Energy and Power Engineering, 2009, 50-53
doi:10.4236/epe.2009.11008 Published Online August 2009 (http://www.scirp.org/journal/epe)
The Research of Anti-Swelling and Low Damage Killing
Fluid System
Qinggong DANG, Hui JIA, Shuang SUN, Meng LI, Zhenqi JIA
College of Petroleum Engineering, Daqing Petroleum Institute, Daqing, China
Abstract: In this paper, we introduced reservoir characteristics in Block Xiao-he-long and evaluate the per-
formance of the existing killing fluid system. According to the production requirements, a anti-swelling and
low damaging system of chemical agents suitable for this block was optimized, including anti-swelling agent,
water lock inhibitor, fluid-loss agent additives, plus a corrosion inhibitor HS-1 developed by in the lab. The
system is composed by base liquid (0.7%X + 2.0%KCl +0.05%SY-1+ 0.05%HS-1+2.0% DST-1 dissolved in
water) and weighting material (NaCl) with its density adjustable range between 1.0g/ml and 1.2g/ml. Its
anti-swelling ratio achieves 53.80%, and the reservoir permeability recovery ratio reaches more than 95.0%.
Keywords: killing fluid, fomula, reservoir protect, low permeability
1 Reservoir Characteristics
Information shows that gas is produced mainly in sec-
tions of Quantou1 (Q1) and Quantou3 (Q3) at Block
Xiao-he-long. The formations are composed of mudstone,
sandy mudstone, siltstone and gravel rough rock with
higher clay content, generally, more than 95.0%. In addi-
tion, the layer also contains a certain amount of Fe-Al
minerals and carbonate minerals. Sections of Q1 and Q3
are high in salinity, of which the average number is
17098.4mg/l, maximum number up to 23216.5mg/l,
minimum value by 122.43.3mg/l. The formation water is
a kind of kalescent fluid of NaHCO3, of which the Ph
values are between 7.0 and 8.5 with the average value by
7.6. Studies show that this block has poor reservoir
properties. The injected fluid such as water, acid or alka-
line liquid would give rise to the sensitivity reaction eas-
ily to cause serious damage to the reservoir.
The average pressure coefficients of Sections of Q1
and Q3 fall between 0.995 and 1.05 while the average
temperature gradients are between 4.21 and 4.75℃ per
100m. So they are systems with normal pressure and
temperature. Based on the requirements of well control
management, killing fluid density should be equal to the
value of pressure coefficient plus 0.07-0.15. Therefore,
the killing fluid density can meet the production re-
quirements of Block Xiao-he-long when the density are
between 1.065 and 1.20g/ml.
2 Existing Killing Fluid Performance
Here we evaluated the conventional performance of
three killing f©luids (Density, Viscosity, Ph value, fluid
loss volume and stability performance) which are used
at the Block Xiao-he-long. The results are presented in
Table 1.
Table 1. Results of evaluation existing killing fluid performance
Reservoir damage ratio %
Killing fluid code Density (g/cm3)Viscosity (mPa·s) PhFluid-loss volume(ml)Stability performance
Q1 Q3
1# 1.23 75.0 11 serious well 88.51 96.97
2# 1.01 37.5 7 ＞50 well 92.86 97.95
3# 1.19 14.5 8 ＞50 well 76.62 83.16

Q. G. DANG, H. JIA, S. SUN, M. LI, Z. Q. JIA
51
We can see from Table 1 that the existing killing flu-
ids have good index as stability performance, density and
viscosity to meet the operational requirements. But the
fluid-loss volumes are too big as the fluid damage rate of
the three killing fluids are more than 75% and the value
of 2# is as high as 97.95%. It no longer satisfies the re-
quirements of the oil and gas reservoir protection.
3 Development of the Killing Fluid System of
Anti-Swelling with Low Damage
Based on the reservoir characteristics of Block Xiao-he-
long, a number of anti-swelling agents, water lock in-
hibitors, corrosion inhibitors and fluid-loss agents and
several additives are studied and optimized.
3.1 Research of Anti-Swelling System
In this section, we used dilatometer NP-1 to study the
anti-swelling effect of KCl and small cation X, and to
determine the anti-swelling system suitable for Block
Xiao-he-long. The results are presented in Table 2.
Experimental results show that anti-swelling effect in-
creases with the increment of KCl and X. When the
amounts of X and KCl reach 0.7% and 2.0%, respec-
tively, there will be a good anti-swelling effect with the
anti-swelling ratio by 53.80%.
3.2 Screening Water Lock Inhibitor
In order to avoid the water lock effect, a few of water
lock inhibitor need to be added to the killing fluid. SY-1
and SY-2 have excellent ability to inhibit the water lock
effect. Effects of the base liquid with 0.7%A and
2.0%KCl on the ratio of reservoir damage are shown in
Table 3.
Table 2. The experimental results of anti-swelling system
anti-swelling agents and the dosagesX (0.5%) KCl (1.2%) X (0.7%) KCl (1.2%) X (0.5%) KCl (2.0%) X (0.7%) KCl (2.0%)
Swelling extent (mm) 24h 1.31 1.24 1.18 1.11
Ratio (%) 5.82 5.51 5.24 4.93
Anti-swelling ratio (%) 45.45 48.36 50.89 53.80
Table 3. The effect of water lock inhibiter on reservoir damage ratio
Water lock inhibiter Amount (%)Reservoir damage ratio (%)
SY-1 0.05 9.70
SY-2 0.05 20.49
Table 4. Experimental results of the HS-1 anti-corrosion ability
Amount of HS-1 (%) Temperature (℃) Corrosion rate (mm/d)
0.00 80.0 1.089
0.05 80.0 0.051
Table 3 shows that the water lock inhibitor added to
the killing fluid can reduce the reservoir damage ratio.
SY-1, which is better than SY-2, could reduced damage
ratio to 9.70%. Therefore, we choose SY-1 for this sys-
tem to control water lock.
3.3 Corrosion Inhibitor HS-1
In order to slow down the corrosion rate of the tubing
and casing, we developed the corrosion inhibitor HS-1
for this killing fluid system. Table 4 is the experimental
results of the HS-1 anti-corrosion ability.
Experimental results shown that a certain amount of
HS-1 to the killing fluid can reduce the corrosion rate in
comparison with the pre-accession. Thus we know that

