| Abstract |
Smectite a hydrated expanding clay mineral is present in significant amounts in the surface facilities of the Mindanao 1 Geothermal Production Field (M1GPF). It is the dominant constituent of total deposits in the Low-pressure Station, and Separator Vessels (SV) 100 and 101. It is found in minor quantities of total deposits downstream of these vessels. The fragmental clay deposits cause recurrent operational problems such as flooding of brine surge tank and flash vessel, clogging of pump at the LP station and subsequent M1GPF plant trip. At present, the solution to the problem is regular inspection and cleaning of the LP station. Petrologic and scanning electron microscopy (SEM) analyses of clay samples reveal micro-textural features and mineral association suggesting that they deposited directly from the brine in the surface facilities, and are not hydrothermal alteration minerals from production wells. Moreover, simulation using SV-100/101 brine chemistry gives a high saturation index of Semite (log Q/K of 10-24) indicating high potential for depositing Semite. Very high saturation index id due to the brine's elevated aluminum content of 640 ppb. Thus, abundant Semite scales likely for in SV-100, SV-101, and LP station where separated brine from SV-100/101/602 is further flashed at 120oC. These soft clay deposits are easily removed from the vessels and transported as fragmental solids downstream of these facilities. Since aluminum is the major parameter that controls smecite saturation index, clay scaling may be controlled by brine treatment with Al-sequestering or complexing agent. |