| Title | RECOVERY OF REINJECTION WELL CAPACITY USING ONLINE DISSOLUTION |
|---|---|
| Authors | F.E.P. Monterozo, G.R.A. Gica and D. Mantri |
| Year | 2021 |
| Conference | New Zealand Geothermal Workshop |
| Keywords | online dissolution, silica scaling, reinjection well |
| Abstract | There are several methods available for cleaning a scaled-up geothermal well. These can either be mechanical or chemical. A typical chemical method is usually acidizing, which objectively is simply a tubular process or cleaning the vicinity of the wellbore to improve the well’s productivity or injectivity. Similar to acidizing, a novel method being explored by Nalco Water is Online Scale Dissolution targeted to dissolve scales in a reinjection well. This method involves injecting GEO991, a strong acid alternative, to the condensate or brine for a specified period of time to be able to dissolve scales in the wellbore; thus, improving well acceptance rate. Prior to deploying the dissolution program in the field, scale samples from the reinjection well were subjected to dissolution tests using different dissolvers to determine the extent of dissolution that can be achieved and the suitable dissolver. From the results of the test, the most suitable dissolver is GEO991 with 100% scale dissolution affecting Si, As and Fe components. Online dissolution sidestream test was done to better understand and evaluate the product performance in a realistic and controlled environment. It was found that GEO991 can dissolve scales composed of 60-70% silica and 20% iron-bearing compound. Observations supporting this claim include the 5.32% reduction in the total weight of the scales, minimal silica crystal observation in the dosed line coupon, higher levels of silica and iron measured in the dosed line. No additional scaling was also confirmed as manifested by the following: constant flowrate maintained in the dosed line, a more stable line pressure and minimal to non-existent scaling in the pipe holder. The study gave us enough information and confidence for a commercial trial to proceed. Full-scale commercial run happened in two phases on the target reinjection well. First phase lasted for 33 days improving the well acceptance rate from 3.74 kg/s (baseline) to 10.1 kg/s. The second phase of the trial lasted for 16 days and was able to reach 35 kg/s final well acceptance rate which was the original acceptance rate. The study was able to confirm that GEO991 dosing can be a favorable alternative to traditional rig and non-rig well intervention techniques based on the capacity recovery achieved, cost, ease of deployment and reduced to eliminated well downtime. |