Abstract: Techniques for determining a drill bit location includes identifying a plurality of acoustic energy signals received at a plurality of sets of acoustic receivers from a passive acoustic energy source that is part of a wellbore drilling system; processing the plurality of acoustic energy signals; determining a location of a drill bit of the wellbore drilling system based on the processed plurality of acoustic signals; and updating a geo-steering path of the drill bit based on the determined location of the drill bit.

Abstract: A method includes generating a seismic shot by a seismic source, the seismic shot directed at a geological subsurface, and receiving, by one or more receivers, a plurality of reflected seismic traces from the seismic shot. The method further includes generating a correlogram of each reflected seismic trace to generate a plurality of correlograms, isolating a coda wave train of each correlogram of the plurality of correlograms, and computing an energy ratio between an energy of the coda wave train of each correlogram and a total energy of a corresponding correlogram of the plurality of correlograms to generate a plurality of energy ratios. The method further includes determining an average of the plurality of energy ratios to generate an average energy ratio of the seismic shot and determining a likelihood of striking a subsurface geohazard when drilling into the geological subsurface based on the average energy ratio.

Abstract: Aspects of the present disclosure relate to a downhole device including an actuator which has a primary purpose to operate the device while also having a secondary purpose to induce controlled pulses into a downhole environment at a first location for detection at a second location. A control package can be connected to the actuator. The control package is operable to detect a trigger event and control the actuator to cause the controlled pulses in the downhole environment in response. In some aspects, the trigger event is the reception of a command sent to the downhole device from the surface and the controlled pulses serve to provide a feedback signal receivable at the surface.

Abstract: Provided is a method of first arrival picking of multi-channel seismic survey data considering sound source-receiver array that can increase the reliability of a first arrival selected from land seismic survey data or marine seismic survey data that includes background noise. Further, provided is a method of first arrival picking of multi-channel seismic survey data considering source-receiver array, which can improve the reliability of a first arrival or a micro earthquake occurrence location selected from measurement data of a micro earthquake seismic survey.

Abstract: Vibrators for producing seismic signals for use in oil and gas exploration are equipped with segmented base plates, each segment being independently controlled and activated. The use of an array of base plate segments allows the individual segments of the array to be activated in a particular pattern, thus generating S-waves and other unconventional wave patterns for seismic use.

Abstract: There is provided an ultrasonic diagnostic apparatus capable of measuring hardness information of a subject with high time resolution and spatial resolution. The apparatus is provided with a ultrasonic probe 1 and a displacement generation unit 10 configured to displace an inside of a subject and is configured to transmit an ultrasonic beam for displacement detection to a plurality of detection positions of the subject from the ultrasonic probe 1, and to detect a shear wave velocity based on the displacement at the plurality of detection positions in a control unit 3 by using a reflection signal detected in a detection unit 20, thereby outputting hardness information of the subject. The ultrasonic beam for displacement detection is transmitted to one of the plurality of detection positions.

Abstract: A technique facilitates determination of fracture attributes through the recording and analyzing of borehole sonic data before and after a fracturing operation. The technique comprises generating broadband acoustic waves at an array of receivers based on output from a plurality of acoustic sources. The waveforms of the broadband acoustic waves are recorded and processed to estimate sonic signatures. The sonic signatures are then used to determine fracture attributes. In some applications, the data may be used to determine whether the fractures in the formation are filled with fluid or soft sediments. Information on the fracture attributes is output to a suitable system, e.g. a computer display.

Abstract: A device for determining a common-mode signal in a power line communication network. The device includes a first line, a second line, and a third line that are connected to a first terminal, to a second terminal, and to a third terminal, respectively. The first, the second, and the third terminal are configured to be connected to a phase line, a neutral line, and a protective ground line of the power line communication network, respectively. The device further includes a common-mode choke configured to couple out the common signal from the first, second, and third line, and the common-mode choke is connected to a termination impedance which is higher than an impedance of the power line communication network.

Abstract: This invention relates to the fiber optic distributed acoustic sensing to detect P and S waves in a solid medium. Distributed acoustic sensing can be achieved using an unmodified fiber optic by launching optical pulses into the fiber and detecting radiation which is Rayleigh backscattered there from. By analyzing the returns in analysis bins, acoustic disturbances can be detected in a plurality of discrete longitudinal sections of the fiber. The present invention extends such fiber distributed acoustic sensing to detection of S and P waves.

