Torque-turns Measurement during Makeup is Insufficient to Indicate Seal Integrity

Operators require gas tight connections for a variety of applications including thermal, HPHT and tight oil wells. Premium connections that incorporate a metal-to-metal seal near the nose of the casing pin end can provide this level of seal performance.

Premium connections do not follow a specific design code. Their performance can vary considerably among manufacturers and even among different casing sizes.

Conventional torque-turns measurements during connection assembly are not adequate to confirm proper metal-to-metal seal engagement.

Ultrasonic Inspection of Seal Surface Indicates Seal Quality

C-FER has developed a specialized tool called Ultrasonic Reflection Amplitude Pressure (URAP). This tool ultrasonically examines the contact stress at the radial metal-to-metal seal of premium connections after they are made up.

The URAP scans describe the uniformity of the contact stress profile on the seal surface. It indicates irregularities that represent potential leak paths across the seal. URAP is used to:

  • Pre-qualify connections used in full-scale qualification programs to ensure that the connections being tested are representative of the design intent;
  • Assess the effects of loading or thermal cycling on the seal contact stress during premium connection test programs;
  • Confirm mill-end make ups, as part of the manufacturer’s quality assurance program; and
  • Evaluate prototype connection designs to help optimize new designs.
Stress Maps of Connection Seals

URAP Service Package

URAP has been used extensively as an integral component of connection qualification test programs at C-FER.

The URAP service can become an integral component of a manufacturer’s standard QA/QC process. It is also a valuable research tool for developing new connections.

C-FER’s URAP specialists can perform scans of production run or specialty connections in the manufacturing facility. Operators may wish to include URAP as part of specialized product or vendor qualification programs.

URAP Capabilities

Specific features that URAP can identify include:

Geometrical and Manufacturing variations:

  • Offset between pin and box seal axes;
  • Mismatch between torque shoulder and pin face angles;
  • Out–of–round seal surfaces; and
  • Radial waviness on seal surfaces (multi–lobe bending).

Make–up variations:

  • Overdoping;
  • Galling;
  • Pock marks;
  • Axial and circumferential scratches; and
  • Pin-top loading.

URAP scans performed during connection load tests have shown changes to the contact stress profile on the seal surface. This could affect connection sealability under various service conditions.


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