1. 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.

2. 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

3. 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

4. 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)

5. 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

6. 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

7. 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

8. 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

9. 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

10. 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

11. 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)