Abstract: A method of determining a shear-wave attenuated vertical component vertical seismic profile (VSP) dataset is disclosed. The method includes, obtaining a multi-component VSP dataset, including a vertical and a horizontal component, transforming the vertical component into a vertical spectrum and the horizontal component into a horizontal spectrum, and designing a band-pass filter based, at least in part, on an energetic signal of the horizontal spectrum. The method further includes determining a muted vertical amplitude spectrum by applying the pass-band filter to an amplitude spectrum of the vertical spectrum, determining an estimated noise model based on the muted vertical amplitude spectrum and the vertical spectrum; and determining the shear-wave attenuated vertical component VSP dataset by adaptively subtracting the estimated noise model from the vertical component of the multi-component VSP dataset.

Abstract: An intelligent completion module comprises a flowmeter that uses one or more electromagnetic acoustic transducer (EMAT) sensors and a flow control valve. The flow rate and the speed of sound in the production fluid from a production zone is measured and used to make reservoir management decisions. The flowmeter comprises at least two EMAT rings, comprising one or more EMAT sensors in a circular distribution which can be used in propagation or pulse-echo modes. In a segregated flow regime, a single EMAT sensor in pulse-echo mode is used to measure holdups of fluid components.

Abstract: A method and apparatus to measure the fluid depth in a well or borehole is described. The approach reduces the effects of acoustic noise occurring near the top of the well or borehole that can interfere with the fluid depth measurement. A resonant acoustic structure between an acoustic transducer and the well or borehole provides efficient coupling of spectrally narrow acoustic signals into the well or borehole, as well as providing a bandpass acoustic filter on the returning signal, to improve the signal to noise ratio of the desired acoustic reflection.

Abstract: Concrete which is used in structural support of freeways, bridges, and large buildings, must be tested for anomalies. The testing equipment consists of probes which are inserted into testing tubes. The tubes are placed within rebar cages before concrete is poured. The prior art involved ad hoc methods of tying the tubes to the rebar. The improvement is pre-fabricated, mass produced cylindrical devices which can be axially snapped onto the testing tube. A first cylindrical device also has a perpendicular receptacle which facilitates connection to a second cylindrical device, where the second device can be axially snapped onto a piece of longitudinal rebar on the edge of the rebar cage. The combined first and second devices safely, accurately, and quickly affix the testing tubes to the rebar.

Abstract: Values for porosity and permeability of core samples in a borehole are estimated by generating radial waves with an acoustic source in fluid around the core sample, and measuring pressure in the fluid. Moreover, the acoustic source operates at frequency close to a resonant frequency of the core sample. After the acoustic source no longer operates at the resonant frequency, pressure in the fluid attenuates over time. The pressure attenuation is recorded by the pressure measurements, along with the pressure in the fluid at the first harmonic (spectral component). The pressure attenuation and spectral component each are dependent on porosity and permeability of the core sample. Thus values for the porosity and permeability are determined based on the arithmetic relationships between pressure attenuation and the spectral component and porosity and permeability.

Abstract: An apparatus for transmitting electromagnetic (EM) telemetry data from a downhole location to surface comprising: an EM signal transmitter configured to generate positive and negative polarity EM pulses corresponding to a telemetry signal; and an electronics subassembly communicative with the EM signal transmitter and comprising a processor and a memory having encoded thereon program code executable by the processor to perform a method comprising encoding measurement data into an EM telemetry signal using a modulation scheme comprising mapping a symbol set to at least one positive polarity EM pulse and one negative polarity EM pulse; and sending a control signal to the EM signal transmitter to generate EM pulses corresponding to the EM telemetry signal.

