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PGE 387K, 2019 spring, HW3 Due 3/9/2019 Summaries of articles 1. Takaqi, S., Pope, G. A., Sepehrnoori, K., Putz, A. G., & BenDakhlia, H. (1992, January 1). Simulation of a Successful Polymer Flood in the Chateaurenard Field. Society of Petroleum Engineers. doi:10.2118/24931-MS Tagaki et al. (1992) studied a comprehensive field polymer flood project, along with UTCHEM simulations, sensitivity analysis and field data comparison. They found that oil recovery increased with better grid resolution, higher adsorption, higher permeability reduction, higher heterogeneity and greater layering effect. After comparing with field data, they found simulation results generally agree with field data. Tagaki et al. (1992) also found out that polymer grading have negligible difference with ungraded method, demonstrating that fingering has negligible effect in this case. The most important point from this paper would be that polymer both increases Esweep and reduces S ¿ . 2. Poulsen, A., Shook, G. M., Jackson, A., Ruby, N., Charvin, K., Dwarakanath, V., … Ellis, M. (2018, April 14). Results of the UK Captain Field Interwell EOR Pilot. Society of Petroleum Engineers. doi:10.2118/190175-MS Poulsen et al. (2018) conducted a comprehensive field analysis regarding polymer flooding in the Captain field offshore UK. Detailed polymer design, sensitivity analysis regarding the economics, injectivity test, polymer performance and evaluations, post flood surveillance studies are all carried out and several operation variables that the operator is unsure is made clearer. In a word, the take away from this paper is that Polymer flooding can be successfully implemented in a subsea project. And it can efficiently improve the NPV, based on an existing water flood (by speeding up and increasing the recovery). 3. Levitt, D., & Pope, G. A. (2008, January 1). Selection and Screening of Polymers for Enhanced-Oil Recovery. Society of Petroleum Engineers. doi:10.2118/113845-MS Levitt, D. and Pope, G. A. (2008) examined the performance of different available commercial polymers, under various settings and tests (ion concentrations/free radicals/pH/thermal & chemical stability) to provide enough information for field application. Generally speaking, the tested polymers are more insensitive to the level of Na+ concentration (viscosity levels out at higher Na+ concentration). Interestingly, sodium carbonate/sodium dithionite can help prevent serious viscosity loss due to higher temperature. The most important point to extract from this paper would be that calcium ions concentration is very detrimental to the polymer’s thermal stability and should be avoided at all cost. 4. Delamaide, E. (2018, October 19). Polymers and Their Limits in Temperature, Salinity and Hardness: Theory and Practice. Society of Petroleum Engineers. doi:10.2118/192110-MS

Delamaide (2018) conducted a study on performance of various polymers, under different settings (high T, high salinity). He found out that HPAM can be used at low temperature (given low salinity of injection water), co-/ter- polymers can be used at higher temperature and salinity, and associative polymers can be used if freshwater injection is not feasible. Except for HPAM, other polymers are more expensive. Therefore, careful decision needs to be made. The most important point is that HPAM generally can be used for most field project, but future work should aim at improving polymer performance at temperatures above 100°C. 5. Chatzis, I., & Morrow, N. R. (1984, October 1). Correlation of Capillary Number Relationships for Sandstone. Society of Petroleum Engineers. doi:10.2118/10114-PA Chatzis and Morrow (1984) studied the relationship between capillary number and residual oil saturation in various sandstones. They found that the value of normalized residual oil ratio is consistent with different definition of capillary number. The most important take away from this paper would be that as the capillary number increases, usually residual oil saturation decreases. However, the derived correlation describing this phenomenon could not be applied to polymer flooding, since the residual oil saturation depends also on IFT, wettability and viscosity ratio. 6. Kamath, J., Meyer, R. F., & Nakagawa, F. M. (2001, January 1). Understanding Waterflood Residual Oil Saturation of Four Carbonate Rock Types. Society of Petroleum Engineers. doi:10.2118/71505-MS] Kamath et al. (2001) studied the effect of pressure gradient and capillary numbers on the remaining oil saturation in carbonate rocks. Four rock samples are used and each sample has different pore size distribution and pore body-throat aspect ratios. Good agreements between unsteady state/ steady state and cleaned/restored measurements are achieved. The important takeaway from this paper is that, correlation between critical N C and remaining oil saturation (ROS) is not valid for carbonate rocks, since various pore size distributions and pore structures exist. However, body-throat aspect ratio has a significant relationship with ROS (higher aspect ratio, higher ROS). 7. Shook, G. M., Pope, G. A., & Asakawa, K. (2009, January 1). Determining Reservoir Properties and Flood Performance From Tracer Test Analysis. Society of Petroleum Engineers. doi:10.2118/124614-MS Shook et al. (2001) discussed the application of tracers in water flooding. Concepts such as residence time, moment analysis, storage capacity Φ and flow capacity F are introduced. Detailed derivations are shown to calculate the variation of oil saturation, swept volume, and sweep efficiency with respect to time and error analysis and comparison with production data of a quarter of five-spot pattern proves the reliable accuracy of results obtained from tracer test. The take away from this paper would be that non-partitioning tracer can keep track of water swept volume, while partitioning tracer can record oil volume.

8. Cheng, H., Shook, G. M., Taimur, M., Dwarakanath, V., Smith, B. R., Muhhamad, S., … Putra, K. A. D. (2011, January 1). Interwell Tracer Tests to Optimize Operating Conditions for a Surfactant Field Trial: Design, Evaluation and Implications. Society of Petroleum Engineers. doi:10.2118/144899-MS Cheng et al. (2011) conducted two interwell tracer tests (ITT) and gained valuable insights from these tests for the second surfactant field trial. Residence time distributions, Swept volume calculations and F- Φ curves are made to interpret the ITT1. However, large discrepancies are found between simulation and the calculations. Then, reservoir drift, higher permeability region, injection rate and earth model are all corrected and better results are obtained in ITT2. Therefore, the most important lesson from this paper would be that tracer tests are very cost-effective, and are able to identify errors in simulation and reduce uncertainty for S/P field trial.

Critical Review Soeder, D. J. (1986, February 1). Laboratory Drying Procedures and the Permeability of Tight Sandstone Core. Society of Petroleum Engineers. doi:10.2118/11622-PA In the paper by Chatzis and Morrow (1984), they provided the detail of core preparation process of the sandstone they acquired. Extensive heating and drying process were undergone to prepare all the sandstone. Nevertheless, Soeder (1986) stated that over-drying may actually change the pore structure of the sandstone with low permeability, such as the cores like “Berea C-O” and “Berea HB-2”. Soeder (1986) explained that high temperature will possibly remove the clay minerals that cause swelling. This would actually improve the absolute permeability and would not render the experimental results representative of the actual reservoir....