Abstract: A method of imaging a subterranean formation. The method includes emitting a primary wave from a source point, such that a portion of the primary wave travels into the subterranean formation and is refracted along a geologic layer in the subterranean formation and then emitted as a secondary wave from a refraction point on a boundary between the geologic layer and another geologic layer. The method also includes allowing a portion of the secondary wave to be reflected from a first reflection point as a tertiary wave. The method further includes allowing a portion of the tertiary wave to be reflected from a second reflection point as a quaternary wave, and collecting data about the quaternary wave at an observation point.

Abstract: An improved method for P-wave modeling in inhomogeneous transversely isotropic media with tilted symmetry axis (TTI media), suitable for anisotropic reverse-time migration, is based on an acoustic TI approximation. The resulting wave equations (2.20) & (2.21) are derived directly from first principles, Hooke's law and the equations of motion, and therefore make no assumptions on spatial variation of medium parameters. Like in the acoustic VTI case, the wave equations are written as a set of two second-order partial differential equations. However, unlike in the acoustic VTI case, the acoustic TTI wave equations contain mixed second-order derivatives. The discretization scheme uses centered finite-difference operators for first- and second-order derivative operators to approximate the mixed and non-mixed second-order derivatives in the wave equation. The discretization scheme is stabilized by slightly weighing down the mixed derivatives, with almost negligible effect on the wave field kinematics.

Abstract: System, methods, and computer-readable storage media that may be used to detect excitation faults for electrical devices, such as generators and/or condensers, connected in a parallel configuration are provided. A method includes determining a change in a terminal voltage of one of the electrical devices with respect to a steady state terminal voltage. The method further includes determining a change in a reactive power of the electrical device with respect to a steady state reactive power. The method further includes determining whether an excitation fault condition exists based on the determined changes in terminal voltage and reactive power.

Abstract: A process for overcoming aliasing using a minimum weighted norm interpolation (MWNI) technique may include computing an initial, regularly interpolated model with no data gaps and computing a plurality of initial spectral weights using the initial, regularly interpolated model. The initial, regularly interpolated model is used to compute the spectral weights as initial constraints in a least-squares solution methodology. The initial spectral weights are used as initial constraints in a constrained minimum weighted norm interpolation data reconstruction. The process may further include converting the initial, regularly interpolated model into a frequency domain and computing unknown spectral weights from frequency data at each frequency slice of the initial, regularly interpolated model using Fourier transform. The process results in reducing aliasing artifacts and improving data regularization.

Abstract: A technique includes a method and apparatus for simultaneous joint inversion of surface wave and refraction data to identify near surface geophysical and geological properties.

Abstract: A computer implemented technique for use in seismic data interpretation and, more particularly, with respect to near-surface geological structures, includes a computer-implemented method, including: jointly interpreting a plurality of complementary data sets describing different attributes of a near-surface geologic structure; and ascertaining a near-surface geomorphology from the joint interpretation. In another aspect, the technique includes a program storage medium encoded with instructions that, when executed, perform such a method. In yet another aspect, the method includes a computing apparatus programmed to perform such a method.

Abstract: Refracted energy travel time can help to derive anisotropic parameters in a target layer. These anisotropic parameters allow us to both explore for new reservoirs and to understand stress and fracturing in existing reservoirs. This information can be used to i) detect oil reservoirs, ii) spot naturally fractured, hence high production zones, iii) detect dominant natural stress directions, iv) better place horizontal wells to optimize production, v) monitoring man made fractures or induced directional stress changes. The method is demonstrated using synthetic and real data.

Abstract: A method and system are disclosed for performing seismic surveys using a seismic vibrator, which generates a sweep signal with enhanced low frequency content by generating a combination of a linear and nonlinear sweep and wherein the nonlinear sweep snonl(t) as a function of time (t) is calculated by a predetermined algorithm.

Abstract: A method for evaluating subsurface formations includes deploying at least two intersecting seismic transducer lines above an area of the subsurface to be surveyed. Each line includes spaced apart seismic transmitters on one side of the intersection and spaced apart seismic receivers on the other side. On each line, one of the transmitters is actuated and signals are detected at one of the receivers. The foregoing is repeated for each of the remaining receivers. The foregoing is then repeated for each of the remaining transmitters on each line. The detected signals are processed to enhance both specular and non-specular seismic events in the subsurface. The enhanced events may be stored and/or displayed.

