Page 32 - Gas Wettability of Reservoir Rock Surfaces with Porous Media

16 Gas Wettability of Reservoir Rock Surfaces with Porous Media

Liu Yijiang et al. [33], changed the wettability of condensate gas reservoir core
with low permeability from preferential water-wet into preferential gas-wet
using a new type of low-cost gas-wet alternation agent, WA12. This study was
done in Henan Dongpu Oil Field in 2006. The experimental results indicate
that WA12 has good thermal stability with resistance to temperature as high
4

as 170 C, which is still effective when the salinity is 7 3 10 ppm. The perme-
ability of gas and liquid phases remarkably increased after gas-wet treatment,
and the saturation of residual water reduced. In 2008, the gas-wet alternation
agent was tested in a gas reservoir in Dongpu. The gas output was found to
have increased notably, and the validity period was short. The analysis sug-
gested that it is caused by the selected gas well being an appraisal well with
high reservoir temperature, low permeability, and high condensate oil viscos-
ity. The author proposed that when the wettability test is conducted on the
field, an oil-producing well should be selected rather than an appraisal well
[34] that has no production history or only worked for a short period of time.
Yao Tongyu et al. [35], with the capillary rise method, Washburn method, and
spontaneous imbibitions experiment, studied gas-wet alternation and effects
of five treatment agents (sodium dodecylbenzene sulfonate, cetyltrimethylam-
monium bromide, octyl phenol polyoxyethylene ether OP215, dimethyl sili-
cone oil GB 201, and dichlorodimethylsilane) on an artificial sandstone core
in 2008. They studied the effects of treatment agents on the seepage of gas/liq-
uid phases with an unsteady seepage flow experiment and measured the rela-
tive permeability before and after the change in gas wettability. Dimethyl
silicone oil GB-201 can alter oil-wet and water-wet cores into preferential gas-
wet alternation, thereby improving the permeability of liquid phase, reducing
the saturation of liquid phase, and moving the equal permeability point to
the left.
In 2010, Shao Changjin et al. [36], constructed a pore network with a throat
radius of 0.05B2.50 µm and studied the effects of pore-throat ratio, wettabil-
ity, initial water saturation, and residual water saturation on gas phase relative
permeability based on the method of the microscopic physical statistics and
the pore network model. Under constant conditions of other controlling para-
meters, the influencing law of wettability on gas relative permeability of gas is:
When water saturation is more than 0.4, the relative permeability of gas gradu-
ally increases in the following order: “water-wet- weak water-wet- weak
gas-wet- gas-wet.” However, when water saturation is less than 0.4, the ten-
dency to increase relative permeability is disrupted, and the relative permeabil-
ity is the least on weak water-wet surfaces. In addition, as the initial water
content increases, the relative permeability of the gas phase generally
decreases; the greater the saturation of residue is, the steeper the relative per-
meability of gas phase and the more rapid the decline.
Zhou Minghui [37], etc., designed a gas-wet alternation agent using a molecu-
lar model and predicted the wettability alternation potential of gas-wet rever-
sal agent theoretically by calculating interfacial tension and CA with Material