Schlumberger Technology Corporation

Westerngeco L.l.p.

Vladimir L'vovich Druskin

Tarek M Habashy

Aria Abubakar

Mikhail Zaslavsky

Abdurrahman Sezginer

David Lee Alumbaugh

Benoit Couet

William John Bailey

Ian D Bryant

Michael David Prange

Hugues A Djikpesse

Carlos Torres-Verdin

Ashok Belani

Metin Karakas

Sheng Fang

Leonid Aronovich Knizhnerman

Ping Lee

To construct a reduced order model of a subterranean structure, a model reduction algorithm is applied to produce the reduced order model that is an approximation of a true model of the subterranean structure. The model reduction algorithm uses interpolating frequencies that are purely imaginary to enhance computational efficiency of the algorithm.

Constructing a reduced order model of an electromagnetic response in a subterranean structure

Source-receiver compression is used to help design surveys and mitigate the computational costs of data set inversion. The source-receiver compression is based on data redundancy and sensitivity. More particularly, a compressed source array is produced for minimum redundancy and maximum sensitivity to reservoir model parameters. The synthesized transmitter array has a reduced number of sources, thereby reducing the number of forward model simulations needed to carry out the inversion. Furthermore, the data collected at the receivers employed in the survey can be compressed. This has the implication of reducing the computational cost of constructing the Jacobian matrix and inverting the corresponding Hessian matrix.

Data set inversion using source-receiver compression

A method is disclosed for performing optimal gridding in reservoir simulation, the method comprising: establishing an optimal coarse grid proxy that can replace all or parts of a fine grid with a coarse grid while preserving an accuracy of a predefined simulation model output, the step of establishing an optimal coarse grid proxy including finding, by using an optimizer, a best fit of a coarse grid output to the output of a training set.

Method for optimal gridding in reservoir simulation

A method of determining the nature of a submarine or subterranean reservoir having an electromagnetic characteristic is described. The method comprises analyzing data associated with the application of a time varying electromagnetic field from above the reservoir using a data analysis methodology that does not utilize an estimate of the reservoir's geometry in determining one or more characteristics of the reservoir.

Pixel based inversion method for surface electromagnetic measurement

The present invention involves a method for modeling the response of an electromagnetic tool to a subsurface formation including: (i) formulating a set of frequency-domain Maxwell equations, including a Maxwell operator, using a three-dimensional representation of the subsurface formation; (ii) generating a Krylov subspace from inverse powers of the Maxwell operator by computing actions of an inverse of the Maxwell operator; and (iii) repeating (ii) as needed to achieve convergence of a frequency-domain solution that characterizes the modeled response of the electromagnetic tool to the subsurface formation. The invention further involves a related apparatus for modeling the response of an electromagnetic tool to a subsurface formation and a related article of manufacture having a computer program that causes a computer to perform the inventive method.

Method, apparatus, and article of manufacture for solving 3D Maxwell

Inception of hydrocarbon extraction from a reservoir causes the oil-water interface to warp and cusp toward the extraction gates along a well. This invention proposes time-lapse DC/AC measurements with an array of permanently deployed sensors in order to detect and estimate the change in geometry and proximity of the oil-water interface as a result of production, and therefore as a function of time. The estimation is carried out with a parametric inversion technique whereby the shape of the oil-water interface is assumed to take the form of a three-dimensional surface describable with only a few unknown parameters. A nonlinear optimization technique is used to search for the unknown parameters such that the differences between the measured data and the numerically simulated data are minimized in a least-squares fashion with concomitant hard bound physical constraints on the unknowns. The proposed estimation procedure is robust in the presence of relatively high levels of noise and can therefore be used to anticipate deleterious water breakthroughs, as well as improve the efficiency with which the oil is produced from the reservoir.

Method for sensing and estimating the shape and location of oil-water

A method of determining the resistivity of an underground formation surrounding a cased borehole including the steps of: a) passing a current along a first pan of the casing and measuring the voltage; b) passing a current along a second part of the casing and measuring the voltage, the second part being spaced from the first part by an intermediate region; c) measuring voltages between the first part of the casing and a point in the intermediate region and between the second part of the casing and the same point; and d) using the measured voltages to derive the resistivity of the formation. A logging tool for use in determining the resistivity of an underground formation surrounding a cased borehole includes a body having first and second pans separated by an intermediate region, wherein: a) the first body part includes a first current source having spaced electrodes arranged so as to enable a current to be passed through a corresponding pan of the casing and a voltage monitor having spaced electrodes for measuring the voltage across the pan of the casing; b) the second body pan includes second current source having spaced electrodes arranged so as to enable a current to be passed through a corresponding pan of the casing and a second voltage monitor having spaced electrodes for measuring the voltage across the part of the casing; and c) the intermediate region includes intermediate voltage monitors including electrodes for measuring a voltage between the first pan of the casing and a point in a corresponding intermediate region of the casing, and between the second part of the casing and the point in the intermediate region of the casing so as to enable the formation resistivity to be derived from the measured voltages.

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Ridgefield, CT, United States of America

Vladimir L'vovich Druskin