Recent Developments in Understanding Gas Behaviour in SAGD Projects Thimm Engineering Presents: Recent Developments in Understanding Gas Behaviour in SAGD Projects Dr. Harald F. Thimm Thimm Engineering Inc.

Henry’s Law and Solubility Henry’s Law governs the solubility of gases in solvents Solubility is inversely proportional to Henry’s Constant (KH) Absolute solubility (y = 1) of a gas = 1/K, where K is the equilibrium constant Solubility of gases in water is normally reduced when temperature rises However As critical point is approached, solubility increases sharply

Henry’s Law (cont.) This increased solubility in water at high temperature is followed by: CH4, C2H6, N2, O2, CO2, noble gases1 H2S2 Asymptotic behaviour near critical point governs at 180°C or even lower in some cases This behaviour is important at SAGD conditions 1. Harvey & Levelt Sengers 2. Suleimenov & Krupp

Henry’s Law Constant for Methane in Water Henry’s Law Constant for CH in H O 4 2 11.5 11.0 10.5 Point of minimum solubility At high temperature, solubility increases dramatically / 1 bar) 10.0 H ln(K 9.5 9.0 8.5 8.0 250 300 350 400 450 500 550 600 650 Temperature (K)

K-Values: The Solubility of Selected Gases in Water K-Values for Selected Gases in Water at Saturated Steam Temperatures 120000 100000 80000 nitrogen CO2 K-Value 60000 methane oxygen 40000 20000 100 115 130 145 160 175 190 205 220 235 250 265 280 295 310 Temperature in Degrees C

Gases in Petroleum Production by SAGD Methane Carbon Dioxide Hydrogen Sulphide Nitrogen (<2%) Hydrogen (<2%) All become significantly soluble in water (steam condensate) in the 180°C - 240°C steam temperature range

SAGD Steam Chamber STEAM Ceiling drainage STEAM Slope drainage Horizontal injection well Horizontal production well Drainage to the production well is essentially only bitumen & water. Gas production is therefore via dissolution in produced fluids Henry’s Law can be used to predict this gas production

Typical Results: Field vs. Predicted Normally GOR = 1 – 8 H2S varies from 1,000 to 30,000 ppm Predictions match field results GOR = 3.8 GOR = 2.6 % CO2 = 47 % CO2 = 59 % CH4 = 52 % CH4 = 40 12,000 PPM H2S 12,250 PPM H2S

Flexibility of Predictive Method In many cases, gas is injected or steam pressure is varied during the life of a SAGD well pair Both have the effect of altering the methane to carbon dioxide ratio in produced gases This method is robust enough to predict the effects of these changes on produced gas composition, as shown on the following slide

Field vs. Theoretical Results Produced Gas Carbon Dioxide Content Carbon Dioxide % 1 2 3 4 5 6 Production Phase Field Measurements Calculated by this theory

Applications of Method Re-pressurisation of gas caps with another gas Greenhouse gas predictions Facilities – prediction of gas partitioning Prediction of hydrogen sulphide - sulphur recovery needs for commercial plants Carbon dioxide and flue gas injection Oxygen breakthrough in firefloods – phenomenon is a possible contributor? Other (corrosion, scaling, etc. - dependent on CO2)