| Title | EVALUATING EFFECTIVENESS OF CALCITE ANTISCALANT FOR FIELD APPLICATION |
|---|---|
| Authors | F. Siega, T. Gresham, A. Calibugan, O. Goh |
| Year | 2018 |
| Conference | New Zealand Geothermal Workshop |
| Keywords | calcite scale deposition, antiscalant, thermal stability, NACE test, well productivity |
| Abstract | Calcite scale deposition can significantly affect the performance of production wells supplying fluids to a geothermal power plant. Depending on the level of fluid oversaturation with respect to calcite and the rate of scale deposition, production from a geothermal well can decline by as much as 50% in one year. Mechanical clean-out and acidising are two commonly used options to recover loss in productivity due to calcite deposition inside the wellbore. These are however expensive options of managing calcite scaling in addition to cost of business interruption with wells needing to be taken off-line from the power plant. Accurate assessment of the calcite saturation index based on the fluid chemistry analysis, and any early indication of calcite scale deposition, is very valuable as scaling within the wellbore can be proactively managed through the use of antiscalant chemicals. The antiscalant is normally dosed below the flashpoint using a capillary tubing to prevent blockage formation inside the wellbore and maintain production from a geothermal well. This option is considered cost-effective but requires a rigorous process of selecting the suitable antiscalant chemical for the chemistry of the fluid produced and the downhole temperaturepressure condition of the geothermal reservoir. This paper will discuss the selection process of antiscalant chemicals available in the market and the subsequent laboratory testing required prior to an actual short-term field trial. This paper will also discuss the requirement for long term monitoring of well performance for an overall evaluation of the antiscalant effectiveness in controlling calcite scaling. |