Feasibility Study of Solvent-Based Huff-n-Puff Method (Cyclic Solvent Injection) to Enhance Heavy Oil Recovery

Abstract

Solvent-based processes have demonstrated a significant potential to enhance heavy oil recovery. However, their applicability needs to be investigated for different solvents and operating conditions. In this study, a comprehensive experimental and reservoir simulation analysis was conducted on the feasibility of solvent-based, huff-n-puff method to enhance heavy oil recovery. Carbon dioxide (CO 2 ), methane (CH 4 ), propane (C 3 H 8 ), and butane (C 4 H 10 ) were tested under different operating conditions. A physical model with a1800-md permeability and 24% porosity Berea core mounted in a high-pressure core holder was designed. For all tests, the core was saturated with a Saskatchewan heavy oil with viscosity of 1423 mPa·s at 22 °C. Fourteen huff-n-puff experiments were conducted. The effect of operating pressure, soaking time, and solvent composition were investigated. According to the results, for all types of solvent the produced oil at elevated pressure was lighter (in terms of density and viscosity) and the recovery factor was higher. The highest recovery of 71% was obtained by injecting pure CO 2 at near-supercritical conditions (7239 kPa at 28 °C), while pure CH 4 at the highest operating pressure of 6895 kPa was 50%. Also, adding 19% hydrocarbon solvent to pure CO 2 increased the recovery factor by 10% at aoperating pressure (e.g., 2317kPa). The governing mechanisms that contributed to the production were recognized to be solution gas drive, viscosity reduction, extraction of lighter components, formation of foamy oil, and to a lesser degree, the diffusion process. The oil viscosity was reduced to 62 mPa·s by injecting CO 2 at 7239 kPa. The highest incremental recovery for CO 2 -based solvents and CH 4 occurred at the 2 nd and 3 rd cycle, respectively. Longer soaking time improved the incremental recovery of the first cycles, though the final recovery did not noticeably change. The result of history matching with the simulated model was quite reasonable with maximum 10% discrepancy between recovery factors of these two approaches.

Huff-n-Puff Experimental Studies of CO2 with Heavy Oil

“…Forty Huff-n-Puff gas injection tests were conducted in total. Experiments coincide with other studies where heavy oil is mainly extracted by the first three cycles of CO 2 Huff-n-Puff injection [11,22]. Then, the received data allowed to distinguish the mixing zone for the light fractions of studied oil samples with CO 2 , proving that it is applicable for possible miscibility evaluation.…”

Parametric Study of the Cyclic CO2 Injection Process in Light Oil Systems

“…Additional studies on the performance of some field-scale cyclic CO 2 injection in USA (e.g., Paradis, West Cote, Timbalier, Magnet, Picket Ridge, and Thompson, Bati field projects) revealed that the presence of a gas cap, gravity segregation, and a higher remaining oil saturation can improve the recovery of the cyclic injection process. − Furthermore, changes in gas–oil relative permeability curves may support the oil production near the well-bore. − Further studies on the effect of CO 2 slug size also revealed that a higher volume of CO 2 injected into the reservoir is able to recover more oil under some specific conditions during the cyclic injection process. , It has also been reported that the cyclic CO 2 injection process profited by lower crude oil viscosity since the diffusion of CO 2 into the oil is accelerated . Experimental study on the cyclic injection of mixtures of CO 2 with hydrocarbon and flue gases also showed that such mixtures increase the oil recovery if they are injected in a particular range of volumetric ratio. − A laboratory and field evaluation of the cyclic CO 2 injection process indicated that a high permeability of the reservoir rock as well as viscous fingering phenomena plays a positive role in the recovery efficiency . The laboratory and numerical simulation results also suggest that oil recovery is improved by a higher matrix permeability during cyclic CO 2 injection in a matrix-fractured system. , …”

Gas Pressure Cycling (GPC) and Solvent-Assisted Gas Pressure Cycling (SA-GPC) Enhanced Oil Recovery Processes in a Thin Heavy Oil Reservoir

“…Solvent-based EOR processes are excellent alternatives to thermal EOR processes in thin heavy oil reservoirs, the latter of which suffers from excessive heat losses to the surroundings, high capital and operating costs, large water consumption and treatments, and considerable greenhouse gas emissions [8]. A number of experimental studies have been published on the applications of solvent-based EOR processes in the heavy oil reservoirs [9][10][11]. For example, two series of laboratory PVT tests were conducted to model the pressure depletion process in the cyclic solvent injection (CSI) in a Lloydminster heavy oil reservoir [9].…”

“…It was found that the primary production and the six cycles had the total heavy oil RF of 50%, which shows the potential feasibility of the CSI process. In another study, a total of fourteen CSI experiments were performed to investigate the operating pressure, soaking time, and solvent composition effects [11]. In each test, first, the Berea core was saturated with a Saskatchewan heavy oil.…”