make-and-break cycles with no loss of seal integrity
+260 °C
connection operating temperature
15,000 psi
maximum working pressure
The problem
The weak point of a tubing string is the thread connection
Industry studies (API, SPE, NACE, DNV GL) attribute 55 % of tubing failures and 86 % of casing failures to the threaded connection. It is here that the coating breaks off and bare steel becomes a hotspot of corrosion and failure. Conventional solutions address the problem only partially, leaving a number of weak points:
Uneven coating
Epoxy coating is thinner on thread crests and thicker in the roots. Make-up creates local overloads and chipping.
Micro-cracks during make-up
Stresses are distributed unevenly. Micro-cracks appear and let the corrosive fluid in.
Rapid coating failure
After 3–6 make-and-break cycles the coating breaks down. Bare steel becomes a site of intense corrosion.
Poor J-area protection
The most vulnerable spot is the pipe end. The coating chips and peels, leaving the metal exposed.
Inter-nipple seal (insert) extrusion
Under high loads and during make-up, elastomeric inserts extrude and shift, reducing the sealing efficiency of the connection.
No make-up torque control
There is no mechanism to control make-up depth and prevent over-torque.
The solution
M2® Modified Coupled Connection
The M2® modified coupled connection is a standard API / GOST coupled connection with an 8- or 10-turn thread, with a polymer ring of a special conical shape installed in the middle section of the coupling. The ring is made of wear-resistant materials (engineering plastics) and works as an elastic barrier.
During make-up the first thread turns of the pipe cut into the polymer ring, sealing the connection and fully covering the J-area.
Asymmetric polymer ring
The special ring geometry compensates for thread tolerances — deviations within GOST and API limits.
J-area protection
Physically covers the pipe end where mill coating typically breaks off. Creates a reliable barrier.
Controlled deformation
The ring deforms within 15–18 % — inside the polymer elasticity range. It fills every micro-gap in the thread.
Load damping
Smooths out the gaps that appear under string tension and cyclic loads.
Repeated make-and-break
8–10+ cycles guaranteed with no loss of seal integrity. Ideal for workover stock.
Make-up torque control
Once optimal deformation is reached, the ring builds up resistance — helping avoid over-torque.
How it works
How the M2® modified coupled connection works
Gap filling
During make-up the pipe thread cuts into the polymer ring. The ring deforms plastically, distributing the load evenly and filling every micro-gap between the threads.
Controlled deformation
Deformation (within 15–18 %) lets the ring act as an elastic damper rather than a rigid stop. This preserves the seal even under cyclic loads and vibration.
Tolerance compensation
The asymmetric ring shape and its plasticity level out thread deviations within GOST / API limits, creating a labyrinth seal along the whole connection.
J-area protection
The ring physically covers the pipe end, preventing contact between the corrosive fluid and the metal. This is where standard coatings break off, while M2® creates a reliable barrier.
Dynamic load damping
The polymer compensates micro-movements caused by string tension, sucker-rod impacts (in SRP wells) and vibration, preventing fatigue failures and preserving the seal.
Natural make-up torque control
As the ring deforms, make-up resistance builds up smoothly. This serves as a natural indicator of the correct torque, ruling out over- and under-torque.
Specifications
M2® connection data
Seal material
PTFE / PE-UHMW / PEEK (selected for the well fluid)
Make-and-break cycles
8–10+ with no loss of seal integrity
Operating temperature
−200 °C to +260 °C (short-term up to +300 °C)
Maximum pressure
up to 10,000–15,000 psi
Compatible tubing sizes
2⅜", 2⅞", 3½", 4½" (API 5CT)
Thread type
API 8rd EUE / BTC and analogues, 8–10-turn GOST threads
Controlled ring deformation
15–18 % (within polymer elasticity)
J-area protection
Full coverage of the pipe end
Applicability
External-upset tubing, including internally coated and lined pipe
Benefits
Key benefits of the M2® connection for oil and gas producers
Full J-area protection
The only solution that physically covers the pipe end, ruling out corrosion at the most vulnerable spot.
8–10+ make-and-break cycles
2–3 times more cycles than standard coated couplings. Ideal for workover stock and frequent tripping.
Tolerance compensation
The asymmetric ring shape and polymer plasticity level out API and GOST thread tolerances.
Load damping
Reduces the risk of fatigue failure under vibration and cyclic loads.
Make-up torque control
Natural make-up torque control helps avoid over- and under-torque.
Lower OPEX
Longer run life and fewer emergency workovers. Lower tubing replacement and downtime costs thanks to high chemical resistance to CO₂, H₂S and highly mineralised fluids.
Easy adoption
Installs like a regular API or GOST coupling, with no changes to technology or equipment.
Comparison
M2® vs standard solutions
Parameter
Standard coupling
M2® coupling
Repeated make-and-break
3–6 cycles
8–10+ cycles
J-area protection
Poor — coating chips and fails
Full — the ring covers the pipe end
Thread tolerance compensation
Low
High — asymmetric ring
Gap filling under load
None
Effective — damping action
Make-up torque control
None
Natural torque feedback
Corrosive environments
Limited
High resistance
Ring materials
Seal ring material selected for your well
The M2® seal ring material is selected individually for the temperature, pressure and chemical composition of the specific well. We offer three engineering plastics, each optimal for particular conditions.
