During the production of offshore oil and gas, the cooling of hydrocarbons toward seafloor temperatures enables the formation of gas hydrates, which may restrict fluid flow and ultimately block the flowline. During the formation of a hydrate blockage, a hydrate film may grow between individual particles or between hydrate particles and the pipeline wall, respectively resulting in a higher slurry viscosity or a reduced hydraulic diameter. This hydrate film growth rate has been previously studied as a function of pressure, temperature, and hydrate guest species, but limited data are available to guide whether naturally-occurring surface active components in the oil may affect the hydrate film growth rate. In this study, we have used a micromechanical force (MMF) apparatus to quantify the film growth rate of cyclopentane hydrate at moderate subcooling. Naturally-occurring surface active species were obtained from an Australian crude oil by solvent extraction to separate out asphaltenes, binding resins, and free resins. Each crude oil fraction was then added to a chemically inert hydrocarbon phase, and the impact of the hydrate film growth rate was measured. The results illustrate that, at mass fractions below 300 ppm, the hydrate film growth rate was reduced by at least one order of magnitude with asphaltenes and free resins being the most and least effective fractions, respectively, at suppressing hydrate film growth rate. The presence of each fraction also caused an increase in the wetting angle of the water droplet on the hydrate particle surface, which suggested that these naturally-occurring components may adsorb to the hydrate particle surface. Measurements with the MMF revealed that each of the three fractions was able to reduce the hydrate particle cohesive force by two orders of magnitude.

Purpose Arterial shear forces may promote the embolization of clotted blood from the surface of thrombi, displacing particles that may occlude vasculature, with increased risk of physiological complications and mortality. Thromboemboli may also collide in vivo to form metastable aggregates that increase vessel occlusion likelihood. Methods A micromechanical force (MMF) apparatus was modified for aqueous applications to study clot-liquid interfacial phenomena between clotted porcine blood particles suspended in modified continuous phases. The MMF measurement is based on visual observation of particle-particle separation, where Hooke’s Law is applied to calculate separation force. This technique has previously been deployed to study solid–fluid interfacial phenomena in oil and gas pipelines, providing fundamental insight to cohesive and adhesive properties between solids in multiphase flow systems. Results This manuscript introduces distributed inter-particle separation force properties as a function of governing physio-chemical parameters; pre-load (contact) force, contact time, and bulk phase chemical modification. In each experimental campaign, the hysteresis and distributed force properties were analysed, to derive insight as to the governing mechanism of cohesion between particles. Porcine serum, porcine albumin and pharmaceutical agents (alteplase, tranexamic acid and hydrolysed aspirin) reduced the measurement by an order of magnitude from the baseline measurement—the apparatus provides a platform to study how surface-active chemistries impact the solid–fluid interface. Conclusion These results provide new insight to potential mechanisms of macroscopic thromboembolic aggregation via particles cohering in the vascular system—data that can be directly applied to computational simulations to predict particle fate, better informing the mechanistic developments of embolic occlusion.

The growth and aggregation potential of gas hydrates in subsea flowlines are critical risk parameters for oil and gas production flow assurance. Hydrate interfaces may be exposed to water and hydrocarbon phases where natural oil surfactants may have a tendency to adsorb. The cohesion and growth between cyclopentane hydrate (structure II hydrate) particles exposed to natural oil surfactants in modified hydrocarbon phases were studied using a micromechanical force (MMF) apparatus. An Australian crude oil (unmodified), isolated asphaltenes and resins obtained via SARA fractionation and, when added to the cyclopentane phase, reduced the hydrate cohesive force by up to 98% (<1 wt % of additive). During cases of flowline shutdown, hydrate particles may have the opportunity to sinter with each other, whereby the force required to separate particles may be representative of the shear requirement to fracture aggregates in a flowline restart. The force required to separate hydrate particles was measured as a function of interparticle contact time to quantify the activity of naturally present surface-active material at resisting sintering-type phenomena. The results indicate that naturally occurring species adsorb to hydrate interfaces and decrease the extent of sintering between particles across the range of contact times studied. In a modified experimental setup, cyclopentane hydrate film growth rate measurements illustrated a comparable suppression in hydrate film growth rate to previous work. These results indicate that naturally derived surfactants from some crude oils may stabilize both water-in-oil emulsions and hydrate-in-oil suspensions. The elimination of otherwise necessary chemical management may be suitable if natural oil surfactants can perform suitable flow assurance functions.

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