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Horizontal Stress Magnitude Prediction

IP.com Disclosure Number: IPCOM000237696D
Publication Date: 2014-Jul-02

Publishing Venue

The IP.com Prior Art Database

Abstract

The invention is a novel method to predict horizontal stress magnitudes in the subsurface. The challenge is that present-day stresses are a snapshot in the context of evolving geologic processes, and that present-day measurements cannot account for the history of a formation, in particular for viscous deformation during burial. The invention combines log-based information from which stress variations with depth can be inferred with stress trend information that encompasses stress history information, and calibrates the predicted horizontal stress magnitude with a data point of measured horizontal stress magnitude and corresponding depth.

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Horizontal Stress Magnitude Prediction

The invention is a novel method to predict horizontal stress magnitudes in the subsurface. The challenge is that present-day stresses are a snapshot in the context of evolving geologic processes, and that present-day measurements cannot account for the history of a formation, in particular for viscous deformation during burial. The invention combines log-based information from which stress variations with depth can be inferred with stress trend information that encompasses stress history information, and calibrates the predicted horizontal stress magnitude with a data point of measured horizontal stress magnitude and corresponding depth.

A detailed description of the invention is provided in the attachments: "Horizontal stress modeling - Text.pdf" and "Horizontal stress modeling - Figures.pdf". A short description: Our method is able to predict effective horizontal stress magnitudes from the following input that is typically available in field applications: a profile of effective vertical stress magnitudes, a data point of effective horizontal stress magnitude and corresponding depth, and a profile of the estimated effective stress ratio. We note that the product of effective stress ratio and effective vertical stress magnitude should deliver the effective horizontal stress magnitude for a zero-lateral strain case with constant, perfectly linear elastic materials. However, typically the behavior of subsurface formations cannot be accurately described this way. Our new method therefore considers the product of estimated effective stress ratio and effective vertical stress magnitude as a base function, and analyzes its trend and perturbations. Using trend and perturbations the method uses a weight function to compute a non-dimensional shape function that reflects the appropriate shape of the horizontal stress magnitude profile. The weight function used in the present work depends on the profile of vertical stress magnitude, but is not so limited and may also be tied to material properties that can be derived from logging data, or obtained otherwise, or estimated. The shape function is calibrated using the data point of effective horizontal stress magnitude and corresponding depth to obtain the final p...