PE-UHMW
up to +90 °C
Ultra-high-molecular-weight polyethylene
An engineering thermoplastic for extreme mechanical loads. Self-lubricating, with minimal moisture absorption.
high resistance to aggressive chemical environments
15× higher wear resistance than carbon steel
high impact toughness and strength
low friction coefficient
Recommended:for wells with abrasive fluids and frequent make-and-break cycles
PTFE
up to +260 °C
Polytetrafluoroethylene
A fluoropolymer with exceptional chemical resistance, including oxidizing acids. The base material of the M2® connection.
outstanding chemical resistance to most aggressive fluids
high thermal stability
flame-resistant, self-extinguishing
resistant to stress cracking
Recommended:for most wells with high temperatures and aggressive fluids (CO₂, H₂S, high salinity)
PEEK
up to +260 °C
Polyetheretherketone
An engineering thermoplastic for especially severe service — gas wells with large pressure and temperature swings.
operates at elevated bottomhole pressures (up to 15,000 psi)
retains elasticity at high temperatures
eliminates the need for drift runs
compatible with internally coated pipe
Recommended:for gas wells with rapid gas bleed-off, and for wells with aggressive fluids at high temperatures
Important.The exact material is selected from well data — temperature, pressure, CO₂ and H₂S content, presence of abrasive particles. Contact our specialists to calculate the optimal option.
Gas wells
Dedicated M2® version for gas wells
For gas wells with high temperatures and frequent, rapid gas bleed-off, the M2® connection is supplied with an additional metal ring in the seal assembly.
Why it is needed:
Anti-extrusion protection
The metal ring acts as a heat-resistant stop, preventing the polymer seal from extruding under sharp pressure swings (gas-dynamic loads).
Seal integrity
The ring compensates the cyclic loads typical of gas wells and keeps the seal intact even after repeated bleed-offs.
Dual barrier
The metal ring works together with the main polymer seal, creating a reliable two-stage protection of the connection.
Applications
Applications of the M2® modified coupled connection
Workover stock and well intervention
Up to 8–10+ make-and-break cycles with no loss of seal integrity — 2–3 times more than standard couplings. Allows more interventions without replacing the tubing string, saving on new pipe.
Challenging well stock
High water cut, CO₂ and H₂S presence. The M2® polymer ring resists aggressive fluids and fully covers the J-area, preventing corrosion at the most vulnerable spot of the connection.
Mature fields with frequent workovers
Intensive operation requires frequent tripping. M2® withstands 2–3 times more make-and-break cycles than standard couplings, cutting pipe replacement costs and downtime.
Injection wells
Corrosion protection when injecting produced water, CO₂ and other aggressive agents. M2® keeps the seal intact even at high injection pressures, preventing leaks and thread damage.
Wells with high downtime cost
Unplanned workovers on such assets are especially expensive. M2® minimises the risk of connection failures, extending run life and reducing emergency tripping.
Assets where price and performance must balance
Where premium connections are economically unjustified and standard coated API couplings are not reliable enough, M2® offers the optimum: below premium prices, with 2–3 times the service life of standard couplings.
Track record
M2® track record in the field
M2® performance is proven by operation on real assets in corrosive environments.
Karasu Operating Company
Mishovdag field, Azerbaijan
delivery — October 2019
Seal ring material: ultra-high-molecular-weight polyethylene (PE-UHMW)
Confirmed effect: more than 35× longer service life of the coupled connections compared with standard API couplings in wells operated with sucker-rod and electric submersible pumps. Sustained seal integrity and effective J-area protection under exposure to aggressive environments.
Azneft / SOCAR
Bibi-Heybat field, Azerbaijan
delivery — February 2017
Seal ring material: polytetrafluoroethylene (PTFE)
Confirmed effect: more than 20× longer service life of the coupled connections compared with standard API couplings in wells operated with sucker-rod and electric submersible pumps. The M2® connection has proven its performance under extreme chemical exposure, including high CO₂ and H₂S content and highly mineralised formation water. Not a single corrosion failure in the J-area was recorded over the whole service period.
RN-Vankor (Rosneft)
Vankor field, Russia
pilot field trials
Seal ring material: polytetrafluoroethylene (PTFE)
M2® connections have been run in hole. Results will be summarised once the tubing string is pulled. Preliminary interim data confirm the efficiency of the solution.
Over more than ten years of operation on producing assets in Azerbaijan, M2® connections have confirmed their performance in aggressive environments, delivering 20× and greater service life of coupled connections compared with standard API couplings.
Next generation
M2® Smart Connect
In development
We are completing the development of the next-generation M2® Smart Connect modified coupled connection — a further evolution of the M2® technology combining reinforced sealing with digital identification.
Today most operators manage their tubing stock without an individual history for each pipe and threaded connection. Coatings, inter-nipple inserts and standalone RFID tags solve the problem only partially: tags fall off, coatings break down, and there is no digital lifecycle passport for the connection at all.
M2® Smart Connect is a combined solution built on four key elements:
Reinforced mechanical and corrosion protection
The combined CRA + PTFE ring fully covers the J-area and protects the thread in aggressive environments.
Integrated RFID tag
Embedded inside the coupling with no drilling of the pipe body, keeping the tubing intact.
Digital passport
Every coupling receives a unique ID with a full history: manufacture date, material, number of make-ups, operating environment, repairs.
Automatic data capture
At every stage: mill → warehouse → run in → pull out → repair → re-use.
What M2® Smart Connect gives your company:
Individual tracking and traceability
A history of the specific “coupling + pipe” connection, not of the batch as a whole.
Data for AI and predictive analytics
Clean structured data for failure prediction and for building digital twins.
Lower failure rates and OPEX
Connections can be withdrawn from service before a failure, not after it.
A digital passport for the connection
Readiness for the expected 2027–28 industry requirements.
Optimised procurement and tubing fleet management
Decisions based on real accumulated run time, not on averaged figures.
Send us your well operating parameters — temperature, pressure, fluid composition and string operating features. We will select the optimal seal ring material and prepare technical recommendations and an individual commercial proposal.
