Innovative Monobore Solid Expandable Tubular System for Isolating Severe Losses

Abstract The monobore solid expandable tubular (MSET) system, which maintains the same drift as the previous casing and enables the operator to maintain an original drilling plan to total depth, is the next generation solid expandable tubular technology - the most advanced expandable liner system available typically to isolate severe losses or trouble zones while drilling. To address the major technical challenges of a large expansion ratio required to meet MSET requirement, and able to deliver potential longer MSET liner without a concern of premature expansion problem, this paper presents an innovative solution consisting of a safe release mechanism (SRM) for running MSET incorporating a dual-stage expansion mechanism. This paper presents an innovative approach to the reliability of this mechanism based on Finite Element Analysis (FEA) simulation and indoor tests, as well as a dual-stage expansion process. The dual-stage expansion offers the advantage of a relative ease on the expandable thread when undergoing a large physical expansion, and therefore leads to a less risk of thread failure during the expansion process. The new SRM transfers the weight of the MSET from the cone surface to a collet-finger type plug-in structure, which can be unlocked by hydraulic pressure when the MSET is run to the intended depth. Based on the result of simulation, an indoor test was conducted and the load capacity of SRM was up to 109 tons, which is safe for at least 1,000 ft MSET. The newly developed tubular with proprietary expandable thread was successfully deployed with a better than expected quality, enabling a successful run of quite long 2,250 feet expandable liner with a steady expansion pressure, and post expansion pressure test without any problem, and as expected, delivered a designed post expansion pipe ID. Most importantly the deployment of expandable liner resolved the severe loss drilling problem, enabled to raise mud weight from 1.05g/cm3 to 1.78g/ cm3,met the requirement of allowing drilling with 190.5mm (7-1/2″) bit and enabled drilling operation to resume and continue drilling a horizontal section without any major problem. This paper presents a combined (computer simulation and indoor tests for calibration) approach to conducting an advanced monobore solid expandable tubular technology development. The innovative safe release mechanism and dual-stage expansion process assures the application success of the MSET system in optimizing well casing designs for effectively addressing challenges in severe drilling losses.