Abstract: A method of inducing fracture in at least a portion of a geologic structure includes inducing acoustic waves into a fluid medium present in a borehole extending at least partially into the structure. Embodiments may include preheating or pressurizing the fluid medium prior to inducing the acoustic wave therein.

Abstract: A method for monitoring a multi-layered system below a surface comprising a slow layer and a fast layer; the method comprising: transmitting one or more seismic waves from one or more seismic sources through the multi-layered system; receiving signals emanating from the multi-layered system in response to the one or more seismic waves with one or more receivers located a distance from the one or more seismic sources; identifying one or more critically refracted compressional (CRC) waves amongst the signals; and inferring information about a change in the slow layer based on the one or more CRC waves; wherein the CRC wave is a refracted wave which has traveled along an interface between the fast layer and an adjacent layer.

Abstract: A method of inducing fracture in at least a portion of a geologic structure includes inducing acoustic waves into a fluid medium present in a borehole extending at least partially into the structure. Embodiments may include preheating or pressurizing the fluid medium prior to inducing the acoustic wave therein. A device for fracturing at least a portion of a geologic structure includes electrodes for producing a spark to generate ordinary acoustic waves in the fluid medium. Embodiments may include structures for preheating or pressurizing the fluid medium prior to inducing the acoustic wave therein.

Abstract: A system and/or method for increasing safety in areas in which people work and/or through which people travel that potentially may become blocked (e.g. mines, mineshafts, tunnels, etc.) is provided. In certain example embodiments, a system and/or method is provided wherein a sensor locates individuals who may be trapped and conveys their location(s) after an area becomes blocked. Sensors may be disposed throughout the area, located on individuals, etc. Sensors may be located behind protected coverings (e.g. glass), and they may locate individuals through, for example, low power, ultrasound, infrared techniques, etc. In certain example embodiments of this invention, one or more conduits may provide a supply of breathable air to individuals who may be trapped after the area becomes blocked.

Abstract: Methods are disclosed employing seismic waves having infrasonic frequencies in the range of about 0.1–20 Hz for generating electromagnetic waves of similar infrasonic frequency in hydrocarbon bearing subterranean formations located at depths up to about 5000 meters, said electromagnetic waves having sufficient voltage amplitudes for detection at the earth's surface. Also disclosed are seismic sources capable of generating infrasonic seismic waves of sufficient amplitude for generating electromagnetic waves in hydrocarbon bearing formations at depths up to 5000 meters, said electromagnetic waves having voltage amplitudes sufficient for detection at the earth's surface.

Abstract: Vibrator comprising a single vibration generator coupled with the medium by a coupling element and means for controlling the generator, suited to apply thereto, on each emission, a single pilot signal obtained by combination of at least two signals of different frequencies (f1, f2), fixed or preferably variable within at least partly separate frequency bands, and non-linear elastic transmission means suited to generate in the medium vibrations at a frequency depending on the frequency difference of the two vibrational signals.

Abstract: A computationally efficient semi-recursive Kirchhoff migration algorithm is capable of obtaining accurate images of complex structures in complex geological environments which commonly give rise to multivalued arrivals. The method alternates wave-equation datuming (downward continuation) and Kirchhoff migration. Breaking up the complicated velocity structure into small depth regions allows traveltimes to be calculated in regions where the computation is well behaved and where the computation corresponds to energetic arrivals. Because traveltimes are computed for small depth domains, the effects of multivalued arrivals are implicitly accounted for in the migration and the adverse effects of caustics and headwaves do not develop. The invention can use any simple first-arrival traveltime algorithm, and thus benefits from the computational efficiency, robustness, and simplicity of such algorithms.

Abstract: The present invention provides a method for interpreting shear-wave seismic data to detect fractures in the subsurface of the earths crust. Seismic shear waves are acquired along medium symmetry planes and their corresponding AVO intercepts and gradients are estimated. The resulting AVO attributes are combined using a weighted least squares solution to estimate the change in splitting parameter and fast shear velocity, which are diagnostic of the presence of fractures. The method is also useful in assessing the porosity of the subsurface. Knowledge of subsurface fracturing and porosity is useful in locating, for example, oil and gas wells.

