Abstract In 2007, work was published on the predictability of hydrogen sulphide production in Athabasca SAGD projects. It was possible to predict the hydrogen sulphide production per unit volume of bitumen produced against steam zone temperature, by assuming pseudo-zero order kinetics, using the Arrhenius energy published by Strausz and his co-workers at the University of Alberta. An examination of field results for carbon dioxide production in Athabasca projects shows that the predictability of carbon dioxide is less simple. The carbon dioxide production is not erratic but goes through a distinct temperature minimum, an important result in view of the dependence of silica production in SAGD and scaling behaviour in facilities on carbon dioxide. Again, as for hydrogen sulphide production, it is possible to estimate carbon dioxide production by a simple graphical technique, which is shown. Partial explanations for the observed temperature minimum are offered. Introduction The production of acid gases in SAGD projects is a matter of some importance. A number of operational characteristics depend on the presence of carbon dioxide as produced through dissolution in produced water. It has been shown previously(1) that silica production is strongly dependent on dissolved carbon dioxide. There is likewise evidence that aggressive degassing of produced water has caused unwanted scales of silicate minerals, such as talc, chrysotile and tremolite, to be deposited in various parts of the facilities(2). A simple production diagram for hydrogen sulphide in SAGD was recently reported by Thimm(3). The hydrogen sulphide produced per unit bitumen could be described as a simple Arrheniustype relationship with steam zone temperature, using an activation energy of 56,220 - 65,920 J/mole (13,450 - 15,770 cal/mole). The assumption of pseudo-zero order kinetics yielded a smooth curve which fitted the field data for most SAGD projects in Athabasca satisfactorily. The behaviour for carbon dioxide was previously expected to be similar, with an Arrhenius activation energy of 17,520 J/mole (4,192 cal/mole)(4).