The Performance Research and Oil Displacement Efficiency Evaluation for Poly Table Agent Solution
Li Liu1*, Jing Li1, Yanming Pi2, Baojun Bai3*, Lingping Zeng1
1. Northeast Petroleum University, Daqing, China
2. EnerTech-Drilling & Production Co., CNOOC, Tanggu, Tianjin, China
3 Geosciences and geological and petroleum engineering, Missouri University of Science and Technology, 65401 Rolla, Missouri, USA
Abstract: From the perspective of viscosity, this paper used the Brinell viscometer to test the viscosity, and studied the stability, salt
resistance and shearing resistance of poly table agent under the different conditions according to the extent and rule of viscosity change. The
experimental results showed that the trend of viscosity change for ploy table agent under the condition of same concentration was rising first
and falling later, and the critical time was the third day, the viscosity rose gradually during the first three days, and fell after the third day
and tended to be stable at the fifteenth day. There was a boundary concentration of poly table agent between different conditions of
concentration, in which retention rate of viscosity was the minimum and stability was the worst for poly table agent. The higher viscosity
retention rate of poly table agent was, the further distance between concentration and boundary concentration was, which meant that the
stability was better, and the boundary concentration of poly table agent under the experiment condition was 1000 mg/L; The shearing
resistance of poly table agent was associated with the permeability of core model under the condition of the same concentration, the higher
permeability was, the higher retention rate of viscosity was, which meant that shearing resistance was better; The salt resistance of poly table
agent was related to the content of NaCl, and the overall rule was that viscosity reduced with the content of NaCl increasing. The
rangeability of viscosity was larger when the concentration of NaCl was less than 3000 mg/L, which meant that the salt resistance was worse
this moment; The rangeability of viscosity was smaller when the concentration of NaCl was greater than 3000 mg/L, which meant that the
salt resistance was better on this condition; The recovery during poly table agent flooding continued to increase by 19% in the oil
displacement experiment after polymer flooding, in which the recovery percent of reserves of low permeability layer increased by 12.13%
and the high permeability layer’s increased by 6.88%.So the poly table agent which has a better oil displacement efficiency is a kind of
chemical agents.
Keywords: poly table agent, stability, shearing resistance, salt resistance, oil displacement efficiency
1. Introduction
Poly table agent is a kind of new high-efficiency oil displacement agent with single component, whose theory is that grafting a variety
of functional groups on the main chain of the molecule for polymer[1], which could conquer the technical defect of Surfactant/Polymer
flooding or Alkaline/Surfactant/polymer flooding[2-6] and could have the better double peculiarities of tackability and reducing oil water
interfacial tension at the same time, which not only have the better effect of sweeping volume enlargement, but also improve the
displacement efficiency greatly [7-9]. The research of poly table agent focuses on the fields of basic character and oil displacement
efficiency mostly. For example, the experiment research aimed at the emulsibility of poly table agent was made by Li lijuan [10] showed
that poly table agent had the better emulsifying behavior, and the kinds of demulsifier named poly-oxypropylene and linear structure fatty
alcohol-polyoxyethylene ether had the better demulsification capability; Niu liwei [11] ect. did the research for the molecular structure of
poly table agent, and thought the molecule structure form of poly table agent presented piece-mesh structure, and the molecules had a better
crosslinking action and higher apparent viscosity; Chang xingwei [12] gave out the injection system evaluation of poly table agent, and
believe that poly table agent have a well oil displacement efficiency. On the basis of previous studies and regarding medium molecular
weight polymer as reference, this paper has developed the research of stability, shearing resistance and salt resistance for the solution of
Huading I poly table agent which has been applied in text field of Daqing Oilfield，searched for the resistance abilities of chemical
degradation (stability) and physical degradation (shearing resistance) and evaluated the oil displacement efficiency after polymer flooding
for Huading I poly table agent.
2. Experiment
2.1 Experimental agent and equipment
Agent: Huading I poly table agent and medium molecular weight polymer whose molecular weight is 14 million; Equipment: different
types of core model, thermostat, viscometer whose type is Brookfield RVDV-VII, liquid mixers, constant pressure and speed pump,
intermediate container, pressure gage, beaker, tube with scale, pipeline which is used for connecting equipment and so on.
2.2 Experiment method
2.2.1 Texting method of stability
Two kinds of agent are confected by fresh water and diluted by sewage, whose concentration respectively is 800mg/L, 1000mg/L,
1500mg/L, 2000mg/L after being diluted; The confected solutions are poured into beakers and put into thermostat whose temperature is
45℃，the viscosity of solutions are being tested by viscometer at different moment.
