The present invention provides a system for drilling boreholes having a downhole subassembly which contains an acoustic measurement-while-drilling system It uses the acoustic velocity through the formations surrounding the borehole and an acoustic transmitter and a set of receivers for determining the bed boundaries surrounding the borehole formation An acoustic isolator on the tool may be used to attenuate body waves traveling between the transmitter and the receivers Additional attenuation of the body waves is provided by a threshold filter based upon the absolute maximum of the received signals Semblance of the data is determined in a slowness/intercept-time domain Coherence and semblance filtering methods are used to differentiate between reflection signals and noise The position and orientation of the bed boundary relative to the tool are determined A further processing step uses the relative position and orientation determined for a number of tool positions to further discriminate against noise and obtain an absolute position and depth of the bed boundaries

Semblance processing for an acoustic measurement-while-drilling system for imaging of formation boundaries

A method, a map and an article of manufacture for the exploration of hydrocarbons. In one embodiment of the invention, the method comprises the steps of: accessing 3D seismic data; dividing the data into an array of relativey small three-dimensional cells; determining in each cell the semblance/similarity, the dip and dip azimuth of the seismic traces contained therein; and displaying dip, dip azimuth and the semblance/similarity of each cell in the form of a two-dimensional map. In one embodiment, semblance/similarity is a function of time, the number of seismic traces within the cell, and the apparent dip and apparent dip azimuth of the traces within the cell; the semblance/similarity of a cell is determined by making a plurality of measurements of the semblance/similarity of the traces within the cell and selecting the largest of the measurements. In addition, the apparent dip and apparent dip azimuth, corresponding to the largest measurement of semblance/similarity in the cell, are deemed to be estimates of the true dip and true dip azimuth of the traces therein. A color map, characterized by hue, saturation and lightness, is used to depict semblance/similarity, true dip azimuth and true dip of each cell; true dip azimuth is mapped onto the hue scale, true dip is mapped onto the saturation scale, and the largest measurement of semblance/similarity is mapped onto the lightness scale of the color map.

Method and apparatus for seismic signal processing and exploration

A marine seismic exploration method and system comprised of continuous recording, self-contained ocean bottom pods characterized by low profile casings. An external bumper is provided to promote ocean bottom coupling and prevent fishing net entrapment. Pods are tethered together with flexible, non-rigid, non-conducting cable used to control pod deployment. Pods are deployed and retrieved from a boat deck configured to have a storage system and a handling system to attach pods to cable on-the-fly. The storage system is a juke box configuration of slots wherein individual pods are randomly stored in the slots to permit data extraction, charging, testing and synchronizing without opening the pods. A pod may include an inertial navigation system to determine ocean floor location and a rubidium clock for timing. The system includes mathematical gimballing. The cable may include shear couplings designed to automatically shear apart if a certain level of cable tension is reached.

Method and apparatus for seismic data acquisition

A method and apparatus for deployment and retrieval of ocean bottom seismic receivers. In one embodiment the apparatus comprises a carrier containing a plurality of receivers attached to a remotely operated vehicle (ROV). The carrier comprises a frame in which is mounted a structure for seating and releasing said receivers. The structure may comprise a movable carousel or a movable conveyor or fixed parallel rails or a barrel. In the case of the barrel the receivers are axially stacked therein. The structure is disposed to deliver said receivers to a discharge port on said frame where the receivers are removable from said carrier. The apparatus includes a discharge mechanism for removing said receivers from said carrier.

Method and apparatus for deployment of ocean bottom seismometers

The present invention relates generally to a method of seismic data processing which provides a superior method of removing or attenuating some forms of seismic noise and can also be used as a basis for seismic attribute analysis and automatic trace editing. In particular, the present invention is directed toward the application of a Very Short-Time Fourier Transform (VSTFT) to seismic data, coupled with a novel approach to organizing and/or displaying the transformed data, so as to provide highly localized frequency analyses of seismic reflection events. The present invention utilizes a very great number of short overlapping Fourier transform windows, together with a Gaussian weight or taper function, to produce a plurality of near single-frequency 'sub-band' traces for each seismic trace so analyzed. Although the present invention can be applied to a single seismic trace, it is preferably applied to a collection of seismic traces that are spatially related. Among the many uses of the transformed seismic data are selective removal of coherent noise events, analysis for seismic attributes related to subsurfaces features of interest, seismic trace creation by interpolation, and automatic identification and removal of noisy seismic traces.

