A new super absorbent polymer to solve formation water of gas
drilling
Feng Guangtong 1,a and Tan Yebang2,b
1Drilling Technology Research Institute, Shengli Petroleum Administration Bureau, SINOPEC.
No. 827, Northern Road #1, Dongying City, Shandong Prov. 257017, China.
Shangdong University.
2No.27, shanda Southern Load, Jinan, Shandong Prov. 250100, China.
afengguangtong.slyt@sinopec.com, bybtan@sdu.edu.cn
Key word: Gas drilling, Formation water, Super-absorbed material, Water
carrying
Abstract：Gas drilling technology have very distinct advantages, it can improve ROP
greatly, shorten the drilling cycle, reduce drilling costs, but it's scope of application
was greatly limited by the problems of formation water and wellbore stability. This
project developed a kind of super-absorbent material which can absorb deionized
water 1484 times，absorb 0.9% NaCl aqueous solution 687 times，absorb 50% ethanol
705 times, that can meet the water carrying requirements of gas drilling. it provides a
new way of gas drilling to solve the water carry problem.
1 introduction
Formation water is the main problem of the gas drilling technology. Formation water
impacts ROP, drilling project quality and cost, and restrains the promotion of the gas
drilling technology. The technology of absorbing formation water and stabilizing
borehole wall is a hot spot.
In 1974, northern institute of American academic department developed a kind of
hydrolysate of starch graft acrylonitrile copolymer, and American is the first county to
research the super absorbent polymer.
In the 1980s, Japan was the dominant county
to develop the super absorbent polymer. And in the field of the petroleum engineer,
the super absorbent polymer might become a important role to solve the formation
water of gas drilling with its super capacity of absorbing water.
2 optimization and design of super absorbent polymer
To study the feasibility which the super absorbent polymer is used in gas drilling, the
researchers made tests to optimize the super absorbent polymer to make sure the
modified method and component, and value the characteristic of the material. The
super absorbent polymer which was composed balanced absorbing water speed,
absorbing water quantity and gel strength. And the water absorbing capacity of the
super absorbent polymer is no less than 300 times under 70℃， and the water
retention rate is more than 70% under the pressure of 5MPa, and the saline water
absorbing capacity is no less than 120g/g.
2.1 The synthesis of organic and inorganic composite crossing linking absorbent
polymer
12.5g compound of monomer acrylic acid（AA）and 2-acrylamide-2-methyl propane
sulfonic acid（AMPS） are injected into pure water, and added suitable amount of
NaOH to adjust the degree of the neutralization, and N,N’- methylene double
acrylamide（Bis）is organic crosslinking agent, and ammonium persulfate (APS) and
tetramethyl ethylene diamine (TMEDA) as REDOX cause the high strength
composite crosslinking absorbent polymer.
Figure 1 The synthesis of organic and inorganic composite crossing linking
absorbent polymer
In the process of synthesis, the proportion of the absorbent polymer was optimized as
the different feeding rate. In the system, the amount of SiO2 is 0.20g, and the amount
of Bis is 0.010wt%-0.025wt% of the monomer, and the amount of AMPS is
15wt%-30wt%, and the neutralization degree is 75%-90%, and the amount of the
initiator is 0.10wt%-0.25wt%.
The amount of water absorbing capacity of super absorbent polymer increases as the
temperature increases, and then remains stable. Through optimization, the absorbing
capacity of pure water is more than 1000g/g after 4 hours, and the absorbing capacity
of pure water is more than 1900g/g after 4 hours at 70℃, and the absorbing capacity
of saline water is more than 120g/g under 1MPa after 4 hours, and the water retention
rate is more than 86%.
2.2 The synthesis and optimization of the modified polyacrylic ternary super
absorbent polymer
10g compound of monomer acrylic acid （ AA ） , acrylamide(AM) and
2-acrylamide-2-methyl propane sulfonic acid（AMPS） are injected into pure water,
and added suitable amount of NaOH to adjust the degree of the neutralization, and
N,N’- methylene double acrylamide （ Bis ） is organic crosslinking agent, and
ammonium persulfate (APS) and tetramethyl ethylene diamine (TMEDA) as REDOX
cause the high strength composite crosslinking absorbent polymer.
Figure 2 The synthesis and optimization of the modified polyacrylic ternary
super absorbent polymer
In the process of the synthesis, suitable water is added into AA to form a certain
concentration solution, and added suitable amount of 40% NaOH to adjust the degree
of the neutralization. And then AMPS is processed through the same method. And the
two kinds of solution are mixed, and added a suitable amount of AM and crosslinking
agent, and transferred to the flask, and added initiator after half an hour at special
temperature in the condition which is full of nitrogen.
The characteristic of the super absorbent polymer is evaluated through a series of tests,
and the conclusions are showed below.
a. Through optimization, the absorbing capacity of pure water is more than 1000g/g,
and the absorbing capacity of saline water is more than 100g/g.
b. The absorbing capacity of saline water is more than 100g/g under 1MPa after 4
hours, and the water retention rate is more than 85%. And this absorbent polymer can
be used in the mud under high pressure.
2.3 The synthesis and optimization of interpenetrating network structure super
absorbent polymer
A suitable amount of NaOH is added to adjust the degree of the neutralization, and 75%
monomer acrylic acid（AA）is attained. Monomer acrylic acid（AA） and poval are
mixed to form 50ml of 10% solution. Glutaraldehyde as crosslinking agent is caused
poval to link together, and AA is dispersed in it, and N,N’- methylene double
acrylamide（Bis） as
crosslinking agent is caused AA to polymerized to form the
interpenetrating network structure super absorbent polymer.
Figure 3 The synthesis and optimization of interpenetrating network
structure super absorbent polymer
In the process of the synthesis, the proportion of the absorbent polymer was optimized
as the different feeding rate. In the system, the amount of PVA is 20%-80%, and the
amount of AA is 80%-20%, and the amount of Glutaraldehyde is 0.025%-0.100% of
PVA, and the amount of Bis is 0.010%-0.025% of AA, and the amount of APS is
0.10%-0.25% of AA.
Through optimization, the absorbing capacity of pure water is more than 1200g/g
after 4 hours at 70℃, and the absorbing capacity of saline water is more than 97.20g/g
under 1MPa after 4 hours, and the water retention rate is more than 99%.
Thermal analysis results shows that the ratio between remote water and bond water is
1:3.375, and free water content depends on water absorbing capacity. And the material
has porous network structure through scanning of infrared spectrum with electron
microscope.
3 Conclusions
a. The amount of water absorbing capacity of organic and inorganic composite
crossing linking absorbent polymer increases as the temperature increases, and then
remains stable. Through optimization, the absorbing capacity of pure water is more
than 1000g/g after 4 hours, and the absorbing capacity of pure water is more than
1900g/g after 4 hours at 70℃, and the absorbing capacity of saline water is more than
120g/g under 1MPa after 4 hours, and the water retention rate is more than 86%.
b. Through optimization, the absorbing capacity of pure water of modified polyacrylic
ternary super absorbent polymer is more than 1000g/g, and the absorbing capacity of
saline water is more than 100g/g. The absorbing capacity of saline water is more than
100g/g under 1MPa after 4 hours, and the water retention rate is more than 85%. And
this absorbent polymer can be used in the mud under high pressure.
c. Through optimization, the absorbing capacity of pure water of interpenetrating
network structure super absorbent polymer is more than 1200g/g after 4 hours at 70℃,
and the absorbing capacity of saline water is more than 97.20g/g under 1MPa after 4
hours, and the water retention rate is more than 99%.
Acknowledge
This work was financially supported by the Sinopec prospective subject.
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