Rapid, High-Temperature, Field Test Method for Evaluation of Geothermal Calcium Carbonate Scale Inhibitors

Summary A new test method is described that allows the rapid field testing of calcium carbonate scale inhibitors at 500° F [260 °C]. The method evolved from use of a full-flow test loop on a well with a mass flow rate of about 1×106 lbm/hr [126 kg/s]. It is a simple, effective way to evaluate the effectiveness of inhibitors under field conditions. Five commercial formulations were chosen for field evaluation on the basis of nonflowing, laboratory screening tests at 500°F [260°C]. Four of these formulations from different suppliers controlled calcium carbonate scale deposition as measured by the test method. Two of these could dislodge recently deposited scale that had not age-hardened. Performance-profile diagrams, which were measured for these four effective inhibitors, show the concentration interrelationship between brine calcium and inhibitor concentrations at which the formulations will and will not stop scale formation in the test apparatus. With these diagrams, one formulation was chosen for testing on the full-flow brine line. The composition was tested for 6 weeks and showed a dramatic decrease in the sealing occurring at the flow-control valve. This scaling was about to force a shutdown of a major, long-term flow test being done for reservoir economic evaluations. The inhibitor stopped the scaling, and the test was performed without interruption.