Hydrate Formation,Slurry Flow Behavior And Inhibition In A Flow Loop And Prevention Of Hydrate Deposition With Coatings

The formation of hydrate in oil and gas production equipment and transportation pipeline will lead to blockage and further lead to production safety accidents.The main reason for the hydrate blockage in oil and gas pipeline is that the gas phase and liquid phase in oil and gas pipeline can be converted into hydrate particles at certain temperature and pressure,and then the accumulation and deposition occur.The adhesion force between hydrate particles and particles,hydrate particles and wall surface is the main factor for aggregation and deposition.Adhesion force between hydrate particles and substrate was measured by micromanipulation.On the basis of understanding the process of hydrate formation and blockage in the flow tube,the mechanism of coating antihydrate aggregation was studied.The experiment of hydrate growth process was carried out in the presence of coating in the visible jacketed reactor.Further more,growth and distribution of methane hydrate on coating were studied using high-pressure reactor.The adhesion between bare substrate and substrate coating and hydrate particles was measured.The three bare substrates are X70,X80 and ZrO₂,respectively.Several coating types are fluorosilane coating,HBN?hexagonal boron nitride?coating and W coating.The adhesion between the coated surface and the hydrate particles is 10%⁹0%less than the adhesion between the bare basement surface and the hydrate particles.It is shown that the presence of coating can reduce the adhesion of hydrate particles.This paper designs and installs a visual loop device which can withstand up to 15Mpa pressure.The total length of the entire loop is 33 meters and the volume is 40L.The entire loop adopts a clamping design with an inner diameter of 25.4 mm.Alcohol is used as a refrigerant in the sleeve to ensure that the temperature can be controlled within the scope of the experiment during the entire experimental process.Tetrahydrofuran?THF?aqueous solution as medium under different system conditions of 50 vol%LL,100 vol%LL and 100 vol%LL+AA.In the visible loop device,the changes of hydrate blockage morphology and blockage formation process were studied.The results show that the system is more likely to form large hydrate particles without adding AA.The system is more likely to form hydrate blockage under the condition of 100 vol%LL.Hydrate deposition is more likely to occur on the wall of the gas phase space on the liquid level of the flow pipe,but less hydrate particles are deposited in the liquid phase.Hydrate blockages are formed by the deposition of hydrate particles on the inner wall.The addition of AA slows down the aggregation of hydrate particles and makes the formed hydrate particles more dispersed and delicate.Under the certain condition of cold quantity input,three system eventually formed hydrate blockage,but the addition of AA significantly reduced the hydrate particle size and relieved the hydrate particles deposit.The observation experiment of THF hydrate growth process under coating was carried out in a jacket reactor.The higher amount of SiO₂ in the coating,the slower hydrate growth rate on its surface.The growth of hydrate on the surface of substrate coating is from edge of the substrate to the middle.The hydrate growth process follows the basic mechanism of heat transfer prior to mass transfer.The decomposition of hydrate on the surface of substrate coating begins with the decomposition of hydrate near the wall.The shape of the substrate has little influence on the decomposition process.The growth experiment of hydrate on substrate coating surface was carried out using high pressure reactor.Compared with coating substrate,hydrate tends to grow on non-coating substrate surface.Near the area of the upper space above the gas phase of hydrate formation,basic is given priority to with hydrate particle exists,near the area of the upper space above the liquid phase of large amount of hydrate formation,mainly hydrate block,and the liquid phase and gas phase in the middle of the part is the main hydrate film on.On the basis of the development of the formation process of hydrate plug flow tube and the particle adhesion mechanism,the growth of the experiment of hydrate in the presence of the coating was carried out,discussed the hydrate particles-coating adhesion and accumulation mechanism,established the relevant schematic process.