Seiscom Delta Inc.

Other

Nigel A Anstey

Michael J Castelberg

Clyde W Hubbard, Jr

Emmett J Klein, Jr

Fulton Koehler

Ronan F O'Doherty

Ronan Francis O'Doherty

Mehmet T Taner

A method for interpolating the environment and geological age at all levels in a borehole from information provided by a limited number of depths and the use of a synthetic stratigraphic cross-section for the interval between these depths. In hydrocarbon exploration, a borehole provides a suite of logs, plus estimates of geologic age at a number of spaced markers. This method uses a sea-level cycle chart, a calculation of subsidence from the thickness of the interval, and postulated values for several variables. If it is known that the supply of sediment always exceeded the available accommodation during deposition, the corresponding synthetic cross-section may then be optimized for geological plausibility (as gauged by visual observation or quantitative criteria) by perturbing the postulated variables and iterating the calculations. Otherwise, the additional step of determining where in the interval the accommodation exceeded the sediment is performed by comparing the signs of the slopes of an observed log estimating sediment grain size and a calculated log estimating layer thickness.

Method of distinguishing types of geologic sedimentation

A method for identifying the boundaries between sequences of rocks laid down in different depositional regimes. The approach used is to search, in well logs or seismic data, for a statistic characteristic of such regimes, and for breaks in that statistic. The preferred statistic used in the method of the present invention is the first moment of the power spectrum of the wavenumber of a suitable physical property as a function of depth. This statistic is calculated rapidly and with excellent depth resolution from the complex-valued autocorrelation function at its zero and unit lag values, respectively, and displayed as a single variable in black-and-white or color. The method of the present invention further includes manipulations that achieve the approximate conversion of the scale (and corresponding display) from its initial dependence on depth to one that is displayed as a function of geologic time.

Method of distinguishing geological sequences and their boundaries

A rotary vibrating system is used in surveys of the acoustic properties of the shallow earth. The vibrator itself is of eccentric-mass (or 'swinging-weight') form. Coupled to a flywheel, it decelerates freely from a selected high frequency to a selected low frequency. The observed deceleration rate is manipulated to give a measure of the acoustic properties of the near-surface. The eccentricity of the vibrator is then annulled, and the flywheel and vibrator accelerated back to the selected high frequency for another measurement at another location. A display in map form is provided to facilitate visual interpretation of the results.

Vibratory ground-survey system

Seismic exploration for hydrocarbons may use an eccentric-mass (or 'swinging-weight') vibrator as the seismic source. According to the invention, a vibrator undergoes alternate periods of acceleration and deceleration, during one of which the vibration may be annulled. For example, the rotating mass may be formed in a plurality of parts; then the several parts are disposed in a manner that rapidly and automatically balances their vibratory forces during the period when the vibration is to be annulled, and that adds their vibratory forces during the other period. The invention further provides for modulation of the frequency-time relation during deceleration, for synchronization of several vibrators, and for modulation of the effective output force by controllable variation of the mass, eccentric radius or relative phase of the several parts of the rotating mass; in such modulation, only resultant forces are applied to the vibrator bearings.

Swinging-weight vibrator for seismic exploration

A method of seismic exploration by which substantially plane or substantially cylindrical seismic energy waves are simulated by combining reflectional signal traces of conventional spherical seismic waves. Seismic sources and receivers are established in sets at positions such that at least one of the sets includes a plurality of positions spaced over an extent of the area being explored having either one or two dimensions which are large relative to a seismic energy wavelength. Seismic energy is imparted into the earth from the sources and signals are generated in response to seismic energy received at the receivers. The generated signals are then combined into a form simulating the reflection response of the earth to seismic energy having a substantially continuous wavefront in either one dimension, simulating a cylindrical seismic energy wave, or two dimensions, simulating a plane seismic wave.

Seismic exploration with simulated plane waves

Apparatus for conducting seismic reflection surveys from oil tankers or other bulk liquid carriers in the course of their normal journeys. Seismic sources and detector apparatus are mounted in the ballast tanks. Pulse compression techniques may be used, and may take the form of a mechanical flail acting on the hull of the ship.

Means for seismic prospecting from bulk liquid carriers

A color dot display and method of forming same by applying colors to dot areas within a matrix of cells in accordance with a color code defining the number of dot areas in the cells, and their locations in the cells, to receive the colors. The proportion of dots of a particular color in a cell defines the representation or saturation of that color in the cell, while the superposition, whether visual or physical or both, of the dots of the various component colors in a cell defines the apparent or resulting color of the cell.

Color dot display

A new and improved method of forming color graphic displays from input data is disclosed. In the displays so formed differing colors quantitatively identify and indicate differing values or ranges of values of the data. The input data are processed to determine sample values for data display points, and numerical codes from an assignment table are assigned according to the sample values. The assigned codes are arranged into output sequences for each of plural component displays of the final display, and the component displays formed and displayed in superposition to form the color graphic display with colors therein graphically indicating the data.

Method of forming color graphic displays from input data

A synthetic display is provided, in cross-sectional form, of the theoretical strength of seismic reflections. The theoretical strength is computed from calculated inverval-velocity values and known or estimated density values. By comparison of this synthetic reflection-strength display with the observed reflection-strength display, useful conclusions may be drawn about the nature of geological materials and the complex origin of reflections.

Synthetic display of seismic reflection strength

The present invention relates to a model, and the making of such model, of subsurface features of the earth, utilizing a plurality of processed seismic sections spaced apart in a manner representing the disposition of the seismic profiles along seismic survey lines from which they came. The technique facilitates the making of interpretive geological judgements, and is of particular utility when direct indications of hydrocarbons exist.

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Sevenoaks, United Kingdom

Nigel A Anstey