| Abstract |
Calcite scale deposition is one of the major causes of decline in output in some of the production wells in MahanagdongûA sector. Analysis of the chemistry of MG-1, MG-7D, MG-19 and MG-23D indicates that their reservoir fluids are saturated with calcite. Flashing of these fluids, specifically in MG-7D and MG-19, leads to supersaturation and thus, calcite precipitation. The same mechanism is seen in MG-1 and MG-23D, but the inflow of cooler fluids apparently suppresses further calcite scale formation. Blockages caused by calcite scale deposition have influenced the shift in dominant feed zones leading to decline in massflows. The WATCH speciation computer program was used to estimate calcite growth rates and scale thickness in each well. The predicted calcite thickness based on growth rates indicates that MG-1 will be fully blocked in 5 months due to its smaller casing diameter, MG-23D in 10 months, MG-7D in 11 months, and MG-19 in 1 year and 5 months. The predicted calcite thickness approximates actual measured scale thickness. |