Monitoring on CO2 EOR and Storage in a CCS Demonstration Project of Jilin Oilfield China

摘要

Jilin oilfield, located in Jilin Province of Northeast China, is conducting the first large scale demonstration project on CO2 EOR and storage. During the first stage, CO2 separated from a nearby natural gas reservoir (20-97% CO2 content) is injected into the northern part of Hei-59 oil block. Currently, the targeted oil reservoir, with an area of 1.7 km2 and oil reserve of 0.78x106 tons, has six CO2 injectors and twenty-five production wells with an inverted seven-spot injector-producer pattern. Up to now, nearly 150,000 tons of CO2 has been injected for a miscible flooding, and an expected incremental oil recovery of 10% would be achieved. In order to better evaluate the reservoir performance and ensure a safe injection and long-term storage of CO2, a monitoring program has been designed and deployed to monitor the EOR performance and the state of CO2 in the reservoir. The monitoring techniques used include CO2 tracers to monitor gas breakthrough in production wells and flow of CO2 across the reservoir, and bottom-hole pressure survey of producers to evaluate the miscibility effect on EOR combined with production data analysis. Geophysical techniques are also employed to detect possible fractures and their orientation and dimensions, which include electric spontaneous potential measurement and micro-seismic detections. Cross-well seismic is intended to monitor the flow and track the front of CO2 between wells. Data of geochemical monitoring from produced water can be used to estimate the amount of CO2 dissolved in reservoir fluids. CO2 dissolution in formation water and residual oil is one of the main storage mechanisms, which can greatly enhance the safety and effectiveness of subsurface storage. In this paper, the results of reservoir monitoring applied in the oilfield are present and analyzed, and forward work will be focused on optimizing EOR performance and verification of the geo-capacity storage in the targeted reservoir.