Mechanical Characterization in Unconventional Reservoirs: A Facies-Based Methodology
- Dave Amendt (ConocoPhillips Company) | Seth Busetti (ConocoPhillips Company) | Quinn Wenning (ETH Zurich)
- Document ID
- Society of Petrophysicists and Well-Log Analysts
- Publication Date
- October 2013
- Document Type
- Journal Paper
- 457 - 464
- 2013. Society of Petrophysicists & Well Log Analysts
- 3 in the last 30 days
- 398 since 2007
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A new core-testing protocol has been created to characterize rock mechanical parameters based on lithologic composition and rock texture. The goal is to characterize the main rock types in the basin using the geologic model as the integration point. Four individual core plugs are cut at the same depth reference and rock facies. Each plug is brought to failure in a single-stage triaxial test, the four independent tests are used to construct a Mohr-Coulomb failure envelop. Bedding perpendicular and parallel Brazilian tests are also performed to measure tensile strength. Mineral composition is determined from the remaining carcass of rock and thin sections are cut for petrographic analysis.
High-quality mechanical core-test calibration data are a fundamental requirement to reduce stress analysis uncertainty. Our workflow includes systematic qualitycontrol measures. Computed tomography (CT) scans are made on bulk core and test plugs to verify the sample condition. Stress-strain data are compared to validate the shear-failure parameters and confirm elastic-parameter repeatability within a test set. Tests that fail the qualitycontrol process are removed and the mechanical characterization is performed with only the remaining data. For each rock type, representative distributions of Young’s modulus, Poisson’s ratio, unconfined compressive strength, cohesion and angle of internal friction are generated.
The mechanical data supports log-based stress models by providing the static-to-dynamic transforms of the elastic properties. The data also supports more complex numerical models, such as those requiring layer-by-layer properties, using the concepts of mechanical lithofacies and mechanical stratigraphy. The mechanical stratigraphy is constructed by integrating the mechanically characterized rock types with a stratigraphic layering model created from core or log descriptions. This geologically conditioned mechanical facies model containing elastic, inelastic, and failure properties is developed as an alternative but complimentary mechanical methodology to the standard log-derived elastic model.
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