Integrated Reservoir Characterization of the Duvernay Play (Alberta, Canada): From Nanometer Scale to Regional Basin Scale

Abstract

The Duvernay Formation has been known for decades as the source rock of the Leduc and Swan Hill oil and gas plays. Today, the Duvernay Formation is also known as an attractive unconventional play because of its ability to produce gas-associated liquids. We believe that diligent reservoir characterization is the key for economic success in this deep unconventional play. One has to adapt to the scale of the observation of unconventional resource plays (1 nm to 1 micron) and to use special imagery techniques (e.g. SEM, Ion-milled SEM) to characterize the nature and classes of the pore system. For the Duvernay Formation, porosity typing was conducted on 2D and 3D Focused Ion Beam SEM images. These images showed that between 69% and 85 % of the porosity is kerogen porosity with an average of 75% for the studied wells. It is important to recognize that although organic porosity is also developed in the less mature wells, the biggest pores were found in the most mature areas. Careful pore measurement allowed a quantified approach. Liquid yield was plotted against average pore size and a clear trend was seen in the pore size distribution. “Pore size” tends to increase with maturity. The pore volume and/or the number of accessible pores would increase (increase in adsorbed gas and HC in pore volume; and thus, in permeability) following the same trend as the mean pore size. With caution, if additional observations from other wells in the Duvernay play confirm these observations, we can conclude that the porosity and more importantly the permeability are primarily the result of thermal maturation of the kerogen. Some previous studies did not find the same results due to an erroneous estimation of maturity using vitrinite reflectance whereas some other studies did not have the appropriate diversity and quality of sample throughout maturation phase window to obtain statistically representative results. This nanoscale pore system characterization is integrated at the regional scale with subsurface data (wells, seismic) and outcrop work from literature. Reservoir modelling and basin modeling were found to be excellent tools to combine TOC, source rock quality and potential (HI/OI) and maturation history at the regional scale of the Duvernay.

AAPG Datapages/Search and Discovery Article #90259 ©2016 AAPG Annual Convention and Exhibition, Calgary, Alberta, Canada, June 19-22, 2016