CORROSION-EROSION CONTROL OF TUBULARS IN GEOTHERMAL DRILLING.

Drilling with aqueous fluids into low pressure fractured geothermal formations results in lost circulation and impaired well productivity. Therefore, early in the development of The Geysers geothermal field in California, air drilling techniques were employed to drill into the geothermal producing horizon. Penetration rates are higher with air drilling than with aqueous drilling fluids, and well damage is avoided. However, corrosion-erosion problems were severe and had to be controlled. Prevention of drill pipe erosion-corrosion under high temperature, abrasive conditions is difficult, but a film forming inhibitor was developed that remained effective when impacted by abrasive solids. The new inhibitor is an organic material that polymerizes into a tough, resinous coating at high temperature.