International Journal of Engineering & Technology IJET-IJENS Vol: 11 No: 04
102
Experimental Study of the Effects of CO2 Gas Kick
on the Properties Water-Based Drilling Fluid
Adebayo, Thomas A1 Harrison Oluwaseyi2 Olusoga Opeyemi3 Igweze Augusta4
1.
2.
3.
4.
Covenant University, Ota-Ogun State, Nigeria
Covenant University, Ota-Ogun State, Nigeria
Covenant University, Ota-Ogun State, Nigeria
Covenant University, Ota-Ogun State, Nigeria
[email protected]
Abstract-- This research investigates the effect of CO2 gas kick
on the properties of a water-based mud during drilling. This
research is necessary because of the global program of CO2
capture and storage in underground reservoir and also because
the success of a drilling operation is greatly dependent on the
drilling mud design as a result of direct relationship between
drilling mud properties and the safety factor of drilling
operation. This research aims at finding the implication of a
CO2 leakage from a nearby CO2 storage reservoir on drilling
activities in a given reservoir. A basic water-based mud was
prepared and the properties of the mud were investigated as
CO2 is injected into the mud at interval to simulate CO2 gas
kick during drilling. The measured properties of the injected
mud indicated that there was a 16.3% reduction in the density
of the mud upon CO2 injection within the first 11days. That is,
there was a thinning of the mud which will result into pressure
under-balance resulting into further influx of the CO2 to the
well been drilled and this is dangerous for the drilling
operation except the surface pressure is increased or a
weighting material added to the mud. The study shows that
there was a corresponding dangerous 75.23% reduction in the
viscosity of the mud within the first 11 days of contact with
CO2 which makes the mud totally ineffective in its ability to
clean the well and transport drill cuttings to surface and this
will result into lower drilling rate and higher drilling cost.
After the first 11 days of CO2 influx, the density and viscosity
of the drilling mud remains constant and this is an indication
that a drilling mud, when reconditioned with a viscosifier, can
be reused after some days of CO2 contamination without a
further CO2 kick altering its density and viscosity properties.
The research also indicated that the pH of the mud reduces
gradually until the 11th day turning an initial basic mud to a
slightly acidic mud. This is an indication of possible reduction
in equipment corrosion. The resistivity of the mud also
increased 58.8% within the first 11days of the research which
is an indication of reduced ionic activities as a result of
reactions between the injected CO2 and the mud.
Index Term-- CO2 kick, drilling mud, mud density, CO2
solubility.
1.
INTRODUCTION
Numerous researches are on-going on the storage of CO2 in
underground reservoir but the safety of this process is still
under serious considerations and this is due to the ability of
the reservoir to retain the CO2 stored in it. The inability of
the reservoir to retain the stored CO2 gas will result into
migration of the gas to nearby reservoirs as seen in the case
of It was discovered that the major properties on the drilling
mud was altered by contact with CO 2.
Ran Qi (2009) research into CO2 transport in aquifer and
applied it to optimize CO2 storage in aquifer and oil
reservoirs. Jens T. Birkholzer et al (2008) carried out
research on the large-scale impact of CO2 storage in deep
saline aquifers with the main objective on investigation of
the three-dimensional region of influence during/after
injection of CO2 and evaluating the possible implications for
shallow groundwater resources. Jennie C. Stephens (2008)
considered the geochemical reactions that enhance
transformation of CO2 gas into dissolved or solid phase
carbon. This involves liberation of cations to neutralize
carbonic acid. They carried out the assessment of potentials
and limitations of various geochemical techniques.
CO2 flooding in practice usually involve alternating CO 2
injection and water injection. Nezhad et al carried out
experimental study of alternative CO2 and water injections
in secondary and tertiary recovery after water flooding and
continuous CO2 injection has been carried out.The result
showed that water-alternating-gas injection was very
effective. This is an indication that CO2 in contact with
water during high pressure flow exhibit a favourable
reaction. Based on this, it can be assumed that at high
pressure, CO2 in contact with water-based mud will exhibit
a reaction with the water component of the mud that affects
the effectiveness of water in the mud and the overall mud
properties.
2.
METHODOLOGY
The methodology followed in the course of this research is
as follows:
1. A water-based mud of 13.5ppg was prepared.
2. Initial properties of the mud were measured such as the
density, shear stress, yield point, resistivity and acidity.
From this the apparent and plastic viscosity were
calculated. The initial measurement is as stated in
Table.I.
3. Mud sample was placed in a modified filter press to
serve as a high pressure vessel in form of a closed
system.
4. CO2 gas was injected into the mud sample at an
average pressure of 850psi and temperature of 290C.
Injection was daily after the first injection of 3days.
5. Just before the injections the following measurements
were carried out:
 The shear stress and gel strength of the mud were
carried out with rotary viscometer. The viscosity
of the mud was then calculated form the measured
properties.
 The filtration properties of drilling fluid.
 The resistivity of the mud.
 pH of the mud.
1110204-8686 IJET-IJENS @ August 2011 IJENS
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International Journal of Engineering & Technology IJET-IJENS Vol: 11 No: 04
3.
RESULTS
The initial properties of the mud were measured before
injection of CO2 and the result is as stated in Table I below.
Apparent
Viscosity (cp)
Plastic
Viscosity (cp)
Yield
point (cp)
Resistivity
45
26.5
7.5
37.5
0.34
pH
Shear stress at
300rpm
52.5
Ωm
Shear stress at
600rpm
Table I
Initial Properties of The Mud Before CO2 Injection.
