lubricant selection using circumferential displacement of ... · sept. 11 - 14, 2007 2007 sucker...

Sucker Rod Pumping WorkshopWyndham Hotel, Houston, Texas

September 11 – 14, 2007

Lubricant Selection Using Circumferential Displacement of Sucker RodsErik Tietz, P.E.Arun SriramanUPCO, Inc.

Sept. 11 - 14, 2007 2007 Sucker Rod Pumping Workshop 2

Goals of this project

• Phase 1 - Testing of lubricants.

• Phase 2 - Verifying and reestablishing the API displacement values for D & HS grade sucker rods.

• Phase 3 – Analyzing the effect of applying lubricant on the face of coupling and sucker rod.

• Phase 4 – Studying the decay that might happen after the rod has been used on multiple occasions.


Synopsis of the paper

1) Why did UPCO decide to take on the testing of displacement? What are our goals?

2) Core Engineering concepts involved in this project.

3) The displacement testing.

4) What was measured during the test?

5) The eight critical parameters

6) The results of UPCO displacement testing.

Summary


1. Why did UPCO perform this project?

• Customer feedback indicated failures due to lack of, loss of and over displacement.

• As a result of this, there were numerous questions which we at UPCO could not answer with adequate proof.

• Some of the questions which were raised and led us into this project are as follows:

– Were displacement values correct?

– What affected these values?

– What type of lubricant is the correct choice for sucker rod – coupling make up?


2. Core Engineering concepts involved in this project

The core engineering concepts used in this project are as follows:

A. Forces acting on a sucker rod coupling make up

B. Circumferential displacement

C. Stress

D. Strain (Shear & Normal Strain)

E. Modulus of Elasticity


Forces acting in a sucker rod coupling make up

A

A

A

Normal Forces acting in a direction parallel to the axis of the rod body. Normal forces are a very desirable attribute in a sucker rod coupling make up process

B

Shear forces acting on the pin which is a detrimental attribute in a sucker rod coupling make up process.

B


Circumferential Displacement

UPCO Minimum Displacement value

UPCO Maximum Displacement value

Circumferential displacement:API states that circumferential displacement is the distance measured after makeup, between the displaced parts of a vertical line scribed across the external surfaces of the box and pin when they are in a shouldered hand tight relationship prior to makeup.

Hand tight level (No displacement)


Stress

• What is Stress?

Stress is the load applied per unit area of cross section. There are 2 types of stress, namely normal and shear stress.

• Stress = Load / Area of cross section

• Example: The area of cross section for a ¾” sucker rod is 0.44 Sq.In

• Units: PSI (Pounds per square inch)


Strain

• Strain is the elongation of the specimen when it is subjected to a load.

• In our case, it will be the stretch of the sucker rod pin during the process of make up.

• Two types strain – Normal and Shear

• Shear & Normal Strain can be measured by strain gauges.

Strain


Strain Gauge

• The pictures depicted below show examples of shear and normal strain gauges (both positive and negative).

Shear Normal


Modulus of Elasticity (MOE)

• MOE = Stress / Strain (Elastic region of the curve)

• Units = PSI

Plastic Region

Elastic Region


3. Displacement testing

The test• The overall test can be broken down to four sub tests

a) Subtest 1: Testing of new rod and new coupling with new rod displacement values (maximum and minimum).

b) Subtest 2: Testing of old rod and new coupling with re-run displacement values (maximum and minimum).

c) Subtest 3: Testing of old rod and old coupling with re-run displacement values (maximum and minimum).

d) Subtest 4: Testing of old rod and old coupling with re-run displacement values (maximum and minimum).

Note: In subtest 4, after hitting the maximum mark and then relieved, the rod is made up until failure.


Displacement Testing Machine (DTM)

Displacement testing machine – A brief overview

• The machine can produce sufficient amount of torque to shear a 1 1/8 ” sucker rod pin.

• The gear ratio is slow enough to perform a test in 30 seconds.

• It has a 1 HP DC drive with variable drive capability.

• The machine is coupled with a data acquisition system which has the capability to sample 10000 data points per second.


A pictorial explanation of the DTM

Displacement Testing Machine (DTM)


Samples for testing

Samples for testing

• A total of 13 test were conducted. 12 lubricant tests and one no lube test.

• The lubricant was applied only on the threads of the sucker rod. No lube on the faces.

• All sucker rod samples were ¾” CD with the same heat number.

• All couplings were ¾” full size with same heat number.


4. What was measured directly from the test?

• The three main measurements needed for this project were

– Torque applied

– Shear Strain

– Normal Strain

• The torque applied (positive & negative) during the displacement process was measured using a load cell with a 12” moment arm.

