An Enhanced Oil Recovery Technology as a Follow Up to Cold Heavy Oil Production with Sand

Abstract

Lloydminster area that straddles Alberta and Saskatchewan border contains vast amounts of heavy oil deposits in thin unconsolidated formations. Cold Heavy Oil Production with Sand (CHOPS) has been successfully implemented in these reservoirs. However, primary recovery is still low averaging below 10%. How to economically recover the large amount of remaining oil in place is a challenge. Therefore, an effective follow up recovery process is required.Steam injection technologies cannot be widely applied because most of the Lloydminster heavy oil reservoirs are thin and the heat losses to overburden and under burden make the process uneconomic. Alternative solvent methods are not commercial yet due to uncertain oil recovery rates and low solvent recovery. Hybrid application of the aforementioned two technologies using hot water together with solvents could be an economic post CHOPS recovery process. The wormholes created during the primary recovery can be used to contact large reservoir volumes with hot water and solvent. This paper contains the results of hot water and solvent oil recovery experiments conducted in preserved heavy oil cores. Experimental work consisted of three phases. Cores were immersed in hot water in the first phase to pre-heat the formation. Next, cores were exposed to heptane as hydrocarbon solvent. Finally, cores were immersed in hot water again to recover the oil as well as the solvent. The ultimate oil recoveries varied between 42% and 88% OOIP and, the asphaltene precipitation varied between 2.5 wt% and 11.7 wt%. Experiments were also carried out with a distillate from Husky's Lloydminster upgrader used for heavy oil transportation in the pipelines. Better results were obtained if the distillate was used instead of the pure hydrocarbon solvent.It was observed that oil recovery at the end of the initial hot water injection phase due to thermal expansion and viscosity reduction was negligible compared to the ultimate recovery. However, the first phase serves to condition the reservoir for better diffusion in the second phase when the solvent is injected. The final phase of hot water injection causes the water to strongly imbibe into the matrix enhancing the oil and the solvent recovery.

Efficiency of Solvent Retrieval during Steam-Over-Solvent Injection in Fractured Reservoirs (SOS-FR) Method: Core Scale Experimentation

“…With an oil recovery of about 26 %, the core sample #8 (decane case) had the lowest oil recovery. Note that these recoveries are relatively lower than observed in the previous studies Babadagli 2008, 2009a;Coskuner et al 2013;Naderi et al 2013). This is mainly due to shorter solvent exposure times applied in the present study, which did not allow sufficient time to produce more oil by gravity drainage.…”

Efficiency of Steam-Over-Solvent-Injection-in-Fractured-Reservoirs (SOS-FR) Method Considering Oil Recovery and Solvent Retrieval: Core-Scale Experimentation

“…With an oil recovery of approximately 26%, Core 8 (decane case) had the lowest oil recovery. Note that these recoveries are relatively lower than those observed in the previous studies (Al Babadagli 2008, 2009a;Coskuner et al 2013;Naderi et al 2013). This is mainly because of the shorter solvent exposure times applied in the present study, which did not allow sufficient time to produce more oil by gravity drainage.…”

“…The density and the viscosity of diluent oil are provided in Table 1. The detailed chemical properties of the distillate are provided in Naderi et al (2013) and Coskuner et al (2013). The refractiveindex readings were used to estimate the oil recovery during this phase.…”

Bitumen Recovery by the SOS-FR (Steam-Over-Solvent Injection in Fractured Reservoirs) Method: An Experimental Study on Grosmont Carbonates

“…In general, the distillate recovery curves tend to reach a plateau in a later time than the heptane cases. Due to its higher carbon number (predominantly C11-13) as reported by Coskuner et al (2013) diffusion rate is expected to be slower than that of heptane (Al-Bahlani and Babadagli, 2009a. However, the ultimate recovery by distillate is significantly higher compared to the heptane cases due to its 20% aromatic content (saturates is 80% and resins and asphaltenes are 0%), which dissolves heavier components compared to heptane (100% saturates).…”