OfiTE 150-50 User manual

Differential Sticking Tester
Part No. 150-50
Instruction Manual
Updated 5/29/2009
Ver. 2.0
OFI Testing Equipment, Inc.
11302 Steeplecrest Dr. · Houston, Texas · 77065 · U.S.A.
Tele: 832.320.7300 · Fax: [phone] · www.ofite.com
©Copyright OFITE 2011

Table of
Contents
Intro.......................................................................................................2
Description ...........................................................................................2
Components.........................................................................................3
Safety ...................................................................................................5
Test Procedure ..................................................................................6
Timed Filtration ................................................................................6
Fixed Cake Thickness....................................................................11
Disassembly.......................................................................................12
Theory.................................................................................................13
Example .........................................................................................15
Worksheet ......................................................................................16
Maintenance.......................................................................................17
Diagrams ...........................................................................................18
Full Unit ..........................................................................................18
Cell Assembly ................................................................................19
OFITE, 11302 Steeplecrest Dr., Houston, TX 77065 USA / Tel: [phone] / Fax: [phone] / www.ofite.com 1

The OFITE Differential Sticking Tester measures the “Stuck Pipe Tendency
Coefficient” of drilling fluids, and also determines how effective lubricants or
treatments might be with any given drilling fluid. This coefficient takes into
account both the friction, or “stickiness”, of the filter cake, as well as the
amount of cake building that must occur in order to freeze or stick the pipe
in the hole. The coefficient is determined by running a Timed Filtration test.
By measuring the area of cake building during a test, the “Bulk Sticking
Coefficient” is obtained and read directly at the conclusion of the test. How
likely a given fluid will be to produce a stuck pipe situation and how effec-
tive a given treatment may be, can be immediately determined on-site.
The unit is normally pressurized by a CO2pressuring assembly, but any
nitrogen source will also work. If nitrogen is used, the tester apparatus
must be fitted with a suitable nitrogen regulator, gauges, valves, and high-
pressure hoses. The standard test uses 477.5 PSI (3,291 kPa) applied to
a 200-mL stainless steel vessel. The unit includes both a flat-faced plate
and a plate of 12½" (31.75 cm) spherical radius, which simulates the pipe
inside the casing or collars in the borehole. For samples that adhere more
to the plate than to the filter paper, stainless steel micro-corrugation disks
are provided. For convenience a stainless steel carrying case is available
as an optional item.
OFITE, 11302 Steeplecrest Dr., Houston, TX 77065 USA / Tel: [phone] / Fax: [phone] / www.ofite.com 2
Description
Intro

Components #130-10-52 Jam Nut, 3/8-24, Qty: 2
#142-56 O-ring
#150-52 Neoprene Gasket
#150-53 Plastic Gasket
#150-54 Torque Wrench
#150-55 Spanner Wrench
#150-56 Test Cell O-ring
#150-57 5⁄16" Socket with 3⁄8" Drive
#150-58 Torque Plate; Flat Bottom
#150-59 Torque Plate; Spherical
#153-16 Glass Graduated Cylinder; 25 mL × 2⁄10 mL
#170-04 CO2Pressurization Unit:
#143-02-10 CO2Puncture Head Assembly
#143-03 Barrel for CO2Cartridge
#170-08 Regulator
#170-20 Manifold Block
#170-32 1⁄8" × 1⁄8" NPT Male Needle Valve
#171-22 Retainer Pin
#171-34 1500-PSI Gauge; 2"; ¼" NPT Bottom
#170-13 Test Cell O-ring; Buna N
#170-15 Base
#170-16 Valve Stem; Qty: 2
#170-17 Valve Stem O-ring; Qty: 10
#170-19 2½" (6.35 cm) Filter Paper; Specially Hardened for Filter
Presses
#170-35 6" Adjustable Wrench
#170-44 ½" Rubber Foot; Qty: 4
#171-79 ¼" Hex Wrench
OFITE, 11302 Steeplecrest Dr., Houston, TX 77065 USA / Tel: [phone] / Fax: [phone] / www.ofite.com 3