Abstract: A high speed microseismic event detector constructed in accordance with the present invention uses a point derivative comb to quickly and accurately detect microseismic events. Compressional and shear waves impinging upon microseismic receiver stations disposed to collect waves are converted into digital data and analyzed using a point derivative comb including assurance of quiet periods prior to declaration of microseismic events. If a sufficient number of quiet periods have passed, the square of a two point derivative of the incoming digital signal is compared to a trip level threshold exceeding the determined noise level to declare a valid trial event. The squaring of the derivative emphasizes the differences between noise and signal, and the valid event is preferably declared when the trip threshold has been exceeded over a temporal comb width to realize a comb over a given time period.

Abstract: Disclosed is a method for processing geophysical data that have been gathered over irregular topography. According to the method, a datum is established that lies above the highest topographic peak. The data are time-shifted from the surface to the datum using a replacement velocity that is an extrapolation of the underlying formation velocity. The wavefields beneath the surface are forwardly modeled using a modeling velocity substantially equal to zero. Between the surface and the datum, the wavefields are upwardly modeled using the replacement velocity.

Abstract: Methods are provided for making use of an apparatus for generating vibrational energy in a borehole, the apparatus utilizes a mass and a rotary source for suspending the mass in a borehole or in casing in a borehole or in an instrument housing that may be positioned in an opened or cased borehole arranged to cause frictional contact with the surface of the rotating mass, the mass being rotatable about is rotational axis in one direction to cause it to backward whirl in the opposite direction, the centrifugal force of the whirling mass serving to generate vibrational energy that is used to obtain geophysical information as to the structure of the earth surrounding and adjacent to the borehole and for enhancing cementing and production enhancing techniques in oil or gas wells.

Abstract: A method for improving the seismic resolution of geologic structures is disclosed. Refracted wave arrivals are gathered into common midpoint trace gathers. Data representations originating inside a critical offset distance are muted, and the remaining data is tau-P summed and projected into zero source-to-receiver offset. Constant velocity stacks can then be displayed. A plurality of common midpoint trace gathers can be used to generate multiple panels of tau-P sums. Portions of several of these panels can be combined to provide a complete image of the subsurface reactors. A near-surface velocity model can then be designed, to provide a solution to near-surface statics in seismic traces.

Abstract: Weathering corrections are determined from first arrival times of refraction stacked traces of common end point gathers. The refraction stacked traces are generated by selecting traces having receiver source offsets greater than the crossover distance and stacking such traces over at least an interval comprising first arrival times. Optionally, a predictor function is used to select first arrivals and the first arrivals are selected from a refraction stacked trace section.

Abstract: A novel method of seismic exploration has been developed to resolve confusing and distorted shear wave reflection seismic data which can be obtained in areas having anisotropic formations. In particular, the present method of shear wave seismic exploration comprises imparting first shear wave seismic energy into the earth at selected points with a first source having a first polarization with respect to the line of survey, and recording first signals representative of the earth's response with first geophones having a first polarization with respect to the line of survey. Also, second shear wave energy is imparted into the earth at selected points along the line of survey, with a second shear wave source having a second polarization with respect to the line of survey, and recording second signals representative of the earth's response with second geophones having a second polarization with respect to the line of survey.

Abstract: A method and system for geophysical exploration including obtaining, processing, displaying and interpreting seismic data. Seismic energy is imparted into the earth's subterranean formation along at least two linear independent lines of action in a seismic survey. At least two linearly independent components of the seismic wave energy imparted along each line of action are detected within the seismic survey. A concord of seismic signals is produced from the seismic wave energy detected for selected combinations of receiver and source locations. An orientation module operates on the concord of the seismic signals so as to generate synthetic concords of seismic signals so as to focus on a particular component of the seismic wave energy in order to infer the geologic characteristics of the earth's subterranean formations.

Abstract: Polarized shear wave surveys are performed to determine azimuthal variations in the earth's subsurface caused by fracture orientation and density. The surveys may be done by using the same polarization (either horizontal or vertical) shear waves along two different seismic lines of profile, or by using different polarization shear waves along one common line of profile. The survey data are then processed and compared; any differences constitute a measure of fracture orientation and density. Subsurface zones of high fracture density, once identified, have been found to afford a higher likelihood of successful well completion.

