Under the expected operating conditions of a Steam Assisted Gravity Drainage (SAGD) pilot project, it is anticipated that both the injection and the production wells will be able to flow unassisted to surface should a loss of well control incident occur. Industry practice regarding the design of such flowing wells dictates that the well completion include double barriers in the production tubing string and the production casing annulus. Unfortunately, downhole equipment suitable for such a high temperature application does not currently exist. To help evaluate the comparative risk between a double and single barrier completion, a reservoir modeling study was conducted to investigate the flowing potential (flow rates, durations and composition of the fluids) of the SAGD pilot wells under various blowout scenarios.

This paper presents the results of this reservoir modeling study in terms of the coupled wellbore/reservoir behavior during the blowout condition. A commercial coupled wellbore/reservoir simulator was used along with a "custom" code developed to include a critical choke velocity constraint into the reservoir simulation considerations.

The various blowout scenarios investigated include flow through both the injection and the production wells, at three different points during the production life of the well pair (beginning of the steam injection phase, middle of the steam chamber development and end of the steam injection phase) and through three possible flow paths (through the tubing, through the tubing-casing annulus and through both the tubing and the annulus).

The reservoir modeling confirmed that both the injection and the production wells in this SAGD application have the potential for a blowout lasting for significant periods of times should a loss of well control occur, and with liquid rates that can be over 50 times the normal production liquid rates.

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