The Industry Challenge:
Premium connections are considered proprietary designs for casing and tubing connections offered by a variety of Vendors that use various connection design approaches to achieve high levels of seal integrity and structural strength.
The operating conditions in thermal and HPHT operations can vary significantly due to well depth, well geometry and operating temperature which makes it difficult for operators to determine which premium connection type is best suited to an application.
While standards exist for testing premium connections at temperatures up to 180°C (356°F), some thermal applications reach temperatures of up to 350°C (662°F).
Under these conditions, stresses in the casing and connections exceed the yield stress of the material, resulting in permanent plastic deformations that can severely impact the sealability and structural integrity of the connection.
How We Help:
C-FER has developed unique analysis and testing procedures to evaluate the performance of a premium connection while simulating the conditions that occur in thermal wells. These include:
- Material testing at high temperature, and in some cases, in sour environments which is required to select a material that can withstand the severe loading environments.
- Robust material performance models are developed to characterize the material response to complex loading conditions including environmental effects and time dependent behaviours; such as, strain aging, stress relaxation and creep.
- Finite element modeling used to evaluate the design basis for the connection by considering the sealability and structural integrity of the connection under the following conditions: installation loads including bending as the casing is run into deviated wells, temperature changes that can cause strains in excess of the yield strength of the casing material and thermal cycles that can cause low cycle fatigue.
- Multiple make-up and break-out cycles to evaluate the galling resistance.
- Large-scale load frames with capacities exceeding 15 MN (3 million pounds) have been developed to subject as many as eight connections simultaneously to simulated pressure, temperature and load cycles representative of thermal operations.
- Precise leak collection and measurement systems have been developed to provide continuous, reliable measurements of gas leakage from connections during all phases of the testing program.
- The connection qualification procedures for SAGD wells were formalized by an industry committee into the Thermal Well Casing Connection Evaluation Procedure (TWCCEP) which was recently re-written as an ISO standard which is currently under review.