Vol.5, No.9, 997-1000 (2013) Natural Science
The study of formulation and performa nce of formate
drilling and completion fluid system
Bingren Wang1, Zehua Wang2*, Y u xue Sun2, Jiuzhou Sun1
1Northeast Petroleum University, Daqing, China
2Reservoir Protection Laboratory, Northeast Petroleum University, Daqing, China;
*Corresponding Author: wangzehua0000@163.com
Received 21 June 2013; revised 21 July 2013; accepted 28 July 2013
Copyright © 2013 Bingren Wang et al. This is an open access article distributed under the Creative Commons Attribution License,
which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Formate drilling and completion fluid system is
a new type of clean organic salt brine system
which has been developed from inorganic salt
brine drilling fluid system. It is beneficial to pro-
tecte and find hydrocarbon reservoir. Due to the
solid free system, the damage of solid phase
particles on reservoir, especially low permeabi-
lity oil and gas layer, can be greatly eliminated,
at the same time, drilling fluid and completion
fluid have greater compatibility. It will avoid that
precipitation which is not compatible with drill-
ing and completion fluid and generates dam-
ages on reservoir. And because mud cake of the
solid free system is thin and resilient, it is con-
ductive to improve cementing quality greatly.
Experiments show that the formate drilling and
completion system has good rheological prop-
erty, strong inhibition ability, good lubricating
performance, good compatibility with reser-
voir rocks and formation water at high tem-
Keywords: Formate; Drilling and Completion Fluid
System; Solid Free System; Hydrocarbon Re servoir
Formate drilling and completion fluid is a new type of
clean brine system which has been developed from inor-
ganic salt brine drilling fluid system. Currently there are
mainly three kinds of formate: sodium formate, potas-
sium formate and cesium formate. Compared with con-
ventional drilling fluid, formate drilling fluid is charac-
terized by no bentonite slurry. It is the theoretical foun-
dation that formate drilling fluid can achieve strong in-
hibitory, and it is also the key to being better than con-
ventional water base drilling fluid. Some scholars have
studied this before, such as Liuyu has published a paper
of “Researches and uses of solids-free high density for-
mate and high temperature crosslinking water base sys-
tems as drill-in fluid” in 2005. Then he has applied the
drilling fluid into Liaohe Oilfield and the petroleum-
in-place has been increased. Wang Yongsheng has stud-
ied the application effect of the formate drilling fluid in
Yingtai gas field in 2012. And this drilling fluid system
has helped to protect the reservoir and save the explora-
tion cost. Based on the previous research, this paper is
studied for some new findings and applications [1].
Formate has the characteristics of high solubility, high
density, high pH value, low crystallization point. With
the increase of alkali metal atomic weight, saturation
concentration, saturation density and pH value become
higher, and crystallization point becomes lower.
Through indoor study, the following features of for-
mate have been found:
1) There is the function of stabilizing shale. Shale is
equivalent to the selective semi-permeable membrane in
the non fractured low permeability shale formation (K
10 × 103 m2). In the high concentration brine, due to
the low water activity, the osmotic pressure can promote
the shale pore water reflux. This reflux will make formation
stress and effective stress of near wellbore zone increase
to stabilize borehole wall.
2) Formate has a good compatibility with the oilfield
commonly used polymer, and can slow the speed of
hydrolysis and oxidation degradation of many thicken-
ers and filtrate reducers under high temperature and
Copyright © 2013 SciRes. OPEN ACCESS
B. R. Wang et al. / Natural Science 5 (2013) 997-1000
3.1. Optimization of Filtrate Reducer
The base slurry: 500 ml Water + 80% Sodium formate.
For the drilling and completion fluid system, filtration
index of effective control system is crucial. We select TJ-
1 for the filtrate reducer. And experiments that addition
amount of TJ-1 is different are conducted. Results are
shown in Table 1.
According to the experimental data in the table, when
addition amount of TJ-1 is 3%, instantaneous water loss
is small, and drilling preliminary requirements can be
satisfied. Combining with the actual use situation, the
TJ-1 that its addition amount is 3% is selected for the
filtrate reducer.
3.2. Optimization of Oil Layer Protective
In order to further improve the comprehensive ability
of reduction in water loss of system and reduce the
damage of oil and gas layer, we select the optimum oil
layer protective agent in the laboratory. Experimental
results are shown in Table 2.
