PETE 3265: Drilling Fluids Laboratory
Experiment #1 omponents o! "asi $"%: mud preparation and property measurement &
'eport by Laura Louise Demar( Lab Partners: )ustin *+ %ar,ue%ar. Don.or /tation #3
Date Experiment Per!ormed: 015201 Date 'eport /ubmitted: 022201
*bstrat
The drilling fluid is one of the most important tools in well engineering so it is important to know if its rheological comportment and constitution attends certain requisites. These characteristics involve the mud weight, its viscosities and its pH, in addition to others. The mud used was made with water and bentonite. To measure these properties, some types of tests are recommended. The most common physical measurements, and executed in this procedure, are the mud weight, Marsh Funnel test, apparent viscosity, plastic viscosity, yield point, initial gel strength and pH measure. The technique
followed is recommended by !".
The
results
were
satisfactory,
corresponding to theorical values. The tests are well known, tested and approved by most of petroleum engineers.
Purpose
This experiment intends to promote the ability of mixing mud used in drilling operations, also measures the properties of the prepared mud, as well as let the students come into contact with equipment for measurement of some mud properties.
&ntrodution
The drilling fluid is an important tool in #rilling $ngineering. The main purpose of the drilling fluid is remove the cuttings that the bit produces while drilling and carry them to the surface, so the bit can keep advancing in depth. nother purpose for the drilling fluid is to exert enough hydrostatic pressure in the formations that are being drilling to prevent that the fluids in the formation enter in the well. The mud has other important attributions, but these two are the most important.
"n order to achieve this specifications, the mud has to have some particular characteristics. Most of the used drilling mud are water%base and its compositions consist in solids, liquids and chemicals. For this experiment, the mud is very simple, composed by water and bentonite, a clay that increase the viscosity of the water. There are many types of commercial bentonites, the most important is &yoming bentonite. The drilling fluid is a non%newtonian fluid, and for this reason it presents different types of viscosity, which depends on the flow rate. The merican !etroleum "nstitute '!"( recommends some tests to help determinate if the drilling fluid is performing its functions properly. The Mud )alance is a test to determine density o! t(e mud . The test consists in fill the cup of the balance and read the density directly from the balance, which gives the density in pounds per gallon 'ppg(. The Marsh Funnel test is basic used for detect an unwanted mud onsisteny, and consist in fill a funnel with mud sample and measure the time of * quart of the mud flow through the funnel. The time is measured in seconds per quart 's+qt(. This measurement does not give the accurately viscosity of the mud because it is a non% newtonian fluid. The viscosity indeed is measured by a rotational viscometer, in this case the Fan iscometer. There are some tests in different rotational speeds made with the same viscometer. The apparent 4isosity '( is read at speed of - rpm, it depends on what type of viscometer is measured, but with the Fan iscometer is measured in centipoise with the equation -.* $quation -.*
AV =
600 RPM reading 2
The rheological parameters of the mud are measured also, and !" recommends that the drilling fluid must follow the )ingham plastic rheological model. To confirm this
behavior, the mud has to be characteri/ed by the plasti 4isosity '!(, measured in centipoise given by the equation -.0 $quation -.0
PV =600 RPM reading− 300 RPM reading
and also characteri/ed by the yield point '1!(, measured in lbf per hundred square feet 'lbf+* sq( and given by the equation -.$quation -.-
YP=300 RPM reading − PV
nother important rheological parameter measured is the gel strength. There are two types of gel strength that !" recommends to measure, the initial gel , consisting in let the mud rest for * seconds after stable rotation, and then note the maximum deflection when the rotating presents a very low speed, generally - rpm. The same measurement is made letting the mud rest for * minutes, and it is called 10 minutes gel.
2ther important parameter measured is the p, consisting in the concentration of hydrogen ions in an aqueous solution, and can be measured using pH paper or pH meter. "n this process, it was used the pH paper.
E,uipment and %aterials
To mix the mud it was used3 • • • • • •
4raduated cylinder of 056 spatula6 common balance6 blender6 water, *.756 bentonite 'Mel 4el(, 8g.
To weight the mud it was used3
•
Mud balance that includes cup, lid, level glass, rider, fulcrum, base, fulcrum and knife edge.
To measure the funnel viscosity of the mud it was used3 • •
The Marsh Funnel and the measuring 9ug6 chronometer.
To measure the other viscosities it was used3 •
The Fann iscometer, that includes the viscometer and the sample cup.
To measure the pH it was used3 • • • • •
pH paper6 caustic solution6 spatula6 graduated cylinder6 graduated pipet with pipet controller.
Proedure
To do the mud, the ratio of bentonite was *: lbs of gel per bbl of water, thus was used 7 lab bbl of water, which meas*.7 liter of water was measured in a graduated cylinder, then placed in the blender. The bentonite was taken from the bentonite bag and 8 grams were measured in the common balance, then displaced in the bender. The blender was turned on at low speed, and the mixture was stirred for five minutes. To measure the weight of the mud, the cup of the mud balance was filled with the mixed mud, closed with the lid, attached in the balance, and then measured moving the rider until the air bubble in the level glass was stabili/ed in the center of the marking. To measure apparent and plastic viscosities as well as the yield point, the cup of the Fann iscometer was filled with the mixed mud, then the cup was displaced in the appropriated platform, raised until the mud cover the marking. The Fann iscometer
was turned on in the speed of 8 rpm, then turned off. nother measurement was made with the speed of - rpm. To measure the initial gel, the Fann viscometer was turned on, with the speed of - rpm, then turned off. &hen the Fann iscometer stopped spinning, the chronometer was used to counter ten seconds. fter that, the Fann iscometer was turned on with the speed of - rpm, marked as ;gel speed<. The maximum deflection was noted. The * minutes gel was not measured. The measurements aforementioned were repeated twice, with the same mud made before. The pH increasing was made by adding *cc of the caustic solution in a sample of mud that was mixed with the spatula then a piece of pH paper was dipped. Thi procedure was made eleven times. The mud was discarded and all equipment were cleaned and stored.