2.2.2 Texting method of shearing resistance
Core model is artificial column core whose length is 100mm and permeability is 200 md, 500 md, 1000 md resperctively; Two kinds of
agent are confected by fresh water and diluted by sewage, whose concentration is 1000mg/L after being diluted; Solution is poured into
intermediate containers after the viscosity is tested, and then the intermediate containers is put into thermostat whose temperature is 45℃,
and the solution in intermediate containers is displaced by constant pressure and speed pump whose speed is 0.3 ml/min to respectively pass
through the artificial column core whose permeability is 200 md,500 md or 1000 md, and the produced fluid is reserved to test the viscosity.
2.2.3 Texting method of salt resistance
Journal of Residuals Science & Technology, Vol. 13, No. 8, 2016
© 2016 DEStech Publications, Inc.
doi:10.12783/issn.1544-8053/13/8/66
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At first, the different concentration saline water is made by pouring the different quality NaCl into distilled water, and the concentration
respectively is 0 mg/L, 1000 mg/L, 3000 mg/L, 5000 mg/L, 6000 mg/L, 7000 mg/L, 9000mg/L. and then use the saline water to confect the
two chemical agents which concentration are both 1000 mg/L. At last use the viscometer to measure the viscosity of solution which has
already been made.
2.2.4 The method of displacement experiment
The core model used in this part is two-tier artificial epoxy resin physical model which injection-production pattern is separate injection
and production and the size is 300*45*45mm and the permeability of low-permeability layer is 400 md and the permeability of
high-permeability layer is 800 md;The core is vacuumized, saturated water and oil, and its parameters which include pore volume, the
capacity of saturated oil, oil saturation and porosity are measured; Then water flooding is conducted until the water contain is above 98%,
and then medium molecular weight polymer whose injection is 0.6 multiples of pore volume(PV) and injection concentration is 1000 mg/L
is injected, and then water flooding is conducted until the water contain is above 98% again, and the recovery ratio of polymer flooding is
gotten; poly table agent whose injection is 1 PV and injection concentration is 1000 mg/L is injected, and after that the water flooding is
conducted until the water contain is above 98% again, and recovery ratio of Huading I poly table agent can be gotten.
3. Experiment result
3.1 The experiment result of stability
Stability is the maintaining ability of viscosity for chemical agent after chemical reaction which is taken place by the influence of
external factor such as oxygen. It’s as shown as Table 1 that the stability of poly table agent was related to its concentration and standing
time. Under the same condition of concentration, the tendency of viscosity for poly table agent was rising first and falling later. At first, the
viscosity rose gradually because of the self-crosslinking rate between molecules was greater than chemical degradation rate, and reached the
top at approximately the third day. The tendency of viscosity declined after three days because of self-crosslinking rate between molecules
was inferior to chemical degradation rate. So the third day was deemed to the critical time of viscosity change for poly table agent. Since the
fifteenth day, because of falling range of viscosity was very small, the chemical degradation was thought basically completed, and the
tendency of viscosity was stabilization; Under the different condition of concentration, no matter the concentration of poly table agent is
higher or lower than 1000 mg/L, the viscosity retention rate was always higher than whose concentration is 1000 mg/L. So the concentration
of poly table agent was concluded to be the border concentration When the concentration of solution was higher than 1000 mg/L,
concentration for poly table agent was increasing, the molecule number was increasing too. So self-crosslinking and the ability of resistance
to chemical degradation enhanced obviously, even when the concentration was 2000 mg/L, the viscosity of poly table agent was higher than
the initial viscosity after 30 days. So the stability of poly table agent was great at this condition. When the concentration of solution was
lower than 1000 mg/L, although self-crosslinking was weaken by the molecule number reduced，but the chemical degradation was weaken
too. So, good stability was showed as well. Nowadays, the concentration of polymer used in oilfields usually is 2000 mg/L[12]. It’s as
shown as Table 1 that on this concentration, the concentration retention rate of polymer was always lower than the poly table agent’s,
whether in the initial or final viscosity.
Table 1 Data of the viscosity change with time of ploy table agent and medium molecular weight polymer
time(d)
Chemical type
concentration(mg/L) 0
1
3
7
10
15
30
viscosity(mPa·s)
800
37.2
52.4
52.5
39.5
36.7
25.8
23.4
Huading I poly
1000
54.5
64.5
62.7
49.4
47.3
32.5
29.8
table agent
1500
219
234.9
286.9
231
226.8
218.6
197.5
2000
328.9
415.9
427.9
424.9
418.9
364.9
331.8
medium
molecular
2000
74.9
87
86.5
78.7
70.6
63.4
59.6
weight
polymer
Viscosity
retention
ratio(%)
62.9
54.7
90.2
100.9
79.6
3.2 The experiment result of shearing resistance
Shearing resistance is the keeping ability of viscosity for chemical agent which is suffered by physical shear(mechanical degradation).
