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UNIVERSITI TEKNOLOGI MARA
FAKULTI KEJURUTERAAN KIMIA
OIL AND GAS ENGINEERING LABORATORY II
(CGE 557)
No Title Allocated Marks % Marks
1 Abstract/summary 5
2 Introduction 53 Aims/objectives 5
4 Theory 5
5 Apparatus 5
6 Procedure 107 Result 10
8 Calculations 10
9 Discussion 20
10 Conclusion 1011 Recommendations 5
12 References 5
13 Appendices 5
Total 100
Remarks:
Checked by:
NAME & : Afuza HusnaSTUDENT ID (2010)
Rozalin Danis (2010467864) Amirul Hakim Bin Mat Azahar
(2010409492) Muhammad Ilham Bin Juanda (2010485804) Mohammad Zhafry Bin Samsuddin (2010873498)
EXPERIMENT : 1DATE PERFORMED : 23 March 2012SEMESTER : 4PROGRAMME/CODE : EH 223GROUP : EH 223 4A
Abstract/summary
An artificial neural networks (ANN) model has been developed to provide accurate predictions of mud density as a function of mud type, pressure and temperature. Available experimental measurements of water-base and oil-base drilling fluids at pressures ranging from 0 to 1400 psi and temperatures up to 400 °F were used to develop and test the ANN model. With the knowledge of the drilling mud type (water-base, or oil-base) and its density at standard conditions (0 psi and 70 °F) the developed model provides predictions of the density at any temperature and pressure (within the ranges studied) with an average absolute percent error of 0.367, a root mean squared error of 0.0056 and a correlation coefficient of 0.9998.
Introduction
The density of a drilling fluid is normally determined at standard conditions of 0 psi and 70
°F. As the drilling operation progresses, the drilling fluid will be subjected to increasing
pressure and temperature. While the higher pressure increases the drilling fluid density, the
increased temperature results in density reduction. Proper planning and execution of drilling
operations, particularly for HPHT wells, requires complete and accurate knowledge of the
behavior of the drilling fluid density as the pressure and temperature change during the
drilling operation. Such information can accurately be obtained only through actual
measurements of the drilling fluid density at desired pressures and temperatures. This,
however, requires special equipment along with difficult and time-consuming procedures.
Prediction of the drilling mud density at various pressures and temperatures is, therefore, very
useful for mud and drilling engineers in planning drilling operations.
McMordie et al1 studied the effect of temperature and pressure on the density of water-base
and oil-base drilling fluids. They presented experimental measurements of densities in the
temperature range of 70 °F to 400 °F and pressure range of 0 - 14000 psi and concluded that
the change in mud density with pressure and temperature is independent of the initial mud
density (at 70 °F and 0 psi). They also concluded that for equal densities at surface
conditions, oil-base drilling fluids become denser than water-base drilling fluids at high
temperatures and pressures. Okoye et al2 used the data of McMordie et al and developed
various correlations of water-base mud density as a function of temperature for various
values of surface mud density. These correlations, however, ignored the effect of pressure on
mud density and are limited to water-base drilling fluids of specific surface density and to the
range of temperatures and pressures covered by the experimental measurements.
Away from empirical correlations and their inherent limitations, artificial neural networks
(ANN) models have been proven in recent years to be very effective means of solving
difficult problems in the oil industry. This paper presents an ANN model that provides, with
great accuracy, predictions of water-base and oil-base drilling fluids density. Identifying the
type of drilling fluid (water-base, or oil-base) and the density at surface conditions, the
developed model predicts the density at any temperature and pressure.
Objectives
To determine the density of different sample of drilling mud
Theory
Apparatus
Mud samples (oil and water base mud), Fan Mud Balance, hydrometer and measuring cylinder.
PROCEDURE
Procedures
Fan mud balance;
Calibration
1. Filled the cup with water.
2. Placed the lid on the cup and seat it firmly. Be sure some mud runs out of the hole in
the cap.
3. With the hole in the cap covered with a finger, all the water from the outside of the
cup and arm are washed or wiped.
4. Set the knife edge into the fulcrum and move the rider along the graduated arm until
the cup and arm are balanced.
5. Read the density of the mud at the left-hand edge of the sliding weight.
6. Report the results to the nearest scale division in lb./gal.; lb./cu. ft.; S.G. (specific
gravity); or psi/1000 ft. of depth.
7. Wash the mud from the cup immediately after each use. It is absolutely essential that
all parts of the mud balance be kept clean if accurate results are to be obtained.
Test procedure
1. The lid from the mud cup is removed and filled with the mud sample.
2. Placed the lid on the cup and seat it firmly. Be sure some mud runs out of the hole in
the cap.
