INTEGRATED ENGINEERING ANALYSIS TO SUPPORT SUCCESSFUL UTILIZATION OF CASING DRILLING IN GEOTHERMAL WELLS

Abstract

Casing drilling has become a common operation for drilling a well nowadays. Instead of using a drill pipe to transfer the energy from the surface to the drill bit, this operation uses casing, so when the bit reaches the end of the section, the casing is already there to protect the well.
One of the problems in drilling a geothermal well in Indonesia is the difficulty of running in-hole the 13 3/8-in casing after drilling a 17 1/2-in section. The openhole exposure may trigger the wellbore to collapse, creating an obstruction to conveying the casing to the final depth. To solve this problem, a nondirectional casing drilling technology was proposed as the solution. The main component of this technology is the drillable alloy PDC casing bit, which is attached to a standard casing that is rotated at the surface. The casing can be fully rotated while applying weight to cut through the obstruction. A comprehensive engineering analysis was performed prior to the job to support the operation.
The casing drilling system successfully set the 13 3/8-in casing 314 m deeper than the initial point of the casing running obstruction. The drilling and reaming capability of the casing bit helped in cutting through all the formation filling the predrilled hole. The cementing process was executed well, with good integrity to the surface. Since then, this operation has become an effective standard practice for our team and has been performed in more than eight wells.
As a way forward, this paper also provides a feasibility study of a fully directional casing drilling technology to be applied in geothermal wells to improve the drilling efficiency. This study includes the readiness of the tools and main engineering aspects: hydraulics and mechanical (torque and drag, casing wear, fatigue, pipe stress, and vibration).