The ability of shearing resistance is better if the viscosity after sheared is closer to its initial, conversely is worse. It’s as shown as Table 2, at
the same condition of concentration and speed, the overall trend of ploy table agent shows that the lower the core permeability, the bigger
the viscosity decreased, and the viscosity is lower too. This is because of the molecular morphosis of ploy table agent is mixed by flakiness
and reticulation, and the crosslinking between molecules. When the core pore size is fixed, the molecular which is bigger than the size or
crosslinked with others will suffer a resistance which is exerted by pore and fracture the molecular chain or intermolecular winding, at the
moment of through the core. The lower the permeability and the smaller the core porosity, the bigger resistance the molecular suffered, and
the stranger the fracturing ability to molecular chain or intermolecular winding. So the apparent viscosity decreased sharply and It means the
shearing resistance of poly table agent is weaker. When the core permeability is more than 500md, the shearing resistance of ploy table
agent is great and the viscosity retention ratio can get more than 67.2%. Under the core shearing of three kinds of permeability, the viscosity
retention ratio of HuadingI ploy table agent is always lower than medium molecular weight polymer’s. This phenomenon is relative to the
linear shape of medium molecular weight polymer [13], which has a low initial viscosity, but also suffer the little resistance by passing the
same pore. That is why the viscosity retention ratio of medium molecular weight polymer is always higher than ploy table agent’s.
Table 2 Data of the viscosity of ploy table agent and medium molecular weight polymer change before and after shearing
Permeability and Viscosity after the shearing Viscosity
Viscosity before the
Speed
Chemical type
concentration(mg/L)
retention
shearing(mPa•s)
(ml/min) Permeability(×10-3μm2) viscosity(mPa·s)
ratio(%)
200
29.5
54.1
ploy table
1000
54.5
0.3
agent
500
36.6
67.2
Journal of Residuals Science & Technology, Vol. 13, No. 8, 2016
© 2016 DEStech Publications, Inc.
doi:10.12783/issn.1544-8053/13/8/66
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medium
molecular
weight
polymer
1000
21.3
0.3
1000
200
500
47.0
16.7
17.3
86.2
78.4
81.2
1000
18.4
86.4
3.3 The experiment result of salt resistance
Salt resistance is the ability of viscosity retention for solution which is under the certain condition of salinity, and the smaller the
viscosity decreased, the better their salt resistance is, conversely is worse. It’s as shown as Table 3, with salinity increasing, the variation
trend of viscosity for ploy table agent is decreases first and stabilized gradually. When concentration of NaCl is between 0 mg/L～3000
mg/L, the rangeability of ploy table agent is great. If the concentration of NaCl is higher than 3000 mg/L, the viscosity of ploy table agent is
slowly to stabilize. This phenomenon is relative to the charge which is on the ploy table agent molecular chain[14]. When the concentration
of NaCl rise from 0mg/L to 3000 mg/L, the viscosity of solution descend gradually because of the decreasing of repulsion effect which is
made by the charge on the molecular chain and disturbed by the concentration of NaCl, and could cause the curl of poly table agent
molecular greatly; the influence of concentration for NaCl is efficiency for medium molecular weight polymer too. From the perspective of
decrease amplitude of viscosity and viscosity number after stabilization, the salt resistance of ploy table agent is better.
Table 3 Data of the research of salt resistance for ploy table agent and medium molecular weight polymer
viscosity
Concentration
of NaCl
mPa·s
1000
3000
5000
6000
7000
9000
mg/L
mg/L
mg/L
mg/L
mg/L
mg/L
0 mg/L
Sample type
ploy table agent
82
81.2
59.3
54.7
52.4
53
52.4
medium molecular weight polymer
55.3
31.1
18.1
14.1
12.7
11.8
11
3.4 Effect evaluation of displacement for ploy table agent
The model of experiment core used in this part imitate the geologic feature and factor of oil layer and the schematic diagram is as
following.
Fig. 1. The schematic diagram of core model
The pore volume of core model is 167 cm3, the saturation oil capacity is 132 ml, oil saturation is 79.04% and the porosity is 27.49%.
