Page 73 - Hybrid Enhanced Oil Recovery Using Smart Waterflooding

CHAPTER 4

Hybrid Chemical EOR Using

Low-Salinity and Smart Waterflood

ABSTRACT previous works (Sheng, 2011; Sorbie, 1991). The two
This chapter describes the application of low-salinity types of polymers, synthetic polymer and biopolymer,
waterflood (LSWF) into various chemical enhanced are commonly used in the polymer and gel EOR appli-
oil recovery (EOR) processes, including polymer flood, cations. The hydrolyzed polyacrylamide (HPAM) is the
gel treatment, surfactant flood, and alkaline flood. The widely used synthetic polymer and xanthan is one of
hybrid process can secure the advantages of both LSWF the biopolymers. The addition of these polymers con-
and chemical EOR improving sweep and displacement tributes to viscosifying the displacing fluid, which is of
efficiencies. Because the properties of chemical addi- interest to the EOR application of polymer. The degree
tives are sensitive to the salinity of brine, the synergetic of viscosifying the fluid is closely associated with the
effects can be introduced by the hybrid process of physical properties of the polymer, including flow
LSWF and chemical EOR. Extensive experiments and behavior, adsorption/retention, and mechanical, chem-
numerical simulations have explored the applications ical, and thermal stabilities as well as polymer concen-
of the hybrid EOR process and quantified the tration. The chemical structure of polymer determines
underlain synergy. This chapter brieflydiscusses the the physical properties. Because each polymer has
important backgrounds of chemical EOR and then different chemical structure, i.e., flexible coil structure
introduces the research studies of a variety of of HPAM and rigid molecule structure of xanthan, its
hybrid chemical EOR using low-salinity and smart physical properties vary.
waterflood.
Polymer viscosity
The polymers are added to the injecting brine to in-
Although the exact mechanism of low-salinity and crease the viscosity of the driving fluid, which in turn
smart waterflood is still under investigation, the appli- improves the mobility ratio between displacing and dis-
cations of low-salinity and smart waterflood into other placed fluids. When water or polymeric solution dis-
enhanced oil recovery (EOR) processes have been pro- places oil, the mobility ratio and mobility are defined
posed and evaluated. This section describes the investi- as in Eqs. (4.1) and (4.2). Generally, the mobility ratio
gations of hybrid processes of the LSWF and chemical equal to or less than one indicates the favorable condi-
EOR processes, including polymer flood/gel treatment, tion for displacement and higher than one means the
surfactant flood, and alkali flood. It addresses the syn- unfavorable condition.
ergy of the hybrid process to enhance oil recovery. The
synergy might introduce effects of LSWF, which are l D
M ¼ (4.1)
mainly wettability modification and/or stability l d
improvement of chemical additives. !
k rj
l j ¼ k (4.2)
m j
POLYMER FLOOD/GEL TREATMENT where M is the mobility ratio of the displacing phase,
Backgrounds of Polymer Flood/Gel l D , to the displaced phase, l d ; l j is the mobility of phase
Treatment j; and the m j is the viscosity of phase j.
Before the description of LSWF application into poly- The viscosity of a polymeric solution is determined
mer flood and gel treatment, it is necessary to discuss by the molecular size, concentration of polymer, and
the fundamental theories of polymer flood and gel extension of polymer in the solution. Conventionally,
treatment, which are related to the synergetic effects of the lager molecular size of polymer has higher viscosity.
hybrid process. This discussion is referred from the There are a number of quantities to describe the

Hybrid Enhanced Oil Recovery using Smart Waterflooding. https://doi.org/10.1016/B978-0-12-816776-2.00004-0
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