Rotary Fatigue Testing Device for Determining Drilling Fluid Compatibility in A Pdm Stator

Abstract

Abstract The purpose of this study was to evolve the understanding between mud motor power section reliability and oil-based drilling fluid chemistry, using novel laboratory data recorded from a proprietary test apparatus and instrumentation. The underlying objective is driven by operator's desire to maximize drilling performance by extending the operating envelope of the PDM/drilling fluid system, beyond what is possible using legacy ASTM immersion testing. This paper describes a new test method and machine, intended to complement currently existing test methodologies, that incorporates multiple interplaying downhole conditions. Twelve fluids were analyzed using the novel test machine and the results compared to data obtained from conventional ASTM immersion testing; The fluids varied with respect to base oil type, as well as concentrations of emulsifier, and wetting agent. The goal of testing was to determine if positive displacement motor (PDMs) elastomer failure mechanisms (abrasion, cracking, chunking) could be replicated in a controlled environment, and if doing so could improve the data and understanding of its lifespan in a PDM. The result of testing provided evidence of two and three body abrasion, compression set, chunking, and chemical swell. It was found that concentrations of additives, as well as base oil type significantly affect runtime in the novel test machine, even if the differences in conventional testing were inconclusive. The novel test machine demonstrated that concentrations of key additives, as well as base oil type significantly affect elastomer runtime, even if conventional testing showed inconclusive results.