Solving Swelling Clay Issues in Egypt's Western Desert: Combination of Fluid Engineering and Steel-Body PDC Bit Displaces Roller Cone in Large Hole Section

Abstract

Drilling the top hole section in Egypt's Western Desert has proven to be a challenge because finding the optimal balance of drilling speed, pulling out of hole without issue, and running the casing without clay swelling is critical. Historically, a standard milled-tooth (MT) bit, slick BHA, and top hole mud system were used for economic considerations. Recently, a problem arose when drilling a 17½-in surface hole in the Western Desert Moghra sand and Dabaa area, where the formation is composed of swelling clays that caused delays and cost increases.The solution to combat clay swelling would require an effective mud strategy; a PDC design that could increase ROP and resist balling while remaining economic; and a slick BHA that ensured hole verticality without the aid of directional tools and minimizes the affect of drillstring dynamics for prolonged PDC bit life. The intent of such optimization is providing enough buffer time for the casing to be run without problems, and the overall solution needs to be more economic than the previous drilling practice.An integrated BHA, bit design, and mud strategy were deployed in a field test with outstanding results. The results showed a step-change in ROP performance and allowed a trouble-free hole. The PDC bit and slick BHA successfully mitigated vibrations and maintained verticality. The application of customized drilling fluid formulation that contained high-performance shale stabilizers with the redesigned mudweight schedules and early fluid displacement resulted in significant enhancements in tripping while drilling as well as in running and cementing the 13 3 ⁄8-in casing.