3. The mud from the outside of the mud cup is washed or wiped.
4. Placed the balance arm on the base, with the knife-edge resting on the fulcrum.
5. Moved the rider until the graduated arm is level, as indicated by the level vial on the
beam.
6. At the left-hand edge of the rider, read the density on either side of the lever in all
desired units without disturbing the rider.
7. Noted down the mud temperature corresponding to density.
Hydrometer;
1. Used the same mud sample as used in the mud balance experiment.
2. Filled the hydrometer cylinder (graduated cylinder) with the drilling mud to within 1
to 2 inches of the top by pouring the sample slowly down the side of the cylinder.
3. Chose the correct hydrometer for measuring specific gravity, SG of the drilling fluid.
4. Inspected the hydrometer to ensure that it is clean and dry.
5. Placed the hydrometer carefully in the cylinder, allowing it to gently settle to the
proper measurement level.
6. Spin the hydrometer and record the reading at which the hydrometer rests.
7. Record the reading and compared with the reading obtained from mud balance
experiment.
Result
Mud Weight ppg lb/ft3 psi/1000ft SG
Oil-based mud 11.6 87.0 602.0 1.098Water-based mud 10.6 79.5 551.0 1.272
Mud density measurement using mud balance
Mud density measurement using hydrometer
Mud WeightSpecific Gravity (SG)
Average Density (SG)1st trial 2nd trial 3rd trial
Oil-based mud 1.042 1.042 1.038 1.0407Water-based mud 1.308 1.310 1.313 1.3103
Calculation
Oil-based mud
Using mud balance,
Mud weight = 11.60 ppg
1 ppg = 7.48 lb/ft3
87.0lb
ft3×
1 ppg
7.48lb
ft3
=11 .63 ppg
1 ppg = 0.12 SG
1.098SG×1 ppg
0.12SG=9.15 ppg
1 ppg = 0.052 psi/ft
602
psi1000 ft
×1 ppg
0.052psift
=11 .57 ppg
Using hydrometer,
1 ppg = 0.12 SG
1.0407 SG×1 ppg
0.12 SG=8 .67 ppg
Water-based mud
Using mud balance,
Mud weight = 10.60 ppg
1 ppg = 7.48 lb/ft3
79.5lb
ft3×
1 ppg
7.48lb
ft3
=10 .63 ppg
1 ppg = 0.12 SG
1.272SG×1 ppg
0.12SG=10 .60 ppg
1 ppg = 0.052 psi/ft
551psi
1000 ft×
1 ppg
0.052psift
=10 .59 ppg
Using hydrometer,
1 ppg = 0.12 SG
1.3103SG×1 ppg
0.12SG=10 .91 ppg
DISCUSSION
For the determination of density of mud using the mud balance, we firstly made a calibration
of the mud balance by using a fresh water to check for error of the mud balance. We got
exactly 1.00 SG for the water. After we done with the calibration, the mud balance is
perfectly fine and ready to go for the mud density determination.
The mud balance can give us a direct measurement of of mud density in four unit that are ppg
(lbm /gal), lb./ft3, psi/1000 ft., specific Gravity (SG) as shown in table in the results above.
While the hydrometer only give the reading of density by SG.
Water base mud weight measured using hydrometer is 1.3103 SG. The result follows
expected values declared in M-I SWACO (2001) which the standard mud weight of water
based mud usually used in drilling operation is between 1.054 to 1.618 SG.
While the oil base mud weight measured using mud balance and hydrometer are
1.0407 SG respectively. These results were also complied with expected value published by
M-I SWACO (2001). In which a standard mud weight of oil based mud is normally between
1.019 to 1.917 SG.
There is difference between reading taken using mud balance and hydrometer. For oil
based mud, the discrepancy is 0.0573 SG while for water based mud is 0.0383 SG. Mud
balance is a more accurate tool to acquire specific gravity of mud. It is because hydrometer is
actually unreliable in drilling fluid because of gelation (Schlumberger oilfield glossary,
2011).
The gelation describe the process of formation jelly like substances within the drilling
fluids that having high property of suspending solid material. Most of mud commonly used
comes with this particular behaviour, due to requirement of the drilling process that want any
excessive material such as cuttings that been encounter via the drilling process can be
suspended by the drilling fluid and regulated through the drilling system so that the cuttings
can removed from the drilling process. Thus such floating additive behaviour will creates
artificial lifting for the hydrometer to suspend with the drilling fluid and affects the reading
obtained. In some other cases the hydrometer usage is an appropriate as the gelation process
occurs in mud will create difficulty on estimating the density of the particular drilling fluid.
Error will often encounter if the gelation exist whereby the fluid density cant determined
properly.