Q. G. DANG, H. JIA, S. SUN, M. LI, Z. Q. JIA
52
1.00
1.05
1.10
1.15
1.20
1.25
0 1020304
Amount of NaCl（%）
Killing fluid density
（g/ml）
0
Figure 1. Relationship between the amount of NaCl and killing
fluid density
HS-1 has good corrosion inhibition ability.
3.4 Density Adjustment
Block Xiao-he-long was buried shallow and has low for-
mation pressure, so NaCl is used to adjust the density of
the killing fluid to meet the requirements of killing well.
Figure 1 shows the relationship between the correlation
of the killing fluid density versus the amount of NaCl.
3.5 Screening Fluid-Loss Agent
We screen a variety of fluid-loss agent to reduce the
fluid-loss volume. Finally, we selected SPN-1 and SPN-2
as the fluid-loss agent. And then, we studied the effects
of mixed system and the individual agent. The results are
presented in Table 6.
DST-1 (SPN-1: SPN-2 = 3:2) and DST-2 (SPN-1:
SPN-2 = 1:1) were mixture of SPN-1 and SPN-2. Table
6 shown that system with both SPN-1 and SPN-2 is bet-
ter than single one agent while DST-1 is the best with the
least of fluid-loss volume of 5.0ml/min (API).
Both SPN-1 and SPN-2 can form polymeric mem-
brane on rock surface to reduce the killing fluid
fluid-loss volume. On the rock surface the mixture of
SPN-1 and SPN-2 will form micellar of different size
Table 6. Results of screening fluid-loss agent
Fluid-loss
agent
Amount
(%)
Viscosity
(mPa·s)
Density
(g/cm3)
Fluid-loss
Volume (ml/API)
SPN-1 2.0 4.62 1.10 7.9
SPN-2 2.0 8.25 1.12 12.5
DST-1 2.0 5.80 1.10 5.0
DST-2 2.0 6.53 1.09 6.7
and shape which complement each other to form a more
dense-permeable membrane to reduce the killing fluid
loss. Therefore, DST-1 is chosen as the system fluid-loss
agent.
3.6 Summary
In sum of the above studies, we have obtained the
anti-swelling and low damage killing fluid system suit
able for Block Xiao-he-long. It is composed by base liq-
uid (0.7%X+2.0%KCl+0.05%SY-1+0.05%HS-1+2.0%
DST-1 dissolved in water) and weighting material
(NaCl).
4 Evaluation of Anti-Swelling and Low
Damage Killing Fluid
According to the formula in F, three configurations of
different killing fluids are made as 4#, 5# and 6# which
are evaluated in experiments. The results are shown in
Table 7.
Table 7 shows that the anti-swelling and low damage
killing fluid have good index as the stability performance,
low viscosity, Ph value by 7.0. It will not give rise to
acid and alkali damage. The fluid-loss volume is about
Table 7. Results of evaluation the performance of anti-swelling and low damage killing fluid
Reservoir damage ratio %
Killing fluid code Density (g/cm3)Viscosity (mPa·s) Ph Fluid-loss volume (ml)Stability performance
Q1 Q3
4# 1.02 5.76 7.04.5 Well 3.98 3.70
5# 1.11 5.78 7.05.5 Well 4.33 4.25
6# 1.20 5.80 7.07.0 Well 4.89 4.68

Q. G. DANG, H. JIA, S. SUN, M. LI, Z. Q. JIA
53
7.0 ml/30min. Its damage to the reservoir is low, and the
reservoir permeability recovery is more than 95.0%.
5 Conclusions
1) A killing fluid system of anti-swelling and low dam-
age is developed with its anti-swelling ratio up to
53.80%;
2) The anti-swelling and low damage killing fluid
system have low fluid-loss volume by 7.0ml/30min (API)
no matter how much killing fluid density. It can recovery
the reservoir permeability value more than 95.0%;
3) A series of additives and their dosages are opti-
mized for this anti-swelling and low damage killing fluid
system. The system is composed by base liquid (0.7%X
+ 2.0%KCl +0.05%SY-1+ 0.05%HS-1+2.0% DST-1
dissolved in water) and weighting material (NaCl). It is
better than existing killing fluids and can satisfy the re-
quirements of oil and gas layer protection in Block
Xiao-he-long.
REFERENCES
[1] SY/T5358-2002, “Formation damage evaluation by flow test,” S.
[2] Fan Shizhong, “Oil and gas layer protection and evaluation,”
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[3] Xu Tongtai, Zhao min, and Xiong Youming, “Protection oil and
gas layer technology,” Oil Press, Beijing, pp. 49-55, 2003.
[4] Li Kexiang, “Oil and gas layer drilling and killing well technol-
ogy,” Petroleum Industry Press, pp. 796-815, Beijing, 1993.