Roller Cone Drill Bits for High-Temperature Applications in Southern Australia

摘要

Geothermal and oil and gas reservoirs in deep and/or geologically active areas are an example where high temperatures place greater demands on the performance of drilling systems. The lithologies drilled to gain access to these reservoirs are often hard rock, requiring the use of roller cone drill bits.rnConventional rubber seal components used in roller cone drill bits are typically rated for temperatures up to 150℃ (302°F), and become thermally degraded leading to bearing failure above these temperatures.rnTo make a roller cone bit capable of operating at higher temperatures, new rubber compounds were developed and tested in laboratory experiments to characterize their high-temperature behavior. Drill bits containing these rubber compounds were used to drill the 216-mm (8 1/2-in.) diameter vertical well section of a geothermal well in the Cooper Basin of South Australia. Maximum bottom hole temperatures were estimated to be 170℃ (338°F) while drilling the granite basement below 3500 m (11,483 ft); however temperature indicators showed the bits were exposed to temperatures greater than 260℃ (500°F). Seventeen drill bits were used: 14 containing mechanical face seals and high-temperature-rated rubber components and 3 containing mechanical face seals and conventional rubber components. Filtered run data shows the high-temperature rubber bits ran 112% longer hours and drilled 74% longer intervals than the bits containing conventional rubber components. Examination of the high temperature rubber components found them pliable and resilient, suggesting they were still functional. The improved performance of the high-temperature rubber components extends the advantages of mechanical seals in high-temperature roller cone drilling applications. Longer runs and footage drilled positively impact the well installation costs that consume betweenrn42% and 96% of capital costs of a typical geothermal power facility [Tester et al., 1994].rnThis paper reviews laboratory tests performed to develop the high-temperature rubber compounds. It discusses the field application, and present the bit run performance data, and dull bit forensic examinations, highlighting the performance improvements achieved.