Selection of Optimal Solvent Type for High-Temperature Solvent Applications in Heavy-Oil and Bitumen Recovery

Abstract

The selection of the most suitable solvent for an efficient heavy-oil recovery process is a critical task. Low carbon number solvents yield faster diffusion, but the mixing quality may not be high. Also, high carbon number solvents yield a better quality mixing (much less asphaltene precipitation), but the mixing process is rather slow. Hence, the understanding of solvent selection criteria for solvent-aided recovery processes has established two main aspects of oil−solvent (liquid−liquid) interaction:(1) oil−solvent mixture quality and (2) rate of mixture formation. Oil−solvent mixture quality is determined by two parameters:(1) viscosity and (2) asphaltene precipitation. The rate of mixing is quantified by the diffusion rate. Both mixture quality and mixing rate need to be quantitatively and qualitatively determined to select the suitable solvent for heavy-oil recovery. In addition to this, experiments that measure the solvent diffusion rate (and oil recovery) into a rock sample saturated with heavy oil at static conditions are needed to support the observations obtained from the liquid−liquid interaction of solvent and oil. This paper focuses on these tests and uses three oil samples with a wide range of viscosities (250−476 000 cP) and three liquid solvents with different carbon numbers varying between C 7 and C 13 . Core experiments at different temperatures were performed on Berea sandstone samples using the same solvent−heavy oil pairs to obtain the optimum carbon size (solvent type)−heavy oil combination that yields the highest recovery factor and the least asphaltene precipitation. On the basis of the fluid−fluid (solvent−heavy oil) interaction experiments and heavy-oil-saturated rock−solvent interaction tests, the optimal solvent type was determined considering the fastest diffusion and best mixing quality for different oil−solvent combinations.

Experimental Comparative Investigation of Hot Solvent/Steam-Assisted Gravity Drainage in Oil Sand Reservoirs

“…Some researchers have studied the mechanism of warm VAPEX. Marciales and Babadagli 21 reported that the selection of the most suitable solvent is a critical task for an efficient warm VAPEX process. Oil–solvent mixture quality and rate of mixture formation solvent are two main selection criteria for solvent-aided recovery processes.…”

Experimental Investigation and Numerical Simulation of Dynamic Characteristics for Multithermal Fluid-Assisted SAGD in Extraheavy Oil Reservoir

“…The solubility of CO 2 in heavy oil is 50-100 m 3 /m 3 at 6.0 MPa, and the volume expansion of crude oil is 10-20%, which reduces the oil viscosity by more than 80% [33,34]. Moreover, CO 2 is highly soluble in the asphaltene components, which can further enhance oil recovery [35]. However, the sweep efficiency is relatively low when only CO 2 is injected [36].…”

Hot Solvent-Assisted Gravity Drainage in Naturally Fractured Heavy Oil Reservoirs: A New Model and Approach to Determine Optimal Solvent Injection Temperature

“…Similarly, the effects of phase behaviour on the SA-SAGD performance has been studied by Khaledi et al concluding that a multicomponent hydrocarbon solvent may be used to significantly improve efficiency 23 . Marciales and Babadagli have also investigated the selection of optimal solvent discussing the need to find a compromise between low carbon number solvents that result in faster diffusion and high carbon number solvents that yield better mixing qualities but slower mixing 24 . However, the concepts of thermal-solvent recovery in fractured reservoirs has not been successfully modelled yet.…”

“…Therefore, studies have been conducted to explore solutions for heavy oil recovery from this type of reservoir over the last couple of years. Experimental studies have shown that hot solvent techniques have the potential to improve heavy oil recovery from fractured reservoirs but gave limited insight into the mechanisms that operate. ,, Pathak et al injected hot solvents into a cylinder containing preserved bitumen saturated cores (from the Grosmont formation) which were in contact with the solvent on all sides representing a matrix-fracture element of a fractured reservoir . The solvent was allowed to soak into the core diluting the bitumen, then the mixture was collected from beneath the core.…”

“…23 Marciales and Babadagli have also investigated the selection of optimal solvent discussing the need to find a compromise between low carbon number solvents that result in faster diffusion and high carbon number solvents that yield better mixing qualities but slower mixing. 24 However, the concepts of thermal-solvent recovery in fractured reservoirs has not been successfully modeled yet. Electromagnetic heating of bitumen to reduce viscosity is another thermal method which has showed promising results through experimental and modeling studies.…”