Abstract
In Kuwait's largest reservoir, the Burgan Field, exploration wells have large potential for drilling optimization and savings; specifically a 22 inch hole, that is drilled conventionally using multiple roller cone bits in multiple trips through challenging inter-bedded formations. Hybrid drill bit technology, roller cone combined with Polycrystalline Diamond Compact, was introduced in search for an economically viable solution to deliver wells faster and achieve yearly operator targets. This paper analyzes the breakthrough drilling performance achieved by a 22 inch hybrid bit in comparison to conventional roller cones offsets and provides conclusions on economic viability.
The main challenges drilling the 22 inch section are drill bit durability and drilling vibrations through 2,000 ft. of inter-bedded limestone, shale and sandstone. In addition to curing fluid losses in certain porous formation layers that negatively affect Rate Of Penetration (ROP). Typically two roller cone bits are used on rotary drive to drill this section at 15 feet per hour, consuming seven drilling days. Using Polycrystalline Diamond Compact (PDC) bit with a performance motor to increase ROP performance is not an economically viable solution. Using hybrid drill bit on rotary drive combines the benefits of PDC blades’ durability and higher cutting efficiency with the cones’ stability by grinding and gouging into the formation.
The deployment of the hybrid technology was a collaboration project between a national oil company and a major oil services company. The teams focused on optimizing the complete drilling system including the bottom hole assembly, hydraulics, drilling parameters and geological factors to match the hybrid drill bit mechanism.
The hybrid design selection and drilling optimization resulted in a 142-percent ROP improvement from offsets average performance. The hybrid design drilled the 22 inch hole after casing shoe to section total depth at 31 feet per hour, using one bit, in three drilling days in comparison to seven days average performance. The total operator savings from this section was approximately USD 175,000 in the first deployment. Such remarkable economical savings and technical optimization proved that the hybrid technology is the viable solution for Burgan 22 inch application.
