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Up-scaling of Rock Mechanical and Petrophysical Properties from Grain Scale to Log Scale by Point-Load and Wedge Indentation Tests
Ramos, G. G. and Chin, L.Y.
ConocoPhillips, Bartlesville, OK, USA
Enderlin, M.B.
Gearhart Co., Fort Worth, Tx, USA
Copyright 2008, ARMA, American Rock Mechanics Association
This paper was prepared for presentation at San Francisco 2008, the 42nd US Rock Mechanics Symposium and 2nd U.S.-Canada Rock Mechanics Symposium, held in San Francisco, June 29-July 2, 2008.
This paper was selected for presentation by an ARMA Technical Program Committee following review of information contained in an abstract submitted earlier by the author(s). Contents of the paper, as presented, have not been reviewed by ARMA and are subject to correction by the author(s). The material, as presented, does not necessarily reflect any position of ARMA, its officers, or members. Electronic reproduction, distribution, or storage of any part of this paper for commercial purposes without the written consent of ARMA is prohibited. Permission to reproduce in print is restricted to an abstract of not more than 300 words; illustrations may not be copied. The abstract must contain conspicuous acknowledgement of where and by whom the paper was presented.
ABSTRACT: This is a laboratory and field technique of scaling-up rock mechanical and petrophysical properties, such as compressive strength and bulk compressibility, from grain-scale to log-resolution scale. The main scaling tools are the point-load wedge penetrometers. The objective is to extrapolate the physical and mechanical properties from core samples to larger volumes of numerical geomechanical models grids or cells. The scaling method starts at grain-scale using a conventional point-load indenter that creates a conical depression onto the rock surface. A single PLP indentation has a scale of investigation of a few grain diameters, but contiguous point-indentations, or linear wedge indentations expand the investigated volume geometrically. The geometry of the dent is a function of rock strength, modulus, petrophysical properties, indenter geometry and applied normal force. The depths and widths of point- and line-indentations were calibrated with plug-measured uniaxial compressive strength, P-wave velocity, and modulus. Laboratory and field cases are presented. Grain-scale strengths show wide variances relative to whole-core strengths. However, the penetrometer indices of compressive strengths are shown to compare favorably with conventional measurements on plugs, core ultrasonic velocity, scratch-tester, and with those predicted by the wells sonic and density logs. With additional log data on porosity and clay-volume, scaling up to a simulators grid scale followed usual geomodeling techniques.
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