7.5
Table II
Shear Stress, Temperature and pH Measurement for CO2 contaminated
mud.
Time
(days)
Temperature
(0C)
Shear stress
600rpm
300rpm
0
29.0
52.5
45.0
7.5
3
29.8
34.0
25.0
8.5
6
29.5
24.0
15.0
8.0
7
29.4
22.0
13.0
7.5
8
29.6
21.0
14.0
7.0
9
29.5
18.0
11.0
7.0
10
29.3
15.0
9.0
6.5
11
29.2
13.0
8.0
6.0
12
29.8
13.0
8.0
6.0
13
29.5
13.0
8.0
6.0
103
tabulated in Table III below while the variation is shown by
Fig.2 and Fig.3 below.
Table III
Density and Resistivity Measurement for CO2 contaminated mud.
Time
(days)
Density
(ppg)
(lb/ft3)
Specific
Gravity
Resistivity
(Ωm)
0
13.5
101.0
1.62
0.34
3
12.0
90.0
1.44
0.36
6
11.8
88.0
1.41
0.37
7
11.6
87.0
1.4
0.40
8
11.5
86.0
1.38
0.46
9
11.35
85.0
1.36
0.50
10
11.3
84.5
1.35
0.52
11
11.2
84.0
1.34
0.54
12
11.2
84.0
1.34
0.54
13
11.2
84.0
1.34
0.54
pH
13.5
13
Mud Density (ppg)
12.5
12
11.5
11
The shear stress and pH measurement are as stated in Table
II above while the variation of the pH with time after
injection of CO2 is as stated in Fig.1 below.
0
5
10
15
Fig. 2. Mud density variation With Time After Injection of CO2
Time (days)
Fig. 1. pH Variation With Time After Injection of CO2
The density of the mud and the resistivity of the mud was
measured before and after CO2 injection and the values
Fig. 3. Resistivity Variation With Time After Injection of CO2
1110204-8686 IJET-IJENS @ August 2011 IJENS
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International Journal of Engineering & Technology IJET-IJENS Vol: 11 No: 04
From Table II above, the viscosities and yield points of the
mud were calculated with time as shown in Table 4 below
while the viscosity and yield point variations is shown in
Fig.4 below.
Table IV
Calculated Viscosity and Yield Point for CO2 contaminated mud.
Time(days)
Apparent
Viscosity
(Cp)
Plastic
Viscosity
(Cp)
Yield
Point
(Cp)
0
26.25
7.5
37.5
3
17.0
9.0
16
6
11.0
7.0
8
7
10.5
8.0
5
8
10.5
7.0
7
9
9.0
7.0
4
10
7.5
6.0
3.0
11
6.5
5.0
3.0
12
6.5
5.0
3.0
13
6.5
5.0
3.0
104
pH must be as a result of formation of carbonic acid
between the gas and the water content of the mud which
may later be dissolved by the mud as a result of thorough
mixing during drilling. The resistivity of the mud also
increased from 0.34 to 0.56, a 58.8% increase and this is an
indication of increased ionic activities which could only be
due to possible reactions between the injected CO2 and the
mud. In conclusion, contamination of water-based drilling
mud by CO2 gas kick will render the mud almost useless in
its ability to clean the well bottom and suspend drill
cuttings.
[1]
[2]
[3]
[4]
[5]
[6]
[7]
REFERENCES
Ran Qi, (2009) Simulation of Geological Carbon Dioxide
Storage, Ph.D. dissertation, Department of Earth Science and
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S.J. Houston, B.W.D. Yardley, P.C. Smalley and I. Collins;
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Berger ,R. L.; Young,J. Francis (1979), Reaction of Calcium
Silicates with Carbon Dioxide and Water, Final report of Jan
1976-Jan 1979 researches, Illinois University At UrbanaChampaign, US.
http://www.columbia.edu/~vjd1/carbon.htm
Peter Zweigel, Rob Arts, Ane E. Lothe & Erik B. G. Lindeberg,
Reservoir geology of the Utsira Formation at the first
industrial-scale underground CO2 storage site (Sleipner area,
North Sea), Geological Society, London, Special Publications;
2004; v. 233; p. 165-180.
C. A. Rochelle, I. Czernichowski-Lauriol & A. E. Milodowski,
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Publications; 2004; v. 233; p. 87-106.
Nezhad, S. A. T., M. R.. R. Mojarad, S. J. Pahitakhti, J.
S.Moghadas, and D. R. Farahmand, “Experimental Study On
Applicability of Water-Alternating-CO2 Injection In The
Secondary and Tertiary Recovery” 1st International Oil
Conference and Exhibition, Mexico, August 31 – September 2,
2006.
Fig. 4. Viscosity and Yield points (cp)
4.
CONCLUSION
The research study shows that there was a dangerous
reduction in the viscosity of the mud from 26.25 to 6.5cp
which is a 75.23% reduction in the viscosity of the mud
within the first 11 days of CO2 injection. With this
reduction the mud will become totally useless for what it
was designed for. The density of the mud also reduced 13.5
to 11.2ppg within the same 11days of contamination with
CO2. During this research there was an indication of pH of
the mud increased on CO2 injection and then from the third
day reduced gradually until the 11th day making the mud to
become slightly acidic mud. The initial slight increase in the
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