| Abstract |
Silica scaling has remained one of the challenges in the Tiwi production field, particularly in the brine disposal systems and the two-phase production facilities. The brine disposal systems include both ¡°cold¡± brine and ¡°hot¡± brine disposal. Cold brine refers to fluid that is collected from atmospheric flash tanks and then flows through the sumps and pipelines to the injection wells. Flashing to atmospheric pressure results in highly over-saturated brine and amorphous silica scales frequently clog-up the brine handling system. In the hot brine disposal systems (MRBDS and SEHBIS), the brine is injected directly from the separators through the pipelines to the injection wells by gravity and this then minimizes the silica saturation. However, scaling of the injection wells still occurs over time, requiring remediation measures at regular intervals. Scaling is also found to occur in the two-phase production facilities, particularly at wellsites where mixing of fluids with different characteristics from the production wells (dry steam vs. two phase) leads to incompatible blends at the production headers, resulting in scaling. In addition, some sectors of the Tiwi reservoir have shown changes with exploitation. some wells that used to produce dry steam have started to produce two-phase fluids while other wells showed cycling behavior or increasing brine production. The chemistry changes brought about by these reservoir changes have also caused the formation of silica scales in the wells and pipelines. This paper reports on some of the engineering solutions and adjustments on operations that have been implemented to minimize the effects of silica scale on Tiwi.s generation. These solutions range from re-designing of the outlets of flash tanks and sumps to re-routing of production lines. For the injection system, cold brine disposal is only used in emergency situations or as back-up to avoid injecting over-saturated brine. However, scaling is still found to occur in both the cold and hot brine injection wells and scale drill-outs and acidizing of the wells is required periodically. A tool (SSI calculator) was also developed to aid in monitoring and modeling the scaling potential of the injection lines. |