Optional:
Yoke for Fixed Cake Thickness Test - Special Order Only
#150-50-SP Spare Parts for #150-50:
#142-56 O-ring; Qty: 12
#143-02-13 O-ring for Puncture Pin Holder Assembly; CO2Cartridge;
Qty: 6
#143-02-14 O-ring for Puncture Pin Holder Assembly; Qty: 4
#143-05 EZ Puncture CO2Bulbs; 8-Gram; UN #1013; Package of
10; Qty: 30
#143-06 Safety Bleeder Valve
#143-07 Regulator Repair Kit for #143-00
#143-22 Gasket for Puncturing Pin; Qty: 12
#150-51 Locking Mesh Disc; Qty: 10
#150-52 Neoprene Gasket; Qty: 10
#150-53 Plastic Gasket; Qty: 8
#153-16 Glass Graduated Cylinder; 25 mL × 2/10 mL; Qty: 2
#170-13 Test Cell O-ring; Buna N; Qty: 4
#170-16 Valve Stem; Qty: 2
#170-17 Valve Stem O-ring; Qty: 20
#170-19 2½" (6.35 cm) Filter Paper; Specially Hardened for Filter
Presses; Qty: 5
#170-23 60-Mesh Screen; Qty: 8
#171-22 Retainer Pin; Qty: 2
#171-79 ¼" Hex Wrench
OFITE, 11302 Steeplecrest Dr., Houston, TX 77065 USA / Tel: [phone] / Fax: [phone] / www.ofite.com 4

Safety Nitrogen must be supplied in an approved Nitrogen Gas Cylinder and
secured to meet safety standards. Do not use nitrous oxide cartridges as
pressure sources.
Due to the high pressures involved in this test, extreme care must be exer-
cised at all times. All safety precautions must be met, especially in the cell
breakdown procedure after the filtration procedure has been completed.
Never transport CO2bulbs or cartridges by airplane without proper packag-
ing. Cabin depressurization could cause them to explode.
Before pressuring, always check to be sure the regulator is in a closed
position by ensuring the T-screw is backed out and free turning. Insert and
puncture the CO2cartridge by turning the barrel only a quarter turn past the
actual puncture point. Adjust the regulator to the desired pressure with the
regulator T-screw. With the Differential Sticking Tester, never exceed 500
PSI (3,450 kPa). When de-pressurizing, shut off the pressure supply, then
bleed off the system of pressure with the valve, and finally back out the
regulator T-screw.
OFITE, 11302 Steeplecrest Dr., Houston, TX 77065 USA / Tel: [phone] / Fax: [phone] / www.ofite.com 5

Test
Procedure
Timed Filtration
The Differential Sticking Tester is capable of performing two different tests.
Both of these tests determine the Stuck Tendency Coefficient and the Bulk
Sticking Coefficient. The Timed Filtration test uses a pre-determined stick-
ing time. The Fixed Cake Thickness test uses an optional yoke assembly
to determine the amount of time required to create a cake of specified
thickness. The general procedure for assembling and operating the instru-
ment is basically the same for either test.
Two torque plates are provided with the unit. The spherical torque plate
(#150-59) has a very slight curve on the bottom. The radius of the curve is
12.5" (31.75 cm) and simulates a 25" (63.5 cm) diameter drill casing or col-
lar. The flat torque plate (#150-58) is completely flat across the surface.
The difference between the two is sometimes difficult to see. To distinguish
between the two, place them next to each other on a flat surface. The
spherical torque plate will rock slightly, while the flat torque plate will sit
firmly.
1. Make sure the unit is clean and dry before beginning a test.
2. Open the test cell. Remove the inner cap by turning the cell over and
removing the two allen screws with the supplied wrench.
3. Inspect the o-ring on the bottom of the inner cap. Replace it if it shows
signs of wear or damage.
OFITE, 11302 Steeplecrest Dr., Houston, TX 77065 USA / Tel: [phone] / Fax: [phone] / www.ofite.com 6
Cell Bottom
Cell - Inside Retaining Ring
Inner Cap - Bottom Inner Cap - Top
Allen Screws O-ring
Inner Cap

