Abstract
The North American hydrocarbon supply market has been transformed by recent discoveries in regionally continuous reservoir units consisting of shale and tight sands. Effective porosity values in these reservoirs average as low as 2% to 6% with nanoDarcy permeability in situ. Classical means of determining resource-in-place values in these unconventional formations involves integrating core and log analysis methodologies, where numerous levels of uncertainty exist. Controlled pressure coring operations were conducted on a sequence of wells drilled into various maturity windows in the rapidly emerging liquids-rich Duvernay Shale through the course of 2011 and 2012. Capturing critical resource-in-place parameters and conducting quantitative analysis of volatile hydrocarbons contained within the cored interval required the development of new field and laboratory methodologies. These procedures represent the only currently available workflow capable of directly capturing and analyzing reservoir hydrocarbons from core material. Field operations and core preservation steps were developed to maintain the integrity of the hydrocarbon system during shipping and core processing. Additionally, a laboratory methodology was developed for preserving and extracting liquid hydrocarbons from core material. By quantitatively recombining these extracted fluids with volatile hydrocarbons captured from the controlled pressure coring operation, in situ PVT behavior of this single-phase volatile oil/condensate reservoir can be determined. As a result, recombined fluids can be compared to production samples for the purpose of studing pore scale mechanisms affecting production. Key breakthroughs were made during all stages of the workflow, and it was determined that core capture and surface handling operations are just as important as developing the new laboratory techniques required to understand resource uncertainty, effective fluid mobility, and PVT behavior. This paper describes and documents the key advancements made in coring operations and specialized core analysis, as well as their role in accurate quantification of hydrocarbons in place and the determination of in situ PVT behavior of the Duvernay Shale.
