The flue gas-solvent assisted steam assisted gravity drainage studies: experiments and numerical simulation in extra-heavy oil reservoirs

ABSTRACT

Steam-assisted gravity drainage (SAGD) has been used successfully for developing extra-heavy oil around the world. But many experiments and field production have pointed out problems, such as heat loss to the overburden and low oil-steam ratio. Compared with SAGD, flue gas-solvent assisted SAGD (FGS-SAGD) is a relatively new thermal recovery technology. FGS-SAGD combines the multiple advantages of gas injection, solvent injection, and thermal recovery processes. In this paper, 3D sand pack models were established to study the steam chamber expansion characteristics and the development performance of different drainage experiments. Numerical models based on the experimental parameters were conducted to further study the gas and solvent migration and its effect on the temperature and oil saturation profiles. The results show that in the process of FGS-SAGD, the accumulation of flue gas effectively inhibited steam override and reduced heat loss to the overburden, which slowed the vertical expansion of steam chamber and improved the lateral expansion of steam chamber. Solvent was vaporized under high temperature and mixed with extra-heavy oil at the edge of steam chamber to reduce oil viscosity, which further improved the profile of steam chamber. Both flue gas and solvent injection significantly improved the heat utilization efficiency and increased the steam sweep volume and oil recovery. The oil recovery of FGS-SAGD (41.9%) was 12% higher than that of SAGD in the experiments. In addition, the oil mobility was increased by 26.2%, and water phase mobility was decreased by 19.7% in the process of FGS-SAGD. The study indicates that FGS-SAGD is a feasible technique for improving development performance in extra-heavy oil reservoirs.

KEYWORDS:

• Extra-heavy oil
• flue gas
• solvent
• development performance
• FGS-SAGD

Nomenclature

B3	=	Similar criterion number, dimensionless
K	=	Reservoir absolute permeability; μm2
g	=	Acceleration of gravity, m/s2
L	=	The effective horizontal length, m
α	=	Thermal diffusivity of reservoir, m2/d
Φ	=	Porosity, dimensionless;
ΔSo	=	Movable oil saturation at steam temperature, dimensionless
m	=	Heavy oil viscosity-temperature index, dimensionless
ʋs	=	Heavy oil kinematic viscosity at steam temperature, m2/d
tD	=	Dimensionless production time, dimensionless
t	=	Production time, d

Acknowledgments

We acknowledge the National Science and Technology Major Projects of China (2016ZX05058-003-017 and 2016ZX05017-001-002HZ) to provide research funding. This work was also supported by the Doctor Foundation of Yanshan University, Qinhuangdao (No.8190002).

Additional information

Funding

This work was supported by the National Science and Technology Major Projects of China [2016ZX05042,2017ZX05039];Doctor Foundation of Yanshan University [8190002].

Notes on contributors

Jie Fan

Jie Fan earned his Master in Oil-Gas Field Development Engineering from China University of Petroleum (Beijing) in Beijing, China, in 2011. He earned his PhD in Oil-Gas Field Development Engineering from China University of Petroleum in Beijing, China, in 2016. From March 2017 to September 2019, he is a teacher in Yanshan University. At present, he is a teacher in Chongqing University of Science and Technology. His areas of interest include oil-gas field development engineering, seepage flowing mechanics and simulation.

Baoguang Jin

Baoguang Jin earned his PhD in Oil-Gas Field Development Engineering from University of Petroleum in Beijing, China, in 2014. At present, he is a engineer in Greatwall Drilling, China National Petroleum Corporation (CNPC), Beijing. His areas of interest include thermal recovery and simulation.

Jing Yang

Jing Yang earned her Master in Oil-Gas Field Development Engineering from China University of Petroleum in Beijing, China, in 2013. At present, she is an engineer in Research Institute of Petroleum Exploration and Development, China National Petroleum Corporation (CNPC), Beijing. Her areas of interest include thermal recovery and simulation.

Xianzhang Fan

Xianzhang Fan earned her Bachelor in Oil-Gas Field Development Engineering from Yanshan University, in 2019. His areas of interest include thermal recovery and simulation.