4. Place a sheet of filter paper on top of the screen on the inner cap. On
top of the filter paper, place the rubber gasket, then the plastic ring.
The locking mesh disk can be used to lock the filter cake to the paper
so that it does not stick to the torque plate face and break lose from the
filter paper. If you choose to use the locking mesh disk, place it on top
of the filter paper, beneath the rubber gasket.
5. Screw the retaining ring in place on top of the filter paper and gaskets.
Be sure to keep the gaskets centered.
6. Place the inner cap back into the cell. Make sure the o-ring seats prop-
erly beneath the inner cap. Refer to the photos on page 8.
7. Turn the cell over and secure the inner cap with the two allen screws.
8. Tighten the retaining ring securely with the supplied retainer wrench.
9. Inspect the o-rings on the valve stems and replace any that show signs
of wear or damage. Screw one of the valve stems into the hole in the
base of the test cell and hand tighten.
OFITE, 11302 Steeplecrest Dr., Houston, TX 77065 USA / Tel: [phone] / Fax: [phone] / www.ofite.com 7

Tip
Retainer Wrench (#150-55)
Retaining Ring
Plastic Gasket (#150-53)
Neoprene Gasket (#150-52)
Locking Mesh Disk (#150-51)
Filter Paper (#170-19)
Inner Cap with Screen
(#150-50-5)

10. Place the cell on the stand. Make sure the four holes in the base of the
cell line up with the stand tips.
11. Fill the cell with sample fluid to the scribed line.
12. Insert the stem of the torque plate through the hole in the cell cap as far
as possible. The face of the plate should be facing towards the inside
of the cell. Be careful not to cut the o-ring.
13. Screw the cell cap onto the test cell body. Make sure the o-ring is
properly seated in the groove in the cell cap.
14. Tighten the cell cap using the supplied spanner wrench. For additional
leverage, place the lever arm horizontally between the two support legs.
Once the cell cap is tightened, rotate the cell on the stand until the
valve stem hole is oriented away from the stand supports. This will pro-
vide more space for the torque lever.
OFITE, 11302 Steeplecrest Dr., Houston, TX 77065 USA / Tel: [phone] / Fax: [phone] / www.ofite.com 8

Tip
Spanner Wrench Lever Arm
Cell Cap
Torque Plate
O-ring
Torque Plate

Lever Arm
Torque Plate Stem
OFITE, 11302 Steeplecrest Dr., Houston, TX 77065 USA / Tel: [phone] / Fax: [phone] / www.ofite.com 9
15. Screw the other valve stem into the hole in the cell cap and hand tighten.
16. Place the CO2assembly onto the top valve stem and secure it in place
with the retaining pin.
17. Unscrew (counter-clockwise) the regulator T-screw until it turns freely.
18. Remove the barrel from the regulator. Place a CO2cartridge into the
barrel and tighten the barrel to the puncture head until the cartridge
punctures.
19. Tighten (clockwise) the regulator T-screw until the gauge reads 477.5
PSI (3,292 kPa).
20. Place the 25 mL graduated cylinder under the cell and open the lower
valve stem by turning it counter-clockwise ¼ turn.
21. Make sure the torque plate is up as far as possible by turning and
pulling it upward.
22. Open the top valve stem ¼ turn to initiate filtration. Record the time of
the start of the test.
23. Continue filtration for 10 minutes, or until the desired filtrate volume is
collected.
If the yoke option is being used, filter until the desired cake thickness is
reached (usually 2/32" / 1.6 mm). Refer to page 11 for details.
24. Align the groove in the lever under the column top cross support and
press the torque plate down into the cell. Continue to hold the torque
plate all the way down against the screen until the pressure equalizes
sufficiently to allow the plate to stick. This usually takes about two min-
utes and will require 50 to 80 pounds (23 to 36 kg) of force on the end
of the lever.

