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The AAPG/Datapages Combined Publications Database
AAPG Bulletin
Abstract
DOI: 10.1306/01221514195
Mineral-chemistry quantification and petrophysical calibration for multimineral evaluations: A nonlinear approach
Douglas K. McCarty,1 Paul N. Theologou,2 Timothy B. Fischer,3 Arkadiusz Derkowski,4 M. Rebecca Stokes,5 and Ann Ollila6
1Chevron ETC, 3901 Briarpark Drive, Houston, Texas 77042; [email protected]
2Chevron ETC, 1500 Louisiana Street, Houston, Texas 77002; [email protected]
3Chevron ETC, 3901 Briarpark Drive, Houston, Texas 77042; [email protected]
4Institute of Geological Sciences, Polish Academy of Sciences, Senacka 1, 31-002 Kraków, Poland; [email protected]
5Chevron ETC, 3901 Briarpark Drive, Houston, Texas 77042; [email protected]
6Chevron ETC, 1500 Louisiana Street, Houston, Texas 77002; [email protected]
ABSTRACT
The mineralogical complexity of mudstone reservoirs has led to the increased usage of multimineral optimizing petrophysical models for estimating porosity, water, and hydrocarbon volumes. A key uncertainty in these models is the log
response parameter assigned for each
log
equation related to each volumetric variable. Default parameter values are commonly used and often need to be modified by considering subjective local knowledge or intuition to achieve a result that is considered acceptable. This paper describes the methods developed at Chevron for calibration of mineral
log
response parameters using core data.
Mineral log
response parameters are controlled by the major and trace element chemistry of the individual minerals in the formation rock matrix. BestRock™ uses a nonlinear approach to optimize whole-rock chemistry with mineralogy to calculate individual mineral structural formulas and trace element associations from which certain
log
response parameters can then be calculated. Accurate quantitative phase
analysis
(QPA) to determine mineral content is a critical step in the process, which is achieved here by rigorous sample preparation methods and QPA by x-ray diffraction (QXRD).
The QXRD in combination with whole-rock elemental analyses are processed using Chevron’s BestRock optimization software to provide refined quantities of the mineral species present in the formation, their structural formulas, and their predicted wireline log
responses. Calibrated petrophysical models are built from the information obtained from the QXRD and BestRock results.
The method described herein provides an independent and robust method for determining petrophysical parameters that is independent of the interpreter, quick to implement, and supported by quantitative measurements.
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