Abstract: In some embodiments, an apparatus and a system, as well as a method and an article, may operate to obtain a plurality of measurements of a formation parameter, each measurement obtained in response to energy propagated into the formation at a plurality of frequencies of propagated energy; to process the measurements over each of the plurality of frequencies to obtain estimated values of the formation parameter; to select an estimated value from the obtained estimated values for each logging depth as a true measurement value for the logging depth based on one or more of the plurality of frequencies and a resistivity range; to generate a combination log that combines a plurality of the true measurement values for each logging depth; and to control a drilling operation based on the combination log. Additional apparatus, systems, and methods are disclosed.

Abstract: An example method includes determining a frequency response of a tuned pulse to be transmitted from a transmission element. A matching frequency envelope corresponding to a frequency envelope of the frequency response may be determined. A time domain signal corresponding to the matching frequency envelope may be determined. A series of digital pulses corresponding to the time domain signal may be determined. An analog output at a switching amplifier corresponding to the series of digital pulses may be generated. A transmission element may be excited with the analog output.

Abstract: A method of performing acoustic imaging includes: selecting a target location, and selecting a group of transducers from a plurality of transducers to transmit an acoustic beam to be electronically directed to the target location; selecting a transmitter having an orientation toward a location proximate to the target location, and transmitting an acoustic signal only by the transmitter; detecting an acoustic return signal by the transmitter and by a plurality of other transducers in the group; estimating a travel time for each of the group of transducers, the estimating including measuring a travel time for each of the other transducers, and estimating a travel time for the transmitter based on the travel time for each of the other transducers; and calculating beamforming delays based on the travel time, the beamforming delay configured to cause the group of transducers to direct an acoustic beam to the target location.

Abstract: The present disclosure relates generally to well logging and measurement in subterranean formations and more particularly, the present disclosure relates to a system and method for identifying anisotropic formations, such as fractures and fracture patterns, in subterranean formations. The method uses waveforms transmitted from a monopole source. After finding the Root Mean Square energy from at least four quadrants, the energy data is normalized. At least one minimum RMS energy point is identified and the azimuth of that minimum is also identified. The azimuth and the minimum are instructive in defining fracture patterns and characteristics.

Abstract: A method for managing a fracturing operation. In one implementation, the method may include positioning a seismic source and at least one seismic receiver near a hydrocarbon reservoir; pumping a fracturing fluid into a well bore of the hydrocarbon reservoir such that the fracturing fluid may include an additive that enhances acoustic impedance between the fracturing fluid and subsurface formations in which the hydrocarbon reservoir is located and that produces a foam; performing a seismic survey with the seismic source and the at least one seismic receiver during the fracturing operation; and identifying locations of the fracturing fluid within subsurface formations in which the hydrocarbon reservoir is located.

Abstract: Hollow rebar may be used for structural reinforcement in a drilled shaft and to provide access tubes for a sonic integrity testing probe. Rebar (short for reinforcing bar) is steel bar used as a tensioning device in reinforced concrete that holds the concrete in compression. According to the system described herein, hollow rebar may provide high strength reinforcement in the drilled shaft while at the same time providing an access tube for a sonic integrity testing process, such as crosshole sonic logging (CSL). The high strength hollow rebar, having ridges, threads and/or other appropriate surface deformations, provides improved adhesion to concrete, thus eliminating the problem of debonding associated with non-structural access tubes made of smooth PVC or steel pipe.

Abstract: The invention provides a system and method for facilitating oilfield operations utilizing auditory data. In one embodiment, the present invention generates one or more auditory mapping structures whereby oilfield data may be mapped to sounds. The present invention provides at least one computer generated selection tool through which the user may select one or more portions of displayed oilfield data for auditory enhancement. Once the user has indicated an area of interest using the selection tool, the present invention may identify the oilfield data displayed within the outlined area of interest, identify auditory data associated with the displayed oilfield data utilizing one or more auditory mapping structures, and emit at least a portion of the identified auditory data to enhance the user's understanding of the displayed oilfield data.

