Session 21: Disposal of Flashed Brine Dosed with CaCO3 Scale Inhibitor: What Happens When the Inhibitor is Exhausted

摘要

Inhibited, flashed brine is thermodynamically poised to deposit CaCO(sub 3). Eventually the scale inhibitor will be overcome by dilution in native reservoir fluid, sorption on rocks, slow overgrowth of CaCO(sub 3), decomposition, or some combination of processes. Consequences to the reservoir which receives the fluid apparently have not been previously explored. However, Huff-Puff tests (monitored backflow of injected tracers), carried out at East Mesa in the summer of 1983, have provided a starting point for addressing the questions. An effective lifetime of about 14 hours is indicated for one inhibitor. Additionally, reactions between injected fluid and native resource fluid have been observed in two contexts: (1) the native fluid around the disposal well is the unflashed counterpart of the injectate; and (2) the native fluid around the disposal well is chemically distinct from the injectate and from its unflashed counterpart. In the two cases investigated, situation (1) yielded significant reaction (deposition of CaCO(sub 3)) whereas, situation (2) appeared unreactive. These outcomes have important implications regarding the mechanics of reservoir management for long-term electricity production.