Leland Stanford Junior University

Petrophysical Consulting, Inc.

Amos M Nur

Jerry M Harris

Gary Mavko

Jack Dvorkin

Hezhu Yin

A section is prepared from a specimen of porous media, e.g., Rock, typically including filling the pore spaces with a dyed epoxy resin. A color micrograph of the section is digitized and converted to an n-ary index image, for example a binary index image. Statistical functions are derived from the two-dimensional image and used to generate three-dimensional representations of the medium. Boundaries can be unconditional or conditioned to the two-dimensional n-ary index image. Desired physical property values are estimated by performing numerical simulations on the three-dimensional representations. For example, permeability is estimated by using a Lattice-Boltzmann flow simulation. Typically multiple equiprobable three-dimensional representations are generated for each n-ary index image, and the multiple estimated physical property values are averaged to provide result.

Numerical method of estimating physical properties of three-dimensional porous media

The present invention includes a method for overpressure detection and pore pressure change monitoring in subsurface gas, liquid hydrocarbon, or water reservoirs from compressional- and shear-wave measurement data. As part of this method, one or more Poisson's ratios are determined from field-based measurement data and are then compared against known Poisson's ratio values representative of the particular subsurface formation type. By applying a Poisson's ratio&mdash;pore pressure criterion that is appropriate for that type of formation, an overpressure in the formation is identified.

Method for overpressure detection from compressional-and- shear-wave data

A low impedance acoustic source suitable for used in down-hole well logging includes a mechanical transformer for impedance matching of the source to the surrounding environment. Elliptically shaped flexible beams are positioned along the long axis of an ellipse, and a pump is oriented along the long axis of the ellipse for driving the flexible beams. In a preferred embodiment the pump comprises first and second stacks of transducers which engage the flexible beams at opposing ends with the two stacks of transducers operating in a push-pull mode of operation. Rigid extension at opposing ends of the flexible beams function as levers in translating the motion of the transducers to the flexible beams. A rigid support rod is positioned along the long axis of the ellipse in engagement with the rigid extensions at fulcrum points, and an adapter associated with each stack of ceramic transducers engages and drives the rigid members about the fulcrum point. In a preferred embodiment the flexible beams permit fluid to flow around the beams for pressure equalization in deep hole applications.

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Stanford, CA, United States of America

Amos M Nur