Page 229 - Gas Wettability of Reservoir Rock Surfaces with Porous Media

Application of Gas Wettability CHAPTER 6 213

wettability of cutting surfaces is altered into oleophobic and hydrophobic, and
the cuttings preferentially contact bubbles formed the bubble/cutting aggre-
gates. The relative density of cuttings is reduced and the pulling force of cut-
tings by the drilling fluid increases with buoyancy, thereby cleaning cuttings
and purifying the annular space of wells.

6.2.2 Preparation and Properties of Cutting Carrying
Agent FGC-1
Acrylate monomer A was slowly added in an anionic surfactant emulsion sys-
tem in a 500 mL four-mouth flask that has a stirrer, condenser pipe, N 2 ingress
pipe, and thermometer to prepare an even preemulsion. The initiator was
added at a certain temperature and allowed to react for 1 hour, and then fluo-
rine monomer B was added and allowed to react further for 3 hours. The pH
was then adjusted to neutral and the emulsion was not stirred thereafter. The
cutting carrying agent FGC-1 was obtained by filtering and purifying the
emulsion.

6.2.2.1 WETTING ALTERATION
The core slice was soaked in FGC-1 (wt.%) water solutions at different concen-
trations for 4 hours, and dried naturally at room temperature for 30 minutes
to remove any unnecessary treatment agent on the core surface (Fig. 6.10).
When the core is treated with FGC-1, the surface wettability shows obvious
changes. With increasing concentration, the core surface gradually becomes
hydrophobic from the initial oil-wet and weak water-wet surface, and the degree
of transformation is increasingly obvious. The maximum contact angle of dis-
tilled water is up to 110.5 degrees, and that of n-Hexadecane is 93.5 degrees. It
can be seen that FGC-1 can change the wettability of core surfaces to make it
oleophobic and hydrophobic, and to be preferentially in contact with gas.

120
100

80
Contact angle º 60

40
n-Hexadecane
Distilled water
20
0
0.0% 0.1% 0.2% 0.3% 0.4% 0.5%
FGC-1 concentration
FIGURE 6.10
Relation of FGC-1 concentration (wt.%) and the contact angle of distilled water.