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Results of the Second Polymer Flooding Pilot at East-Messoyakhskoe Oil Field and Future Plans
- Publisher: European Association of Geoscientists & Engineers
- Source: Conference Proceedings, IOR 2021, Apr 2021, Volume 2021, p.1 - 10
Abstract
East-Messoyakhskoe is a giant oil field located onshore in Artic conditions with original oil reserves about 1 bln. tones. The field was discovered in 1980-s, but development started only in 2016. The main reasons, beside remote location, are geological and reservoir challenges. The main reservoir is PK 1–3 reservoir, which was formed in fluvial deposition environment, is highly heterogeneous (permeability 50–5000 mD), cold (16 °C) and unconsolidated reservoir, located at shallow depth (800 m) with viscous oil (111 cP).
The field is developed by 1 km length horizontal wells with short spacing (150 m). Waterflooding was selected as base reservoir development method with predicted recovery factor below 15%. And reservoir engineering team was not going to agree with this fact and proactive search of technologies started. After EOR screening it was obvious that polymer flooding is technology with the highest potential.
From October 2017 till June 2019 first polymer flooding pilot was made with polymer solution injection in two wells (SPE 201822). 10% pore volume was injected with surveillance program. Incremental oil of 17200 tons of oil or 43 tons of oil per 1 ton of polymer was achieved and pilot was successful. However initially selected viscosity of 60 cP was high, which lead to high injection pressure and injectivity decline, not clear pressure limits.
So it was decided to run the second field pilot in different geological zones. Polymer solution was continuously injected from July 2019 till February 2020, during which 3 % pore volume was injected. Viscosity was reduced to 10 cP, which allowed maintaining initial target injection rates. The maximum injection pressure was increased from 78 atm up to 85 atm at wellhead without fracturing with signs of stabilization. Also all 3 injection wells were selected in different geological zones and 3 different pattern were formed. Water injection history was increased from 3 to 12 months which allowed to have accurate “baseline” for comparison. Detailed analysis for each pattern was performed. Thus, incremental oil production was calculated by analytical methods and dynamic model, which was history matched on pilot injection. Economic analysis showed that pilot is economically viable.
Therefore, the second pilot was considered to be successful, although not all initially planned polymer was injected. Based on the updated dynamic model polymer injection forecast was made, which resulted in economically efficient business cases in different geological zones. Also remaining uncertainties are highlighted and future plans are discussed.