25. Record the filtrate volume.
26. Allow the torque plate to stick in the down position for 10 minutes.
27. Remove the lever and attach the socket to the torque wrench. Place
the torque wrench and socket on the hex top of the torque plate stem.
Wedge the lever between the columns above the cell platform so it can
be used as a counter-torque lever.
If the filter paper tears when the torque plate is rotated, cell pressure
will be lost through the valve stem. A standard HTHP Filter Press back
pressure receiver may be substituted for the graduated cylinder while
the torque readings are being taken. A length of rubber or tygon tubing
can also be attached to the valve stem with the outlet end attached to a
closed container.
28. Measure the torque by rotating the torque plate in either direction with
the torque wrench. Observe the dial reading.
29. Repeat the torque measurements three to six times, allowing 30 sec-
onds between each check. Record each reading.
30. Calculate the average torque reading and record the plate sticking time.
OFITE, 11302 Steeplecrest Dr., Houston, TX 77065 USA / Tel: [phone] / Fax: [phone] / www.ofite.com 10

Important
!

To determine the time required to develop a fixed cake thickness, a modifi-
cation of the Timed Filtration test may be used. This test determines the
Bulk Sticking Coefficient (Ksc). Both torque plates can be used for this test.
If you use the spherical torque plate, you must allow enough time after the
plate sticks for the cake to build before the r = 1" condition exists. To run
this test, an accessory yoke mechanism must be used. This yoke attaches
onto the cell cap and is used to set the torque plate at a given distance
from the filter surface. This distance will be the desired cake thickness and
is usually 2/32" (1.6 mm).
1. Assemble the cell as described in the Timed Filtration test procedure on
page 6, steps 1 through 21.
2. Install the yoke assembly onto the cell cap by fitting the two setscrews
on the sides of the yoke into the holes in the side of the cell cap.
Tighten these screws by hand.
3. Fit the stem of the T-screw over the stem of the torque plate. Align the
hole in the T-screw stem with the hole in the torque plate stem. Insert
the retaining pin through the hole to secure the assembly in place.
4. Turn the T-screw down until the torque plate touches the filter paper (or
the locking mesh). Now turn the T-screw back until the torque plate
face is the desired distance from the filter paper. One turn of the T-
screw raises the torque plate 1/32" (.8 mm).
5. Open the top valve stem and record the time as the start of the test.
6. Allow the cell to filter until the plate becomes stuck. You will know the
plate is stuck when you hear an audible click. This indicates that the
locking pin is bound in place because the plates are sticking. The stick-
ing time will vary according to the cake-building properties of the sam-
ple.
7. If you are using the flat torque plate, take the torque readings as
described in steps 27 - 30 on page 9 immediately after the plate is
stuck.
8. If you are using the spherical torque plate, the time required for addi-
tional cake to build will have to be determined by trial and error. The fil-
ter cake must build up to, but not around, the edge of the plate. After
waiting, take the torque readings.
9. As an alternative method, you can set a finite time for the test. At the
end of the time period, measure the stuck cake area on the spherical
torque plate. If the radius is equal to 1", record the average edge
height for use in the calculations later.
OFITE, 11302 Steeplecrest Dr., Houston, TX 77065 USA / Tel: [phone] / Fax: [phone] / www.ofite.com 11
Test
Procedure
Fixed Cake Thickness


Important
!
Disassembly 1. Turn the regulator T-handle counter-clockwise until the pressure gauge
reads 0. Once the T-handle turns freely, open the bleeder valve.
2. Unscrew the barrel on the CO2assembly and remove the empty car-
tridge.
3. Remove the torque wrench and socket from the test cell.
4. Remove the CO2 pressure assembly from the top valve stem.
5. Slowly open the valve stem to relieve any remaining pressure inside the
test cell.
6. If you used the yoke, unscrew the locking pins and remove it from the
cell cap.
7. Remove the cell cap. If the torque plate remains in the cell cap, care-
fully push it through the lid by the stem.
8. Empty the test cell.
9. Gently wash the sample from the edge of the torque plate.
10. Note the diameter of the depression from the torque plate. If this diam-
eter is less than 2 inches or if any cake is adhering to the edge of the
torque plate, estimate the edge height of the cake from the filter paper.
If the cake is stuck to the torque plate rather than to the filter paper,
then the test is invalid. Repeat the test using the locking mesh.
11. Using the retainer wrench, unscrew the retaining ring. Remove the slip
ring and gasket. Remove the locking mesh, filter paper, and filter cake.
Examine the filter cake as desired and note any observations.
12. Remove the cell from the stage and thoroughly clean all parts. Polish
any surface where corrosion is noted.
13. Check all o-rings for damage or wear and replace as needed.
Lubricate all o-rings with grease.
OFITE, 11302 Steeplecrest Dr., Houston, TX 77065 USA / Tel: [phone] / Fax: [phone] / www.ofite.com 12