Data and *nalysis
The measurements made in class are shown the table below Table *. Measurements of mud properties sample 600 rpm 300 rpm
1 27 20.5 44"1 0 13.5 6.5
FV (s/qt) AV (cp) PV (cp) YP (lbf/100 sq) 14 Int!l #l 15 $#%t (pp) &.6
2 26.5 20
avera ge 26.75 20.25
45"41 13.25 6.5
44"75 13.375 6.5
13.5 14
13.75 14.5 Font3 The autor.
&.5
&.55
The measurements of pH are shown in the Table 0.
Table 0. Measurement
cc caustic sol. 0 1 5 6 7 & '
pH 6.50 7.00 7.30 7.40 7.50 7.70 &.10
of pH
Font3 The autor.
The theorical weight of the mud was computed using the density of water of ==> kg+m , or .==> g+cc and the specific gravity of the bentonite of 0.-:. -
To find the weight of the mixture of the mud was used the following calculations, using one lab bbl of water, which means -: cc of water, and *:g of bentonite.
volume of bentonite Vb=15
g ∗1 cc = 6.383 cc 2.35 g
total volume of mixture per bbl Vt = 350 cc + 6.383 cc =356.383 cc
water weight Mw =350
cc ∗0.998 g =349.3 g 1 cc
)entonite weight Mb =15 g
Total weight Mt = Mb + Mw= 15 g +349.3 g =364.3 g
#ensity of the mixture, in ppg 364.3 g 356.383 cc
Mt = ρ= Vt
∗3785.41 cc ∗1 lbm
1 gal
=8.637 ppg
448 g
'esults
&ith the measurements made, it is possible to show that the mud made in class was a non%newtonian fluid, as it presented different viscosities in different speeds of rotation. lso, the theorical weight of the mixed mud is related with the measurement, indicating that the dimension was relatively accurated. The experimental error is shown below.
|experimental ρ −theorical ρ| |8.55−8.637| ∗100 = ∗100
error ( )=
theorical ρ
8.637
error =1.01
The results of the raise of the pH in the mud can be better seen in the 4raphic *. s it suggests, the pH is increasing with every cc of caustic solution that is added, even thought the pH of = was not reached, it can be predicted how much cc of caustic solution is necessary to reach the pH of =. 4raphic *. !lot pH versus cc of caustic solution
p !stc sltn '.00 &.00
f() 0.01-3 0.12-2 * 0.55 * 6.52 7.50 7.70 7.30 7.40 0.37 * 6.' f() 6.'1 ln() -0.05 +, 17.00 7.00 p +, 0.6& 0.66 6.50 6.00 5.00
0
1
2
3
4
5
6
cc f c!stc sltn
Font3 The autor.
7
&
'
&.10
10
?olving the expression given in the graphic, it is possible to find and amount of *.- cc of caustic solution that need to be added in the sample of mud to reach the pH of =.
Disussion
s seen in the analysis, the measured mud weight presented a small deviation from the theorical measurement, therefore it is presumable that this experiment was well conducted. The Marsh Funnel viscosity is generally used to measure sudden changes in the viscosity of the mud, thus this experiment was meant to familiari/e with the equipment. From the analysis of the data, it is possible understand that the mud behaves as expected, acting like a )ingham plastic fluid, hence having different viscosities in different speeds of rotation of the Fann iscometer. The pH of the mud was too low in the first measurement, and as estimated previously, it was necessary add many portions of caustic solution and even thought, the pH of = was not reached in class. This particular aspect is very important in the drilling mud because the low pH cause corrosion in the parts of the drilling string, thus it is necessary to control the pH closely. The behavior of the pH displayed in the graphic suggest that the mud has a buffer solution.
onlusion
The experiment was meant to teach the students how to prepare a drilling fluid and also how to deal with the equipment and measure simple mud properties. s expected, the elaboration of the mud was effortless and relatively accurate. The properties measured were satisfactory and proved the expected behavior of the mud. "t is possible to emphasi/e that mud presented a non%newtonian behavior and the properties measured were consistent with the theorical behavior. The pH was acid, then it was used some caustic solution to raise the pH. $ven thought it was not possible to reach the pH of = in class, however being predictable.
omments
The procedure was effortless and harmless, unless the part of the addition of the caustic solution. This part should be done more carefully and emphasi/e the accuracy of the instruments. "t was used a graduated cylinder instead of using the graduated pipet. The pipet controller was wet during the procedure, preventing a properly use of the equipment and compromised the results. The lab coat and the latex gloves are essential to do this experiment.
'e!erenes
@yen Aaenn, H.A.H., #arley, and 4eorge @. 4ray. 0**. omposition Properties o! Drilling and ompletion Fluids . &altham, M3 B?. 4ulf !rofessional !ublishing. .T. )ourgoyne Cr, D.D. Millheim, M.$. Ahenevert E F.?. 1oung Cr. *=>8. *pplied Drilling Engineering ol+ 2 . @ichardson, T3 B?. ?!$ Textbooks. "entonite 7alliburton 8el9 . Halliburton. ccess date on =+*G+0*7. @etrieved from https3++docs.google.com+viewerurlIhttpJ-J0FJ0Fwww.halliburton.comJ0Fpublic J0FcemJ0FcontentsJ0FchemKcomplianceJ0FwebJ0Fh0>>.pdf
