Post on 18-Dec-2015
Investigation of Polymer Adsorption on
Rock Surface of High Saline Reservoirs
Mohammed M. AmroPetroleum & Natural Gas Eng. Dept.
King Saud University
2008 SPE Saudi Arabia Section Technical Symposium
Outline
• Introduction• Oil Recovery Methods
– EOR Mechanisms– EOR Processes
• Experimental WorkExperimental Procedures
Material Used
Results and Discussion
• Summary
• Physical Reasons:Existence of the interfacial tension between oil
and water, and wettability (capillary forces)High mobility ratio between water and oil
(viscous forces)
• Geological Reason:The heterogeneities in the reservoir rock
Causes for Poor Recovery
EOR Mechanisms
• The mechanisms of EOR:Eliminate or reduce capillary and Interfacial
tension to improve the displacement efficiency
Improve sweep efficiency by reducing the mobility ratio between injected and displaced fluids (Polymer, Thermal)
Act on both phenomena at same time (Nc)
CN
Capillary number
Displacing fluid velocity [m/day]
Displacing fluid viscosity [mPa.s]
Interfacial tension [mN/m]
For waterflooding, Nc is 10-6 to 10-7 (under certain assumptions)
If the Nc can be increased to 10-4 to 10-2,
the residual oil saturation will be reduced significantly.
Pk
L
Ratio of viscous forces to capillary forces
Apr 18, 2023
EOR Processes
Tertiary Recovery
Thermal ChemicalMiscible/
ImmiscibleOther
Steam drive
Steam stimulation
Hot water
In-situ combustion
Polymer
Surfactant
Caustic
Combination
CO2
Inert gas
Miscible Solvent
Flue gas
Microbial
Vibration
Electrical
• Offers good opportunity to maximizing the reserves in many depleted and waterflooded reservoirs
• Opportunities exist under economic conditions and current oil prize
Chemical Properties Desirable:• Good solubility (low concentration)• High injectivity• Long-term stability against:
– Electrolytes, - Bacteria, - Temperature– Oxidation, - pH-Value changes
• Low adsorption on the rock, special focus on carbonate reservoirs (Polymer flooding)
• Simple handling and Low cost
Chemical Flooding
• Decreasing the mobility ratio (M)
• Influence on volumetric sweep efficiency EV
EV =EA EI
Therefore, ED→Sorw will be reached more faster
EA = Areal efficiency and
EI = vertical sweep efficiency
Polymer Flooding
Apr 18, 2023
Mathematical Description of Polymer Rheology
*w w
ww
K P
V l
*
, (Resistance Factor)
w pa
w
pa wf
w w p
K P
V l
PTherefore R
P
Effective water viscosity
Effective polymer viscosity
Assumption: Vw = Vp (No ‘‘Inaccessible Pore Volume‘‘ for polymer)
Case 1: Only viscosity increase : Kw = Kp
*p p
pp
K P
V l
w pK K
*, (Resistance Factor)
*w pw
fp p w
KTherefore R
K
Case 2: Viscosity increase and permeability decrease:
Residual resistance factor (RRF)
1 2
2 1
(Residual Resistance Factor)w wrf
w w
PR
P
Mathematical Description of Polymer Rheology
0
2
4
6
8
10
12
14
16
0 1 2 3 4 5 6 7 8 9 10
Injected PV
RF
& R
RF
Resistance factor (RF) and Residual resistance factor (RRF)
RF & RRF are important factors to determine the concentration of polymer needed to perform polymer flooding (e.g. RF = 7 - 8 &
RRF = 1.5) or water shut off (Rf = 6 & RRF = 4).
Experimental Procedure
• Polymer solutions were prepared and evaluated at different salinities, shear rates, temperatures and concentrations.
• Core samples were flooded with polymer solutions (const. flow rate = 2.5 ft/day) until full adsorption (const. Pressure drop and const. effluent viscosity); RF was calculated
• The core samples were flooded with brine (Pressure drop and effluent viscosity were monitored); RRF was calculated.
Experimental Work
• Polymers (Xanthan, PAA),
• Biocide (Formaldehyde)
• Brine (83% NaCl and 17% CaCl2)
• Core samples (Berea SS with different Kranged from 200 – 1300 mD)
• Flooding apparatus.
Conclusions
• The viscosity decreases with increasing the shear rate up to a certain value beyond which it becomes almost constant.
• Xanthan viscosity is more affected by the shear rate rather than salt concentration, while PAA viscosity depends strongly on both factors.
• A reduction of permeability using polymer solution depends on the porous medium, the particular polymer, concentration of polymer, salinity, and injection rate.
• Polyacrylamide (PAA) can reduce the heterogeneity in reservoir at low salinity. High PAA concentration will be needed to tolerate the high salinity.
Cont. Conclusions
• Partially reversible adsorption (physical) from the rock surface occurred by brine flooding (RRF).
• The flooding velocity and the permeability have great effect on the adsorption.
• The temperature increase leads to delay the full adsorption on the rock surface. Therefore, more PV of solution is necessary .
• Thus, xanthan can be recommended, as a good polymer candidate to be used in high salinity reservoirs.