Tetra-n-butyl ammonium bromide (TBAB) was widely used in the research fields of cold storage and CO₂ hydrate separation due to its high phase change latent heat and thermodynamic promotion for hydrate formation. Agglomeration always occurred in the process of TBAB hydrate generation, which led to the blockage in the pipeline and the separation apparatus. In this work, we screened out a kind of anti-agglomerant that can effectively solve the problem of TBAB hydrate agglomeration. The anti-agglomerant (AA) is composed of 90% cocamidopropyl dimethylamine and 10% glycerol, which can keep TBAB hydrate of 19.3–29.0 wt. % in a stable state of slurry over 72 h. The microscopic observation of the morphology of the TBAB hydrate particles showed that the addition of AA can greatly reduce the size of the TBAB hydrate particles. CO₂ gas separation experiments found that the addition of AA led to great improvement on gas storage capacity, CO₂ split fraction and separation factor, due to the increasing of contact area between gas phase and hydrate particles. The CO₂ split fraction and separation factor with AA addition reached up to 70.3% and 42.8%, respectively.

The capture and storage of carbon dioxide (CO₂) are urgent and crucial to achieve the goal of carbon neutrality. Hydrate-based CO₂ capture technology is one of the promising technologies for capturing and storing CO₂. This work studied the nucleation and growth of CO₂ hydrate provoked by direct current–voltage accompanied by charge flow with the agitation of 450 rpm at an initial pressure of 3.5 MPa and a temperature of 274.15 K. The results show that the physical bubble behavior and electrochemistry mechanisms could influence CO₂ hydrate formation process in the application of voltage. The induction time and semi-completion time of CO₂ hydrate formation were decreased by 51% and 27.8% in the presence of 15 V, respectively. However, more product of electrolysis, Joule heat and ions, could inhibit the CO₂ hydrate formation process in the application of a high voltage (60 V). In addition, a high voltage (60 V) could change the morphology characteristics of CO₂ hydrate from gel-like to whisker-like. This study provides valuable information on the formation of CO₂ hydrate under the action of charge flow.

The swelling characteristics of porous media in the offshore natural gas hydrate reservoir have an important effect on the stability of the reservoir. In this work, the physical property and the swelling of porous media in the offshore natural gas hydrate reservoir were measured. The results show that the swelling characteristics of the offshore natural gas hydrate reservoir are influenced by the coupling of the montmorillonite content and the salt ion concentration. The swelling rate of porous media is directly proportionate to water content and the initial porosity, and inversely proportionate to salinity. Compared with water content and salinity, the initial porosity has much obvious influence on the swelling, which the swelling strain of porous media with the initial porosity of 30% is three times more than that of montmorillonite with the initial porosity of 60%. Salt ions mainly affect the swelling of water bound by porous media. Then, the influence mechanism of the swelling characteristics of porous media on the structural characteristics of reservoir was tentatively explored. It can provide a basic date and scientific basis for furthering the mechanical characteristics of the reservoir in the hydrate exploitation in the offshore gas hydrate reservoir.