Related to the GasOilSands connection, I finally found a link to a paper explaining how the gas-field pressure can affect the SAGD extraction and the reason officials felt compelled to shut in a number of gas wells.

The development of SAGD projects in the region has been of great concern to natural gas producers. Natural gas producers in the greater Athabasca region have thousands of producing wells representing billions of dollars of investment. The source of the problem is that in many cases in the region, the Wabiskaw-McMurray geological zones in particular, rights have been issued to different lease holders, permitting the production of oil or natural gas in the same zone. When natural gas pools are in pressure communication with underlying bitumen reservoirs, the depletion of the gas pool causes lower pressures in the zone above the bitumen reservoir and when steam is injected into the bitumen reservoir, there is a high potential for the steam to escape into the depleted gas pool. In addition, in situations where a water zone exists above the bitumen, operating at lower pressures increases the risk of water invading the bitumen reservoir.

http://www.bus.ualberta.ca/CABREE/pdf/2005%20Spring-FortMac/BUEC%20560/Wooley-Gas%20Over%20Bitumen-B UEC%20560.pdf