Yield stress fluid flows occur in a great many operations and unit processes within the oil and gas industry. This paper reviews this usage within reservoir flows of heavy oil, drilling fluids and operations, wellbore cementing, hydraulic fracturing and some open-hole completions, sealing/remedial operations, e.g., squeeze cementing, lost circulation, and waxy crude oils and flow assurance, both wax deposition and restart issues. We outline both rheological aspects and relevant fluid mechanics issues, focusing primarily on yield stress fluids and related phenomena.

Integrated water electrolysis is a core principle of new process configurations for decarbonized heavy industries. Water electrolysis generates H₂ and O₂ and involves an exchange of thermal energy. In this manuscript, we investigate specific traditional heavy industrial processes that have previously been performed in nitrogen-rich air environments. We show that the individual process streams may be holistically integrated to establish new decarbonized industrial processes. In new process configurations, CO₂ capture is facilitated by avoiding inert gases in reactant streams. The primary energy required to drive electrolysis may be obtained from emerging renewable power sources (wind, solar, etc.) which have enjoyed substantial industrial development and cost reductions over the last decade. The new industrial designs uniquely harmonize the intermittency of renewable energy, allowing chemical energy storage. We show that fully integrated electrolysis promotes the viability of decarbonized industrial processes. Specifically, new process designs uniquely exploit intermittent renewable energy for CO₂ conversion, enabling thermal integration, H₂ and O₂ utilization, and sub-process harmonization for economic feasibility. The new designs are increasingly viable for decarbonizing ferric iron reduction, municipal waste incineration, biomass gasification, fermentation, pulp production, biogas upgrading, and calcination, and are an essential step forward in reducing anthropogenic CO₂ emissions.

Paraffin gel formation in sub-sea petroleum transportation pipelines is a common problem encountered during operational and emergency production shut-down periods. Restart of a gelled oil pipeline usually requires the application of a large pressure drop across the pipeline length. In severe cases, permanent wax plugs have formed, resulting in the loss of production capacity. In this investigation, the structural breakdown of a quiescently-formed model wax-oil gel is measured at shear rates ranging from approximately 10⁻⁵ sec⁻¹ to 1 sec⁻¹. It is demonstrated that gel breakdown can be mathematically modeled using a time-dependent Bingham equation in which the yield stress follows third order degradation kinetics. The Bingham plastic viscosity term becomes significant at shear rates above ∼10⁻¹ sec⁻¹ and follows a similar third order decay profile with time. When the imposed shear rate is altered in a step-wise manner during the course of the gel breakage, transient non-linear viscoelastic effects are also observed in the mechanical stress response. Finally, explicit evidence is presented which indicates that after fracture, the gel strength behaves as a point function of the absolute strain, signifying a path-independent gel structure in terms of the single-dimensional flow history.

Xanthan gum and scleroglucan are assessed as environmentally friendly enhanced oil recovery (EOR) agents. Viscometric and interfacial tension measurements show that the polysaccharides exhibit favorable viscosifying performance, robust shear tolerance, electrolyte tolerance, and moderate interactions with surfactants. Non-ionic surfactants and anionic surfactants bind to xanthan gum and transform the backbone conformation from a strong helix to a more flexible structure, reducing the viscosifying efficacy of xanthan. In contrast, non-ionic surfactants and anionic surfactants bind to scleroglucan and increase the viscosifying efficacy by non-electrostatic interactions or imparted electrostatic effects. The two polysaccharides are technically viable as viscosifying agents in typical EOR injection fluid formulations.

Paraffin wax deposition is a ubiquitous phenomenon in the petroleum production industry. Many types of internal pipe coating materials have previously been tested for preventing wax deposition, but none have demonstrated successful performance. It has become increasingly evident that an improved knowledge of the chemistry and physics of wax deposition will be required in order to develop new wax-repellent materials. In particular, it is important to understand the mechanisms used to inhibit similar deposition problems in outside industries. In order to achieve these objectives, a state-of-the-art literature survey was performed to identify the role and function of nonstick and anti-adhesive surfaces in the food, paint, marine, automotive, biomedical, tribological, optical, and petroleum industries. Information was derived from academic, industrial, and intellectual property sources. This review presents a comprehensive compilation of materials and surface modification techniques that show potential for inhibiting or eliminating paraffin wax deposition. A wide variety of metal surface treatments and synthesized polymers are discussed. It is established that nanotechnology surfaces based on fabricated microstructures are inapplicable for use in preventing solid-liquid deposition. On the other hand, self-assembled polymers and nanocomposite materials exhibiting smooth surfaces and low surface free energies may provide appropriate surface technologies for prevention of wax deposition. Based on current adhesion theory postulations, as well as analogies to similar deposition processes, promising new material classes include fluoro-siloxanes, fluoro-urethanes, oxazolane-based polymers, and DLC-polymer hybrids.