Using Molecular Transformations to Monitor Thermal Recovery Operations in Oil Sands and Heavy Oil Reservoirs

Marcano, Norka¹; Bennett, Barry; and Larter, Steve
¹[email protected]

Experiments to assess production upgrading of heavy oil and oil sands under simulated high temperature thermal recovery reservoir conditions were conducted to evaluate mechanisms and sources of the produced light hydrocarbon compounds that directly affect oil fluid properties. The experiments also enabled the identification of geochemical proxies to monitor in situ upgrading operations. The main results demonstrate that native oil sands bitumens are naturally characterized by a lack of n-alkane and isoprenoid alkane hydrocarbons and generate a relatively uniform pattern of n-alkanes up to C30 and isoprenoid alkanes such as pristane and phytane, under high temperature simulated thermal recovery conditions. The generation of tricyclic condensed aromatic hydrocarbon molecules, some of which are not present, or are at very low concentration in the original oil sand, appear to be good indicators of the progress of thermal conversion.The calibration of such systems may be used to track process oil temperature histories from produced oil analysis. The results also suggest that the asphaltene fraction is the main source of the light hydrocarbons produced during the simulated upgrading process. A case study from the Alberta basin is shown to demonstrate the use of the identified geochemical proxies in combination with geochemistry baseline studies to monitor thermal recovery operations of oil sands. We conclude that the neoformation of compounds such as alkylanthracenes at thermal recovery conditions, components absent or not abundant in unaltered oils, are suitable proxies to monitor steaming chamber progression and temperature from analysis of produced oils from steam assisted thermal recovery (SAGD) processes, as well as for monitoring more dramatic changes under high temperature in situ upgrading conditions. Monitoring of all fluid compositions prior to and during a recovery operation assists in optimizing recovery and reducing costs and is thus recommended. The results also suggest that severely biodegraded oils, with high contents of asphaltenes, may have a high potential to be significantly upgraded through very high temperature (350°C) CSS steam recovery.

AAPG Search and Discovery Article #90166©2013 AAPG International Conference & Exhibition, Cartagena, Colombia, 8-11 September 2013