According to the data in the table, by optimizing, TJ-1
plus JYW-3 can reduce water loss greatly after 150˚C
high temperature hot rolling. So JYW-3 that its addition
amount is 3% is selected for the oil layer protective agent.
3.3. Optimization of Tackifier
Because the viscosity of formate fluid can not meet
needs of drilling fluid viscosity in practical application,
proper tackifier must be added in drilling fluid. We had
carried on the contrast experiment to select tackifier. The
results are shown in Table 3.
Formula 1: The base slurry + 3% TJ-1 + 0.5% TXZ-1
+ 3% JYW-3;
Table 1. Optimization experiment of filtrate reducer.
Formula φ600 φ300 φ6 φ3 Gel pa/pa API ml
The base slurry
+ 1% TJ-1 25 13 00 0/0.5 -
The base slurry
+ 2% TJ-1 32 18 11 0.5/0.5 18 (18)
The base slurry
+ 3% TJ-1 42 24 00 0/0 18 (10)
Table 2. Optimization experiment of oil layer protective agent.
Formula φ600 φ300 φ6 φ3Gel pa/pa YP PaAPI ml
Formula 1 113 64 8 62/2.5 7.5 23.5
Formula 2 187 117 6 42/2.5 23.5 6.5
Formula 3 141 81 3 20.5/1 10.5 2.6
Note: Test conditions of 150˚C, hot rolling for 16 h.
Table 3. Optimization experiment of tackifier.
Formula φ600 φ300 φ6 φ3 Gel pa/paAPI ml
Formula 1 29 15 0 0 0/0 16.5
Formula 2 99 74 17 12 1.5/2.5 8
Formula 3 32 17 0 0 0/0 14
Note: Test conditions of 180˚C, hot rolling for 16 h.
Formula 2: The base slurry + 3% TJ-1 + 0.5% TXZ-2
+ 3% JYW-3;
Formula 3: The base slurry + 3% TJ-1 + 0.5% 80A51
+ 3% JYW-3.
By experimental contrast, we know that TXZ-2 has
good viscosifying action and resistance to high tempera-
ture. So TXZ-2 that its addition amount is 0.5% is se-
lected for the tackifier [2].
Through the above research, finally, the overall for-
mula of the formate clay free drilling and completion
fluid system was determined for: water + 80% sodium
formate + 3% TJ-1 + 0.5% TXZ-2 + 3% JYW-3.
4.1. Rheological Properties Evaluation
Drilling fluid rheological property is usually described
with rheological curve, plastic viscosity (PV), yield point
(YP), gel strength (Gel), apparent viscosity (AV) and
other rheological parameters of drilling fluid.
According to the experimental data in Ta ble 4, when
the aging temperature is below 150˚C, rheological prop-
erty and building capacity of drilling fluid are stable, the
change is not big. When the aging temperature is higher
than 150˚C, filtration of system increases by much, and
rheological property and building capacity of system
become bad. So temperature resistance capacity of for-
mate drilling fluid system can reach 150˚C.
4.2. Pollution Resistance Experiment
In drilling process, soluble salt and clay which are the
main pollution sources can affect the rheological prop-
erty and filtration property of drilling fluid system. In
view of this, the capacity of soil penetration resistance
and soluble salt pollution resistance of the formate drill-
ing fluid system was evaluated. The results are shown in
Table 5.
According to Ta bl e 5, after formate drilling fluid was
16 h under high temperature 150˚C, in the drilling fluid
system which added soil powder, its plastic viscosity,
yield point and API filtration quantity increased. And
after being polluted with soluble salt, its plastic viscosity
reduced, yield point and API filtration quantity increased.
Changes are within the acceptable range [3].
Copyright © 2013 SciRes. OPEN ACCESS
B. R. Wang et al. / Natural Science 5 (2013) 997-1000 999
Table 4. Rheological properties of formate drilling fluid under
high temperature.
Rheological parameters
Conditions PV (mPa·s) YP (Pa) Gel pa/pa
ml PH
Before the high
temperature 32 7.0 1/2 0.8 9
120˚C/16 h 31 7.0 1/2 1.1 9
150˚C/16 h 29 6.5 1/2 1.6 9
180˚C/16 h 25 3.5 1.5/2.5 8 9
Table 5. Anti pollution experimental results under high tem-
Formula PV mPa·s YP Pa API Fl ml
1#: The base slurry + 3% TJ-1 +
0.5% TXZ-1 + 3% JYW-3 29 6.5 1.6
2#: 1# + 5% bentonite 44 16 3.5
3#: 1# + 6% CaCl2 23 7 3.4
Note: Test conditions of 150˚C, hot rolling for 16 h.