Theory Bulk Sticking Coefficient (Ksc) Derivation:
The Bulk Sticking Coefficient (Ksc) is the ratio of the force necessary to initi-
ate sliding of the plate (Fs) to the normal force on the plate (Fn).
Where:
Tu= Average of readings from Torque Wrench (inch-pounds)
r = Radius of Plate (inches)
h = Height above flat surface of cake around the edge of the plate
(inches)
P = Cell Pressure (PSI), differential (inlet to outlet)
Fs= Sliding force
Fn= Normal force on plate
Ksc = Bulk Sticking Coefficient
Kst = Stuck Tendency Coefficient
a. The Sliding Force (Fs):
The Sliding Force (Fs) is a function of the measured torque (Tu).
This equation should only be used when the radius is 1 and edge
effects are not being considered.
Fs= 1.5 × Tu
b. The normal force (Fn):
The Normal Force (Fn) is determined by multiplying the area by the
differential pressure. This assumes that a pressure of 477.5 PSI
was used during the test.
Fn= 1,500 × r2
If you are considering edge effects:
Fn= 1500 × (1 + 4/3h)
OFITE, 11302 Steeplecrest Dr., Houston, TX 77065 USA / Tel: [phone] / Fax: [phone] / www.ofite.com 13

c. The Bulk Sticking Coefficient (Ksc)
The Bulk Sticking Coefficient (Ksc) is calculated by dividing the
Sliding Force (Fs) by the Normal Force (Fn): Ksc = Fs/ Fn
Ignoring Edge Effects:
= 1.5 Tu/ πPr3
For a standard pressure of 477.5 PSI (3,292 kPa):
Ksc = 1.5 Tu/ 1,500 r3= .001 × Tu/ r3
And for r = 1":
Ksc = .001 × Tu
Taking into account Edge Effects:
Ksc = Fs/ Fn= (1.5 Tu/ r) / (πPr2+ 4/3πrhP)
= (1.5Tu) / [πPr2× (r + 4/3h)]
For a standard pressure of 477.5 PSI (3,292 kPa) and r = 1":
Ksc = (1.5 × Tu) / [1,500 × (1 + 4/3h)]
Ksc = (.001 × Tu) / (1 + 1.33h)
The Stuck Tendency Coefficient (Kst) is equal to the Bulk Sticking
Coefficient (Ksc) multiplied by the variable stuck area.
Kst = Ksc × (Variable Stuck Area) = Tu
Kst is not valid for the flat plate because the stuck area is
either 0 or 3.14 in2(r = 1) and not a variable.
OFITE, 11302 Steeplecrest Dr., Houston, TX 77065 USA / Tel: [phone] / Fax: [phone] / www.ofite.com 14

Note

Theory
Example
The drilling fluid sample is mixed and then loaded into the cell and pressur-
ized at 477.5 PSI (3292 kPa) for 10 minutes. The torque plate is seated
using the lever and held for two minutes. Eight additional minutes are then
allowed to pass. The breaking torque is then measured in four breaks at
30 seconds apart:
- 36 inch pounds (41.47 kg-cm)
- 39 inch pounds (44.93 kg-cm)
- 40 inch pounds (46.08 kg-cm)
- 41 inch pounds (47.23 kgt-cm)
The drilling fluid sample has an average 0.039 Stuck Tendency Coefficient.
The pressure is then removed and the cell is carefully opened, leaving the
torque plate set in the filter cake. The torque plate and cake are washed
and the torque plate is turned (not lifted) loose. The diameter of the imprint
of the torque plate impression (smoothed dome area) is measured at 1.57"
(3.95 cm) diameter, which gives a radius of 0.785" (1.98 cm).
Therefore, (using inch dimensions):
Ksc = (.001 x 39.3) / (.785)3= 0.081
OFITE, 11302 Steeplecrest Dr., Houston, TX 77065 USA / Tel: [phone] / Fax: [phone] / www.ofite.com 15

