Simulation of wellbore pipe flow in oil production engineering: Offshore concentric double-tube CO2-assisted superheated steam wellbore during SAGD process of heavy oil reservoirs

Heavy oil reservoirs are widely distributed around the world and play an important role in offshore oil and gas development. For heavy oil reservoirs, industrial productivity can only be obtained by effectively reducing the viscosity. In addition, by improving the steam injection pipe string, the production degree of the heavy oil reservoir can be effectively improved. In this paper, with the development of offshore heavy oil reservoirs as the background, the heat transfer characteristics of concentric double pipes are studied. Considering the influence of carbon dioxide on the superheated steam, a concentric double pipe flow model is established. The typical flow characteristics and the influence of carbon dioxide content are analyzed. The conclusions are as follows: (a) In the sea water section, the overall heat conduction rate of the concentric double pipe is reduced from 70.5 J/s (at 0 m) to 67.8978 J/s (at 120 m). In the formation section, the overall heat conduction rate of the concentric double pipe is reduced from 67.8978 J/s (at 120 m) to 61.5368 J/s (at 290 m). (b) For the integral joint tubing, the pressure of the mixed fluid of carbon dioxide and superheated steam in the integral joint tubing drops from 4.7 MPa (0 m) to 4.2399 MPa (290 m). (c) For the annular space, the pressure of the mixed fluid of carbon dioxide and superheated steam in the annular space drops from 4.7 MPa (0 m) to 4.3247 MPa (290 m).