Expansion Velocity Model of Steam-Assisted Gravity Drainage considering Thermal Convection

Abstract

Steam-assisted gravity drainage (SAGD) is an important method used in the development of heavy oil. A heat transfer model in the SAGD production process is established based on the heat transfer effect caused by the temperature difference at the front edge of the steam chamber and the heat convection effect caused by the pressure difference. The observation well temperature method is used in this model to calculate the horizontal expansion speed of the steam chamber. In this manner, an expansion speed model considering heat convection and heat conduction is established for a steam chamber with a steam-assisted gravity drainage system. By comparing this with the production data extracted from the Fengcheng Oilfield target block, it is verified that the model can be effectively applied for actual field development. Simultaneously, by using the derived model, the temperature distribution at the edge of the steam chamber and production forecast can be predicted. Sensitivity analysis of the expansion rate of the steam chamber demonstrates that the larger the thermal conductivity, the faster is the steam chamber horizontal expansion speed, and the two are positively correlated; the larger the reservoir heat capacity, the slower is the steam chamber horizontal expansion speed. A larger heat capacity of the convective liquid indicates that there are more water components in the convective liquid, the viscosity of the convective liquid is low, and the expansion speed of the steam chamber increases accordingly. This research closely integrates theory with actual field production and provides theoretical support for the development of heavy oil reservoirs.

New Gas Tracer Convection–Diffusion Model between Wells in Heavy Oil Reservoirs

“…Su 6 created a multiphase and multitracer mathematical model that considers the diffusion, convection, and adsorption of the tracer based on the basic theory of tracer percolation. Although this research has perfected the gas tracer flow model and established a multiphase and multitracer flow model, it has neither considered the oil phase migration velocity in heavy oil reservoirs nor has it explained the gas tracer in the oil phase; 7 thus, it does not match the actual reservoir conditions. Wang 8 presented a mathematical model and a numerical approach to simulate the transport velocity and sweep efficiency of gas tracers.…”