Abstract: A device for acoustic measuring in a medium in a borehole such as velocity of sound in the medium or velocity of the medium, includes at least a first acoustic array situated in a first, slanted sidewall of a measuring area and operating to emit a series of acoustic waveforms across a measuring area. In one form, the device includes a second acoustic array situated in a second, slanted sidewall of the measuring area and operating to receive an acoustic signal resulting from the emitted series of acoustic waveforms or to receive said acoustic signal and emit a second series of acoustic waveforms.

Abstract: Systems and methods for cement evaluation by determining a shear velocity of a shear wave (26) propagating within a medium (20) located between a formation (12) and a casing (13) in a borehole (11) are presented. The method can include positioning an ultrasonic transducer array (21) in the borehole inside the casing. The method can also include in a pushing mode, generating a shear wave in the medium with the ultrasonic transducer array inside the casing. The method can also include in an interrogation mode, measuring a shear velocity of the shear wave in the medium with the ultrasonic transducer array. The shear velocity may be used to determine whether the medium is solid or liquid.

Abstract: Disclosed herein are various embodiments of a technique to monitor hydro-fracturing in oil and gas wells by use of active seismic sources and arrays of monitoring sensors. The invention utilizes combinations of seismic sources such as vertical vibrators in anti-phase pairs. The invention utilizes combinations of multi-component rotational seismic sensors, and/or multi-component linear sensors, and/or pressure sensors. Sensors are jointly deployed in arrays on the surface and/or in shallow monitoring wells to avoid the complicating effects of the free surface of the earth. The emplacement of sensors on the surface or in the shallow monitoring wells may be permanent. Fractures are monitored by combinations of physical effects such as propagation time delays, shear reflections, birefringent shear wave splitting, and amplitude variations. The method has a wide range of application in oil and gas exploration and production.

Abstract: Methods and apparatus for performing sonic well logging within a wellbore based on optical Distributed Acoustic Sensing (DAS) are provided. A sonic well logging system based on DAS may be capable of producing the functional equivalent of tens, hundreds, or even thousands of acoustic sensors. In this manner, the emplacement of the sonic well logging system based on DAS may not be nearly as complex or expensive as emplacing a sonic well logging system based on traditional methods. Furthermore, multiplexing may be simpler, downhole electronics need not be used, and the sonic well logging system may be used in extreme, high temperature environments.

Abstract: A system, apparatus and method for determining an acoustic property of a fluid in a wellbore is disclosed. A faceplate is placed in the wellbore with a stepped surface of the faceplate in contact with the fluid. The stepped surface includes a non-stepped face and a stepped face. A first portion of an acoustic pulse passes from the faceplate into the fluid via the non-stepped face and a second portion of the acoustic pulse passes from the faceplate into the fluid via the stepped face. A first reflected acoustic pulse related to the first portion of the acoustic pulse is received. A second reflected acoustic pulse related to the second portion of the acoustic pulse is received. A measurement of the first reflected acoustic pulse and a measurement of the second reflected pulse are used to determine the acoustic property of the fluid in the wellbore.

Abstract: At least one acoustic sensor registers a pressure response to a low-frequency non-oscillating pressure signal generated in a borehole by at least one source. At least one characteristic of a transient process of pressure change is determined from the registered signal. A thickness of a mudcake is determined. Then, based on the values received, a mudcake piezoconductivity or a fluid mobility or both are determined.

Abstract: A device for acoustic measuring in a medium in a borehole such as velocity of sound in the medium or velocity of the medium, includes at least a first acoustic array situated in a first, slanted sidewall of a measuring area and operating to emit a series of acoustic waveforms across a measuring area. In one form, the device includes a second acoustic array situated in a second, slanted sidewall of the measuring area and operating to receive an acoustic signal resulting from the emitted series of acoustic waveforms or to receive said acoustic signal and emit a second series of acoustic waveforms.

