Reverse-Circulation Cementing and Foamed Latex Cement Enable Drilling in Lost-Circulation Zones

Abstract

Drilling in geothermal locations can pose significant challenges for conventional cement systems and circulation methods. To overcome these challenges in a geothermal well in California, a special cement system and circulation method was used. Because conventional Portland cement systems are vulnerable to chemical attack and mechanical stress typical in geothermal wells, a specially formulated foamed latex-cement blend was developed to provide good zonal isolation under these conditions.
In addition, a geothermal well often experiences lost-circulation problems that require the reduction of circulation pressures while circulating cement in place. To help minimize these circulation pressures, cement was pumped in reverse. Reverse circulation significantly reduced placement pressures and allowed placement of the cement with no apparent losses. This paper details how these technologies and techniques were successfully used in the cementation of one casing string in a geothermal well.