Successful Casing-While-Drilling Operation in West Kuwait Saves 17 Rig Days and Reduces Well Delivery Time and Well Cost

Abstract

Drilling the 16-in. section in Umm Gudair field in western Kuwait faces a lot of challenges while drilling. Challenges include drilling through severe loss conditions, destabilized shale, and deteriorating hole conditions. These conditions can result in hole collapse or lost in hole of the drill string that requires sidetracking. The objective of project presented in this paper was to develop an engineered solution to drill through the difficult zones, lessen nonproductive time, and reduce the total well cost. The solution proposed was to use casing-while-drilling technology with a drillable bit and drill through the fractured dolomitic limestone and sandstone formation while simultaneously setting casing. The drillable casing-while-drilling bit was specifically designed and engineered to conform to the formations in the field. The drillable casing-while-drilling bit is manufactured with a material that can be drilled out with either conventional roller cone or fixed cutter bits. A plastering process was used, which smears the cuttings generated by drilling against the borehole wall, seals the pores or fractures in the formation, and helps reduce fluid losses while maintaining well integrity. The successful implementation of 16 × 13.375-in. casing-while-drilling job in Umm Gudair field reduced well delivery time for the operator and saved 17 rig days with cost savings of 450,000 US Dollars considering rig rate only. The section was drilled successfully while encountering total mud losses through fractured dolomitic limestone and sandstone formations. Preventing the risk of losing the bottomhole assembly in the hole and alleviating the use of multiple cement plugs saved additional cost for loss-cure plugs to heal the loss-prone formations. After reaching the target depth, cementing, pressure testing of the casing were carried out successfully. Lesson learnt from the first job were applied in the subsequent job completing the section with faster ROP with substantial savings to operator. For both the jobs, drillout of the drillable casing-while-drilling bit using a fixed cutter bit and Rotary Steerable bottom-hole assembly were performed successfully, the drillout bit continued drilling to section TD in one run. With the successful implementation and the savings obtained by using this casing-while-drilling technology in the West Kuwait field, there is the potential for substantial annual cost savings, aiding the operator deliver wells in less time, and eventually increase production by increasing the number of wells drilled per year.