Numerical Simulation of Gas Mobility Control by Chemical Additives Injection and Foam Generation during Steam Assisted Gravity Drainage (SAGD)

ABSTRACT

Gas mobility control is highly required to obtain a sufficiently-expanded and uniformly-developed steam chamber, which is conducive to steam-assisted gravity drainage (SAGD) production. Adding chemical additives with in-situ generation of foam (CAFA-SAGD) is an approach to improve sweep efficiency, displace residual oil and reduce heat loss, enhancing SAGD performance in terms of both oil production and steam oil ratio (SOR). With the input of the obtained chemicals and foam parameters and the consideration of the principle mechanisms (steam foam mobility control and IFT reduction), it depicts the dynamic distribution of components and compares the performance of CAFA-SAGD and SAGD with numerical simulation. Foam generation and foam collapse are also incorporated. Simulation study demonstrates that steam mobility control is conducive to generate a larger oil displacement area in the lower part of the model. Also, residual oil is more depleted owing to higher injection pressure and interfacial tension reduction. The optimization from this study ensures that the oil recovery factor is improved by 5.34%.

KEYWORDS:

• SAGD
• steam foam
• chemical additives
• numerical simulation
• surfactant

Nomenclature

Roman Symbols	=
$\mathrm{a}$	=	foam generation reaction coefficient, (mol surfactant*min)−1
${\mathrm{A}}_{\mathrm{H}}$	=	Hamaker constant, J
${\mathrm{C}}_{\mathrm{e}\mathrm{l}}$	=	electrolyte number concentration, cm−3
${\mathrm{C}}_{\mathrm{s}\mathrm{i}}$	=	surfactant concentration at the interface, mol/cm3
$\mathrm{e}$	=	elementary charge, C
$\mathrm{h}$	=	film thickness, cm
${\mathrm{h}}_{\mathrm{c}\mathrm{r}}$	=	film critical thickness, cm
$\mathrm{k}$	=	Bolzman constant, J/K
${\mathrm{L}}_{\mathrm{s}}$	=	length of liquid slugs, cm
${\mathrm{L}}_{\mathrm{B}\mathrm{D}}$	=	dimensionless group
${\mathrm{n}}_{\mathrm{L}}$	=	foam texture, 1/cm
${\mathrm{n}}_{\mathrm{s}}$	=	surface concentration of surfactant, mol/cm2
${\mathrm{N}}_{\mathrm{s}}$	=	dimensionless group
$(\mathrm{P}{)}_{\mathrm{c}}$	=	empirical constant, dimensionless
${\mathrm{r}}_{\mathrm{b}}$	=	body radius, cm
${\mathrm{r}}_{\mathrm{B}}$	=	bubble radius, cm
${\mathrm{r}}_{\mathrm{c}}$	=	plateau border radius, cm
${\mathrm{r}}_{\mathrm{c}\mathrm{a}\mathrm{p}}$	=	capillary radius, cm
${\mathrm{r}}_{\mathrm{l}}$	=	radius of the position where lamella locates, cm
${\mathrm{r}}_{\mathrm{t}}$	=	throat radius, cm
$\mathrm{T}$	=	temperature, K
${\mathrm{v}}_{\mathrm{g}}$	=	gas velocity, cm/s
${\mathrm{z}}_{\mathrm{i}}$	=	valence of ion, dimensionless
Greek symbols	=
$\mu$	=	solution viscosity, cp
${\mu }_{\mathrm{s}}$	=	foam apparent viscosity, cp
${\mu }_{\mathrm{w}}$	=	water viscosity, cp
$\sigma$	=	interfacial tension, dyne/cm
$\stackrel{\sim }{\mathrm{\Gamma }}$	=	surface excess concentration, mole/cm2
$\stackrel{\sim }{{\mathrm{\Gamma }}_0}$	=	equilibrium surface tension gradient, mole/cm2
$\alpha$	=	mass transfer rate constant, 1/s
$\theta$	=	contact angle, degree
${\theta }_{\mathrm{f}\mathrm{r}\mathrm{o}\mathrm{n}\mathrm{t}}$	=	contact angle, degree
${\theta }_{\mathrm{b}\mathrm{a}\mathrm{c}\mathrm{k}}$	=	contact angle, degree
$\mathrm{\Gamma }$	=	foam quality, dimensionless
${\mathrm{\Pi }}_{e1}$	=	eletrostatic repulsion, Pa
	=	van der Waals attraction, Pa
${\mathrm{\Psi }}_{\mathrm{o}}$	=	surface potential, J/C
$\kappa$	=	inverse of Debye length, cm−1
$\epsilon$	=	dielectric constant of the medium, C2/(J*m)
${\rho }_{\mathrm{g}}$	=	gas density, kg/m3