Abstract: Seismic wave sources and related methods are provided. A seismic wave source includes a housing, plural pillars and an excitation system. The housing is split in two halves along a plane including a longitudinal axis of the housing. The plural pillars are made of piezoelectric elements and are positioned inside the housing to have one end in contact with a semi-cylindrical middle portion of one half of the housing and another end in contact with a semi-cylindrical middle portion of the other half of the housing. The excitation system connected by wires to the plural pillars and is configured to provide electrical signals to the piezoelectric elements. Upon receiving the electrical signals from the excitation system, the pillars generate forces on the housing thereby generating seismic waves.

Abstract: A communication method includes: receiving input data at a transmitter, the transmitter including at least one convolutional encoder and at least one modulator; applying the input data to a trellis-coded modulation (TCM) scheme to encode the input data and produce one or more TCM symbols representing the encoded data; applying the one or more TCM symbols to a second modulation scheme, the second modulation scheme including a pulse modulation in combination with an additional modulation; and generating one or more modulation symbols representing the encoded data based on the second modulation scheme.

Abstract: One or more embodiments and methods of analyzing a formation sample with in a coring tool are disclosed herein. The methods and embodiments may include extracting a first core from a sidewall of a wellbore with a coring tool at a first depth, ultrasonically measuring a sound speed of the first core, transmitting the ultrasonically measured sound speed of the first core to a surface display unit, analyzing the ultrasonically measured sound speed in real time, determining the quality of the first core, extracting a second core at the first depth if the first core is determined to be low quality, and extracting the second core at a second depth if the core first is determined to be high quality.

Abstract: The present disclosure relates to determining the attenuation of an electromagnetic signal passing through a conductive material. An antenna is provided and placed in relatively close proximity to the conductive material. An alternating current is passed through the antenna and the impedance of the antenna is measured. The attenuation is determined using the measured impedance. A single frequency measurement may be made, or multiple measurements using different frequencies may be made. Grouped parameters based on properties of the material and the frequency of the current are used to relate the coil impedance to the attenuation. A current frequency for which the ratio of the antenna's resistive part of the impedance to the angular frequency of the current is substantially insensitive to at least one of the parameters is preferred.

Abstract: Hollow rebar may be used for structural reinforcement in a drilled shaft and to provide access tubes for a sonic integrity testing probe. Rebar (short for reinforcing bar) is steel bar used as a tensioning device in reinforced concrete that holds the concrete in compression. According to the system described herein, hollow rebar may provide high strength reinforcement in the drilled shaft while at the same time providing an access tube for a sonic integrity testing process, such as crosshole sonic logging (CSL). The high strength hollow rebar, having ridges, threads and/or other appropriate surface deformations, provides improved adhesion to concrete, thus eliminating the problem of debonding associated with non-structural access tubes made of smooth PVC or steel pipe.

Abstract: A method and apparatus for radially cutting tubulars in a downhole environment by emitting acoustic energy into the jet, the acoustic energy having a wavelength selected such that the jet acts as a waveguide, detecting reflected acoustic energy in the jet, and determining the depth of cut from a travel time of the acoustic energy.

Abstract: Methods of generating radial survey images of a borehole and methods of orienting downhole operational tools are disclosed. The disclosed techniques are used to generate a radial survey of the borehole in the form of one or more rose-plots and/or a radial image of the borehole and surrounding area that can be used to properly orient downhole operational tools in the desired direction. The tool string includes, from the top to bottom, a telemetry module, a non-rotating centralizer, a motor module, an imaging sonde used to survey the borehole, a rotating centralizer and a downhole operational tool. The motor module can be used to rotate the imaging sonde to generate the radial survey and then rotate the downhole operational tool to the desired direction based upon a review of the radial survey.

Abstract: A system for measuring an acoustic property of material penetrated by a well borehole. The system uses a borehole logging tool comprising preferably one acoustic transmitter and preferably a plurality of acoustic receivers. An independent measurement is used to determine azimuthal orientation of the tool within the borehole. Firings of the transmitter are based upon azimuthal orientation of the tool. Receiver responses resulting from preferably a plurality of transmitter firings per tool revolution are combined to form at least one composite transmitter response. The composite receiver response is compensated for adverse effects of the tool operating eccentered within the borehole.

