56 results about "Dipole source" patented technology

A method and tool using a continuous electromagnetic wave from a transverse magnetic-dipole source with a coaxial electric-dipole receiver is described for the detection of external sidewall cracks and other anomalies in boiler tubes and other enclosures. The invention utilizes the concept of radar backscatter rather than eddy-currents or ultrasound, which are sometimes used in prior art crack-detection methods. A numerical study of the distribution of the fields shows that the direct transmission from the source to the receiver is reduced from that in free space. Further, if the diameter of the receiver dipole is made sufficiently small, it should be possible to detect cracks with a scattering loss of up to -40 dB in thin-walled boiler tubes.

An electromagnetic survey method for surveying an area that potentially contains a subterranean hydrocarbon reservoir. The method comprises detecting a detector signal in response to a source electromagnetic signal, resolving the detector signal along at least two orthogonal directions, and comparing phase measurements of the detector signal resolved along these directions to look for a phase separation anomaly indicative of the presence of a buried hydrocarbon layer. The invention also relates to planning a survey using this method, and to analysis of survey data taken using this survey method. The first and second data sets may be obtained concurrently with a single horizontal electric dipole source antenna. The method is also largely independent of a source-detector pair's relative orientation and so provides for good spatial coverage and easy-to-perform surveying.

An apparatus and method for determining fast and slow shear wave velocities and orientations in an anisotropic earth formation that reduces the error and ambiguity in calculating these parameters and eliminates the need for dipole receivers and multiple dipole sources. The apparatus generally includes a single dipole source capable of generating an acoustic signal within a borehole. The acoustic logging tool contains multiple levels of receivers. At each level, four receivers, which may be conventional pressure transducers, receive shear/flexural wave signals which propagate along the borehole earth formation. These receivers measure the pressure fields from the wave signals. A processing device, preferably a UNIX(TM) based computer, interpolates the measured pressure fields between any two adjacent receivers. The processing device performs cross-component decomposition on the pressure field to determine shear wave orientation and velocity. Using the shear wave orientation and velocity the processing device determines transit time anisotropy, energy anisotropy, and slowness anisotropy.

Method for determining time-dependent changes [73] in the earth vertical and horizontal electrical resistivity and fluid saturations from offshore electromagnetic survey measurements. The method requires both online and offline data, which should include at least one electromagnetic field component sensitive at least predominantly to vertical resistivity and another component sensitive at least predominately to horizontal resistivity [62]. Using a horizontal electric dipole source, online Ez and offline Hz measurements are preferred. For a horizontal magnetic dipole source, online H2 and offline E2 data are preferred. Magnetotelluric data may be substituted for controlled source data sensitive at least predominantly to horizontal resistivity. Maxwell's equations are solved by forward modeling [64,65] or by inversion [66,67], using resistivity models of the subsurface that are either isotropic contrast, and [64,66] or anisotropic [65,67]. Fluid saturation is determined from the vertical and horizontal resistivities using empirical relations or rock physics models [70].

Apparatus and method for a steerable horizontal electric dipole source system for underwater deployment as a moving source in electromagnetic surveying of subsurface regions for hydrocarbons. Position locating sensors (195) are placed near each electrode (26, 27), and means (197, 198) are provided for correcting the electrodes to be at the same elevation with azimuth aligned with the source tow line (11) and the electrode mid-point positioned over the source tow line, based on instantaneous location information from the sensors. The streamer (28) connecting the electrodes may also be monitored for shape by sensors, with corrections made by lateral and vertical control means disclosed herein. The invention can be applied to any marine streamer used in geophysical surveys, including a towed streamer (191) of electromagnetic or seismic receivers (192).

Method for performing a full wavefield inversion (FWI) without simulating free-surface multiple reflections. The free-surface multiples are removed from the field gathers of seismic data, which are then used to generate a subsurface velocity model by FWI. In the FWI, the field monopole sources and receivers are replaced with dipole (actual and mirror image) sources and receivers (21) when model-simulating (23) synthetic survey data. Also, direct arrivals at the mirror receiver locations are preferably simulated (25) with the dipole sources for each shot location and added (26) to the synthetic survey data (24) for that shot location, resulting in corrected synthetic survey data (27), which is used in the FWI to generate residuals. A model update may be computed by back-propagating the residuals by injecting them at both mirror and actual receiver locations.

