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.
Highlights
Steam-assisted gravity drainage (SAGD) is one of the most important methods currently used for the development of heavy oil
For SAGD production, the degree to which the steam chamber is developed directly determines the developmental effect of the steam-assisted gravity drainage system as well as the efficiency of the oil displacement and its recovery factor
Gravity pulls the condensate and heavy oil down from the drain zone to the edge, and down to the production well, while the heat exchange is predominantly produced by heat conduction and convection at the edge of the steam cavity
Summary
Steam-assisted gravity drainage (SAGD) is one of the most important methods currently used for the development of heavy oil. The newly changed steam chamber expansion speed in this study takes into account the influencing factors when the steam cavity expands but again idealises the reservoir conditions while ignoring the heat convection phenomenon caused by the pressure difference This steam cavity expansion model is based only on the heat transfer that considers heat conduction. As the steam cavity’s heat transfer model considers both heat conduction and heat convection, the observation well temperature method is used to establish the expansion velocity model of the steam cavity This is used to calculate the horizontal expansion velocity of the drain zone and predict the temperature distribution in both the drain zone and in SAGD production. The first term on the left side of the equation represents the heat conduction of the steam chamber, and the second term on the left side represents the heat convection that runs perpendicular to the direction of the steam chamber: K
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