Abstract: A downhole imaging system includes a downhole imaging tool, a surface workstation, and a real-time data feed configured to connect between the downhole imaging tool and the surface workstation.

Abstract: Methods and apparatus for estimating stress characteristics of formations. The method comprises: (a) acquiring sonic anisotropy data, image data or both associated with at least one borehole (b) employing sonic anisotropy data to estimate fast shear direction (FSA) to extract FSA observed data; (c) computing FSA from forward modeling, forward modeling utilizes a first deviatoric stress tensor to extract FSA predicted data; (d) computing FSA misfit from difference between FSA observed data and FSA predicted data to obtain computed FSA misfit relating to first deviatoric stress tensor; (e) if computed FSA misfit is equal to or less than a defined value, then store computed FSA misfit, otherwise repeat steps (d)-(h) using another deviatoric stress tensor so a different deviatoric stress tensor is used for each repeat; (f) selecting smallest stored computed misfit from group consisting of stored computed FSA misfit, at least one other stored computed misfit or combination thereof.

Abstract: A method for imaging a subsurface material, the method including: receiving a first image of the subsurface material and a second image of the subsurface material, the first image displaying a first property of the subsurface material and the second image displaying a second property of the subsurface material wherein the first property is different from the second property; and combining the first image and the second image to create a combined image. A system and computer program product are also disclosed.

Abstract: One or more embodiments and methods of analyzing a formation sample with in a coring tool are disclosed herein. The methods and embodiments may include extracting a first core from a sidewall of a wellbore with a coring tool at a first depth, ultrasonically measuring a sound speed of the first core, transmitting the ultrasonically measured sound speed of the first core to a surface display unit, analyzing the ultrasonically measured sound speed in real time, determining the quality of the first core, extracting a second core at the first depth if the first core is determined to be low quality, and extracting the second core at a second depth if the core first is determined to be high quality.

Abstract: A method and apparatus is disclosed for monitoring microseismic activity in a formation. The method and apparatus include placing a tool string having a shuttle including a sensor thereon in a stimulation well, and activating the shuttle to acoustically couple the sensor to an inner surface of a casing. The sensor is acoustically decoupled from the tool string. Fluid is then injected into the formation via the tool string. The sensor is reengaged with the tool string. The tool string may then be removed from the stimulation well or moved to another position along the wellbore.

Abstract: A borehole receiver for seismic testing has a support frame and an inflatable membrane configured to form a single, compact unit. The inflatable membrane has at least one sensor, such as an accelerometer affixed to the membrane. The at least one accelerometer may be adhesively affixed to an interior portion of the membrane with a cyanoacrylate adhesive. A pneumatic inflation system is used to inflate the membrane with pressurized air. In use, the membrane is slipped over the support frame and secured with a pair of O-rings. Once the borehole receiver is properly positioned in the borehole, pressurized air from the pneumatic inflation system inflates the membrane such that the at least one accelerometer achieves intimate coupling with a wall of the borehole to accurately measure dynamic seismic waves.

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: An artificial neural network, ANN, and method of training the ANN for inversion of logging tool signals into well logs of formation parameters is disclosed. Properly selected synthetic models of earth formations are used to train the ANN. The models include Oklahoma and chirp type of formations. In each model parameter contrasts of from 10 to 1 to about 100 to 1 are included. Models including maximum and minimum parameter values spanning the operating range of the selected logging tool are included. Parameter contrasts at interfaces are limited to realistic values found in earth formations. The selected models are used to generate synthetic tool signals, which are then used as inputs to the ANN for training. When the ANN coefficients are properly adjusted to produce an output matching the original models, the ANN can be used for inversion of any real signals from the selected logging tool.

