Page 242 - Gas Wettability of Reservoir Rock Surfaces with Porous Media

226 Gas Wettability of Reservoir Rock Surfaces with Porous Media

5 4
Permeability 10 –3 µm 2 3 2 Injecting modification water and permeating

0 1
5 10 15 20 5 10 15 20 25 50 75 100 125 150 175 200 225 250 275 300 325 350 375 400
Volume pumped in pores PV
FIGURE 6.18
Experimental results of KCl antiswelling cycle evaluation.

6.3.2.6 TREATMENT RADIUS AND CONCENTRATION
While injecting water, the trapezoid protection agent A is normally used
for pretreatment, where the application concentration is 6%. Due to the
pressure drawdown distribution around wells adjacent to the water-
injection ones, the radius is normally less than 3 m. Therefore, the
treatment radius of trapezoid protection agent A is determined to be
between 4B6m.

6.3.3 Trapezoid Protection Agent B
To solve the technical issues associated with decreasing pressure and increasing
injection, trapezoid protection agent B, which has good oil displacement
effects and reduces damage due to water-blocks, was studied. Fluorocarbons
were identified as the main component.

6.3.3.1 PREPARATION OF TRAPEZOID PROTECTION AGENT B
First, an emulsifier (PAB-1, 1.23 g), NaHCO 3 (1 g), and 170 mL water were
mixed in 500 mL four-mouth flasks and stirred for 30 minutes at high speed
(440 460 r/min). Then, a mixture of 6 g PAB-2, 12 g PAB-4, 2 g PAB-3, 3 g
PAB-5, 0.1 g PAB-6, and 10.3 g fluorine monomer was slowly dripped into
the emulsifier mixed liquid. It was then poured into 400 mL flasks and
stirred to prepare even preemulsions. It was then transferred to 500 mL four-
mouth flasks, then injected with nitrogen, heated, and stirred. When the tem-
perature of water bath rose to 65 C, 1/2 APS(0.21 g APS was dissolved in

water in advance) was added. When the temperature increased to 75 C, the

remaining APS was added. The reaction was stopped after 3 hours, when
the temperature naturally declines to below 60 C. NaHCO 3 was then added

to adjust the pH value to neutral. It was continuously cooled to below 50 C,

and was no longer stirred. Finally, the trapezoid protection agent B
was extracted.