Time-frequency processing and analysis of seismic data using very short-time fourier transforms

Method for removing coherent noise from a series of seismic traces. Each seismic trace included in the series is Fast Fourier Transformed into the frequency domain. For each frequency of the resultant f-x representation, a series of N complex numbers, one corresponding to each trace, is selected. The selected series of complex numbers corresponding to each frequency are processed to produce autoregressive model coefficients from which a polynomial rooting provides complex roots related to wavenumbers and decay constants. Amplitudes and phases for complex non-stationary spatial sinusoids associated with the estimated wavenumbers are then determined. For all frequencies f, the collection of determined wavenumbers, decay constants, amplitudes and phases constitute an f-k representation of the seismic traces. The produced f-k representation is examined to identify components corresponding to seismic data and the f-k components which correspond to seismic data are summed to reconstruct frequency components of an f-x representation of the acquired seismic traces with coherent noise removed.

Method for removing coherent noise from seismic data

Method for restoring seismic data to missing or severely noise contaminated traces included in a seismic section. The seismic section is transformed into a data localizing space and muted to retain only the localized data components of the seismic section. The muted transform space is inverse-transformed into the x-t domain to produce first estimates of the seismic data to be restored. The first estimates of the restored data are substituted for the corresponding traces in the original seismic section. Fully restored traces corresponding to the missing or severly noise contaminated traces are determined from the single estimate of the restored traces.

Method of restoring seismic data

Method and apparatus for removing sinusoidal noise from seismic traces comprised of a seismic data component and a sinusoidal noise component. Seismic traces acquired by conventional seismic exploration of a subsurface formation are utilized to produce a frequency domain amplitude spectrum of the traces. The amplitude spectrum is analyzed to determine a line frequency equivalent to the sinusoidal noise frequency to be removed. A filter order N (number of filter weights) is selected and the exact autocorrelation function of the selected sinusoidal frequency is determined for lags 0, 1, . . . , N-1. An autocorrelation matrix is produced utilizing the determined autocorrelation values and predictive deconvolution techniques are applied to the autocorrelation matrix to produce a convolutional filter which will remove sinusoidal noise at the determined frequency while leaving other frequencies minimally attenuated. The sinusoidal noise is then removed from the seismic data by convolving the acquired seismic traces with the filter.

Method and apparatus for removing sinusoidal noise from seismic data

Method of interpolating additional seismic traces between existing seismic traces obtained during the exploration of a subsurface formation. Seismic traces are recorded upon a datum surface in accordance with standard seismic data acquistion methods. Forward and backward wave equation datuming of the data set at the same velocity estimates new measurements for originally acquired data deemed unsatisfactory by propagating measured seismic traces to a fictitious datum plane using wave theory to create a second set of seismic traces and datuming the second set of seismic traces, again using wave theory, back to the original datum plane to create a third set of seismic traces. The third set of seismic traces will include new seismic traces to be used in place of the originally acquired unsatisfactory data.

Method for seismic trace interpolation using a forward and backward application of wave equation datuming

Method of restoring null traces in seismic records. The seismic record is transformed from the x-t domain to the f-k domain by a series of fast Fourier transforms. The f-k transform of the seismic record is filtered to retain only coherent events and the filtered f-k transform is inverse-transformed back to the x-t domain. A first determination of the restored trace corresponding to the null trace is selected and substituted for the null trace. The first determination of the restored trace is used to determine a fully restored trace.

Seismic trace restoration using F-K filtering

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