Mechanical screen strength testing
The laboratory conducts complex strength downhole screen testing. The testing is carried out in the set of benches used for various mechanical stress testing arising during equipment usage.
The main mechanical testing bench is a MPF-100 (Mechanical Power Frame) bench for axial loads used for screen construction tensile/compression (force up to 100 tons) testing.
The bench of HPF-100 screen mechanical testing. 1–load frame, 2 – cylinder, 3 – adapter ring, 4 –sample, 5 – hydroelectric station.
The mechanical bench is used for downhole sand screens testing based on API 19SS (2016), ISO 17824:2009, GOST 32504–2013– “Petroleum and natural gas industries-Downhole equipment-Sand screens”, except pre-pack screens. To test the working capacities with applied loads, the testing simulates sand screen components with operational loads.
MPF-100 bench specification:
- Bench outline dimensions (L x W x H) – 4850х680х1060 mm
- Bench weight – 2150 kg
- Piston stroke – 200 mm
- Screen sample length from 1000 to 10000 mm
- Size of testing screen sample from 4 to 7 "
- Highest cylinder rod load (extension and retraction) – 100 tons
MBM-1 wire separation bench
The MBM-1 (Mechanical Breaking Machine) with a force capability up to 1 ton is used for the wire separation testing. Special equipment is used for the testing. The speed of punch movement from 0.01 mm/min to 500 mm/min and the wire separation moment are set with the mechanical press.
MTM-80 hydraulic wrench
MTM-80 (Mechanical Torque Machine) hydraulic wrench with a torque capability of 80 kN m is used for torsion testing. The bench allows screen testing basic sizes up to 250 mm in diameter.
Description of the main types of mechanical testing are below:
1. Pull Test, Push off Test, End Ring Push off Test, Supporting screen elements push
Testing performed at MPF-100 multifunctional testing bench The main task is to determine the downhole screen’s mechanical strength to axial loads according to the declared specifications. The bench consists of a support frame, a hydraulic cylinder of two-way axial loads, adapters for mechanical fasteners of the screen, and the bench control system. Screen testing sample fixed on the load frame is used for testing.
The scheme of fixing screen sample testing using the special fastening equipment on load frame MPF-100 bench.
The testing involves the applied axial loads to the testing screen sample. This requires the sample to be fixed reliably to the load frame and the fixation between the sample and the hydraulic cylinder rod. Testing is performed by following programs:
- Push off testing (wrap-on-pipe screen)
- Retaining ring push off testing
- Shrouded screen or cemented winding push off.
- Perforated basepipe pull push
Testing work scheme:
- Testing plan, which includes:
- Type of performed testing
- Maximum axial force applied on the sample
- Allowable construction elements push values and slot clearances changes
- Quantity of the testing repetitions of the sample
- The sample is cemented at the screen element field up to 1500 mm in length, screen sample surface must be fastened and not make the contact with screen basepipe.
- The shear of the wire wrap section of 304.4 mm length and the length of the basepipe screen sample of 1000 mm are studied during the shear testing support screen elements of the screen wire wrap.
- The mechanical adapters for fixation on the load frame of the stand are selected for the sample. The slot clearances of the testing screen element are preliminarily measured.
- An axial load is applied to the sample and the load is increased according to the specified speed. The testing process ends when reaching the target force and holding the load for one minute. The testing procedure is repeated, if necessary.
- At the end of the test procedure, the load is shed, the screen sample is released from the fasteners, and the visual inspection of the sample and re-measurement of the slot clearances in the marked areas is performed.
- The force and rod position of the hydraulic cylinder as a function of time is recorded in the electronic journal. At the end of the test, the results are analyzed and the report is generated.
The MPF-100 mechanical testing bench is certified and calibrated by independent certification authorities.
Mechanical wire wrap separation testing (Weld Separation Test)
Coupon testing process on the MBM-1 bench
Wire wrap separation testing is performed on the MBM-1 bench. The task of the testing is to determine the mechanical strength of the wire wrap screen weld. The testing is performed with the rectangular wire wrap coupons cut from the screen. MBM-1 mechanical press punch movement produces the separation force to the wire wrap from the guide rods. The value of this force is the strength of the wire screen weld.
