Polymer flooding Daqing

Luo et al (2002). The tested core permeability was 0.7 to 1.8 and the porosity was 0.2. In addition, the displaced oil was 9.5 mPa s at 70°C. Table 5.5 compares the performance of KYPAM with HPAM 1285 at a concentration of 1000 mg/L. A 0.4 PV injection volume was used. We can see that the flow behavior of KYPAM was better than HPAM 1285. KYPAM has been widely used in polymer flooding, ASP, and profile control projects in Daqing, Shengli, Huabei, and Xingjiang fields. Several field test cases are presented next. 

Bei-l-Qu-Duan-Xi was the first large-scale polymer flooding field application in the northern Saertu field, Daqing. There were 25 injectors and 37 producers in the test area in five-spot patterns. The target layers were PI1.4. The well spacing from injector to producer was 250 to 300 m. Some of the reservoir and flnid data are shown in Table 5.22 (Chang et al., 2006 Yan et al., 2006). 

Most of polymer floods in Daqing were conducted in oil zones. There are a significant amount of reserves in transition zones. In 1995, the Sabei transition zone was selected for a polymer flooding pilot test. The target formation was PI1.4. The basic reservoir, fluid, and well data are shown in Table 5.24 (Niu et al., 2006). The well pattern was irregular four-spot. 

Basically, the polymer flooding performance in the transition zone was similar to that in other oil zones. Some of the observations in performance compared with the oil-zone polymer floods in Daqing (Niu et al., 2006) follow. 

Daqing polymer flooding performance showed that incremental oil recovery factor peaked when the amount of polymer injected was 180 to 210 mg/L PV. 

Daqing polymer flooding performance shows that oil rate increased before produced polymer concentration increased. Produced polymer concentrations peaked at 400 to 900 mg/L, approximately half of the injected concentration. As mentioned earlier, the produced water with polymer may be re-injected to save water cost and polymer cost. 

Almost all chemical flood projects are started after some waterflood history. We want to know whether early chemical injection could be a better option. To do that, we change the water injection PV before chemical injection so that average oil saturations (So) before SP are different. The results are shown in Table 9.2. We can see that different total injection PVs are required to achieve about the same incremental recovery factor. The incremental oil recovery factor (RF) is defined as the RF from an SP case minus the RF from the 1.5 PV waterflooding case. The later SP is started, the higher the total injection PV is reqnired. Therefore, it is better to start snrfactant-polymer flood earlier to accelerate prodnction, and thns, less water will be injected. Such results have been confirmed by the ASP corefloods in Daqing (Li, 2007). 

Liao, G.-Z., 1998. Comprehensive Study of Daqing Oilfield Alkaline-Surfactant-Polymer Flooding. Post-doctoral report, Daqing. 

Liu, H., 1995. Status and prospect of polymer flooding research in Daqing Field. Petroleum Exploration and Development 22 (2), 64-67. 

Wang, B.-Y., Zhang, J., Jia, Z.-S., 1997a. Study of commercial scale application of polymer flooding in Daqing Oil Field. Petroleum Exploration and Development 24 (6), 51-55. 

Wang, D.-M., Cheng, J.-C., Li, Q., Li, L.-Z., Zhao, C.-J., Hong, J.-C., 1999b. An alkaline biosurfactant polymer flooding pilots in Daqing Oil Field. Paper SPE 57304 presented at the SPE Asia Pacific Improved Oil Recovery Conference, Kuala Lumpur, 25-26 May. 

Wang, D.-M., Liu, H., Niu, J.-G., Chen, P.M., 1998b. Application results and understanding of several problems of industrial scale polymer flooding in Daqing Oil Eield. Paper SPE 50928 presented at the SPE International Oil and Gas Conference and Exhibition, Beijing, 2-6 November. 

Wang, D.M., Zhang, Z.-H., Cheng, J.-C., Yang, J.-C., Gao, S.-T., li, L., 1997c. Pilot tests of alkaline/surfactant/polymer flooding in Daqing Oil Eield. SPERE (November), 229-233. 

There are many faults whose cUstribution is complex in Daqing Oilfield SW-II (Wei Jide, 2001 j.The basic well pattern is put into development by Une well pattern in 1964. In 1990, primary infill wells pattern uses two sets of layer system to develop S and PII poor oil layers. Secondary infill wells pattern is used to adjust S and PII thin and poor oil layers and untabulated reservoir in 1998. In 2000, as P15-1-61—7 oil layers and PI 1-4 oil layers have differences in geologic feature, the polymer flooding is only put into development in PII—4 oil layers. So far, there are only some wells of line well pattern is under production in PI5-F61—7 oil layers. And the flood pattern of P I5-F61—7 oil layers is very incomplete. 

Dong, H., S. Fang, et al. (2008). Review of Practical Experience Management by Polymer Flooding at Daqing. SPE/DOE Symposium on Improved Oil Recovery. Tulsa, Oklahoma, USA. 

On the basis of theoretical calculations. Fig. 1 provides a relationship between water cut and water saturation for the reservoir conditions at Daqing. If ixJUw = 15 (mobihty ratio is 9.4), the oil-displacement efficiency Eo) is only 50% when the water cut achieves 98% and the remaining oil saturation So) is 0.4. However, if the = 1 (mobihty ratio is 0.63), the oil-displacement efficiency can increase to 61% when water cut reaches 98% and the remaining oil saturation is 0.31. Thus, Ed can be increased greatly by polymer flooding. 

In recent years, polymer flooding has been expanded to more-heterogeneous parts of the Daqing field. For these cases, the viscosity of injected polymer solution has been designed at 50 cp or more, with new polymers. 

To achieve an effective polymer flood, the well-pattern design and the combination of oil strata must be optimized. To obtain the best benefit, the connectivity factor should be above 70% and the permeability ratio should be less than 5 in a single unit of flooded zones. For the main-target oil zones in the best class and second class oil strata at Daqing, well spacing with five-spot patterns should be 150 to 250 m. 

To recover unswept mobile oil at Daqing, foam is being explored for possible application after polymer flooding. 

Fu, T. et al. 2004. Calculation Method of Connectivity Factor for Polymer Flooding. Petroleum Geology Oilfield Development in Daqing 23 (3) 81-82. 

Li, R. and Chen, F. 1995. Reasonable Well Pattern and Spacing for Polymer Flooding in Daqing. Yearly Report 11. 

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