Exxon Production Research Company

Exxonmobil Upstream Research Company

Richard E Duren

Dewey R Young, Ii

Mark A Meier

Andrew P Shatilo

Stanley Morris

Roy K Warren

Kenneth D Andersen

Eugene C Trantham

Mohamed T Hadidi

Erik A Eriksen

Carol J Zimmerman

Method for marine seismic acquisition using both monopole () and dipole () source types. Through a combination of source design and operation and/or combination or summing of the data in a processing step, the source ghost is either attenuated or, if desired, enhanced (). The properties of the two different source types allow them to be adjusted so that the first down going wave from each has either opposite polarity or the same polarity, whereas the source-ghost wave will have, respectively same polarity or opposite polarity. This allows cancellation or enhancement of the source ghost. If the survey also employs two-component sensor acquisition, then the combined data sets may be both sensor de-ghosted and source de-ghosted.

Two component source seismic acquisition and source de-ghosting

Method for controlling the phase spectrum of seismic data to match assumptions inherent in subsequent processing steps. The source signature, after processing with the same initial processing steps used on the data, is used to design a phase control filter that shapes the seismic data to have a minimum phase spectrum or whatever other phase spectrum the subsequent processing algorithms may assume. The processed data is then filtered with a second phase-control filter, also designed using the parallel-processed signature, to shape the data to zero phase or whatever other phase may be desired for interpretation of the data.

Phase control of seismic data

A marine seismic source method capable of retaining low frequencies is disclosed. One embodiment of the method comprises a seismic source that generates an up-going wave and first down-going wave with opposite polarity. The up-going wave reflects off the ocean surface as a second down-going wave having the same polarity as the first down-going wave and the first and second down-going waves combine substantially in-phase to form a third down-going wave. A source apparatus to accomplish the method is also disclosed. One source apparatus embodiment comprises a device wherein at least part of the device is below the surface of the water and the device is adapted to cause oscillations below the surface of the water, and means for oscillating the device in the water to create an up-going wave and a first down-going wave and the up-going wave has reverse polarity relative to the first down-going wave.

Marine seismic acquisition method and apparatus

The invention is a method for attenuating noise in seismic data traces, in which at least a portion of the noise is noncoherent in the common-shot domain but coherent in the common-receiver domain, the coherent noise having a move-out velocity different from the move-out velocity of the data signal in the seismic data traces. The method comprises sorting the seismic data traces into common-receiver order and using the difference in move-out velocities to separate the coherent noise from the data seismic signal. This method is useful in suppressing noise in two and four-component ocean bottom cable data.

Method for attenuating noise in seismic data

The invention is a method for removing trapped water bottom multiples, receiver side peg-leg multiples, and source side peg-leg multiples from dual sensor OBC data, where the data includes both pressure signals and velocity signals. The pressure and velocity signals are compared to determine any polarity reversals between them. Polarity reversals are used to identify and separate up-going and down-going wavefields in the pressure and velocity signals. A matching filter is applied to a portion of the velocity signal where polarity reversals exist. The down-going wavefield is then estimated by calculating the difference between the portion of the velocity signal where polarity reversals exist and the portion of the pressure signal where polarity reversals exist and applying a scaling factor to the result. An attenuated up-going pressure wavefield is then determined by combining the estimated down-going wavefield and the pressure signal.

Trapped water bottom multiple and peg-leg multiple suppression for ocean bottom seismic data

A method for reconstructing a selected seismic wavefield at a designated common midpoint and offset location from a set of prestack seismic data traces. The method uses actual data traces from other common midpoint and offset locations to reconstruct the selected wavefield at the designated reconstruction location. The method may be used to reconstruct any selected wavefield, including both primary reflection wavefields and secondary wavefields such as water-bottom multiple wavefields, and may be used with both 2-D and 3-D seismic data. If the reconstructed wavefield is a secondary wavefield, it may be subtracted from the prestack seismic data traces to eliminate interference between wavefields. The method may also be used to reconstruct data from missing shots to avoid spatial aliasing problems in other data processing operations.

Method for reconstructing seismic wavefields

Radar is used to detect and map near-surface geochemical alteration of rock and soil. The radar waves penetrate a buildup of carbonate and silica on the earth surface above micro-seepage of hydrocarbons dissolved in water. The hydrocarbon source may be an oil or gas reservoir buried many thousands of feet, or it may be from near-surface, man-made features. The thickness and sensitivity of the buildup is related to the size of the underground source or reservoir. Radar echoes from the bottom of the buildup provide a reservoir detection and mapping tool.

