Impact of Shale Barriers on Steam Chamber Evolution and Heat Distribution during the Rising Stage of Steam-Assisted Gravity Drainage (SAGD).

Shale barriers negatively impact thermal recovery processes of oil sand or ultraheavy oil, particularly during the rising stage of SAGD, by affecting oil flow, steam chamber evolution, and heat distribution. Existing mathematical models for the rising stage of SAGD often overlook the influence of shale barriers on the evolution of the steam chamber and heat distribution. This study includes experiments to investigate the impact of a single shale barrier above the production well during the rising stage of the SAGD. Additionally, a new mathematical model for the SAGD rising stage, which accounts for the impact of shale barriers, is developed, and the predicted chamber evolution is compared with laboratory-measured temperature data to verify its accuracy. Following the model validation, the impact of the shale barrier on steam chamber evolution and heat distribution was investigated. The results indicate that the moment of contact between the steam chamber top interface and the shale barrier represents a critical transition point. Prior to this contact, the steam chamber exhibits a vertical growth trend; however, after the contact, the chamber expands laterally along the shale barrier. Furthermore, increasing the distance between the shale barrier and the production well delays the moment of contact between the steam chamber top and the shale barrier, while enlarging the length of the shale barrier significantly prolongs the time required for steam to reach the barrier boundary. More importantly, after the top interface of the steam chamber makes contact with the shale barrier, the heat distribution pattern changes, leading to an increase in heat loss, which reduces the effective heat available for steam chamber expansion and consequently slows down the lateral-expansion velocity of the steam chamber.