The Role of Emulsions in Steam-Assisted-Gravity-Drainage (SAGD) Oil-Production Process: A Review

Abstract

Summary Studies that investigate and attempt to model the process of steam-assisted gravity drainage (SAGD) for heavy-oil extraction often adopt the single-phase-flow assumption or relative permeability of the moving phases as a continuous phase in their analyses. Looking at the emulsification process and the likelihood of its prevalence in SAGD, however, indicates that it forms an important part of the entire physics of the process. To explore the validity of this assumption, a review of prior publications that are related to the SAGD process and the modeling approaches used, as well as works that studied the emulsification process at reservoir conditions, is presented. Reservoir conditions are assessed to identify whether the effect of the emulsion is strong enough to encourage using a multiphase instead of a single-phase assumption for the modeling of the process. The effect of operating conditions on the stability of emulsions in the formation is discussed. The review also covers the nature and extent of effects from emulsions on the flow mechanics through pore spaces and other flow passages that result from the well completion and downhole tubing, such as sand/flow-control devices. The primary outcome of this review strengthens the idea that a multiphase-flow scenario needs to be considered when studying all flow-related phenomena in enhanced-oil-recovery processes and, hence, in SAGD. The presence of emulsions significantly affects the bulk properties of the porous media, such as relative permeability, and properties that are related to the flow, such as viscosity, density, and ultimately pressure drop. It is asserted that the flow of emulsions strongly contributed to the transport of fines that might cause plugging of either the pore space or the screen on the sand-control device. The qualitative description of these influences and their extents found from the review of this large area of research is expected to guide activities during the conception stages of research questions and other investigations.

A Population Balance Model for Emulsion Behavior of Alkaline Water–Heavy Oil Systems in Bulk Phase

“…After the phase inversion, the water droplet distribution in the W/O emulsion phase is determined by the GA as shown in Figure . The majority of the water droplet size distribution ranges from 0.1 to 10.0 μm, which is consistent with the previous works. , As can be observed, the water droplets have a smaller median and a more centralized distribution at higher temperatures. This finding is consistent with those documented elsewhere; that is, the water droplets in the inversed W/O emulsion phase have a smaller mean radius at a lower viscosity and a higher surfactant–oil ratio .…”

“…15 The in situ generated surfactant helps to reduce the interfacial tension (IFT) between oil and the aqueous phase, while amphiphilic components (e.g., resins, asphaltenes, and natural petroleum acids) in crude oil strengthen the stability of a water−oil emulsion. 16,17 The lower the IFT is, the more easily the crude oil could be emulsified with water. 18,19 Once an O/W emulsion is formed, the mobility of the oil phase can be greatly improved.…”

“…Alkaline flooding has been found to be an efficient and economical enhanced oil recovery (EOR) technique for decades. − In recent years, alkalis have also been integrated with other EOR techniques such as steam-assisted gravity drainage (SAGD), − surfactant and/or polymer flooding, − and nanoparticle-assisted processes − by taking the advantages of reducing the surfactant adsorption loss, protecting surfactant against divalent ions, and reacting with the petroleum acids to form in situ surfactant . The in situ generated surfactant helps to reduce the interfacial tension (IFT) between oil and the aqueous phase, while amphiphilic components (e.g., resins, asphaltenes, and natural petroleum acids) in crude oil strengthen the stability of a water–oil emulsion. , The lower the IFT is, the more easily the crude oil could be emulsified with water. , Once an O/W emulsion is formed, the mobility of the oil phase can be greatly improved . The formation of a W/O emulsion increases the viscosity of the displacing fluid, leading to an improved mobility ratio, , reducing water channeling, damping viscous fingering behavior, and then enhancing oil recovery. , However, the dispersed water droplets in W/O emulsions make the refinement of the crude oil a difficult and expensive task.…”

Measurement of the flow behavior index of Newtonian and shear-thinning fluids via analysis of the flow velocity characteristics in a mini-channel

“…2. For a Newtonian fluid ( n = 1 ), (11) the velocity profile shows the expected parabolic/Poiseuille profile [22]. For shear thinning fluids ( n < 1 ), the velocity profile approaches a top-hat shape and this shape intensifies as the power law index of the flow decreases.…”

“…The utilization of an ex-situ measurement is also limited for applications operating at high pressure and temperatures, e.g. the rheology of bitumen in SAGD process [11]. The rheology of the fluid flowing through different channels at various conditions as per the application could therefore be identified using a non-intrusive method for in-situ rheological measurement [12][13][14].…”