We always have different advantages and disadvantages when we used varies of method. If
we use the mud balance, we will have a better and more accurate reading compare with
hydrometer. For the first reason is the trapped air inside the mud cup can be freed as the mud
cup lid allows the air to escape from the mud cup as closed. This therefore gives us a correct
measurement of the density of the mud. On the other hand, we can’t expel the trapped air
when we use the hydrometer. Thus, less accurate data will be obtained through this method.
Moreover, measurement using hydrometer involves indeterminate errors cause a measuring
process to give different values of densities when that measurement is repeated many times.
The effect that indeterminate errors have on results can be somewhat reduced by taking
repeated measurements then calculating their average. The average is generally considered to
be a "better" representation of the "true value" than any single measurement, because errors
of positive and negative sign tend to compensate each other in the averaging process. In a
comparison, mud balance will a definite reading as we first do a careful calibration of that
apparatus. There is no different values of densities and indeterminate errors.
Hydrometer is not very suitable to be used for measuring mud density because it is fragile.
Most importantly, before measuring using hydrometer, the most suitable hydrometer scale
must be first determined. The reason is hydrometer has varies scale; and only one hydrometer
will suit for certain type of fluid density. Therefore, this trials and error method is also
complicated and time consuming. As compared to mud balance, it provides a simple,
practical method for the accurate determination of fluid density. Most importantly, it contains
no easily broken parts like hydrometer. The item's durable construction makes it is ideal for
field use.
After determined both densities of the mud, then only we can decide if the mud is suitable to
be used during the drilling operation. From our research, both sample of mud are suitable to
use during the beginning of the drilling operation. This is because, the density of both water-
based mud and oil-based mud are low. It is enough to maintain the pressure inside the
wellbore to withstand the formation pressure. It is important because it prevents the borehole
from collapsing and prevents the influx of formation fluids.
We can’t use these muds when we reached a very high depth of borehole. This may cause
kicks or blowout as it can’t maintain the formation pressure. This is because the mud pressure
will be less than the formation pressure as the formation pressure increases when the depth
increases. This is also known as underbalance. Thus, we need to use higher density of mud to
overpower the formation pressure. The pressure exerted by the mud must be greater than the
formation pressure. This is called overbalance which is crucially needed to be kept through
the drilling operation.
Even though, the mud pressure can’t be too high. Otherwise, lost circulation will happen.
This incident occurs when the mud pressure is too high and overwhelming the formation
pressure. This will lead to the reduction of penetration rates, breaking down of formation, and
causing stuck pipe.
In another word, we must stay alert and check the formation pressure frequently so that we
know when we need to change the mud to be pumped inside the borehole.
Conclusion
From the experiment we get the density of the oil and water base mud by using mud balance
and hydrometer. As we measured we get 10.60ppg of water base density while for oil base
mud the density is 11.60ppg. The value of the mud weight is varies with different fluid as
every fluid have it own properties. As a conclusion the density of the water based is higher
than the oil base mud for both instrumental used. By knowing the density of the mud, we can
avoid some problem during drilling prosesses for example prevent the substance to float after
the mixture or avoid lost circulation. Beside that we can predict how much mud that we need
to carry out the cutting rock. Therefore the experiment is sucessful.
Recommendation
There are some recommendation should be taken to give the better results. There is also some
precaution that should be taken to prevent error in this experiment. For example;
1. Wipe the cup cleanly to have the accurate specific gravity.
2. The cup must be clean and dried to have the accurate specific gravity.
3. The water based mud should be stirred by using the mixer to prevent the precipitation
inside it.
4. Use suitable size of measuring cylinder to make sure that the hydrometer will have the
ability to float and sink inside the mud
5. Take the average reading as the result to avoid error.
6. Pressurized mud balance is recommended in order to get the best measurement of mud
density.
7. The pressurized mud balance looks like the convention one, but it has a pressurized
sample cup. When you press mud sample in the cup, any gas in fluid phase is compressed
to very small volume so the mud weight measurement is more accurate.
References
1. Drilling Engineering Laboratory Manual; Oil and Gas Engineering Laboratory 2
(CGE 557)
2. Drilling Engineering; J.J. Azar, G. Robello Samuel; PennWell Corporation.
3. http://en.wikipedia.org/wiki/Drilling_fluid
4. http://www.drilling-mud.org/mud-weight-or-mud-density/
5. http://www.glossary.oilfield.slb.com/Display.cfm?Term=mud%20weight
6. http://en.wikipedia.org/wiki/Hydrometer
7. http://www.glossary.oilfield.slb.com/Display.cfm?Term=mud%20balance
8. http://en.wikipedia.org/wiki/Mud_balance
Appendices
Expected result
Mud balance;
Type
Mud weight
SG psi/1000 ppg
Oil base
Water base
Hydrometer;
Type SG Density mud
Oil base
Water base