Theory
Worksheet
1. Using the spherical torque plate and inch dimensions:
Kst =
==
For a standard pressure of 477.5 PSI (3,292 kPa):
Kst = (Average Torque Wrench Reading) × .001
= ( ) × (.001) =
2. Using the spherical torque plate and 477.5 PSI (3,292 kPa) and inch
dimensions:
a. For cake with less than 1" stuck radius:
Ksc =
= =
b. Using either the spherical or flat torque plate and 477.5 PSI (3,292
kPa) and inch dimensions:
For cake with 1" radius, edge effects considered and a pressure
477.5 PSI (3,292 kPa):
Ksc =
= =
3. For tests using the yoke attachment, the cake thickness before sticking
should be recorded, and the data in 1, 2a and 2b above apply.
OFITE, 11302 Steeplecrest Dr., Houston, TX 77065 USA / Tel: [phone] / Fax: [phone] / www.ofite.com 16
(Average Torque Wrench Reading) × (.001)
1 + 1.33 (Cake Height on Edges)
( ) × (.001)
(1 + 1.33 ( )
(Average Torque Wrench Reading) × (.001)
(Measured Stuck Cake Radius)3
( ) × (.001)
( )3
(Average Torque Wrench Reading) × (Pressure) × (.001)
477.5
( ) × ( ) × (.001)
477.5

Maintenance 1. Disassemble the test cell after each test and thoroughly clean and dry
all surfaces.
2. Check all o-rings and o-ring grooves for signs of wear or damage.
Replace any damaged o-ring and lubricate all o-rings before they are
installed.
3. Wash and dry the support screen and the locking mesh disk (If used).
4. Wipe any spilled fluid or other debris from the stand. Some materials
may damage the finish of these parts if allowed to remain for a long
period of time.
5. Sample fluids can cause corrosion in the test cell and cap. The stan-
dard cell is made of 303 stainless steel, however other materials, which
are more corrosive resistant, are available. Periodically inspect the
inside of the cell for evidence of corrosion. Light corrosion may be
removed using 329 or finer wet or dry sand paper. Deeper corrosion
pitting may be removed by sand blasting the area of the corrosion. If
severe corrosion is evident, the cell should be replaced.
6. A metal-to-metal pressure tight seal is made between the valve stem
and its seat. Leaks can occur if either the valve stem or the seat is
damaged. The conical point of the valve stem should be inspected for
damage by removing the stem from the cap or cell body and replacing
the stem if the point is damaged. If the point is in good condition, the
seat in the cell or cap may be rough. A 5/16" drill bit can be used to re-
surface the seat, or a special resurfacing tool may be ordered from OFI
Testing Equipment. Valve stems should also be inspected for possible
plugging of the passages by dried fluid samples. A small drill or wire
may be used to insure that both the cross-bore and the main passage
openings are clear.
OFITE, 11302 Steeplecrest Dr., Houston, TX 77065 USA / Tel: [phone] / Fax: [phone] / www.ofite.com 17

Diagrams
Full Unit
OFITE, 11302 Steeplecrest Dr., Houston, TX 77065 USA / Tel: [phone] / Fax: [phone] / www.ofite.com 18
Valve Stem (#170-16)
Retainer Pin
(#171-22)
Valve Stem (#170-16)
Torque Wrench (#150-54)
Socket (#150-57)
Test Cell O-ring (#150-56)
Torque Plate
(#150-58 / #150-59)
Cell Assembly (See Page 19)
CO2Pressurization Unit
(#170-04)

Diagrams
Cell Assembly
OFITE, 11302 Steeplecrest Dr., Houston, TX 77065 USA / Tel: [phone] / Fax: [phone] / www.ofite.com 19
Retainer Wrench (#150-55)
Retaining Ring
Plastic Gasket (#150-53)
Neoprene Gasket (#150-52)
Locking Mesh Disk (#150-51)
Filter Paper (#170-19)
Inner Cap with Screen
(#150-50-5)