Page 223 - Gas Wettability of Reservoir Rock Surfaces with Porous Media

Application of Gas Wettability CHAPTER 6 207

100
Formulation I
90
Permeability recovery value (%) 70
Formulation IV
Formulation VII
80
Formulation X
60

50
40
30
0.04 0.06 0.08 0.1 0.12 0.14 0.16 0.18 0.2
Flowback pressure (MPa)
FIGURE 6.9
Curves indicating the relation of permeability recovery and flowback pressure for different formulations.

rock samples, and alters their wettability to exhibit hydro-oleophobicity. It blocks
the drilling fluid from entering the reservoir, prevents direct contact of drilling
fluid with rock surfaces and reduces damage to reservoirs caused by hydration
swelling of clay minerals and water-blocks. In addition, when the concentration
of acrylate polymer-based oil protection agent LCM-8 is 2%, the permeability
recovery is greater than 90%. However, when the concentration exceeds 2%, it
has almost no change. Therefore, when these evaluation results for degree of
plugging are combined, 0.3% fluorinated acrylate polymer-based oil protection
agent FCS-08 and 2% water-block resistance agent LCM-8 can be added in the
well slurry, as an optimum formulation to shield the temporary plug.

6.1.4.3 EVALUATION OF TECHNOLOGY FOR BACKFLOW AND
PLUG REMOVAL
Some of the rock samples that were polluted by the drilling completion fluid
containing LCM-8 and whose permeability plugging rate and recovery value
were greater than 90%, were selected to measure the permeability of reverse
oil-phase, under different flow pressures. The permeability recovery value was
then calculated under different conditions, as shown in Fig. 6.9.
As the backflow differential pressure increases, the permeability recovery value
also increases, which offers better relief to the shielding ring plug. Normally,
under the same backflow pressure, the permeability recovery rate is greater
than that of the well slurry, when LCM-8 is considered as the temporary
plugging agent. During the actual production process, the flow pressure of
underground oil and gas in the wells will always be greater than that of
the backflow pressure calculated in this study. Therefore, it is undoubtedly
possible to relieve the plug.