Abstract: A method and apparatus for assessing the permeability of a subterranean formation and the hydrocarbon and/or water content of the formation. The method includes emitting an acoustic signal, such as a Stoneley wave into the formation and sending an electro-magnetic pulse into the formation. An analysis of the response of the Stoneley wave in conjunction with an analysis of a measurement of the electrical potential within the wellbore provides information pertinent to permeability and fluid composition.

Abstract: Method for determining an expected value for a proposed reconnaissance electromagnetic (or any other type of geophysical) survey using a user-controlled source. The method requires only available geologic and economic information about the survey region. A series of calibration surveys are simulated with an assortment of resistive targets consistent with the known information. The calibration surveys are used to train pattern recognition software to assess the economic potential from anomalous resistivity maps. The calibrated classifier is then used on further simulated surveys of the area to generate probabilities that can be used in Value of Information theory to predict an expected value of a survey of the same design as the simulated surveys. The calibrated classifier technique can also be used to interpret actual CSEM survey results for economic potential.

Abstract: Methods for characterizing a geological formation, the methods include retrieving measured data provided by a measuring tool along one or more logged borehole length for a borehole, another borehole or both in order to produce a borehole imaging log. Selecting depth-defined intervals of the borehole imaging log as training images for inputting in a multi-point geostatistical model. Determining pattern based simulations for each training image using a pixel-based template of the multi-point geostatistical model so as to obtain training image patterns. Using the pattern based simulation of each training image to assign to each of the training image a corresponding training image pattern. Constructing from the training image patterns one or more fullbore image log of a borehole wall of the borehole. Repeat the second to fourth steps through the one or more logged borehole length in order to construct fullbore images from successive, adjacent training images.

Abstract: A method for acquiring and analyzing time-series data using singularities is described. This method allows for the analysis of data over a wide spectrum of frequencies. Once the data is acquired in an oil field, singularities of the data are extracted; and the extracted singularities are utilized to interpret the formation properties related to the data.

Abstract: Method and system for determining a characteristic of a subsurface formation traversed by a wellbore. A fluid flow rate in the wellbore is established, the flow being associated with fluid movement in one or more layers in the formation. Fluid data is generated from the fluid flow. The fluid flow rate in the wellbore is selectively altered, and fluid data is re-generated pertaining to the altered flow rates. The fluid data is processed to determine desired reservoir parameters and/or characteristics of an identified stratum in the formation. A method identifies inflexion points on a single phase oil only curve plot using the fluid data to determine layer characteristics and flow stability.

Abstract: A simulation system includes a case manager adapted for organizing and managing a plurality of sets of input data being used by the simulation system. The case manager includes a plurality of case scenarios organized in a tree-like structure, some case scenarios being supersets of other case scenarios in the tree-like structure. An operator selects one or more of the case scenarios in the case manager. A case builder receives keywords associated with the one or more of the case scenarios selected by the operator allowing the operator to edit or change the keywords from the selected case scenarios when necessary and generates a set of edited keywords representing edited case scenarios. A run manager submits the edited case scenarios to a simulator which generates a set of simulation results that are stored in a results file for subsequent display and viewing.

Abstract: The present invention provides a method and apparatus for using an acoustic logging tool conveyed in a borehole in an earth formation for determining a characteristic of the formation. The method comprises using a first acoustic source for generating an acoustic signal in the earth formation at a first frequency. A second acoustic source spaced apart from the first source is used for generating an acoustic signal in the earth formation at a second frequency different from the first frequency. An acoustic receiver is used for receiving a third acoustic signal indicative of said characteristic. The third acoustic signal has a frequency substantially equal to a difference between the first frequency and the second frequency. The third acoustic signal is produced by a nonlinear interaction between the first signal and the second signal in a portion of said earth formation.

