Page 199 - Gas Wettability of Reservoir Rock Surfaces with Porous Media

Effect of Gas Wettability on Capillaries CHAPTER 5 183

(A) (B)

(C)
FIGURE 5.16
Front shape of oil-displacing gas in capillaries having different gas wettability. (A) Nongas-wettability (concavity, θ oil 5 38.50
degrees), (B) neutral-gas-wettability (plane, θ oil 5 93.26 degrees), (C) preferential-gas-wettability (convexity, θ oil 5 110.86 degrees).

gas-wetting alteration agent solutions of 25% and 40% concentrations, neutral-
gas-wettability and preferential-gas-wettability are realized, respectively.

5.2.3.1 EVALUATION OF GAS WETTABILITY OF GAS/OIL SYSTEM IN
SINGLE-STRAIGHT CAPILLARIES
The displacing fronts of gas/oil systems are as shown in Fig. 5.16, when the
static oil-displacing gas experiment is conducted on single-straight capillaries
treated with gas-wetting alteration agent solutions of 0.01%, 25%, and 40%
concentrations. The neutral kerosene is processed with low concentration
Sudan red.

5.2.3.2 EFFECT OF GAS WETTABILITY ON GAS/OIL PERCOLATION STATE
Nongas-wettability model: From Fig. 5.17A, it can be seen that in nongas-
wettability (oil-wet) model, there is serious spontaneous capillary imbibition.
Oil enters the model preferentially along the throat walls and advances toward
the outlet end of the model in a nonpiston way. The water-displacing gas front
presents meniscus and oil presents concavity.

Neutral-gas-wettability model: From Fig. 5.17B, it can be seen that in neutral-
gas-wettability model, oil displaces gas in the throat like a piston, and the
interface of oil and gas is a plane.

Preferential-gas-wettability model: From Fig. 5.17C, it can be seen that in the
preferential-gas-wettability model, the displacing front presents meniscus and