Wax deposition in oil and gas pipelines is considered one of the most severe operational problems, and significant efforts have been made to prevent and remediate this flow assurance issue. Chemical wax control strategies have received considerable attention, especially in certain cases where applying the mechanical and thermal treatment is inconvenient and difficult. However, until now expensive and inefficient “trial-and-error” procedures were used in fields, possibly due to the lack of the fundamental understanding of how these chemicals work in different operating conditions. Here, a comprehensive review of the available literature on chemical wax control strategies is presented. The key performance parameters used in assessing the chemicals in the laboratory are systematically reported. All commonly used wax inhibitors, pour point depressants, and wax dispersants are described based on the types, affecting factors, working mechanisms, and testing facilities. Solvents that are used to dissolve the wax deposits or to reduce the viscosity of the fluid are also discussed. Finally, future challenges ahead for chemical wax control research are discussed.

This paper presents the development of a novel stimulus-responsive SMP that is capable of shape deformation under UV light and shape fixation in visible light. Finally, the original shape is recovered at higher temperature.

No abstract

Abstract:In this paper, we developed a photo-thermo staged-responsive shape-memory polymer network which has a unique ability of being spontaneously photo-responsive deformable and thermo-responsive shape recovery. This new type of shape-memory polyurethane network (A-SMPUs) was successfully synthesized with 4,4-azodibenzoic acid (Azoa), hexamethylenediisocyanate (HDI) and polycaprolactone (PCL), followed by chemical cross-linking with glycerol (Gl). The structures, morphology, and shape-memory properties of A-SMPUs have been carefully investigated. The results demonstrate that the A-SMPUs form micro-phase separation structures consisting of a semi-crystallized PCL soft phase and an Azoa amorphous hard phase that could influence the crystallinity of PCL soft phases. The chemical cross-linking provided a stable network and good thermal stability to the A-SMPUs. All A-SMPUs exhibited good triple-shape-memory properties with higher than 97% shape fixity ratio and 95% shape recovery ratio. Additionally, the A-SMPUs with higher Azoa content exhibited interesting photo-thermo two-staged responsiveness. A pre-processed film with orientated Azoa structure exhibited spontaneous curling deformation upon exposing to ultraviolet (UV) light, and curling deformation is constant even under Vis light. Finally, the curling deformation can spontaneously recover to the original shape by applying a thermal stimulus. This work demonstrates new synergistically multi-responsive SMPUs that will have many applications in smart science and technology.

No abstract