Page 30 - Gas Wettability of Reservoir Rock Surfaces with Porous Media

14 Gas Wettability of Reservoir Rock Surfaces with Porous Media

experimental results show that intermediate-wet augmented injection agent
can reduce the oil/water interfacial tension to 0.12 mN/m from 5.825 mN/m,
which significantly reduces the capillary resistance. At the same time, the
intermediate-wet augmented injection agent can change the oil-wet reservoir
into weak water-wet reservoirs. The change in wettability promotes spontane-
ous imbibition during water injection, and the capillary force transforms into
power from resistance. The augmented injection agent can effectively reduce
the injection pressure, and 40% 50% of the injection pressure of sand-filled
pores with low permeability can be reduced. It effectively resolves problems
such as high water injection pressure of reservoirs with low pores and perme-
ability, increasing water injection pressure as time grows and rapidly decreas-
ing the water injection pressure, abnormal match injection, reduced recovery
speed, etc.
In 2010, Liu Huaizhu et al. [29], studied the effects of wettability on flow law
in low, medium, and high permeability cores, making use of artificial outcrop
sandstones. Wettability of artificial core changes to intermediate-wet and oil-
wet from water-wet by use of chemical agents including methylsilicone oil,
simulated oil, etc. The following inclusions are obtained by studying the wet-
tability effects of oil-water single-phase flow when the wettability changes:
1. In the same initial state (water phase permeability) of cores, there is an
obvious change in the seepage characteristics of single-phase flow (oil
or water) in the core because of different wettability.
2. When water flows in the cores with different wettability, as the reducing
of the water-wet and increasing of oil-wet of cores, the percolation resis-
tance of water in cores is increased gradually. When oil flows in cores
with different wettability, as the reducing of the water-wet and increas-
ing of oil-wet of cores, the percolation resistance is decreased gradually.
3. For cores with different permeability, changing the wettability of cores
from water-wet and oil-wet to intermediate-wet enhances the oil flow
capacity and the flow resistance. In this case, the mobility ratio is
decreased and water displacement is improved. In chemical displace-
ment of long-term water-injected reservoirs, the wettability of rocks is
always weakly oil-wet or intermediate-wet. Translating wettability into
intermediate-wet from oil-wet is an important mechanism to improve
oil recovery.

In 2010, Jiang Renyu et al. [30], studied the wettability effects of acidification
cleanup. Currently, most studies on acidification cleanup in China and over-
seas merely pay attention to the influence of low surface tension of working
liquid flow, neglecting the role of strata wettability affecting fluid drainage.
However, low surface tension doesn’t mean change in strata wettability. Based
on it, they quantitatively studied the connection between surface tension, wet-
tability, and acidification cleanup efficiency and verified the effects of reducing
surface tension and increasing the CA on acidification cleanup efficiency,
which are equally important. They applied the above theories to develop