Page 95 - Hybrid Enhanced Oil Recovery Using Smart Waterflooding

CHAPTER 4 Hybrid Chemical EOR Using Low-Salinity and Smart Waterflood 87

the ultimate heavy oil recovery of 19.4%. The conven- model of polymeric solution. The additional trial of
tional polymer flood and LSWF increase the oil recovery LSPF will be described in the numerical simulation of
by 5.6% and 5.9%, respectively. Because the low- alkali/surfactant/polymer flood.
salinity water condition remedies the injectivity loss of
polymer flood, the injectivity constraint of the process
limits the oil recovery by less injection. As a result, the
LSPF recovers 10% additional oil over conventional SURFACTANT FLOOD
waterflood because of the synergy of wettability modifi- Backgrounds of Surfactant Flood
cation and mobility ratio improvement. The synergy Surfactant EOR process is described to understand the
can be enhanced if LSPF is not involved with injectivity experimental and numerical studies of low salinitye
constraint consideration. Additional simulations inves- augmented surfactant flood. The backgrounds are
tigate the potential of infill drilling on the performance summarized from a couple of references (Lake, 1989;
of hybrid LSPF and observe the more oil production by Sheng, 2011). The EOR process of surfactant flood in-
the infill drilling. jects surface-active agents or surfactants, which are
Khorsandi, Qiao, and Johns (2017) reported the organic compounds to reduce the IFT between the
analytical solution of LSPF considering the cation- liquid and surfactant and residual oil saturation. The
exchange reaction, wettability modification, adsorp- surfactant is composed of tail, which is a nonpolar
tion, inaccessible pore volume, and salinity-dependent and hydrophobic hydrocarbon chain, and head, which
behavior of polymeric solution for sandstone reservoirs. is a polar hydrophilic group. The amphiphilic surfac-
The study simulated the LSPF model using the in-house tant is soluble in both organic solvents and water.
compositional simulator, PennSim. The modeling of The balance between the hydrophilic of head group
LSPF assumes that the wettability modification underly- and hydrophobic of tail part determines the character-
ing LSWF mechanism is caused by cation-exchange reac- istics and type of surfactants. The hydrophilic head
þ
tion. In detail, the adhered amount of Na on the clay group interacts with water, and the hydrophobic tail
surface controls the relative permeability and capillary part interacts with organic solvent, i.e., oil. These inter-
pressure of Brooks-Corey model and residual oil satura- actions form the water-in-oil and oil-in-water microe-
tion. Although the rheology model of polymeric solu- mulsions. When the surfactant is adsorbed at a surface
tion takes the polymer concentration and salinity into of solid or concentrated at an interface between fluids,
consideration, it neglects the mechanical degradation the interfacial and surface energies significantly
by shear rate and viscoelastic behavior of polymeric so- decrease, i.e., IFT/surface tension reductions. There
lution. The polymer rheology model incorporates the are primary surfactant and cosurfactant to distinguish
residual oil reduction by capillary number or trapping their roles in surfactant EOR process. The primary sur-
number. The study developed the analytical solution factant directly forms the microemulsion, and the
for LSPF as well as LSWF and tried to match a number cosurfactant augments the activities of the primary sur-
of experimental results (Seccombe, Lager, Webb, factant modifying the surface energy, the viscosity of
Jerauld, & Fueg, 2008; Shaker Shiran & Skauge, 2013) the liquids, etc. The surfactants are, conventionally,
using the simplified analytical solution. For the LSPF classified as anionic, cationic, nonionic, and zwitter-
experiment of Shaker Shiran and Skauge (2013),a ionic surfactants based on the ionic nature of the hy-
number of properties including CEC, residual oil satu- drophilic head group. Because the anionic surfactant
ration at high salinity threshold condition, and residual exhibits the relatively low adsorption on negatively
oil saturation reduction by polymer using the simplified charged clay, it is widely used for sandstone reservoirs.
analytical solution are tuned to match the experimental Although the nonionic surfactant has higher tolerance
result of oil recovery. Another LSWF simulation at- to the salinity, its ability reducing IFT is not sufficient
tempts to match the LSWF experiment of Seccombe as anionic surfactant. Cationic surfactant can be used
et al. (2008). The simulation refers the data of relative for the carbonate reservoirs rather than the sandstone
permeability provided from the experiments, and only reservoir because of higher adsorption in sandstone
CEC is tuned as the history-matching parameter. The reservoir. Because the zwitterionic surfactants have
simulation result accurately reproduces the no oil recov- two active groups, they are classified as nonionic/
ery for the small slug injection because of the mixing. anionic, nonionic/cationic, and anionic/cationic sur-
This study successfully developed the analytical solu- factants. The expensive zwitterionic surfactants have
tions incorporating the geochemistry-induced wetta- higher tolerance to the temperature and salinity.
bility modification and comprehensive rheology Most of surfactants used in the application of