Improved Efficiency of Solid Trap Installed in Brine Injection Pipeline of Leyte Geothermal Production Field, Philippines

Abstract

The original 20” single pipeline solid traps installed in Tongonan-1 and in most geothermal fields of Energy Development Corporation (EDC) are ineffective in capturing minute solids carried by the brine, resulting to capacity decline in injection wellbores. Installation of a modified and enlarged solid trap at well 1R8D consisting of 36” parallel pipeline was completed on t January 2003. The minute solids that go with the brine are removed by significantly reducing the fluid velocity in the modified solid trap allowing the solids to settle in the solid trap prior to brine injection into the well. When it was opened and evaluated in June 2003 after 167 days of utilization, the solids collected at the modified solid trap were composed of polymerized silica (50%), corrosion products (40%) consisting of magnetite and hematite, and formation materials (10%). The total weight of solids collected was 3,445 kg for an estimated deposition rate of 21 kg/day. Iron catalyzed or enhanced polymerization of silica also likely occurred in the brine enriched with magnetite, which induced polymeric silica formation as evidenced from the debris collected. Removing the bulk of the solids from the brine before it is injected significantly reduces the potential of enhanced silica polymerization and minimizes the rapid decline in injection capacity of the well. The documentation and evaluation showed that the modified solid trap installed had an improved performance in capturing the minute solids suspended in the brine compared to the old design. Similar observation was noted when a solid trap of similar design was installed in other injection wells which showed an improved efficiency. This paper demonstrates that even a very simple technology can be very useful is solving some complicated problems in geothermal operations.