First Successful 16 X 13.375-in. Casing-While-Drilling Operation in Kuwait Saves 27 Rig Days and Reduces Well Delivery Time

Drilling the 16-in. section in Minagish field wells in western Kuwait is among the most challenging well sections. 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 first successful 16 × 13.375-in. casing-while-drilling job in Minagish field reduced well delivery time for the operator and saved 27 rig days with substantial savings in the total well cost. The section was drilled successfully while encountering total mud losses through fractured dolomitic limestone and sandstone formations. Continued drilling managed to reduce losses with 30 to 50% returns and reached the target depth. 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, and drillout of the drillable casing-while-drilling bit using a rerun fixed cutter bit were performed successfully. On an average, eight wells are drilled per year in this field. With the successful implementation and the savings obtained by using this casing-while-drilling technology in the first test well, there is the potential for substantial annual cost savings, help the operator deliver wells in less time, and eventually increase production by increasing the number of wells drilled per year.