The application of the first open-hole expandable liner in Tarim Basin has demonstrated the value of the numerical models developed to assess the effects of the required large expansion ratio, particularly on connection sealability. This paper discussed the modeling, the assessment of the highly expanded thread form, lab testing to confirm its performance, and the field application.
The expandable casing was required to span 127 m of open-four hole to prevent the closure of a section of mobile mudstone. The 10 ¾ in. in originally planned across the interval could not be run due to the tight hole, and the expandable was successful in allowing the well to continue below the mudstone in an 8 ½ in. hole. The concern was the effect of the large expansion ratio on the sealability of the connector. ABAQUS was utilized to build a model which was then calibrated with ten groups of expansion tests with a variable diameter cone. Tests included both internal and external pressure loads.
Expansion ratios of 20.2% were achieved in the lab without tube failure or thread leakage at the loads expected in the Tarim Basin application. The casing was successfully installed and expanded in June 2016, and drilling continued to the planned total depth. The success of the modeling in lab and field applications creates confidence that the model itself can be used to develop designs for other loading conditions in other applications with minimal full-scale lab testing. While there is an additional opportunity in the Tarim Oilfield, confidence in a generalized model will encourage engineers to assess other opportunities.
The ability to predict expansion stresses and sealability are also seen as the first step for the operator in the development of a monobore system that provides full pass-through and a casing-to-casing seal that can be deployed economically in the low-cost Tarim Basin operations.