The invention provides a surface exciting method applicable to calculation of direction diagrams of waveguides in different shapes. The method comprises the following steps of: 1, setting an exciting surface of a shape corresponding to the shape of the cross section of a waveguide according to the the shape of the cross section of a waveguide; 2, dividing the exciting surface into even two-dimensional meshes, wherein an equivalent electric dipole source and a magnetic dipole source are arranged in the center of each mesh; 3, obtaining electric current of all the equivalent electric dipole sources and magnetic current of all the magnetic dipole sources on the exciting surface according to an equivalence principle, wherein an electromagnetic filed on the exciting surface is a main mode in which electromagnetic wave spreads in the waveguide; 4, carrying out mesh generation on the surface of the waveguide by virtue of triangular binning so as to obtain radiation fields generated by all the equivalent electric dipole sources, wherein the radiation fields serve as exciting fields of the surface of the waveguide; establishing an electric filed integral equation according to boundary conditions of the surface of the waveguide and obtaining the induction current of the surface of the waveguide by solving the equation according to a moment method; and 5, calculating the scattering direction diagram of the waveguide according to the induction current. Waveguides in different structures and shapes can be excited by the method provided by the invention instead of different methods separately.

The invention relates to an electric dipole source three-dimensional time domain finite difference direct interpretation imaging method. The method includes the steps of loading Gaussian pulses on an electric dipole source, establishing Maxwell equations and constitutive equations for the ocean air space, the seawater space and the seabed ground space, conducting uniform mesh generation on prism object models of the three spaces, obtaining difference equations of seawater and the seabed ground through a time domain finite difference method according to meshes obtained through mesh generation by consuming that the conductivities and the magnetic conductivities of all the meshes obtained through mesh generation are unchanged, processing the Maxwell equations of ocean air through analysis solutions, calculating the electromagnetic field of the air above the sea surface, processing the boundary conditions of the generation space, setting stabilization conditions, solving the established difference equations through the combination with the processing results of the boundary conditions and the set stability conditions, and obtaining the distribution of the electromagnetic field of the seawater and the seabed ground at any moment.

The invention brings forward an optical nanometer antenna with dual unidirectivity, and a design method thereof. A basic unit of the optical nanometer antenna is composed of a metal-dielectric-metal sandwich type structure, and under excitation of incident planar waves, the structure excites two different surface plasma resonance modes, i.e., electric dipolar resonance and magnetic dipolar resonance. Through a multistage decomposition method, a generalized Kerker condition (i.e., an electric dipole and a magnetic dipole are equivalent) for forward scattering and backward scattering is given. Besides, the influence of the nanometer antenna on far-field radiation of an electric dipole source is also argued, and for an array type metal-dielectric-metal nanometer structure, the excitation position of a dipolar radiation source plays a crucial role in deciding whether the antenna has dual unidirectivity. A theoretical base and a reference standard are provided for design of a nanometer optical device.

A logging tool having a tool body, which can be positioned in a fluid-filled borehole, including a receiver section and a dipole transmitter; wherein the dipole transmitter includes a transducer with a shell having a reaction mass and a motor located therein, the motor operatively connecting the shell and the reaction mass such that only an outer surface of the shell is in contact with the fluid in the borehole. This new type of dipole source for well logging involves shaking all or part (axially) of a dipole tool body to produce a pure, broadband acoustic dipole signal while at the same time coupling as little energy as possible into the tool body. Important variations on this idea include a linear phased array of shaker sources, and active cancellation of tool borne noise.

The invention provides a numerical calculation method of an electromagnetic field response of a dipole source at an arbitrary position under layered geological conditions. The calculation method comprises the steps of: step S100, defining stratums according to the position of the dipole source in the layered stratums; step 200, performing orthogonal decomposition on the dipole source; step S300, deriving a Lorentz vector potential expression generated by the unit dipole source in each stratum; step S400, deriving an electromagnetic field expression in each stratum according to the Lorentz vector potential expression; step S500, calculating a Bessel functional integration in the electromagnetic field expression by adopting a Gaussian extrapolation method to obtain a numerical solution of the electromagnetic field; step S600, and acquiring the electromagnetic field response of the dipole source by multiplying the numerical solution by a dipole source moment. The calculation method utilizes the expressions that Lorentz vector potential between the adjacent stratums satisfy, utilizes the particular solution of the stratum where the dipole source locates for circulating recursion to obtain the Lorentz vector potential expressions of all stratums, and obtains the electromagnetic field expression by means of the Lorentz vector potential, finally calculates the Bessel functional integration in the electromagnetic field expression by adopting the Gaussian extrapolation method to obtain the electromagnetic field response of the dipole source, and has the advantages of clear theory and high calculation precision.

