Monitoring on CO2 migration in a tight oil reservoir during CCS-EOR in Jilin Oilfield China

Jilin Oilfield is conducting a large-scale demonstration project on CO2 FOR (enhanced oil recovery) and storage in China. CO2 separated from a nearby natural gas reservoir (15-30 mol% CO2) is injected into the northern part of H59 oil block with permeability and porosity of 3.5 mD and 12.7%, respectively. After about six years of operation, nearly 0.26 million tons of CO2 (0.32 HCPV (hydrocarbon pore volume)) has been injected into the thin oil layers with well-developed natural fractures. In order to track the movement of CO2 in the oil reservoir, a microseismic monitoring program has been implemented to map the CO2 flow anisotropy and estimate its sweeping efficiency. Gas tracer testing has also been conducted to examine the inter-well connectivity. The temporal change of produced CO2 has been analyzed in a real-time mode to monitor the dynamic response in production wells. It is demonstrated that the migration of CO2 in the thin oil layers can be successfully detected by the microseismic technique, and the sweeping profiles of CO2 obtained from the inverted microseismic are in good agreement with the produced CO2 rate from production wells as well as the reservoir's petrophysical properties. (C) 2016 Elsevier Ltd. All rights reserved.