Abstract: A method and system for geophysical exploration including obtaining, processing, displaying and interpreting seismic data. Seismic energy is imparted into the earth's subterranean formation along at least two linear independent lines of action in a seismic survey. At least two linearly independent components of the seismic wave energy imparted along each line of action are detected within the seismic survey. A concord of seismic signals is produced from the seismic wave energy detected for selected combinations of receiver and source locations. An orientation module operates on the concord of the seismic signals so as to generate synthetic concords of seismic signals so as to focus on a particular component of the seismic wave energy in order to infer the geologic characteristics of the earth's subterranean formations.

Abstract: The invention permits the measurement of the propagation anisotropy of a transverse wave between two given reference points of a non-isotropic medium (M), particularly a shear wave in a stratified or fissured rock.According to the invention: a source (S) and two detectors (G.sub.1, G.sub.2) are arranged along a single ray vector, the detectors being positioned at the location of respective reference points; the source is excited by an excitation signal producing a transverse wave in the medium; the respective resultant measurement signals produced by each of the detectors are received; from the excitation signal and the measurement signals the transfer function of the medium along each of the respective source-detector paths is determined; the differential transfer function of the medium between the two reference points is deduced.

Abstract: The present invention is a downhole seismic source capable of generating seismic forces in excess of 1000 newtons. The source produces seismic waves for seismic applications, particularly cross borehole measurements and vertical seismic profiling. Coupled with motion sensing devices, the present invention also performs as a seismic logging tool. The source is comprised of an outer housing, a means for clamping the source securely to the wellbore, and a linear electromagnetic actuator which utilizes permanent magnetic material having remanent magnetic field exceeding about 0.9 T such as rare earth permanent magnetics. The source has a diameter of about 12.5 cm to fit within a typical wellbore and the acuator has a length of about 1 meter.

Abstract: A method useful in seismic data processing for correcting data for the effects of the low velocity layer. At least three sets of traces having common offsets are displayed as a function of centerpoint. From this, the first refraction arrival for each trace may be hand picked, this first refraction arrival representing a compressional wave refracted along the lower boundary of the low velocity layer. An equation is set up for each source-receiver pair in which the transit time of the first refraction arrival is a function of three independent factors: the source to receiver distance; a low velocity layer component for the source; and a low velocity layer component for the receiver. These equations are solved in a simultaneous, least squares fashion to yield surface consistent solutions to the low velocity layer component at each source and receiver location.

Abstract: Acoustic logging of low velocity formations is made possible by the introduction of gas bubbles in the liquid in a borehole where logging equipment is present. Acoustic logging cannot be performed where the compressional wave velocity in the borehole liquid exceeds the compressional wave velocity in the formation to be logged because in such case, the acoustic compressional waves do not refract in the formation. The gas bubbles are introduced to lower the compressibility of the borehole liquid, resulting in a decreased velocity in the liquid so that refraction of the compressional waves can take place, making acoustic logging feasible.

Abstract: A method of determining source and receiver statics in a marine exploration area overlying a near surface low velocity layer employing a marine vessel for towing a seismic energy source and a marine detector cable, and an on-bottom seismic energy source and seismic detector located at an offset from the marine seismic line of exploration. The towed seismic energy source generates a seismic reflection signal for detection by the towed marine detector cable and a seismic refraction signal to be detected by the on-bottom seismic detector. The on-bottom seismic energy source generates a seismic refraction signal for detection by the towed marine detector cable.

Abstract: The present invention provides for the accurate mapping of shallow crustal earth formations by means for refractive seismic waves to identify structure as well as elastic parameters of the strata undergoing survey to indicate deposits of ore, marker rock, economic minerals and the like. In one aspect of the present invention, a "roll-along" technique is used in the field, such technique being both practical and economical. In accordance with another aspect of the invention, there is a provision for (i) stacking displays that allow for accurate identification of shape of the surveyed strata; and (ii) final depth displays of the refracting bed segments associated with seismic shear and compressional wave velocities as well as Poisson's ratio to indicate presence of ore, marker rocks, economic minerals and the like.

Abstract: A method for migration of velocity spectra is disclosed wherein migration of common depth point gathers is accomplished without prior determination of the velocity/depth field.

