Investigation of Cyclic Solvent Injection Process for Heavy Oil Recovery

Abstract

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, so an effective follow-up process is required.The cyclic solvent injection (CSI) experiment consisted of primary production followed by 6 solvent (28% C 3 H 8 -72% CO 2 ) 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 behavior of the experimental results. A history match of the primary production portion of the experiment was obtained using an Alberta Research Council foamy oil model. This resulted in the characterization (fluid saturations and pressures) of the oil sand pack at the start of the solvent injection process. The history match of the subsequent 6 solvent injection cycles was used to validate the numerical model of the CSI process developed at the Alberta Research Council.This model includes non-equilibrium 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 CH 4 , C 3 H 8 , and CO 2 in oil and CO 2 in water were considered, as was exsolution of CH 4 , C 3 H 8 , and CO 2 from oil and CO 2 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

Enhanced Oil Recovery Techniques for Indian Reservoirs

“…Surface mining is suitable for reservoirs with depth less than 70 m and recovers~5 % of OOIP. On the other hand, CHOP/CHOPS recover~5-10 % of OOIP (Ivory et al 2010;Jiang et al 2014). The largest percentage of OOIP is produced during primary recovery and over the period of time the decline starts when the reservoir is no longer productive, water flooding is done to augment the oil recovery and further enhancement is done through various enhancement methods (see Fig.…”

Enhanced heavy oil recovery in thin reservoirs using foamy oil-assisted methane huff-n-puff method

“…For these thin reservoirs, thermal methods, such as cyclic steam stimulation, steam flooding, and steam-assisted gravity drainage, tend to be neither effective nor economical, due to significant heat loss and water resource requirements [5][6][7]. Thus, non thermal recovery techniques, such as cyclic solvent injection (CSI), cyclic production with continuous solvent injection (CPCSI), and vapor extraction (VAPEX), have attracted an increasing amount of attention in recent years [8][9][10][11][12][13][14]. Among these methods, the methane huff-n-puff process for enhancing heavy oil recovery in thin reservoirs has its advantages from the view of availability and economic efficiency [15][16][17][18].…”

A new solvent-based enhanced heavy oil recovery method: Cyclic production with continuous solvent injection

“…Surface mining is effective but it is only economically applicable to those reservoirs with a depth of less than 70 m. Only about 5% of the heavy oil reservoirs can be recovered with this technique [5]. CHOP/CHOPS can recover approximate 5-10% of the initial heavy oil in place, before becoming uneconomical because the pressure depletion and water encroachment [6]. Solvent injection techniques, such as vapour extraction (VAPEX) and cyclic solvent injection (CSI), use a vapourized solvent to extract heavy oil or bitumen deposits.…”

“…A pure light hydrocarbon or a mixture of several light hydrocarbons or CO 2 is usually used as the solvent. The injected solvent is dissolved into the heavy oil to reduce the oil viscosity, in situ de-asphalting, so that the diluted oil can be produced by gravity drainage or pressure depletion [2,6,7].…”

“…The traditional CSI process is also known as solvent huff-n-puff process, which comprises of several cycles and each cycle has three periods: an injection period, a soaking period and a production period [6,[15][16][17]. The light hydrocarbon gas is injected into the reservoir to increase the reservoir pressure, part or portion of which is dissolved into the heavy oil to reduce the oil viscosity, and then the reservoir pressure is depleted to produce the diluted oil.…”