Evaluation of Scale Inhibitors Suitable For Deepwater Fields

Abstract

Abstract The increasing demands for oil and gas require production from increasingly deeper water depths resulting in demands for production chemicals that are suitable for deepwater and ultra-deepwater fields. The specific challenges for production chemicals in deepwater fields include bigger temperature fluctuations from seabed temperature to high-temperature/high-pressure (HTHP) environments, higher shear rates, greater pumping pressures, longer residence time and limited injection lines. To address these issues, this paper demonstrates the whole suite of laboratory evaluation techniques that simulates the conditions experienced in the deepwater fields. These techniques include the exposure of production chemicals to a high-pressure flow loop with cyclic temperature variation from seabed temperature to 212°F (100°C), the measurement of rheology profiles at ambient and high pressure (5,000 psi), thermal stability and material compatibility. Several scale inhibitor products, including combined scale/corrosion inhibitors, have gone through the full suite of deepwater condition testing to determine their suitability for deepwater fields. Performance testing was also conducted for both pre- and post-flow loop samples. The best candidates have been designed to maintain similar inhibition performance after the flow loop with a viscosity less than 33 cP at 39.2°F (4°C) under 5,000-psi conditions; these products also have to be thermally stable and compatible with methanol/glycols and various elastomers used. This paper provides insights into the suitable laboratory techniques and criteria for the evaluation of deepwater products. The wide range of temperature variations, high shear, long residence time and HTHP environment for the deepwater fields has been successfully simulated in the laboratory and used to evaluate deepwater scale inhibitors.