Abstract
A novel experimental procedure was proposed to investigate the phase behavior of a solvent mixture (SM) (64 mol% CH4, 8 mol% CO2, and 28 mol% C3H8) with heavy oil. Then, a theoretical methodology was employed to estimate the phase behavior of the heavy oil–solvent mixture (HO–SM) systems with various mole fractions of SM. The experimental results show that as the mole fraction of SM increases, the saturation pressures and swelling factors of the HO–SM systems considerably increase, and the viscosities and densities of the HO–SM systems decrease. The heavy oil is upgraded in situ via asphaltene precipitation and SM dissolution. Therefore, the solvent-enriched oil phase at the top layer of reservoirs can easily be produced from the reservoir. The aforementioned results indicate that the SM has promising application potential for enhanced heavy oil recovery via solvent-based processes. The theoretical methodology can accurately predict the saturation pressures, swelling factors, and densities of HO–SM systems with various mole fractions of SM, with average error percentages of 1.77% for saturation pressures, 0.07% for swelling factors, and 0.07% for densities.
Highlights
The observed performance from many heavy oil reservoirs in Canada, China, and Venezuela, such as the Orinoco Oil Belt, Lindbergh, and Tuha Fields, has been significantly better than that from conventional heavy oil reservoirs during primary production processes (Abusahmin et al 2017; Guan et al 2008; Maini 1999; Sun et al 2017a, 2019a, b; Zhou et al 2016)
The density of the heavy oil (HO)–solvent mixture (SM) system can be calculated as follows: mix noMo + ngMg Vof where ρmix is the density of heavy oil–solvent mixture (HO–SM) system in kg/m3; no and ng are the amount of substance of HO and SM in kmol; Mo and Mg are the molecular weight of HO and SM in kg/kmol; Vo is the volume of HO in m3
The high values of the measured saturation pressures indicate that the dissolved SM is released from the oil phase during the production period of cyclic solvent injection (CSI) processes, providing sufficient energy for driving solution gas
Summary
The observed performance from many heavy oil reservoirs in Canada, China, and Venezuela, such as the Orinoco Oil Belt, Lindbergh, and Tuha Fields, has been significantly better than that from conventional heavy oil reservoirs during primary production processes (Abusahmin et al 2017; Guan et al 2008; Maini 1999; Sun et al 2017a, 2019a, b; Zhou et al 2016). The beneficial mechanisms of solvent-based processes mainly include enhanced oil swelling and oil mobility improvement, as well as reductions in interfacial tension (IFT), oil viscosity and density (Dong et al 2013; Haddadnia et al 2018a, b; Liu 2019; Yu and Shen 2008; Zhang et al 2019b) All of these mechanisms can be determined by phase behavior data (Li et al 2011, 2012a, 2013). Haddadnia et al (2018a) and Azinfar et al (2018a, b) reported the viscosity and solubility data of butane-Athabasca bitumen (up to 260 °C) They investigated the thermos-physical properties of n-pentane–bitumen systems and n-hexane–bitumen systems at different temperatures (30–190 °C), pressures (2–8 MPa), and solvent mass fractions (0.05–0.5) (Haddadnia et al 2018b). Based on the aforementioned phase behavior data, many models were developed to predict thermos-physical properties of various solvents (such as C H4, C2H6, CO2, C3H8, and so on) in bitumen (heavy oil). A theoretical methodology was proposed to predict the theoretical phase behavior of the HO–SM systems with various mole fractions of SM
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