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Polymer flooding
Definition
Polymer is a material that contains molecular structure that have a large number of units bonded together. Polymer flooding is used in the enhanced oil recovery (EOR) to reduce water mobility, increase water viscosity which will improve oil recovery. The most common polymers used in EOR are hydrolyzed polyacrylamide (HPAM) and Xanthan Gum.
Fractional flow (fw) effect
Polymer flooding reduces the water cut and improves the oil recovery by reducing the mobility of water. There are several properties of polymer that affect the fractional flow, such as, the type of polymer, its concentration, and its molecular weight. Increasing the water viscosity reduces the mobility ratio, which reduces the fractional flow. (Demin W., et al., 2000) Stated that, the higher the molecular weight, the higher the recovery but a too high molecular weight of the polymer can block the pores in the pay zone. They reported that PAM reduced the water cut from 90 – 95% to 70% and increase recovery by 12%.
Fig. 2 shows a comparison between the fractional flow of the polymer flooding and water flooding.
Screening Criteria
The reservoir properties that are desirable for polymer flooding are summarized below[3][4][5]
| Criteria | Values |
| Reservoir lithology | Sandstone |
| Heterogeneity | Decreases sweep efficiency |
| Rock permeability (md) | > 10 |
| porosity | > 10% |
| Residual oil saturation (%) | > 30 |
| Reservoir temperature (C) | < 135 |
| Oil viscosity (cp) | < 10,000 |
| Salinity (ppm) | < 150,000 TDS |
Cost
When it comes to any project cost, NPV is one of the main factors to look at and consider. In the planning stage NPV is not the only value that helps the engineers in deciding; risk and uncertainties should be takes into consideration. Ibiam et al. (2020) did an optimization of polymer flooding to see the relation between NPV and different factors such as concentration, time of deployment, Shale cutoff, number of injectors and injection rate. The tornedo chart below was done by them to show which parameter is the most sensitive to NPV.[6]
The polymer concentration is an important factor, after that we can notice that NPV is sensitive to time of deployment and shale cutoffs. We can conclude from this that reservoir geology is an important factor in polymer flooding.
Ibiam et al. (2020) did a case study to compare polymer flooding to water flooding. They carried out reservoir simulations using the data from Watt field and found out that polymer flooding can increase the NPV in the range of 300 million dollars to 1.5 billion dollars.[6]
Low Vs High salinity polymer
Salinity
Injectivity and late arrival of oil are important factors when it comes to EOR, one of the main reasons why both issues might happen is the salinity of the formation water. (Unsal et al., 2017) did a detailed study on polymer salinity and its effect on injectivity.[7]
To evaluate the difference between low and high salinity polymer, the authors constructed a graph showing the pore volume injected vs pressure change and flow rate using the same core sample. As we can see below. for pressure profile, the low salinity polymer gives better results but when it comes to the flow rate high salinity polymer is more favorable.[7]
References
- ↑ "Polymer Flooding", Eor-alliance.com. [Online]. Available: https://www.eor-alliance.com/solutions/polymer/.
- ↑ Ding L, Wu Q, Zhang L, Guérillot D. Application of Fractional Flow Theory for Analytical Modeling of Surfactant Flooding, Polymer Flooding, and Surfactant/Polymer Flooding for Chemical Enhanced Oil Recovery. Water. 2020; 12(8):2195. https://doi.org/10.3390/w12082195
- ↑ Qian Sun, Turgay Ertekin,Screening and optimization of polymer flooding projects using artificial-neural-network (ANN) based proxies, Journal of Petroleum Science and Engineering,Volume 185,2020,106617,ISSN 0920-4105,https://doi.org/10.1016/j.petrol.2019.106617. (https://www.sciencedirect.com/science/article/pii/S0920410519310381)
- ↑ Ali Mohsenatabar Firozjaii, Hamid Reza Saghafi,Review on chemical enhanced oil recovery using polymer flooding: Fundamentals, experimental and numerical simulation, Petroleum,Volume 6, Issue 2,2020, Pages 115-122, ISSN 2405-6561, https://doi.org/10.1016/j.petlm.2019.09.003. (https://www.sciencedirect.com/science/article/pii/S2405656119300434)
- ↑ Delamaide, Eric "Polymer Flooding of Heavy Oil - From Screening to Full-Field Extension." Paper presented at the SPE Heavy and Extra Heavy Oil Conference: Latin America, Medellín, Colombia, September 2014. doi: https://doi.org/10.2118/171105-MS
- ↑ 6.0 6.1 6.2 Ibiam, Emmanuel , Geiger, Sebastian , Demyanov, Vasily , and Daniel Arnold. "Optimization of Polymer Flooding in a Heterogeneous Reservoir Considering Geological and History Matching Uncertainties." SPE Res Eval & Eng 24 (2021): 19–36. doi: https://doi.org/10.2118/200568-PA
- ↑ 7.0 7.1 7.2 E. Unsal, A.B.G.M. ten Berge, D.A.Z. Wever, Low salinity polymer flooding: Lower polymer retention and improved injectivity, Journal of Petroleum Science and Engineering, Volume 163, 2018, Pages 671-682, ISSN 0920-4105, https://doi.org/10.1016/j.petrol.2017.10.069.
External links
1 - polymer flooding | Oilfield Glossary (slb.com)
2 - Polymer waterflooding - PetroWiki (spe.org)
3 - Polymer Flooding for Enhanced Oil Recovery (stanford.edu)