--> Mapping Duvernay Mineralogy: From Core to Log to Field

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Mapping Duvernay Mineralogy: From Core to Log to Field

Abstract

Chevron Canada, in partnership with KUFPEC, has acquired rights to the Devonian Duvernay Formation across 325,000 acres of land in West-Central Alberta. The Duvernay Formation in this region is dark organic-rich calcitic/siliceous marine shale interbedded with argillaceous limestone with an average thickness of 50 m at depths of 3000 - 4000 m. Organic content ranges between 2% - 6%, porosity between 3% - 8%, pore pressure gradient between 18-20 kPa/m and fluid varies from black oil to dry gas. Like other shale plays, the Duvernay Formation requires hydraulic fracture stimulation to maximize extraction of hydrocarbons. Economic production will not merely come from intervals of favorable properties but will also depend on the completion design. The rock elasticity property has significant controls on hydraulic fracture effectiveness and is directly related to the mineralogy of the formation. Understanding and being able to map the mineralogy of the Duvernay Formation will assist us in prioritizing development areas and fracturing strategies. Mineral modeling with Multimin in Geolog®* Formation Evaluation software requires some advance logging suites but most of the wells in this field do not have suitable log data to be properly modelled. Whole cores from six Chevron wells (350 m) from the Duvernay Formation across the Chevron land base were tested with QXRD and Best rock from 180 samples. A process called NIMBLE in Geolog® allows calibration from these core data sets to wells with only quad combo logs. This allows for maximum use of legacy data to understand mineralogy and rock property variation vertically and laterally. One of the challenges involved during multimin modeling of a field is in understanding when normalization of the logs is needed. Utilization of multi-vendor historic logs introduces additional uncertainty in the multimin model, however additional constraints, such as quartz and calcite volume relationship, reduce the model uncertainty. Utilization of distinct stratigraphic packages in the Duvernay and applying different models to each zone has also reduced the uncertainty. Geologically distinct areas in the Duvernay are more carbonate rich than others and this impacts log reading throughout the area. Integration of geology, petrophysics and rock mechanics will ultimately allow for more effective hydraulic fracture design in appraisal and development. *Trademark of Paradigm Geophysical Ltd.