Scale and Corrosion Inhibitor Evaluation under High Shear Flow Conditions

Abstract

Scale and corrosion testing under high surface shear flow conditions, and selection of effective inhibitors, is of increasing importance in oilfield production. Extremely high wall shear stresses, up to 10,000 Pa, can be generated in production systems, for example in inflow control devices, and as such there is a need for high shear corrosion and chemical testing techniques. A jet impingement test technique is presented that enables performance testing of both scale and corrosion inhibitors under these challenging conditions and demonstrates the effect of elevated shear on inhibitor performance. A test system has been developed that allows routine laboratory evaluation of scale and corrosion processes at moderate to high shear stresses using a jet impingement method. A series of tests has been conducted to determine the extent of scale deposition and corrosion observed with a mild scaling system, both independently and combined, and then to assess the effectiveness of inhibitors under high shear conditions. Static tests and low shear rotating cylinder tests have been carried out with the same brine system to allow comparison of results from the different methods. The results show that the jet impingement approach is effective in generating scale deposition and corrosion under the high shear, field representative conditions. The effect of the scale and corrosion processes occurring simultaneously in the same system was demonstrated. Both scale inhibitor and corrosion inhibitor performance were found to be affected by the flow conditions with higher concentrations of each being required as surface shear stress was increased although this was also dependent on the chemical nature of the inhibitors. Comparison of the jet impingement results with those obtained from static and rotating cylinder methods showed that the developed technique is more suitable and allows both scale and corrosion processes to be observed in the same system, under the same hydrodynamic conditions. This test method therefore provides an additional laboratory technique that can be used to evaluate both scale deposition and corrosion under very high shear stresses that cannot be readily achieved by alternative approaches. This work also highlights the importance of testing under field representative conditions and advances the understanding of inhibitor performance in these systems.

Characteristics of scales and their impacts on under‐deposit corrosion in an oil production well

“…[ 38‐41 ] In addition, other variables, such as temperature, pressure, ions, pH, flow regimes, seeding, and nucleation, affect the corrosion and scale formation. [ 42‐44 ]…”