Exxonmobil Upstream Research Company

Xinyou Lu

Dennis E Willen

Scott C Hornbostel

Leonard J Srnka

James J Carazzone

Charlie Jing

Thomas A Dickens

Brent D Wheelock

Olivier M Burtz

Enru Liu

Brian J Fielding

Shiyu Xu

Dezhi Chu

Philip J Summerfield

Yaping Zhu

David D McAdow

Michael A Payne

Carrie X Zhan

Ruben Quintanilla

Anne K Rutledge

John E Bishop

Xin Zhan

Carrie Xin Zhan

A method for inversion of 4D seismic data, including: determining time shift between baseline and monitor geophysical datasets; determining time strain from the time shift; iteratively repeating until a stopping criteria is satisfied, performing an iterative elastic AVO inversion with a 4D difference providing an update, from an initial model including the time strain, to generate an updated time strain and an updated physical property model, wherein the stopping criteria is a misfit between synthetic data generated from the updated physical property model and the 4D difference being within a predetermined noise level generating final values for the physical property model; and converting, with a rock physics model or a reservoir simulation model, the final values to saturation and/or pressure changes for a subsurface region.

4D time shift and amplitude joint inversion for obtaining quantitative saturation and pressure separation

A method and apparatus of constructing a signal for a controlled source electromagnetic survey is described. In one embodiment, a method is described that includes determining a first waveform and a second waveform, the first waveform and second waveform related to a combined frequency spectrum and bandwidth associated with a geophysical survey line. Then, a signal is constructed by sequencing the first waveform with the second waveform. This signal may be utilized in a transmitter, which may be pulled by a vessel along the geophysical survey line.

Method and apparatus for utilizing time division multiple waveform transmitting

A hydrocarbon exploration method is disclosed for generating anisotropic resistivity models of a subsurface reservoir from seismic and well data using a rock physics model. In one embodiment, the method comprises: selecting wells within a region of interest (); obtaining a plurality of rock properties () and adjusting selected rock parameters () in the calibration of the rock physics model at the well locations; inverting porosity and shale content from seismic data (); propagating the calibrated rock physics model to the region of interest () and calculating effective resistivity for the entire region of interest (). The inventive method also provides for analyzing the uncertainty associated with the prediction of the resistivity volume.

Method for generating anisotropic resistivity volumes from seismic and log data using a rock physics model

Method for real time monitoring of the waveform transmitted by an electromagnetic survey source, using a near-source monitoring receiver to measure electromagnetic field and transmitting the measured signal in real time to a control location.

Source monitoring for electromagnetic surveying

A method for suppressing measurement system signature, or artifacts, that arise when controlled source electromagnetic survey data are inverted to obtain a resistivity image of a subsurface region. The method involves identifying regions () where the image has low or rapidly varying sensitivity to data acquired by a given receiver, typically regions close to and under the given receiver. Then, in the iterative inversion process where a resistivity model is updated to minimize an objective function, the model update is modified () to reduce the impact of such low sensitivity regions on the update.

Inversion of CSEM data with measurement system signature suppression

Method for efficient inversion of controlled-source electromagnetic survey data to obtain a resistivity model of the subsurface of the survey area. The method extracts the dimensions and location of sub-surface structures as they may be revealed by existing seismic or other available high resolution survey data from the subsurface area (). This structure geometry information is used to construct a discretization (grid, or mesh) for the inversion computation () that is different from the mesh used for the forward modeling calculations () in that (a) it has fewer and hence larger cells; and (b) the cells honor the assumed structural information. The inversion need only extract resistivity information (), the geometry of the resistive structures being specified by the inversion mesh.

Method for determining physical properties of structures

Method and computer program for accepting controlled-source electromagnetic ('CSEM') source and receiver data () as time series, transforming these data into the time-frequency domain, and reducing these data and survey metadata to a form suitable for interpretation or inversion. The invention includes: a number of processing tools or programs (), each designed to take a specific action on CSEM data or metadata, combine data types in some way, and/or provide a visual representation of data; a Graphical User Interface () to specify the action of specific tools () on specific data, supply parameters to tools, and monitor progress of the processing project; and a specified common internal data format, so that processing tools may be applied in various orders () during different processing flows and processed CSEM data can be passed on to interpretation or inversion systems.

Electromagnetic data processing system

A method, apparatus and computer program for improving the signal-to-noise ratio of a signal S(t), S(t) containing Signal and noise, are disclosed. A measurement of S(t) at a frequency-of-interest is obtained. Noise measurements of S(t) at one or more noise frequencies where the Signal portion of S(t) is expected to be small are obtained. The noise at the frequency-of-interest is estimated using the noise measurements at the one or more noise frequencies. The estimated noise is subtracted from the measurement of S(t) at the frequency-of-interest.

Estimating noise at one frequency by sampling noise at other frequencies

A method is disclosed for determining earth vertical electrical anisotropy from offshore electromagnetic survey measurements. The method requires both online and offline data, which includes at least one electromagnetic field component sensitive at least predominantly to vertical resistivity and another component sensitive at least predominantly to horizontal resistivity. Using a horizontal electric dipole source, online Eand offline Hmeasurements are preferred. For a horizontal magnetic dipole source, online Hand offline Edata are preferred. magnetotelluric data may be substituted for controlled source data sensitive to horizontal resistivity. Maxwell's equations are solved by forward modeling or by inversion, using resistivity models of the subsurface that are either isotropic or anisotropic.

Method for determining earth vertical electrical anisotropy in marine electromagnetic surveys

Method for completely specifying orientation of electromagnetic receivers dropped to the ocean bottom in an electromagnetic survey. Survey data are selected, rejecting noisy data with long offsets and data where the receiver has saturated with short offsets (). A model is developed comprising three independent receiver orientation angles completely specifying the receiver orientation in three dimensions, and an earth resistivity model including a water layer and possibly an air layer (). Maxwell's equations, applied to the model and the selected data, are then inverted to determine the receiver orientations ().

Method for determining receiver orientations

System and method for maintaining vertical alignment of the electrodes of a dipole antenna as it is towed submerged in water. The system includes a source of vertical tension on the antenna, a towline attachable to a tow vessel at one end and to a negatively buoyant tow body at the other, a source of balancing force to make the net vertical force on the antenna when submerged substantially zero, and at least two tag lines used in specified ways to connect the antenna to the tow body or directly to the towline.

System and method for towing subsea vertical antenna

Waveforms for controlled source electromagnetic surveying. The waveforms have frequency spectra that include three or more frequencies spaced at substantially equal intervals on a logarithmic frequency scale and spanning a bandwidth of about one decade or more, at least three of which frequencies have approximately equal corresponding amplitudes.

Logarithmic spectrum transmitter waveform for controlled-source electromagnetic surveying

A method for tracking a sinusoidal electromagnetic signal in noisy data using a Kalman filter or other tracking algorithm. The method is useful for controlled source electromagnetic surveying where longer source-receiver offsets can cause the source signal to decay significantly and be difficult to retrieve from magnetotelluric or other electromagnetic background.

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Missouri City, TX, United States of America

Xinyou Lu