Detection and mapping of hydrocarbon reservoirs with radar waves

A method of correcting a seismic pulse waveform for use in deconvolution of reflected pulse data. The source pulse waveform is measured by a hydrophone positioned vertically beneath the acoustic source. The phase error is calculated based on the depth of the source and the depth of the measuring hydrophone. The calculated error is subtracted from the phase spectrum of the measured waveform. The resulting waveform provides an accurate representation of the true far field waveform, leading to an improved expression of the waveform actually incident upon the marine floor.

Method for correcting a seismic source pulse waveform

Controlled phase marine seismic subarray for use in a marine seismic array and methods for constructing such subarray are provided. A controlled phase marine seismic subarrays of the present invention are arranged to operate at a preselected depth and to provide generally downgoing (for angles of emergence from the array that are of interest) far-field pulses having phase spectra that match the phase spectrum of the vertically downgoing far-field pulse up to a ghost-notch frequency. The methods select the depth of operation and type of sources for the subarray, select a maximum number of identical elements and spacing based upon the highest incidence angle and frequency for which phase control is desired, and construct a plurality of parallel, linear, subarrays.

Controlled phase marine source subarray

Disclosed is a seismic surveying and data processing method to filter from seismic data any energy contributions that are not in the seismic line of profile. The surveying method requires a receiver geometry wherein at least one receiver is in and at least one receiver is out of the line of profile, so that in common offset gather or shot record plots, seismic events along the line of profile are aligned in time and out-of-plane energy takes the form of a series of sawtoothed seismic events arriving at different times in the different lines of receivers. Knowing the number of out-of-plane energies and their respective dips allows for the design of a filter, which is applied to the data with a computer, to null and thereby remove the effects of unwanted out-of-plane energy from the seismic survey data.

Reduction of sideswipe noise from seismic data by null steering

A method of deterministically computer generating a model of a response voltage waveform of a seismic receiver employed in a seismic, particularly marine, data gathering system, the model incorporating factors that have been identified as significant contributions to amplitude, such as directivity, divergence, attenuation, interbed multiples, and transmissivity. The model is generated from the mathematical manipulation of well log data and data gathering system characteristics into a seismic range equation, namely: ##EQU1## where E.sub.r (f)=received energy density

Method of generating seismic wavelets using seismic range equation

Methods for the construction of and controlled phase marine source arrays provide phase control for source array pulses radiated into emergence (or incidence) angles of interest. Phase control means that the phase spectra associated with source array pulses radiated in a generally downgoing direction, (i.e. for angles of emergence from the array that are of interest) will match the phase spectrum associated with a vertically downgoing source array pulse out to the 'ghost-notch' frequency associated with the vertically downgoing pulse. Although the range of emergence angles over which phase control is possible may be limited by the array geometry, proper attention to and control of array geometry and the radiation characteristics of the individual array source elements provide such controlled phase marine arrays.

Controlled phase marine source array

A marine seismic cable network including cables towed parallel to the surface of the sea at at least two depths for providing time analysis of reflected seismic data to dimensionally clarify characteristics of reflecting surfaces.

Marine seismic receiving system employing multiple depth hydrostreamer

An endfire seismic array comprises one or more marine seismic cables having a plurality of acoustic-to-electrical hydrophone receivers spaced therealong, each being operatively connected in combination so that as a unit an endfire receiving beam pattern with respect to any frequency across the seismic band is formed by causing the signals from the individual hydrophone receivers to be additive for that frequency. A plurality of cables results in a more narrow beam than a single cable. A geologic or lithologic formation that is a dip change from the norm may be detected either as an extra strong increase or decrease in signal, depending on the mode of use.

Endfire seismic receiver and method of use

A detailed seismic survey is achieved when there is general knowledge of a formation with generally steep dip by first locating the central location point and then mapping radial shot lines and receiver lines therefrom. The shot lines need to extend across the dip and beyond. The receiver lines need to extend a normal distance as with conventional 3-D seismic surveys. Shots from the central location progressing outwardly will reflect first with equal incident and reflector paths, then with a short incident to long reflector path, and finally to where long incident and short reflector paths are achieved. The data collected radially to describe the formation is near one-tenth of that required for conventional 3-D surveys where the shot lines and the receiver lines are mapped in parallel survey lines.

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Spring, TX, United States of America

Richard E Duren