Chemical EOR: Polymer Flooding
1. If polymer degradation could be substantial @ elevated temperatures (over 70 deg C), can’t we expect the stability of polymers @ a relatively deeper depths (over 1.5 km)?
Feasible to effectively prevent the thermal degradation of partially hydrolyzed polyacrylamides that leads to an elevated hydrolysis of HPAM amide groups, which subsequently leads to precipitation with divalent cations;
and to what extent,
the application of copolymers/monomers such as ATBS (Acrylamide-Tertiary-Butyl Sulfonate) and NVP (N-Vinyl-Pyrrolidone) would do the needful in HPHT reservoirs, especially @ elevated salinities?
Also, @ field-scale, how easy would it remain to arrest the interactions of hydrolyzed polymers with divalent ions, which eventually lead to the reduction of polymer coil size, and which subsequently either lead to reduction in solution viscosity or leading to precipitation of polymers?
2. How successful a polymer flooding would remain to be, when (a) reservoir permeability falls below 100 md; and (b) molecular weight of used polymers often exceed 25 million Daltons?
Whether mechanical entrapment (which negatively affects the propagation of polymers in the reservoir as larger polymer molecules tend to plug in relatively smaller pore throats, which subsequently reduces the reservoir permeability and polymer solution concentration) would just ruin polymer flooding under the above two conditions?
3. Whether polymer flooding would be able to produce increased oil, even, if the oil happens to be heavy?
If so, then, how lesser - could the injected polymer viscosity be - with reference to the oil viscosity?
How much smaller ‘end-point relative permeability to water’ be – with reference to that of ‘end-point relative permeability to oil’ in such cases?
Favorable mobility ratio is no more a constraint in polymer flooding?
4. If polymer flooding could remain to be - at its best, with around 100-1000 md permeability; 1000-50,000 ppm salinity; 100-1000 m depth; 15-70 deg C temperature; then, could we seek ML/AI in order for the polymer flooding to perform better with permeability lesser than 100 md; with salinity greater than 50,000 ppm; depth greater than 2 km; and temperature greater than 100 deg C – by playing with various polymer parameters that critically influences stability to (a) temperature; (b) elevated water salinity; (c) mechanical degradation; (d) biodegradation; (e) dissolvability; (f) viscosifying characteristics; and (g) adsorption to rock surface?
5. Why does the price of xanthan (the most extensively used biopolymer) remain to be much larger than that of HPAM (the most widely used polymer in the world)?
How do generally overcome problems with dissolving HPAMs in a real field scenario?
Whether the lack of thermal and brine hardness stability of synthetic HPAMs in a real field scenario is no more, a concern?
6. As far as polymers are concerned, whether, elevated temperature remains to be more sensitive than elevated salinities?
7. Whether the pseudo-plastic behavior observed during core-flooding experiments with xanthan solution (that imparts enhanced resistant to mechanical degradation @ lab-scale) could be extrapolated to field-scale as well?
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