Abstract: A method of determining source and receiver statics in a marine seismic exploration area overlying a near surface low velocity layer employing a seismic marine energy source, an on-bottom seismic detector cable for measuring seismic reflection signals, and an on-bottom remote seismic monitor for measuring seismic refraction signals.

Abstract: The present invention provides for the accurate mapping of shallow crustal earth formations by means for refractive seismic waves to identify structure as well as elastic parameters of the strata undergoing survey to indicate deposits or ore, marker rock, economic minerals and the like. In one aspect of the present invention, a "roll-along" technique is used in the field, such technique being both practical and economical. In accordance with another aspect of the invention, there is a provision for (i) accurate separation and determination of seismic shear and compressional responses using two-dimensional hodographs; (ii) stacking displays that allow for accurate identification of shape of the surveyed strata; and (iii) final depth displays of the refracting bed segments associated with seismic shear and compressional wave velocities as well as Poisson's ratio to indicate presence of ore, marker rocks, economic minerals and the like.

Abstract: The present invention provides for the accurate mapping of shallow crustal earth formations by means for refractive seismic waves to identify structure as well as elastic parameters of the strata undergoing survey to indicate deposits of ore, marker rock, economic minerals and the like. In one aspect of the present invention, a "roll-along" technique is used in the field, such technique being both practical and economical. In accordance with another aspect of the invention, there is a provision for (i) accurate separation and determination of seismic shear and compressional responses using three-dimensional hodographs; (ii) stacking displays that allow for accurate identification of shape of the surveyed strata; and (iii) final depth displays of the refracting bed segments associated with seismic shear and compressional wave velocities as well as Poisson's ratio to indicate presence of ore, marker rocks, economic minerals and the like.

Abstract: The present invention provides for the accurate mapping of shallow crustal earth formations by means for refractive seismic waves to identify structure, elastic parameters and lithology of the strata undergoing survey to indicate deposits of ore, marker rock, economic minerals and the like. After a "roll-along" technique has been used in the field to collect the refraction data and preliminary processing steps undertaken in which there are provisions for (i) accurate separation and determination of seismic shear and compressional responses; (ii) stacking displays that allow for accurate identification of shape of the surveyed strata; and (iii) final depth displays of the refracting bed segments associated with seismic shear and compressional wave velocities as well as Poisson's ratios, in accordance with the present invention, additional processing then occurs.

Abstract: In seismic exploration, refracted seismic energy is detected by seismic receivers to produce seismograms of subsurface formations. The seismograms are produced by directing seismic energy from an array of sources at an angle to be refracted by the subsurface formations and detected by the receivers. The directivity of the array is obtained by delaying the seismic pulses produced by each source in the source array.

Abstract: We have found it possible to investigate subsurface formations in the expectation of locating promising gas fields by a unique refraction seismic technique. Basically one carries out a two-way seismic refraction profile for a fixed spread of geophones and explosions (or equivalent impulse sources) beyond the critical reflection range for shallow refractors, but still rather close to the spread. Then without moving the spread, reproducible records are also made for a two-way seismic refraction profile with the explosions or equivalent sources spaced as far away as convenient, so the refraction paths to the detector groups in the spread is up-going to the detectors for the maximum thickness of beds intervening between the refractor and the group of geophones.

Abstract: Data for use in producing a tomograph of subsoil structure between boreholes is derived by placing spaced geophones in one borehole, and if desired also on the earth surface, and by producing a sequence of shots at spaced apart locations in the other borehole. The signals, detected by each of the geophones from the various shots, are processed either on a time of arrival basis, or on the basis of signal amplitude, to provide information of the characteristics of a large number of incremental areas (pixels) between the boreholes. Such information is useable to produce a tomograph of the subsoil structure between the boreholes. By processing signals of relatively high frequencies, e.g., up to 1000 Hz, and by closely spacing the geophones, a high resolution tomograph can be produced.

Abstract: A method for correcting seismic data for the effects of the low-velocity-layer. According to the method, estimates of the seismic velocity in the low-velocity-layer and the depth of the low-velocity-layer are used to extrapolate the seismic data to simulated source and receiver positions located at the base of the low-velocity-layer. The data are then extrapolated to an arbitrary reference datum using a selected replacement velocity. The principles of wave equation datuming are used for these extrapolations.