector a first and second light signals indicative of the physical status of at least one first cable section and at least one second cable section, respectively, wherein the first and second sections are selected so as to provide first and second information items, respectively; optionally, further processing at least one of the first and second information items so as to produce derivative information; and outputting at least one of the first, second, and derivative information items to a display; wherein the second item differs from the first item in at least one aspect selected from the group consisting of: resolution, area, and location.

Abstract: Systems and methods identify and/or detect one or more features of a well casing by utilizing one or more downhole measurements obtainable by a downhole component. The one or more features of the well casing are identifiable and/or detectable from the one or more measurements associated with one or more properties of the one or more features of the well casing. The one or more measurements for indentifying and/or detecting a presence and/or a location of the one or more features of the well casing include sonic measurements, nuclear measurements, gamma ray measurements, photoelectric measurements, resistivity measurements and/or combinations thereof.

Abstract: A tool and processing system to provide an acoustic radial profile. A frequency semblance is performed on received time signals obtained from an array of acoustic receivers (FIG. 2, blocks 204, 206) so as to provide a set of frequency semblance values in frequency-slowness coordinate space. These frequency semblance values are transformed to a set of frequency semblance values in wavelength-slowness coordinate space (FIG. 2, block 208), from which a radial profile (FIG. 2, block 210) may be provided by utilizing a relationship between wavelength and radial depth.

Abstract: Embodiments of the present invention include a fiber optic seismic sensing system for permanent downhole installation. In one aspect, the present invention includes a multi-station, multi-component system for conducting seismic reservoir imaging and monitoring in a well. Permanent seismic surveys may be conducted with embodiments of the present invention, including time-lapse (4D) vertical seismic profiling (VSP) and extended micro-seismic monitoring. Embodiments of the present invention provide the ability to map fluid contacts in the reservoir using 4D VSP and to correlate micro-seismic events to gas injection and production activity.

Abstract: A method of testing the through cut of a pipeline comprising at least the steps of: (a) transmitting an electromagnetic signal through the pipeline; (b) monitoring any reflected signal(s); and (c) interpreting the or each reflected signal to test for the through cut of the pipeline. In this way, a non-invasive electromagnetic signal can be passed through, along, across or otherwise within the pipeline, and any reflected signal(s) can be interpreted and analysed based on one or more characteristics of the received signal(s) to ascertain the change in the conductivity of the pipeline due to the cutting thereof, in particular when or whether the cutting of the pipeline is complete or has been completed such that there is a through cut.

Abstract: The method for a productive formation properties determination comprises positioning a complex well-logging tool in a borehole, the well-logging tool consists of the device for the formation temperature impact and two similar logging probes located symmetrically along the well-logging tool relative to the device for the formation temperature impact. During the logging tool movement in the borehole continuous formation temperature impact and formation temperature measurement are performed. Based on the obtained dependencies of the formation parameters in question as a function of temperature the productive formation properties are determined.

Abstract: This invention relates to well logging instrumentation, specifically, to measuring devices which use an advanced slip-free borehole contact interaction mechanism. A measuring probe for an oil and gas wells and/or casings includes a main body and at least one robotic arm, fixed to the main body and provided with a polygonal rotating contact tip at the arm's free end. The measuring probe is used as a measuring device and provides a successive slip-free continuous contact between the rotating surface of the tip and the inner wall of the oil & gas wells and/or casings. The tip is furnished with at least one sensor that picks up the geological formations response to a signal emitted directly to the geological formation via the points of contact.

Abstract: Example methods and apparatus to determine the compressibility of a fluid are disclosed. A disclosed example method includes capturing a fluid in a chamber, pressurizing the captured fluid to first and second pressures, measuring first and second values representative of first and second densities of the fluid while pressurized at respective ones of the first and second pressures, and computing a third value representative of a compressibility of the fluid using the first and second values.

Abstract: An assembly for passive detection of features at known locations of a conduit. The assembly is a sensor assembly particularly well suited for detection of casing collars at known locations of cased wells, such as segmented hydrocarbon wells. Thus, the assembly is able to provide real time positioning information relative to any tool coupled thereto which is being advanced in the well pursuant to a well application. Given that the detection takes place in a passive manner via the combination of a magneto-responsive sensor and voltage responsive device, no separate dedicated power source or additional electronics are required.

Abstract: Embodiments of the present invention include a fiber optic seismic sensing system for permanent downhole installation. In one aspect, the present invention includes a multi-station, multi-component system for conducting seismic reservoir imaging and monitoring in a well. Permanent seismic surveys may be conducted with embodiments of the present invention, including time-lapse (4D) vertical seismic profiling (VSP) and extended micro-seismic monitoring. Embodiments of the present invention provide the ability to map fluid contacts in the reservoir using 4D VSP and to correlate micro-seismic events to gas injection and production activity.

Abstract: This invention relates to an apparatus and a method for a wireless sensor to monitor barrier system integrity, such as used or employed during sequestration of greenhouse gases. This invention includes an apparatus for integrity monitoring of a borehole suitable for sequestration of greenhouse gases. The apparatus includes one or more sensors for placement outside of a casing to monitor a borehole, and a tool for movement within the casing to power and interrogate the one or more sensors. This invention also includes a method for monitoring integrity of a borehole suitable for sequestration of greenhouse gases or other types of well. The method includes the step of disposing one or more sensors outside a casing and the step of powering the one or more sensors with a tool inside the casing. The method also includes the step of interrogating the one or more sensors with the tool to monitor an engineered borehole and/or a natural caprock seal.

Abstract: Methods and apparatus to measure physical parameters such as density and porosity of the rock matrix in a near wellbore area are provided. A borehole tool having a number of transducer elements in a transducer array is placed at an outermost surface of the borehole tool and is capable of emitting focused high frequency ultrasound beams into the rock matrix in the near wellbore area. The transducer array may be placed on the ribs or stabilizers of the borehole tool, and/or on a sleeve with a lower rotational speed, and may include a fronting material with similar acoustic impedance as the rock matrix. A method for measuring physical parameters of the rock matrix in a near wellbore area is also provided where a focused high frequency ultrasound beam is emitted into the rock matrix in the near wellbore area from one or more transducer arrays on a borehole tool.

Abstract: Embodiments of the present invention include a fiber optic seismic sensing system for permanent downhole installation. In one aspect, the present invention includes a multi-station, multi-component system for conducting seismic reservoir imaging and monitoring in a well. Permanent seismic surveys may be conducted with embodiments of the present invention, including time-lapse (4D) vertical seismic profiling (VSP) and extended micro-seismic monitoring. Embodiments of the present invention provide the ability to map fluid contacts in the reservoir using 4D VSP and to correlate micro-seismic events to gas injection and production activity.