Page 235 - Gas Wettability of Reservoir Rock Surfaces with Porous Media

Application of Gas Wettability CHAPTER 6 219

displacement and reduce damage due to water-blocks, are developed.
A trapezoid protection technology has been established for low-permeability
water-injection reservoirs, using trapezoid protection agents A and B along
with a proper injection method.

6.3.2 Trapezoid Protection Agent A
Through the performance evaluation, an injected water expansion agent with
low dosage and good antiswelling properties was screened, and as trapezoid
protection agent A. The screening method included making use of X-ray
diffractometer to choose the optimum working concentration and evaluating
the antiswelling effects at the formation temperature. The swelling height is
then measured to determine the appropriate antiswelling agent.

6.3.2.1 SCREENING OF TRAPEZOID PROTECTION AGENT A

6.3.2.1.1 Choosing an Antiswelling Agent With X-ray
Diffractometer
Various antiswelling agents were used to make solutions of different concen-
trations that can react with montmorillonite. An X-ray diffractometer was used
to measure the interplanar spacing d 001 of montmorillonite under certain
humidity conditions. The smaller the interplanar spacing d 001 , the better the
antiswelling effect of samples. The interplanar spacing d 001 of various
antiswelling agents at different concentrations is as shown in Table 6.11.
Table 6.11 shows that the antiswelling effects of inorganic salts such as KCl
are the poorest. For six other kinds of antiswelling agents, when the concentra-
tion is between (3%B5%), the interplanar spacing of montmorillonite is the
smallest. However, comprehensive evaluation of antiswelling effects and cost
reveals that the optimum working concentration of A and FSJ-03 is 3%, and
that of ① sample is 5%, while for the remainder it is 4%.

Table 6.11 Effects of Clay Antiswelling Agents at Different Concentrations on the Surface
Distance d 001 Between Montmorillonite Crystals
Concentration (%) KCl A FSJ-03 GD-09 ① ② ③
0.5 21.3635 19.3241 19.0414 18.5247 20.6207 21.0467 19.209
1 18.6419 18.5247 18.0704 16.5486 19.2 19.7673 18.4806
2 16.8321 15.2469 17.8515 16.2475 18.7606 18.5247 15.6413
3 16.2745 14.573 14.6609 15.5386 18.6419 15.0812 15.2371
4 16.1852 14.5839 14.6953 14.7967 15.3163 14.5839 14.6322
5 16.1678 14.9285 14.6322 14.5599 14.9285 14.2779 14.2474
6 15.8943 14.5263 14.925 14.4207 15.4771 14.6731 14.5599
① is “Triethanolamine methyl chloride (M-I company product)”; ② is “Polygnlactomannas (Rhone-Ponlene company product)”; ③ is
“Chlorovinyl formamide (Ciba company product),” FSJ-03 and GD-09 are commonly used products, possessing the best qualities in the
Shengli Oilfield.