The wire separation testing bench is designed to test loads up to 10 kN. For manufacturers, the validity criterion of the direct screen wrap is that at a tensile load of at least 1.23 kN (125 kgf) no splitting occurs of the welded wire connection and stiffeners.
Work scheme:
- Rectangular-shaped wire wrap coupons are cut from the wire wrap screen, at least 50 mm x 150 mm in size. Two coupons minimum, taken from different areas of the screen element, are for testing.
- The testing is performed when the coupon sample is placed on the bench and the press punch produces the force on the wire separation from the guides.
- The testing is performed for the individual coils of the wrap until it separates from the guides. At this point, the separation moment is recorded. Each coupon is tested at least 3 times. The series of testing determine the average force values.
- The test is completed if the average force values are higher than 1.23 kN.
- Based on the testing, the report is drawn up.
The wire wrap separation test bench is regularly checked for accuracy and calibration of the generated forces. Wire wrap separation testing is a part of comprehensive mechanical strength screen testing.
Mechanical screen torsion testing (Torsion Test)
Slot clearance measurement after torsion testing at the MTM-80
It tests the mechanical strength of the screen for torsional loads. The liner rotates with the screen, and the screen shall withstand specific torsional loads. Testing performed at MTM-80 bench.
The testing is performed at the hydraulic wrench bench, the main purpose of which is to install couplings on the nipple part of the base pipe. The hydraulic wrench bench is used to control the applied force torque to the support foot of the screen basepipe end holder, rotating around the sample axis. The screen in the second wheelbarrow is fixed to the cemented part of the screen element. The practical validity criterion in practice is to withstand a nominal torsional torque of 25 kN m by the screen.
Work scheme:
- Prepare the screen sample for the torsion testing. Cement the screen part according to the pull/push test procedure.
- After that, the screen sample is placed on the stand of the hydraulic wrench to fix the cemented part of the screen and the end of the base pipe. Conduct a test measurement of the slot clearance of the testing part of the screen by three selected areas arranged with a rotation of 120 degrees with respect to each other around the screen axis.
- Torque force is applied to the mechanical foot in the testing mode. Increase the load gradually up to the limit value for this test. Repeat the testing process after the load is released, if a series of tests is provided.
- A visual inspection of the screen sample is performed during the tests. The operator is in the remote control area of the test bench. The load is shed on the sample when the force moment limit is reached. The stand is switched to idle mode. The screen slot clearances in the designated areas are re-checked.
- Based on the results of the tests, the validity report of the screen torsional loads is drawn up.
Mechanical screen bending tests (Bending Test)
Screen bend testing
The testing verifies the screen’s mechanical strength against bending load. A downhole liner consists of a connection of different equipment and must be flexible. It stems from the fact that the drilled trajectory of the well has a spatial curvature, and the running liner must include screen bending. To assess the effect of bending loads on the screen, special tests are performed.
The screen supports, weighting agent, laser level, and leveling rod are used for the bend testing. The screen sample bending shape in a circle is taken into account. The minimum requirement of the screen bend sustain is 45ª by 30.3 m (100 ft) in length.
The bend testing should be repeated at least 10 times. The screen must retain its characteristics after testing. The change in the slot clearances must be less than 5%, and the quality of the welds must be retained.
Work scheme:
- The screen sample should be placed on supports of equal height to give space for the screen and the supports for the bend testing. Two areas of the sample are examined:
- The middle part of the screen
- Part of the screen with an ending ring in the center
- Conduct a test measurement of the slot clearance of the testing part of the screen by three selected areas arranged with a rotation of 120 degrees with respect to each other around the screen axis.
- The screen supports must be in the same horizontal plane. The central part of the screen sample between the supports is held by a crane beam with slings. A weighting agent is attached to the sample at the center of the testing area. The level of deflection of the screen area under test is measured with a leveling rod and laser level.
- The center of the screen testing area is slowly lowered by the crane beam with the weighting agent. The screen sample deflects. The metric tools are used to record the amount of deflection. The calculated value of the minimum deflection must be reproduced in the test. The process is stopped when the required deflection value is reached, then the sample shape is gradually restored by lifting the crane beam. The testing is repeated at least 10 times for each testing area.
- After the end of the testing series, a control measurement of the slot clearance is made at the marked areas of the sample. The test is considered successful when the deflections caused by the applied load are within the allowable limits.
