N. Taskin Akpulat1, Cynthia L. Riediger1, Lisa Griffith2, Norm Corbett2, Brian A. Zaitlin2
(1) University of Calgary, Calgary, AB
(2) PanCanadian Petroleum Limited, Calgary, AB
ABSTRACT: Sedimentology and Geochemistry of the Lower Cretaceous Ostracode Zone with Implications for Hydrocarbon Generation Kinetics and Quantitative Basin Modeling, Western Canada Foreland Basin
The Ostracode Zone in southern Alberta represents predominantly lacustrine deposition, and is a key stratigraphic unit within the Mannville Group of the Western Canada Sedimentary Basin due to its regional extent, complicated stratigraphy, hydrocarbon source and reservoir potential and the presence of limestones within a predominantly siliciclastic stratigraphic succession. The purpose of this study is to show the facies changes within the Ostracode Zone across the basin and to display the main characteristics of these two major facies associations by integrating source rock geochemistry, hydrocarbon generation kinetics and quantitative basin modeling.
Two major facies associations within the Ostracode Zone are recognized, the Restricted (RLFA) and the Open-Lacustrine Facies Associations (OLFA). RLFA is composed of three informal stratigraphic units that include the Basal Ostracode Sandstone Unit (BOSU), Bantry Shale and Ostracode Limestone Facies. OLFA is made up of three informal stratigraphic units that include the Mixed Ostracode Unit (MOU), Bantry Shale Equivalent and Ostracode Limestone. The MOU was differentiated in the lacustrine foredeep (high accommodation) while BOSU was deposited in low accommodation space. The hydrocarbon source rock facies of the Ostracode Zone is best developed in the MOU and reservoir facies are developed in the BOSU.
The Lower Cretaceous Ostracode Zone hydrocarbon source rock has contributed significant quantities of oil (oil family Q) to Lower Cretaceous Mannville Petroleum Systems. Quantitative basin modeling suggests that the Ostracode Zone passed through the main oil window between about 40 to 30 Ma. The Ostracode Zone has been in the late mature stage of hydrocarbon generation since Middle Oligocene time.
AAPG Search and Discovery Article #90906©2001 AAPG Annual Convention, Denver, Colorado