Page 25 - Gas Wettability of Reservoir Rock Surfaces with Porous Media

Concept of Gas Wettability and Research Status CHAPTER 1 9

wettability of the core from “preferential liquid-wet” into permanent “prefer-
ential gas-wet” and keep the temperature resistance up to 140 C. The flow test

of single core and parallel core indicate that the optimized gas-wet alternation
treatment can increase the fluidity of liquid and improve the gas production
without decreasing the absolute permeability of the core.
Under the condition of simulated reservoirs, Al-Anazi et al. [19], evaluated the
effects of fluoride and silane treatment (totally 13 kinds) in relieving conden-
sate liquid block, thereby improving relative permeability of gas and postpon-
ing condensate liquid accumulation in 2007. The results of core flow tests
prove that fluoride FS-B significantly improves the relative permeability of gas
in a sandstone core, and that the effects of gas-wet alternation are closely
related to factors including core volume processed, core aging time, core per-
meability, and experimental temperature. Gas-wet alternation caused by silane
treatment requires less injection volume and shorter aging time, and the effect
is related to factors including core permeability, saturation of bound the water,
etc. The effects of gas-wet alternation for the core surface that has undergone
silane treatment, where the CA of water is 116 degrees and that of condensate
liquid is 114 degrees, realizing the gas-wet alternation. In addition, the analy-
sis from the ESEM experiment proves that silane can realize the gas-wet alter-
nation of sandstone.
In 2008, Noh and Firoozabadi [20] conducted a study on the use of gas wetta-
bility and its effects on decreasing the productivity decline of condensate gas
reservoir caused by water blockage. Preferential oil-wet reservoir core can be
converted into preferential gas-wet reservoir when it is processed by fluoride
products 11-12P and L-19062 from 3M. During any initial liquid saturation,
treatment agents produce a gas-wet alternation effect. Gas wettability alterna-
tion is generated by the agent under all initial liquid-containing saturation
conditions. The one-way water injection test of gas-saturated core in the tem-

perature range of 20 140 C indicates that the degree of fluidity increases
when the wettability of cores is altered into gas wettability, and the degree of
fluidity is directly proportional to the condensation of gas-wet alternation
treatment. Similarly, gas wettability alternation also promotes the fluidity of
oil in the core, but the fluidity degree is relatively smaller than that of water.

Wu and Firoozabadi [21] studied the influence of synergistic effects of salinity
and fluoride on the wettability alternation effect in 2009. The results showed
that when the core is saturated with saline solution, water-wettability increases
and the absolute permeability of gas is reduced with the increasing concentra-
tion of NaCl. The effects of CaCl 2 salinity on wettability are different from
that of NaCl, where the effects on permeability are less. In addition, NaCl,
KCl, and CaCl 2 salinity have a negative influence on gas wettability alterna-
tion. In order to reduce the influence of salinity on gas wettability alternation
agents, they conducted water displacement experiments first with the core con-
taining salt water. This step was preceded with nitrogen gas displacement as a
pretreatment, which then improved the effect of gas wettability alternation.