CO2 Sequestration-EOR in a Tight Oil Reservoir: Estimation of Dynamic CO2 Storage Capacity Using a Two-Stage Well Test

Abstract

Evaluation of an accurate CO2 dynamic storage capacity, ultimate recycled CO2 and enhanced oil recovery (EOR) are key factors for a successful CO2 EOR project. The Yanchang Petroleum Company (YP)’s low permeability oil field is located at Ordos Basin - China with a very short and inefficient primary and secondary oil recovery and, therefore, YP proposed CO2 EOR as a potential tertiary oil recovery approach. In this work, the Wuqi reservoir in the Yanchang field is selected to evaluate the feasibility of full-field CO2 sequestration-EOR. The Wuqi reservoir has been in production for over a decade with historical data that can be used for a history matching process. To acquire essential dynamic data for evaluation of the CO2 injectivity/dynamic storage capacity, a specific two-stage pilot well test is proposed to inject first water and then CO2. It will provide relatively accurate calculated permeability for water (test phase 1) and CO2 (test phase 2) at the injection well. Also, the test will qualitatively estimate the location of water and CO2 fronts in the reservoir over time. Using two monitoring wells simultaneously, significantly increases the radius of investigation (ROI) that can be achieved for a given injection scenario and will also describe directional heterogeneity in the reservoir. When informed by the pilot test data, the model can be used to estimate the CO2 injection rate, ultimate cumulative CO2 injection and oil production and CO2 injection well numbers over 15 years of CO2 sequestration-EOR, which can be utilised for further techno-economic analysis of the project.