NUMERICAL SIMULATIONS OF NITROGEN FOAM AND GEL-ASSISTED STEAM FLOODING FOR OFFSHORE HEAVY OIL RESERVOIRS

Abstract

Chemical-assisted steam flooding is a promising method for heavy oils. However, few researches have investigated the performance of nitrogen foam and gel-assisted steam flooding (NFG-A-SF) on offshore heavy oil reservoirs. In addition, the effects of operational parameters on the performance of NFG-A-SF are still unclear. In this study, a numerical simulation model was developed to simulate NFG-A-SF processes for offshore heavy oil reservoirs. Then, a comparison of NFG-A-SF and steam flooding was made to assess the feasibility of NFG-A-SF in a well group at Oilfield L, a typical offshore heavy reservoir of Bohai Bay, China. Finally, sensitivity analysis was conducted to investigate the effects of the chemical agent type, injection mode, injection timing, cycle number of gel and nitrogen foam, polymer concentration, crosslinking agent concentration, foaming agent concentration, and gas-liquid ratio on NFG-A-SF performance. The results showed that, compared with SF, the NFG-A-SF has better performance, which is a potential and effective method for offshore heavy oil reservoirs. The NFG-A-SF should be implemented as early as possible. During the NFG-A-SF processes, gel slugs should be injected alternately with nitrogen foam slugs, and the gel slugs should be injected first before nitrogen foam slugs. Considering the economic benefit, there are optimum cycle numbers of gel and nitrogen foam, gas-liquid ratio, concentrations of polymer, crosslinking agent, and foaming agent.