A study of CO2 injection well selection in the naturally fractured undulating formation in the Jurong Oilfield, China

•Analysis of leakage and injection indicate that N3 is the optimal injection well.•ScCO2 had a larger vertical migration and not moved into fractures in 30 years.•Capacity coefficient J is defined as Jg and Jaq to differ ScCO2 and dissolved CO2. Oilfields are major sites for the implementation of carbon dioxide capture, utilization, and sequestration technology. The Jurong oilfield is located in the Subei Basin, which is an important petroleum exploration region in southern China. This study focused on evaluating the CO2 leakage risks and injection capacities of the exploration wells in the Jurong oilfield. A three-dimensional geological model was established to depict the naturally fractured undulating formation. The burial depth of selected wells N3, N10, Rong3, and Jubei1 decreases in order. Wells N3 and Jubei1 located in the greatest stratigraphic fluctuation. The results indicate that ScCO2 do not migrate into the fracture zones for a 30 years injection period, and they are conducive to pressure diffusion. The larger fluctuation causes a larger migration of CO2 in vertical, which is more obvious in the synclinal structure than in the anticlinal structure. The injection volume is proportional to the burial depth of wells. The 30 years’ injection volume of well N3 is 2.57 × 106 t which would not reduce more than 5% if there are other injection wells nearby. According to the analysis of the leakage risk and injection capacity conducted in this study, well N3 is the optimal injection well. We defined an effective injection coefficient J to represent the injection capacity of well, and we concluded that the injection capacity of ScCO2 and dissolved CO2 for study area are 8.96 × 108 t and 4.69 × 107 t, respectively.