Investigation of Cyclic Solvent Injection Process for Heavy Oil Recovery

Abstract

Summary This paper summarizes numerical and experimental simulation results of a cyclic solvent injection process study, which was part of a continuing investigation into the use of solvents as a follow-up process in Cold Lake and Lloydminster reservoirs that have been pressure-depleted by cold heavy oil production with sand (CHOPS). Typically only 5% - 10% of the original oil in place (OOIP) is recovered during cold production; therefore, an effective follow-up process is required. The cyclic solvent injection (CSI) experiment consisted of primary production followed by six solvent (28% C3H8 - 72% CO2) injection cycles. Oil recovery after primary production and six solvent cycles was 50%, which indicates the potential viability of the CSI process. Concurrently with the laboratory physical simulation, a numerical simulation model was developed to represent the physical behaviour of the experimental results. A history match of the primary production portion of the experiment was obtained using an Alberta Innovates - Technology Futures (AITF) foamy oil model. This resulted in the characterization (fluid saturations and pressures) of the oil sandpack at the start of the solvent injection process. The history match of the subsequent six solvent injection cycles was used to validate the numerical model of the CSI process developed at AITF. This model includes nonequilibrium rate equations that simulated the delay in solvent reaching its equilibrium concentration as it dissolves or exsolves in the oil in response to changes in the pressure and/or gas-phase composition. Dissolution of CH4, C3H8 and CO2 in oil and CO2 in water were considered, as was exsolution of CH4, C3H8 and CO2 from oil and CO2 from water. Reduced gas-phase permeabilities resulting from gas exsolution were also included. The history match simulations indicated that: The important mechanisms were represented in the simulations. Significant oil swelling by solvent dissolution occurs during solvent injection periods. This can reduce solvent injectivity and penetration into a heavy oil reservoir during solvent injection periods. Low oil and gas-phase relative permeabilities are required during production periods to match the experimental oil and gas production during solvent cycles. A parametric simulation study showed that the quantity of gas injected in an injection period was relatively insensitive to the oil-phase diffusion coefficients, but was sensitive to solvent solubility in oil, dissolution rates, gas-phase diffusion coefficients, molar densities in the oil phase, gas-phase relative permeability and capillary pressure. It was shown that oil production is highly dependent on how quickly solvent can dissolve in the oil during injection and exsolve from the oil during production.

Evaluation of Diffusion of Light Hydrocarbon Solvents in Bitumen

“…In addition, Alberta and Saskatchewn contain significant remaining oil resources in post-CHOPS environments, where the presence of wormholes and non-thermal wellbores will make steam processes a challenge. Processes such as cyclic solvent injection (Ivory et al, 2010), and variations of this process (Jiang et al, 2013;Kristoff et al, 2008) focus on the injection of vapour-phase solvents for heavy oil recovery. The concept behind these technologies is that solvent will mix with oil, thus reducing its viscosity and allowing for enhanced flow of the oil.…”

A Follow-Up Recovery Method After Cold Heavy Oil Production Cyclic CO2 Injection

“…It is believed that both of these effects, coupled with higher free gas saturation, are responsible for the low pressure drop during solvent cycles which was comparable to maximum pressure drop obtained in the slow primary depletion of 8 days, although all solvent production cycles were conducted on 1 day depletion basis. Low pressure drops during solvent cycles were also recorded by Ivory et al, (2010). …”

History Matching of Electromagnetically Heated Reservoirs Incorporating Full-Wavefield Seismic and Electromagnetic Imaging

“…Stated differently, electrical energy is transformed into heat energy by means of dielectric losses as the radiated field propagates within the formation. The generated heat then leads to an increase in temperature of the oil-bearing formation, resulting in a reduction of viscosity (Jha and Chakma 1999). The internal heat generation further enables a more-uniform heating of the medium (Jha et al 2011), and targeting the heating of certain parts of the reservoir with directional antennas is possible.…”

“…Ovalles et al (2002) provide a comparison of the experimental results obtained from a sample from the Orinoco River basin with the results computed with a commercial heat-equation solver. In an attempt to experimentally replicate a heavy-oil reservoir, Jha and Chakma (1999) conducted laboratory experiments with EM heating that resulted in oil-recovery rates as high as 45% of the original oil in place as compared with the estimated primary-recovery rates of less than 5%.…”

“…History matching for heavy-oil reservoirs was used for a number of years (Ivory et al 2010;Al-Gamdi et al 2013). Johnson et al (1992) performed history matching with steamflooding in the Kern River field in California, optimizing formation-temperature, fluid, and permeability parameters with the relative permeability parameters corresponding with the data from laboratory experiments.…”