| Abstract |
San Jacinto Tizate is a high temperature geothermal field (~310 °C) with a serious operational issue of silica scaling formation from production wells that are in PAD 12 and have high silica content between 900 and 1000 ppm with a silica saturation index (SSI) of 1.35. Due to technical problems related to silica deposition, mainly occurring in surface equipment, reinjection pipeline and injection wells in the North zone of the field, at the end of 2016 field trials were performed using a silica test skid followed by online testing. In both scenarios, pH buffer, citric acid and acetic acid were tested to assess the effectiveness of these chemicals to control the silica polymerization process by modifying the brine pH in a range of 4.5-5, which usually delayed silica precipitation long enough to be disposed to injection. From the trials carried out in the silica skid test, it was determined that citric and acetic acid allow modification of the brine pH in the desired range to delay silica polymerization. The same results were obtained with the online test, and so it was decided to use acetic acid because there is a local supplier, low cost, and stock availability. These pilot and online tests were very useful for finding the best chemical option, based on cost-benefit, to control silica scaling. From 2017 to the present, acetic acid has been used to modify the brine pH coming from cyclonic separator HPS-3, and ongoing monitoring shows that silica polymerization is prevented in the injection pipeline. Furthermore, the injection capacity of wells SJ11-1 and SJ11-2 have been maintained. |