UBC Theses and Dissertations
Utility of instrumented indentation for the optimization of horizontal wellbore completions with examples from the Montney formation of Alberta and British Columbia Hazell, Arthur James Scott
Unconventional shale reservoirs are commonly exploited by drilling horizontal wellbores up to several kilometers in length. Hydraulic fracture completions of a wellbore are designed, in part, based on the geomechanical properties of the reservoir. The completion program is executed in a series of stages, typically spaced at regular intervals along the length of the lateral, without consideration of variable lithology and geomechanical properties that may exist along the length of the borehole. Assessing the geomechanical properties and stress conditions along the lateral has proven difficult due to the cost and challenge of obtaining core samples for analyses. Drill cuttings derived during drilling provide an opportunity to characterize the reservoir geomechanical properties, including the elastic moduli. If such small samples can be tested reliably and be shown to be scalable to the reservoir, the geomechanical variability along a wellbore can be measured and exploited with planned hydraulic fracture completions at geomechanical sweet spots. In this thesis, the utility of instrumented indentation for characterizing geomechanical variation in shale core chips and drill cuttings is evaluated. Indentation testing on mineral and shale samples assesses the effects of indentation and sample parameters on indentation results, suggesting that samples of size 841 µm, tested at 50 – 200 mN load, with at least 83 standard indentations are likely to provide repeatable and representative mean indentation results. Indentation can characterize geomechanical variability between shale core chips and drill cuttings samples with centimeter differences in sample depth. Repeatable indentation results are compared for indentation tests, as well as unoriented and oriented subsamples; oriented subsamples showed 2 – 18 % greater mean indentation modulus in samples with bedding oriented parallel to the direction of indentation, compared to bedding perpendicular, indicating the effects of mechanical anisotropy on indentation results. Moderate correlations are presented between mean indentation modulus and static (R² = 0.53) and dynamic (R² = 0.45) Young’s moduli, for Montney Formation shales. Geomechanical correlations with mineralogy suggest mean indentation results are controlled by dominant, stiff components of shale, with minimal influence from clay composition. Variability in indentation results can be applied as an index through geomechanical depth profiles.
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