Drilling with liners has long been recognized as a potential solution to problems in oil and gas wells that are associated with drilling conventionally and running a liner to cover the interval in two separate steps. The most prevalent problems are covering time-sensitive formations with pipe prior to the hole sloughing in, and the detrimental effects of swab and surge when running tools into and out of open hole, leading to potential well control and casing/liner installation problems.
Basic drilling with liners incorporating a bit made up to the end of the liner and then drilled to total depth helps solve these issues, however, sacrifices the ability to run more sophisticated tools in the bottom hole assembly (BHA). Also, traditional liner top equipment was neither designed to endure the rigors of drilling dynamics, nor the balance of minimizing the equivalent circulating density (ECD) in the drilling mode while maximizing the performance characteristics related to the mechanical properties of the liner top equipment.
The ability to reliably overcome the above problems has been accomplished through the careful design and construction of a purpose-built liner drilling system. Specific consideration has been taken to balance the high bypass necessary for ECD reduction during both drilling and tripping operations, yet provide high burst, collapse, and tensile capacities of the liner top equipment while maintaining full drift through the tools. The system also allows for multiple BHA change-outs while leaving the liner parked in tension anywhere in the parent casing.
This paper covers the drilling tests that have been performed with a liner system purpose-built for drilling applications with sophisticated BHAs that require the ability to be returned to surface for change out due to worn or malfunctioning equipment or once total depth is achieved.