This invention relates generally to a method of simulating the signal of an electromagnetic source using one or more dipole sources. In the method a dipole source is located at an excitation location corresponding to a segment of the electromagnetic source to be simulated. The dipole source is activated, and an electromagnetic signal recorded at one or more receiver locations. This process is repeated for additional excitation locations corresponding to additional segments of the electromagnetic source. The data from the sequence of dipole source excitation locations is processed to determine the simulated signal of the electromagnetic source.

The invention provides a well-to-ground joint electrical-method testing method and system. The well-to-ground joint electrical-method testing system comprises an in-well emission power supply subsystem, a ground collecting and acquiring subsystem and a master control and processing subsystem. By controlling emission electrodes in the in-well emission power supply subsystem and measuring electrodes in the ground collecting and acquiring subsystem, the well-to-ground joint electrical-method testing system can provide three power supply modes of in-well point source power supply, in-well dipole source power supply and well-to-ground joint power supply. The master control and processing subsystem can process and interpret the acquired data of the ground collecting and acquiring subsystem, and the geologic features of the surrounding area of boreholes can be effectively acquired. The well-to-ground joint electrical-method testing system is flexible in power supply modes, power supply, data acquisition and real-time simple processing of the data are integrated, and the well-to-ground joint electrical-method testing system is highly flexible and high in systematization and intelligence degrees.

A logging system has a sonde in a borehole, which transmits sonic waves with one or more dipole sources to optimally excite dipole flexural mode sonic waves in the borehole. The system first determines the Airy frequency of the borehole. Then, the dipole sources are fired at a dipole firing frequency selected based on the Airy frequency.

Two embodiments of marine geo-electric probe methods for hydrocarbon deposits survey comprise—excitation of electromagnetic field in a surveyed medium by transmitting two rectangular current pulses therethrough, the first—during forward traveling of a probe device along a profile and the second—during backward traveling thereof, —measuring instant values of the first and second electric potential differences during the time between the pulses, wherein, the equal-zero condition of the electric potential differences along the profile is ensured, —calculating three sets of normalized electrical parameters based on difference values, —solving an inverse problem via a differential equation for the dipole source voltage in an electrochemically polarizable medium using the parameters, —producing data according to said electrical parameters, and—determining conductivity of the medium, induced-polarization factor and decay time constant of the polarization potential difference. The first embodiment is deployed for circular survey profiles, the second is for linear profiles.

The invention relates to a method and system for positioning a dipole interference source in earthquake geoelectric observation, wherein the method comprises the following steps of: taking a leakage interference source as a ground surface dipole source, and establishing an influence model of the ground surface dipole source on the geoelectric observation; measuring the potential generated by the ground surface dipole source at different measuring points; calculating the position coordinate of the ground surface dipole source according to the potential difference between any two measuring points. According to the technical scheme, the leakage interference source is taken as the ground surface dipole source, the influence model of the ground surface dipole source on the geoelectric observation is established, the potential generated by the ground surface dipole source at different measuring points is measured, and the position coordinate of the ground surface dipole source are calculatedaccording to the potential difference between any two measuring points, so that the consumed manpower and material resources of the prior interference source investigation can be greatly reduced, therapid and accurate positioning can be achieved, the interference source is limited in a small area range, and the problems of long time consumption, low efficiency and low accuracy for positioning the leakage interference source in the prior art are solved.

The invention discloses an electromagnetic scattering simulation method for an electrically large-size target under a near-field condition. The method comprises the following steps: S1, constructing an antenna radiation characteristic equivalent model composed of a dipole array according to radar antenna parameters corresponding to a real target radar scene; s2, setting a physical parameter and a position parameter of the target platform and a physical parameter and a position parameter of the observation region, so that the target platform and the radar antenna are in a near-field state; s3, taking a dipole source in the dipole array as a radiation source, and calculating an electromagnetic scattering total field of the target platform under radiation of the radiation source by adopting a high-frequency method under scattering condition parameters; and S4, carrying out visualization processing on the electromagnetic scattering total field. The method has very high simulation precision and undistorted characteristics, and also has very low memory calculation loss and fast calculation efficiency.