This review includes the current state of the art understanding and advances in technical developments about various fields of gas hydrates, which are combined with expert perspectives and analyses.

The present work uses a micromechanical force apparatus to directly measure cyclopentane clathrate hydrate cohesive force and hydrate-steel adhesive force, as a function of contact time, contact force and temperature. We present a hydrate interparticle force model, which includes capillary and sintering contributions and is based on fundamental interparticle force theories. In this process, we estimate the cyclopentane hydrate tensile strength to be approximately 0.91 MPa. This hydrate interparticle force model also predicts the effect of temperature on hydrate particle cohesion force. Finally, we present the first direct measurements of hydrate cohesive force in the gas phase to be 9.1 ± 2.1 mN/m at approximately 3 °C (as opposed to 4.3 ± 0.4 mN/m in liquid cyclopentane).

Gas hydrates are crystalline inclusion compounds, where molecular cages of water trap lighter species under specific thermodynamic conditions. Hydrates play an essential role in global energy systems, as both a hinderance when formed in traditional fuel production and a substantial resource when formed by nature. In both traditional and unconventional fuel production, hydrates share interfaces with a tremendous diversity of materials, including hydrocarbons, aqueous solutions, and inorganic solids. This article presents a state-of-the-art understanding of hydrate interfacial thermodynamics and growth kinetics, and the physiochemical controls that may be exerted on both. Specific attention is paid to the molecular structure and interactions of water, guest molecules, and hetero-molecules (e.g., surfactants) near the interface. Gas hydrate nucleation and growth mechanics are also presented, based on studies using a combination of molecular modeling, vibrational spectroscopy, and X-ray and neutron diffraction. The fundamental physical and chemical knowledge and methods presented in this review may be of value in probing parallel systems of crystal growth in solid inclusion compounds, crystal growth modifiers, emulsion stabilization, and reactive particle flow in solid slurries.

The mechanisms by which hydrates deposit in a petroleum production line are related to pipeline surface properties, fluid composition and properties, and water cut. In this work, adhesion forces between cyclopentane hydrates and solid surfaces were investigated as a function of the solid material, the presence of water and the presence of petroleum acids in the oil phase. The influence of dissolved water on hydrate adhesion forces was also investigated. The results show that the adhesion force between hydrates and solid surfaces was dependent on the surface material; solids with low surface free energy lead to the lowest adhesion forces. The adhesion force was strongly dependent on the presence of water in the system. When a water drop was deposited on the solid surface, the adhesion force between the hydrate and the solid surface was more than 10 times larger than hydrate-hydrate adhesion forces. The presence of a water-saturated oil phase also led to an increase in adhesion force between hydrate particles. Adhesion forces were highest when the solid surfaces are water-wet. Addition of petroleum acids to the oil phase drastically reduced adhesion forces.

Cyclopentane (CyC5) hydrate interparticle adhesion force measurements in the presence of small amounts of crude oil (up to 8 wt % in cyclopentane) were performed at 3.2 °C, under atmospheric pressure, using a micromechanical force apparatus. The adhesion forces obtained for cyclopentane hydrate in small amounts of crude oil in CyC5 bulk fluid were lower than those measured for CyC5 hydrate in pure CyC5 bulk fluid. CyC5 hydrate-normalized adhesive forces were measured to be on the order of 0.5 mN/m for samples containing approximately 5−8 wt % of Caratinga and Troika crude. Hydrate-normalized adhesive forces were found to increase when the surface-active components (including acids and asphaltenes) were removed from the crude oil. These results suggest that crude oils with high contents of acids and asphaltenes may be more likely to exhibit nonplugging tendencies in oil and gas flowlines.