Load cell set up with a 12”moment arm for measuring

the torque


5. The eight critical parameters

1. Average Maximum Torque

2. Total Energy Absorbed

3. Overall minimum % of design yield

4. Overall maximum % of design yield

5. Overall maximum % of actual shear

6. Overall difference index with torque

7. Overall difference index without torque

8. Overall relief index


Sample graph with data

Normal force curve

Shear force curve

Torque curve


Average Maximum Torque

• This is the average maximum torque of all four tests on one sample.

• The final result is the average for all samples of one type of lubricant.

• The average maximum torque was rated as the smallest value being the best and the largest value being the worst.

• Units: ft-lb


Average Maximum Torque – Results Table


Total amount of energy absorbed

• This is the total amount of energy absorbed for all four tests on one sample.

• This value includes the energy required for maximum displacement and it also includes the energy to break the joint for all four tests.

• The total amount of energy absorbed was rated as the smallest value being the best and the largest value being the worst.

• Units: ft-lb


Total amount of energy absorbed

Total amount of energy absorbed = Difference in the numerical values between the two discrete points


Total amount of energy absorbed – Results Table


Overall Minimum % of Design Yield

• This is the average normal stress in the stress relief at the minimum displacement divided by API design stress (85000 PSI).

• The overall minimum % of design yield was rated as the smallest value being the worst and the largest value being the best.

Note: Values above 100 % are unacceptable.

• Units: %



Maximum value indicated in the region of the curve / 85000 PSI


Overall Maximum % of Design Yield

• This is the average normal stress in the stress relief at the maximum displacement divided by API design stress (85000 PSI).

• The overall maximum % of design yield was rated as the smallest value being the worst and the largest value being the best.

Note: Values above 100 % are unacceptable.

• Units: %



Maximum value indicated in the region of the curve / 85000 PSI


Overall Maximum % of Actual Shear

• This is the average shear stress in the stress relief at the maximum displacement with torque applied divided by the actual measured shear force.

• The overall maximum % of actual shear was rated as the smallest value being the best and the largest value being the worst.

• Units: %


Overall maximum % of Actual Shear

Maximum value indicated in the shear force curve / Shear Stress calculated by tensile test

Maximum Value indicated in the shear force curve / shear stress calculated by tensile test


Overall maximum % of Actual Shear


Overall Difference Index with Torque

• This is the average difference between the normal and shear stress in the stress relief at the maximum and minimum displacement positions with the torque applied.

• The overall difference index with torque was rated as the smallest value being the worst and the largest value being the best.




A

B

C

DAverage of (A-B) & (C-D)

A

BD

C

Average of (A-B) & (C-D)


Overall Difference Index without Torque

• This is the average difference between the normal and shear stress in the stress relief at maximum and minimum displacement positions with the torque backed off to zero.

• The overall difference index without torque was rated as the smallest value being the worst and the largest value being the best.

• Units: PSI



A

B

C

D


A

B D

C



Overall Relief Index

• Overall relief index is the relative amount of relaxation the system undergoes when the torque is released.

• From our tests, it has been proven that this value represents a conversion of shear stress to normal stress .

• The overall relief index was rated as the smallest value being the worst and the largest value being the best.




A

B D

COverall relief index is the average of (A-B) & (C-D)

A

B D

CAverage of

(A-B) & (C-D)


6. Results of UPCO Displacement Testing

• The following graph shows the test data for ALB 2983


Lube 12 – Medium performance lubricant

• The following graph shows the test data for Lube 12 (medium performance lubricant)


Results of no lube test

• The following graph shows the test data from dry face testing (no lube)


Ranking & Final Results of lubricants


The actual test results

• Considering all the data and other critical factors, ALB 2983 showed the best performance among all lubricants for Sucker rod – Coupling make up.

• Any conclusions should be verified by field application or trials.

• All test related data is available for further scrutiny.


Disclaimer

The following disclaimer may be included as the last page of a Technical Presentation or Continuing Education Course. A similar disclaimer is included on the front page of the Sucker Rod Pumping Workshop Web Site.

The Sucker Rod Pumping Workshop Steering Committee Members, the Supporting Organizations and their companies, the author(s) of this Technical Presentation or Continuing Education Course, and their company(ies), provide this presentation and/or training at the Sucker Rod Pumping Workshop "as is" without any warranty of any kind, express or implied, as to the accuracy of the information or the products or services referred to by any presenter (in so far as such warranties may be excluded under any relevant law) and these members and their companies will not be liable for unlawful actions and any losses or damage that may result from use of any presentation as a consequence of any inaccuracies in, or any omission from, the information which therein may be contained.

lubricant selection using circumferential displacement of ... · sept. 11 - 14, 2007 2007 sucker...

Documents