4.3. Inhibitory Experiment
The linear expansion rate of shale in drilling fluid sys-
tem is tested to obtain the ability of system to inhibit
shale swelling. The experimental results are shown in
Tables 6 and 7.
According to experimental data, we can see that for-
mate clay free drilling and completion fluid is superior to
the polymer drilling fluid and similar to oil-in-water drill-
ing fluid in inhibiting clay hydration expansion ability. It
has a good ability that hydration expansion of mineral
composition such as the shale is prevented to avoid dis-
persion and migration of micro-sized particles.
Rolling recovery rate of the shale is used to describe
inhibition dispersion capacity of drilling fluid system to
shale [4].
Shale recovery experiment results show that optimal
formate clay free drilling and completion fluid system is
superior to the polymer drilling fluid and similar to oil-
in-water drilling fluid in inhibiting clay dispersibility. It
can effectively inhibit clay dispersion and has a good
stability in shale.
4.4. Compatibility Experiment
350 ml drilling fluid mixed with 50 g reservoir rock
debris, then hot rolled 16 h under 120˚C. Rock debris
recovery rate was 98.5%, the shape and size of rock de-
bris were little changed. It shows that the drilling fluid
has good compatibility with reservoir rocks.
Formate drilling and completion fluid filtrate mixed
with the certain proportion simulation formation water.
Then we used the method for the visual and flocculation
to evaluate the compatibility of drilling fluid and forma-
tion water. It can be seen that chemical reaction and
Table 6. Swelling experiment results.
Type 30 min 1 h 2 h 3 h
Oil-in-water drilling fluid0 0.01 0.02 0.03
Formate drilling fluid 0.01 0.02 0.03 0.04
Polymer drilling fluid 0.07 0.09 0.11 0.11
Table 7. Rolling recovery experiment results.
Type 10 mesh 20 mesh 30 mesh
Oil-in-water drilling fluid 97.3% 99.3% 99.7%
Formate drilling fluid 97% 98.7% 99.3%
Polymer drilling fluid 70.7% 79.3% 80%
sediment were not generated between drilling fluid fil-
trate and simulation formation water. It shows that for-
mate drilling and completion fluid has good compatibil-
ity with reservoir fluid.
4.5. Lubricity Experiment
Lubricity evaluation needs three main parameters, the
drilling fluid lubrication coefficient K, the extreme pres-
sure film strength P and mud cake friction coefficient Kf.
Evaluation data and the results are shown in Table 8.
According to the above table, the lubrication perform-
ance of system is good. It provides a powerful guarantee
in order to decrease the friction torque of drill tool. The
drilling fluid can fully meet the needs of the deep drilling
as long as strengthening solid phase control.
The formate drilling and completion fluid system has
been applied to the deep well of Lungu area in Tarim.
Through the field experimentation, some new and good
performance of the formate drilling fluid can be found
out. The formate drilling fluid is of good rejection capa-
bility and shale stability. In the conditions of low viscos-
ity, the shear thinning and capability of bringing cuttings
of the formate drilling fluid are also excellent. It can
meet the drilling requirements. As the formate drilling
fluid is of low density and no solid phase, it helps to find
problems in time so as to protect reservoir. The formate
drilling fluid system has removed the damage caused by
the solid particles, which block the hydrocarbon reservoir.
At the same time, the compatibility between the formate
and common treating agents of oil field is fine. Therefore,
the operating temperature of CMC and biopolymer can
be enhanced to 140˚C. According to the experimental
results, it can be concluded as follows.
1) It uses single treatment agent optimization experi-
ment such as the optimization of filtrate reducer, oil layer
protective agent and tackifier in laboratory. Finally, the
Copyright © 2013 SciRes. OPEN ACCESS
B. R. Wang et al. / Natural Science 5 (2013) 997-1000
Copyright © 2013 SciRes.
Table 8. Unctuosity evaluation results.
System Kf P (pound/cun2)
Formate system 0.15 0.0602 47,360
Formate system + 20% Drilling cuttings 0.19 0.0730 39,520
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