Recent Material and Geometrical Changes in Impreg Technology on Turbine Drive Lead to Reduced Drilling Costs in Hard Rock Application

Abstract

Abstract Oman's principal LNG producer is Petroleum Development Oman and their largest producing field is the Saih Rawl Field. Rigs are currently drilling in the reservoir section on the Saih Rawl Field as part the development activity on this field. The Saih Rawl Field is an important producer of the Sultanate of Oman's gas reserves. These deep gas wells have an average TD of 5000m. The reservoir zones are in Barik and Miqrat sandstones at 4500 and 4900m TVD, respectively. The formations in the 8-3/8" section are made up of sandstone, siltstone, shale and dolomite. The Barik, Al Bashair, Miqrat and Amin formations in the 8-3/8" section are extremely hard (up to 30,000 psi unconfined compressive strength - UCCS) and abrasive. These difficult formations have traditionally been drilled with a mixture of roller cone and turbine driven impregnated diamond bits. The roller cone bits deployed in the past lacked durability. The initial impregnated bits faced ROP, durability and float equipment drill-out challenges. Six years of material research, development, and testing on impregnated bit materials has culminated in a 260% increase in durability and a 5% increase in ROP in these formations during the past year using innovative new impregnated diamond bit designs. In addition new cutting structures and innovative bit head geometries for drill out of float equipment have allowed consistent successful drill out of the 9-5/8" shoe track displacing the use of rock bits in this application. Together these advances have reduced the time taken to drill the 8 3/8" section by an average of 10 days. This has results in an average cost saving of $430,000USD in time and materials in the 8 3/8" section. These performance advances have contributed significantly to the reduction in average well drilling time from 90 days in 2004 to 68 days in 2005. These developments in impregnated bit technology have been extended to applications in Saudi Arabia, Algeria, Syria and Venezuela.