An ultrasonic system(20 kHz,0—150 W) of natural gas hydrate formation was built up to investigate the induction time of gas hydrate formation in the presence of sodium dodecyl sulfate (SDS).The experimental results indicated that the concentration of SDS solution did not affect the induction time distinctly and no critical micelle concentration(CMC) phenomenon was observed.The induction time decreased with the increase of ultrasonic power or reaction pressure.
The flow assurance problem of pipelines in offshore production is becoming more and more serious because oil fields in more and more unusual environments have been brought in production.HCFC-141b and THF were selected as the substitutes to study the flow behavior and mechanism of hydrate blockage in pipelines on the newly built flow loop,which was a two pass loop consisting of a 42 mm diameter stainless pipe,30 m long.Slurry-like hydrates and slush-like hydrates were observed with the formation of hydrates in pipeline.There are critical hydrate volume concentrations of 37.5% for HCFC-141b hydrate slurry and 50.6% for THF hydrate slurry respectively.The pipeline would be free of hydrate blockage when the hydrate volume concentration was lower than the critical volume concentration; while otherwise the pipeline would be easily blocked.A safe region,which is defined according the critical hydrate volume concentrations,is firstly proposed for hydrate slurry,and it can be used to judge if the pipeline can be run safely or not.
