Article pubs.acs.org/IECR
Determination of Saturation Pressures and Swelling Factors of Solvent(s)−Heavy Oil Systems under Reservoir Conditions Ping Yang, Huazhou Li,† and Daoyong Yang* Petroleum Systems Engineering, Faculty of Engineering and Applied Science, University of Regina, Regina, Saskatchewan S4S 0A2, Canada S Supporting Information *
ABSTRACT: Techniques have been developed to experimentally and theoretically determine saturation pressures and swelling factors of solvent(s)−heavy oil systems under reservoir conditions. Experimentally, PVT tests are performed to measure saturation pressures and swelling factors of a C3H8−heavy oil system and a CH4−C3H8−heavy oil system under reservoir conditions, respectively. Theoretically, the volume-translated Peng−Robinson equation of state (PR-EOS) together with the modified alpha function has been used to model phase behavior of the aforementioned solvent(s)−heavy oil systems. A binary interaction parameter (BIP) correlation has been developed for CH4−heavy oil systems based on the literature data. As for the CH4−C3H8− heavy oil system with a fixed composition, both saturation pressure and swelling factor increase with temperature. The PR-EOS together with the modified alpha function and the newly developed BIP correlation is able to predict the saturation pressures and swelling factors of the CH4−C3H8−heavy oil systems with average absolute deviations of 8.53% and 2.21%, respectively.
1. INTRODUCTION The Lloydminster area accounts for about 20% of the total Canadian oil production.1 The original oil in place (OOIP) in this region is about 19 billion barrels, 80% of which is discovered in formations with a thickness of less than 5 m. Primary reservoir drive energy in the Lloydminster area includes solution gas drive, rock compaction, and possibly limited edgewater drive.2 Due to the high oil viscosity, low solution gas available, and high sand production, the primary recovery factor is only 4−6% of OOIP.3 Waterflooding in some oilfields in this area resulted in oil recovery less than 10% because of the adverse mobility ratio of water and oil.2 After primary and secondary recovery, there is still about 90% of OOIP which is the target of the potential enhanced oil recovery (EOR) methods.4 Cold heavy oil production with sand (CHOPS) appeared to enhance primary production in the Lloydminster area in the mid to late 1980s.5 Due to no new sites for cold production, watering out of wells, and pressure depletion, CHOPS becomes uneconomic when the recovery attains 8−15% of OOIP.1 Therefore, numerous attempts have been made to apply thermal and nonthermal processes as the follow-up oil recovery strategies for the mature cold production reservoirs in the Lloydminster area. Thermal processes including cyclic steam simulation (CSS), steamflooding, and steam-assisted gravity drainage (SAGD) have been successfully used to recover heavy oil from thick sandstone formations with large porosity, high permeability, and high initial oil saturation.6 As an energy source, natural gas or other hydrocarbons are most frequently utilized to generate the steam as the heat carrier for thermal processes. Since onefifth to one-third energy content of the produced oil is required to generate the steam, there exists a significant operating cost for fuel consumption, while imposing an adverse environmental impact on the associated greenhouse gas (GHG) emissions. As for thin-formation reservoirs (i.e.,
