Performance Study Of Gas Hydrate Additives

The Tetrahydrofuran (THF) solution test method is one of the evaluation methods for hydrate additives. The effect of Super Absorbent Polymer (SAP), Zeolite-like Metal-Organic Frameworks (ZIFs), Polyvinyl Pyrrolidone (PVP), Xanthan Gum(XTG)and GHI (inhibitor made by ourselves) on hydrate formation of THF solution had been studied by different ways. Results are as follows:(1)During succeccional cooling, THF solution each with 0.004% and 0.03% (wt%) SAP are first reacted completely, the induction time of which is 16～29min,14～31min, respectively. Meanwhile, the 19% THF solution without SAP are completed the reaction later with the induction time of 25～62min. At the same time, the pictures recorded the THF hydrate formation with and without SAP additive are compared. It is found that SAP does not change the morphology of the hydrate;(2) The effect of ZIFs on hydrate formation for static THF solution is unobvious. Two reasons are responsible for: (A) The randomicity of hydrate formation for static system; (B) ZIFs can't suspend well in solution, which will deposit at the bottom of the bottle if left too long. So the effect of ZIFs on hydrate formation for THF solution needs further study;(3) In the process of cooling to -7.0℃and then holding, induction times of static THF solution in five tests are 7.72h,10.07h,6.57h,4.88h and >13.00h, the highest temperature in hydration of which is between 3.4～3.5℃. However, induction times of THF-PVP(0.5%) solution are 1.04h,0.82h,5.57h,0.86h and 0.97h, induction times of THF-PVP(1.0%) solution are 0.95h,1.78h,2.24h,0.73h and 0.95h, induction times of THF-PVP(2.0%) solution are 1.30h,0.87h,2.39h,0.72h and 0.90h, the highest temperatures in hydration of these three solutions are all between 3.5～3.8℃;(4) In the process of cooling to -3.0℃and then holding, the induction time of dynamic THF-XTG(0.01%) solution is 0.42～0.47h; Meanwhile, the induction time of THF solution is 0.26h;(5) By comparison of fifteen GHIs in the process of cooling to -2.0℃and then holding , GHI (1) is the best, the induction times of two tests for GHI (1)-THF solution are longer than 22.04h when adding 2.0%; the second best inhibitor is GHI (3), the longest induction time in first test is 7.22h when adding 2.0%, and the longest induction time in second test is 7.36h when adding 0.8%; the rest are not very effective, the longest induction times of which are all shorter than 6h.Finally, hydrate inhibitor evaluation apparatus with several reactors bathing in air had been designed to study the effect of inhibitors at high pressure. Several reactors are at the same pressure and temperature, which can greatly reduce the accidental error, simplify the operation, select inhibitors and determine the optimum dosage quickly.