| Title | LOW-TEMPERATURE THIXOTROPIC CEMENT DESIGN OVERCOMES SURFACE SECTION DRILLING CHALLENGES – DEEP GEOTHERMAL EXPLORATION PROJECT, JAVA - INDONESIA |
|---|---|
| Authors | H. Permana, and K. Tambunan |
| Year | 2021 |
| Conference | New Zealand Geothermal Workshop |
| Keywords | drilling, cement slurry design, thixotropic cement, drilling challenges, unconsolidated andesitic lava, boulders, loss circulation, hole problem |
| Abstract | A low-temperature thixotropic cement design was utilized to successfully overcome surface drilling challenges in a deep geothermal exploration well in Java island - Indonesia. This solution was provided for the second exploration well after unexpected surface challenges were encountered during drilling of the surface hole section, where hole destabilization and total loss of circulation occurred because of unconsolidated Andesitic Lava Boulders, also encountered in the first well. The other challenge was a low surface temperature because of the high elevation of the well pad, which was higher than 2,000 feet above sea level. Before this low-temperature thixotropic cement design was implemented, several cementing plugs had been pumped to stop the losses and stabilize the formation, with no significant result. Therefore, a decision had been made to perform a plug and abandonment (P&A) operation on this first well. To avoid this P&A outcome, a low-temperature thixotropic cement was designed to have a slurry that would enable the operator to stabilize the surface hole so that the surface casing could be run and set at bottom-hole. The processes involved leading up to the utilization of this effective slurry design to stabilize the hole are listed below: • Met with all parties to discuss options for thixotropic material that could be added to the slurry • Selected two possible thixotropic additives (Material A and Material B) • Performed a total of 58 lab tests to determine the thickening time and thixotropic properties of each slurry, as well as their different weights, concentrations, and temperatures • Selected the slurry that had a thickening time below 90 minutes Upon successfully inventing the most effective slurry, the operator was able to drill the surface section to target depth, and the surface casing was set at maximum depth. The drilling was continued in the well to a planned total depth (TD) at 11,300 feet. At the time of the writing of this publication, this well was the deepest geothermal well in Indonesia. |