Abstract: A downhole crystal-based clock that is substantially insensitive to the factors that cause frequency deviation. The clock may be maintained at a predetermined temperature using a temperature sensing device and a heating device, where the predetermined temperature corresponds to the temperature at which the crystal experiences only slight frequency deviation as a function of temperature. A microprocessor may monitor the clock and compensate for long-term aging effects of the crystal according to a predetermined algorithm. The predetermined algorithm may represent long-term aging effects of the crystal which were derived by comparing the crystal clock to a more accurate clock (e.g., an atomic clock) prior to placing the clock downhole. In this manner, the crystal-based clock may be substantially free from the factors that cause frequency, and therefore time variations.

Abstract: A method of producing images of formations surrounding a borehole, comprises: obtaining values of a first parameter in the borehole as a function of depth and azimuth at a first resolution; obtaining values of a second parameter in the borehole as a function of depth only at a second resolution; establishing a relationship between the first and second parameters at a matched resolution; using the relationship to derive values of the second parameter as a function of depth and azimuth; and producing an image of the second parameter as a function of depth and azimuth using the derived values of the second parameter.

Abstract: A method for determining the maximum and minimum horizontal stresses of formations surrounding a borehole includes the following steps: suspending a logging device in the borehole; transmitting sonic energy from the logging device to establish flexural waves in the formations; receiving, at the logging device, sonic energy from the flexural waves, and producing, from the received sonic energy, measurement signals at a number of frequencies; determining, at the number of frequencies, the fast and slow flexural wave velocities in the formations, to obtain fast and slow flexural velocity dispersions; establishing a model of formation stresses in which stresses of a loaded state are represented by the sum of an omnidirectional hydrostatically loaded mean reference stress, a vertical stress perturbation, and maximum and minimum horizontal stress perturbations; establishing an inversion model that includes inputs from the fast and slow flexural velocity dispersions and also includes unknown horizontal perturbations

Abstract: A system and method for acquiring seismic data are disclosed. The system comprises a controller for causing the generation of a seismic signal, where the controller has a first clock used for time-stamping a record of the generated seismic signal. A seismic receiver is deployed in a wellbore so as to detect the generated seismic signal. An atomic clock is disposed in or with the seismic receiver for time-stamping a record of the detected seismic signal. The atomic clock is synchronized with the first clock prior to being placed downhole.

Abstract: Methods and apparatus for attenuating waves in a bore hole, and seismic surveying systems incorporating the same. In one embodiment, an attenuating device includes a soft compliant bladder coupled to a pressurized gas source. A pressure regulating system reduces the pressure of the gas from the gas source prior to entering the bladder and operates in conjunction with the hydrostatic pressure of the fluid in a bore hole to maintain the pressure of the bladder at a specified pressure relative to the surrounding bore hole pressure. Once the hydrostatic pressure of the bore hole fluid exceeds that of the gas source, bore hole fluid may be admitted into a vessel of the gas source to further compress and displace the gas contained therein. In another embodiment, a water-reactive material may be used to provide gas to the bladder wherein the amount of gas generated by the water-reactive material may depend on the hydrostatic pressure of the bore hole fluid.

Abstract: A method for the design of VSP surveys for the purpose of imaging a reef in the formations surrounding the well in question. The basic steps include: building a geophysical model; defining receiver locations in the well within the model; defining the target (reef); ray tracing from receivers to surface via target; defining source locations on surface based on ray density pattern; and validate by ray tracing from source locations to receiver locations via target.

Abstract: Methods and apparatus for suppression of wave energy within a fluid-filled borehole using a low pressure acoustic barrier. In one embodiment, a flexible diaphragm type device is configured as an open bottomed tubular structure for disposition in a borehole to be filled with a gas to create a barrier to wave energy, including tube waves. In another embodiment, an expandable umbrella type device is used to define a chamber in which a gas is disposed. In yet another embodiment, a reverse acting bladder type device is suspended in the borehole. Due to its reverse acting properties, the bladder expands when internal pressure is reduced, and the reverse acting bladder device extends across the borehole to provide a low pressure wave energy barrier.