Page 103 - Gas Wettability of Reservoir Rock Surfaces with Porous Media

Gas-wetting Alteration Agent and Gas-wetting CHAPTER 3 87

feature. They can significantly reduce the surface tension of a solution
when the concentration is very low. Normally, when the concentration
of the fluorocarbon surfactant is about 0.01%, the surface tension of the
water solution can be reduced to 15B20 mN/m.
2. High chemical stability: The C F bond in fluorocarbon surfactants is
quite stable, ensuring high resistance to strong acids, alkalis, and oxi-
dants, and they can be used under the harsher environments.
3. High thermal stability: In general, fluorocarbon surfactants do not

decompose when heated to 400 C, due to the stable C F bond.
4. Hydrophobic and oleophobic: The fluorine-containing hydrocarbon
group in the fluorocarbon surfactant molecule has both hydrophobic
and oleophobic groups, which prevents some fluorine-containing sur-
factants from adhering to water-based or oil-based substances, thus
greatly reducing pollution.
5. Good wetting permeability and foaming stability: Fluorocarbon surfac-
tants greatly improve liquid wettability and permeability, and improve
wettability and spreadability on the surface of various substances. The
fluorocarbon surfactant can generate foam stably in the material in cases
where the common surfactant cannot generate foam.
6. Excellent compound performance: Fluorocarbon surfactants have stron-
ger capacity for reducing surface tension, when compounded with
hydrocarbon surfactants, which can greatly reduce the usage cost of fluo-
rocarbon surfactants. Also, fluorocarbon surfactants can form water-
containing stable liquid crystals in water, become water-insoluble active
substances, and disperse in water. Thus, any two different types of fluo-
rocarbon surfactants can mutually combine [5,6].
7. Environment-friendly: Fluorcarbon surfactants have very low toxicity
and are used in small concentration, causing less environmental
pollution.
8. Other advantages: Include emulsion dispersion, antistatic properties,
lubrication leveling, de-filming, etc.

3.1.2 Fluorocarbon Surfactant Synthesis and Evaluation of
Gas-wetting Alteration Effect
3.1.2.1 SYNTHESIS OF INTERMEDIATE (N-[3-(DIMETHYLAMINO)-PROPYL
GROUP] PERFLUORINATED SULFONYL FLUORIDE)
1. Chemical equation
The synthesis reaction equation for intermediate N-[3-(dimethylami-
no)-propyl group] perfluorinated sulfonyl fluoride is shown as follows:

CH 3 CH 3
SO 2 F+H 2 N (CH 2 ) 3 N SO 2 NH (CH 2 ) 3 N CH 3 +HF
CF 3 (CF 2 ) 7 CH 3 CF 3 (CF 2 ) 7