It’s as shown as Table 4, the recovery ratio of early water flooding is 34.5%. and it is mainly contributed by the high permeability layer,
which compare with the low permeability layer. The overall recovery efficiency enhance 17.09% after injecting 0.6 PV medium molecular
weight polymer, and 12.07% efficiency enhance is contributed by low permeability layer which oil production higher than high permeability
layer. This phenomenon means that the main ability of medium molecular weight polymer is profile modification which could displace
remaining oil at unswept areas in low permeability layer. But the 49% remaining oil cannot be displaced which means that the oil field has
an enormous potential in mining after medium molecular weight polymer flooding. HuadingI poly table agent can enhance 19.01% recovery
ratio, which include 12.13% recovery ratio contributed by low permeability layer and 6.88% recovery ratio contributed by high permeability
layer. the recovery effect of both the two layers displaced by poly table agent is better than medium molecular weight polymer’s. According
to the mechanism of oil displacement for medium molecular weight polymer[15], when the medium molecular weight polymer is displacing
the oil ,it both can enlarge swept volume and improve oil displacement efficiency at the same time. So can conclude that poly table agent
has the same abilities and the abilities are better than medium molecular weight polymer. So it has the better oil-displacing efficiency.
Table 4 Data of displacement experiment for poly table agent
The ratio between oil produced and total reserves(%)
Flooding stage
Low permeability
High permeability
Total recovery
layer
layer
efficiency
recovery efficiency of water flooding stage
9.33
25.17
34.5
recovery efficiency of medium molecular weight polymer flooding
12.07
5.02
17.09
stage(including post-water flooding)
recovery efficiency of poly table agent flooding stage(including
12.13
6.88
19.01
post-water flooding)
recovery efficiency contributed by each permeability layer
33.53
37.07
70.6
Figure 2 and Figure 3 are drew by the data which is got in the course of experiment. It’s as shown as Figure 2, when poly table agent is
injected after polymer injects over and the pressure sharply rising and moisture content drop to about 80% for a long time. The profile
inversion phenomenon happens until poly table agent injects over.
Journal of Residuals Science & Technology, Vol. 13, No. 8, 2016
© 2016 DEStech Publications, Inc.
doi:10.12783/issn.1544-8053/13/8/66
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Fig. 2. Data dynamic figure of oil displacement experiment
It’s as shown as Figure 3, in the course of injection for poly table agent, the shunt rate of low permeability layer has greatly increased,
which means the condition of imbibition for low permeability layer is improved by poly table agent. Combine with the pressure of poly table
agent, we believe that because of the high pressure, poly table agent shows the better effect of sweeping volume enlargement, and could
displace the area of the low permeability layer which medium molecular weight polymer failed.
The above factors mean, the performance of viscosity stability, salt resistance and oil displacing efficiency for poly table agent are
better than medium molecular weight polymer, only the shearing resistance is worse than medium molecular weight polymer. The poly table
agent is a kind of high quality chemical displacement agent which could displace the low permeability layer and high permeability layer
again after medium molecular weight polymer displaced and enhance the overall recovery efficiency more than 19%.
Fig. 3. Curve figure of shunt rate of oil displacement experiment
4. Conclusion
The tendency of viscosity of poly table agent is first and decreased afterwards with the passage of time. The third day is critical time
and the viscosity rises gradually during the first three days and falls after the third day and tends to be stable at the fifteenth day. Under the
same condition, the ability of stability for poly table agent is higher than medium molecular weight polymer’s.
Because of the effect of molecular size and structure form, the ability of shearing resistance for poly table agent is getting worse when
the core permeability falls off. When permeability is more than 500 md, the ability of shearing resistance for poly table agent is better, and
the viscosity retention ratio can get more than 67.2%. From the perspective of viscosity retention rate, the shearing resistance of poly table
agent is worse than medium molecular weight polymer, but at the same shearing condition, the viscosity of poly table agent is still higher
than medium molecular weight polymer.
With the increase of content of NaCl, the whole change trend of viscosity for poly table agent is declining. When the concentration of
NaCl is between 0 mg/L～3000 mg/L, the charge repulsion effect of poly table agent molecule is disturbed obviously, which curled up
seriously and viscosity declined greatly. When the concentration of NaCl is more than 3000 mg/L, the interspace which molecule could curl
become smaller, and the viscosity trend to stability. At the same condition, the salt resistance of poly table agent is better than medium
molecular weight polymer.
Under the condition of this experiment scheme, the poly table agent displacement after medium molecular weight polymer could
enhance the recovery ratio 12.13% by low permeability layer and enhance the recovery ratio 6.88% by high permeability layer. it could
enhance the whole recovery ratio19.01%. poly table agent is a high quality chemical which means that could replace molecular weight
polymer to displace oil.
Acknowledgment
The research work was both supported by the Innovation Fund Petro-China “The research of the influence of the polymer functional
groups to the oil-displacement mechanism and permeability rules” (2015D-5006-0214) and the Natural Science Foundation of Heilongjiang
Province, China <The research of the oil-displacement mechanism of functional polymer (polymer surfactant) in reservoir conditions>
(E2016016).
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