| Title | Upper Mahiao Brine OEC Plant Functional Test |
|---|---|
| Authors | Ruperto R. Villa, Jr., Edwin H. Alcober, Joselito P. Villena and Mike M. Abrasaido |
| Year | 2007 |
| Conference | PNOC-EDC Geothermal Conference |
| Keywords | |
| Abstract | The Upper Mahiao Brine OEC Plant was commissioned in 1966 and was designed to utilize the separated brine from the Upper Mahiao and South Sambaloran sector. This plant operates on a binary cycle system where the high temperature brine vaporizes the pentane used in the binary cycle. The brine requirement is 350 kg/s to generate a gross output of 4.6 MW at 20oC brine temperature drop across the plant for an acceptable silica saturation index (SSI) of <1.2. Mass extraction from Upper Mahiao and South Sambaloran sectors promoted reservoir drawdown and resulted to the significant decline in available brine. The OEC plant wad temporarily decommissioned. After 10 years and prudent field management strategies adopted resulted to the increase in brine supply in Upper Mahiao sector. The reservoir processes also led to the SSI of the brine to decline from around 1.1 to 0.7. This provided an opportunity to allow higher temperature drop across the plant (~40oC) to generate within rated capacity even with only around 57% (~200 kg/s) of brine flow available. Treatment of brine by dosing Geogatd SX silica inhibitor was conducted in anticipation of actual temperature drop to be higher and SSI simulated values exceeded during the test. This scheme facilitated the Brine OEC plant functional test before its ownership, operation and maintenance was turned-over by CalEnergy to PNOC-EDC. CalEnergy completely rehabilitated the plant and repaired the leaking condenser and vaporizer tubes. The plant was finally tested starting June 27, 2006 and it started commercial operation on July 6 at a load of 3.8-4.2 MW. The inlet and outlet temperatures were 189oC and 147oC, respectively. The brine plant operation was however short and wad made only to satisfy the requirements of a functional test prior turnover to PNOC-EDC. This is because injection returns of cooler brine may pose a bigger risk to the production wells in the sector. The long term solution is to develop Pad 4RD for condensate injection and transfer brine injection farther north to Pad 4RC, to allow continued utilization of the Upper Mahiao Brine OEC plant. |