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• Non-amide kinetic hydrate inhibitors are reviewed systematically. • The inhibition performance of non-amide KHIs is related to their chemical structures. • Several non-amide KHIs are with great potential for commercial development. • The inhibition mechanisms of non-amide KHIs are discussed. Kinetic hydrate inhibitors (KHIs) have been used for several decades to solve the hydrate formation problem in oil and gas flowlines. Traditional KHIs are amide-based polymers, e.g., poly(N-vinyl pyrrolidone) (PVP) and poly(N-vinyl caprolactam) (PVCap). With the requirement of high performance, well fluid compatibility, and biodegradable KHIs in oil and gas production and transportation assurance field, more and more non-amide KHI categories have been developed. According to the functional groups, synthetic non-amide KHIs can be classified into amine-based KHIs, amine oxide-based KHIs, phosphonate-based KHIs, sulfonate-based KHIs, hydroxyl-based KHIs, acrylate-based KHIs, urethane-based KHIs, etc. Some natural non-amide polymers, e.g., polysaccharides, are also found with inhibition effect. The inhibition performance of the non-amide polymers is related to their chemical structures. Different functional groups in the polymers have different effects on their inhibition performance. However, the inhibition performance of a polymer largely depends on the type and size of the hydrophobic groups connected to the functional groups. Some of the non-amide KHIs with suitable hydrophobic groups show better inhibition performance and higher cloud point (T Cl) in brines than some of the well-known commercial amide-containing KHIs, which provides a great potential for further development for field applications. In addition, aspects of the KHI inhibition mechanism related to the amphiphilic groups in the polymers and their hydrogen-bonding ability are discussed. [ABSTRACT FROM AUTHOR]

[Display omitted] • Raman spectroscopy can record the formation process of methane hydrate from the solution droplet in the presence of KHI. • The hydrate formation process of KHI-containing systems can be divided into four different stages. • Lactam and non-lactam KHIs have different effects on different stages of the hydrate formation process. • The evolutions of water molecules and guest molecules during the hydrate formation process can be affected differently by varying types of KHIs. In-situ microscopic observation on methane hydrate formation in the presence of kinetic hydrate inhibitor, poly (vinyl caprolactam) (PVCap) or poly (N -isopropyl acrylamide) (PNIPAM), is conducted with a confocal Raman imaging microscope, and the behaviors of CH 4 molecules and water molecules in hydrate formation process are studied to understand the inhibition mechanism. It is found that both PVCap and PNIPAM have influences on hydrate formation, but their interactions with host and guest molecules are different. PVCap with cyclic pendant groups works better on preventing hydrate formation from the gas–liquid interface into the bulk solution, while PNIPAM with acyclic pendant groups is more effectively on inhibiting hydrate growth to well-ordered clathrate structures. Those are caused by the difference in the prominent inhibition mechanism of the two types of kinetic hydrate inhibitors, lactam-based PVCap mainly limiting the diffusion of CH 4 molecules from the gaseous phase to the liquid phase, while non-lactam PNIPAM undermining hydrate growth by retarding the rearrangement of water molecules to form clathrate structures. [ABSTRACT FROM AUTHOR]

Experiments are performed to study the closed-loop effect of gas hydrate formation and decomposition on the flow properties of a fine-grained quartz sand specimen. The high resolution X-ray CT images of the test specimen at different experimental stages are acquired. In order to elucidate the changes in pore structure of the test specimen, topologically representative pore networks are established. The evolution of the flow properties during gas hydrate formation and decomposition is further evaluated. The results show that, gas hydrates occupancy in pore space exhibit different modes; they grow mainly as the grain-cementing mode except some intermediate stages, where pore-filling or load-bearing hydrates are observed. It is also found that the formation and decomposition of gas hydrates can cause the pore structure and flow properties changed. Increase of gas hydrate saturation results in a sharp decline in water relative permeability, larger irreducible water saturation and smaller gas-water percolation zone, while gas relative permeability does not exhibit obvious changing law. The decomposition of gas hydrates will exert a greater influence on the flow properties described above than gas hydrate formation does. The increase in frequency percentage of 10–20 μm pores within the fine-grained test specimen after experiments might be caused by gas hydrate decomposition induced damage of pore structure. [ABSTRACT FROM AUTHOR]

• A Quasi-Langmuir kinetic model is demonstrated for emission. • 6 kinetic models are compared in predicting the emitted shale gas. • The relationship between minerals and the emission is discussed. Gas-in-place (GIP) is a significant parameter in the assessment of gas resources and reserves, design of production strategy, and enhanced gas recovery. To precisely estimate GIP of shales, a direct method often sums experimentally measured desorbed gas by canister desorption testing (CDT), predicted lost gas in the recovery of the fresh core via CDT data in situ on the surface, and measured residual gas in the lab. However, the critical kinetic emission behavior remains poorly understood. A series of CDTs were collected from our previous work on 33 fresh shale cores. This work, based on experimental observation, proposes a Quasi-Langmuir model, which well fits the experimentally measured data with a coefficient of determination, R 2 , up to 0.9992. We also compare the model to 5 other potential kinetic gas sorption models, including Pseudo First Order (PFO), Bangham, Elovich, Ritchie, and Pseudo Second Order (PSO) models in terms of the proposed relationship between changes of emitted gas and time. Results show that the Quasi-Langmuir model fits the kinetic data best, followed by Bangham, Ritchie, PSO, PFO, and Elovich models. Ritchie and PSO models give comparable fittings, and the Elovich model deviates from measured data far more than other models. This work improves understanding of the emission behavior and process of shale gas in CDT, which will provide a robust estimation of lost gas in the borehole, and a more accurate GIP estimate for production in the petroleum industry. Results from this work have significant implications for monitoring the treatment of water and air contamination based on adsorption. [ABSTRACT FROM AUTHOR]