Page 244 - Gas Wettability of Reservoir Rock Surfaces with Porous Media

228 Gas Wettability of Reservoir Rock Surfaces with Porous Media

0.9
The ratio of experimental permeability and initial permeability 0.8 Formation water 1

0.7
0.6
Trapezoid protection agent
Formation water 2
0.5
0.4
0.3
0.2
0.1
0
0
1.2
1
1.6
1.4
0.4
0.2
0.6
0.8
Injection pore volume multiples
FIGURE 6.19
Permeability damage rate at different injection core volume multiples.
6. Natural core is used to determine concentrations of C 1A and C 1B and
the volume V 1A and V 1B , using indoor experimental data. This is when
the adsorption volume of trapezoid protection agent on the rock surface
decreases to a certain degree, and lower concentrations of trapezoid pro-
tection agents A and B are injected. Normally, C 1A 5 6%, C 1B 5 0.1%,
V 1A 5 V 1B 5 0.02 PV.
Field applications indicate that making use of trapezoid protection agents A
and B, and combining the above technical skills, where injection pressure is
greatly relieved, the injection volume is increased, formation ability is effec-
tively supplemented, and the production of corresponding wells improves at
lower cost.
Using varying quantities of injected water and different injection pore volume
multiples, the ratio of core permeability and initial permeability were mea-
sured, as shown in Fig. 6.19.
Experimental results reveal that adding a trapezoid protection agent to injected
water can significantly decrease the rate of permeability damage to cores and
protect the reservoir. As the injection pore volume multiples increase, the dif-
ference in permeability damage rates of cores caused by the injected water
gradually increases. This is because the interaction between trapezoid agent
protection and cores give rise to effects such as antiswelling, antiscaling, water-
block resistance, wettability alteration, etc., which remarkably reduce damage
to cores caused by injected water.

6.3.5 Field Application of Trapezoid Protection Agents for
Reservoirs
The established trapezoid protection technology for low and extra-low-
permeability reservoirs was tested on site, promoted, and applied to 20 sec-
tions of Shengli Oilfield, and 5 sections of Changqing Oilfield. The field test