Breakthrough in 22-in.-Hole Drilling in Kuwait Deep Wells

Abstract

High-pressure/high-temperature exploration activities in Kuwait include the drilling of deep wells (approximately 16,500 ft) to search for high-quality oil from the Jurassic formations. Recent discoveries of commercial gas and light oil in six of the North Kuwait oil fields have resulted in the startup of the North Kuwait Gas Development Project. This project is a major venture with a planned production growth up to 1,000 MMscf/D of gas and 350,000 B/D of light oil, which requires a total of more than 90 new wells. For this new phase of development, the challenge was to change the approach to the drilling of deep wells to reduce overall project timing and cost. A rethinking of current drilling methods was required along with the application of new technology solutions to optimize drilling times.The North Kuwait deep-well design is complex and requires surface/intermediate casings to be set at maximum depths to reach target depth (TD) in a workable hole size. The 22-in. hole is drilled from 6,000 to 9,500 ft and was considered to have a potential for improvement. A conceptual project was set up that would attempt to replace multiple 22-in.-insert-bit runs, rotary driven, with a single polycrystalline-diamond-compact (PDC) bit design run on a downhole motor. The objective was to establish a partnership approach with the bit manufacturer and motor provider and to develop bit designs, equipment specifications, and operational parameters over the project period.The bit design team identified the main aspects on which the new PDC-bit design was to be based, and a prototype bit was manufactured. Results from the first run of the bit were analyzed, and the design was modified for the second run. A critical element was the development of the downhole motor, with a more-powerful 12¾-in. motor with precontoured stator being used for the second and subsequent runs. Bit designs and downhole-motor and rigequipment specifications were developed and improved on over the project, resulting in the achievement of the project goal with the drilling of the entire 22-in. section with one bit from shoe to shoe. The performance improvements in the trial wells gave substantial increases in rate of penetration (ROP) and reduced drilling times.