Studies Of Gas Hydrate Kinetic Inhibitors By Dynamic Evaluation Method

The plugging of gas hydrate in oil and gas pipeline is more and more prominent during drilling oil and natural gas in deep-sea, it’s urgent to hunt for kinetic hydrate inhibitors(KHIs) which is low-dosage and low-cost. Dynamic evaluation is a more accurate method for KHIs’ performance evaluation, it avoids calm disturbance of static evaluation method which can’t accurately simulate the situation of gas pipeline. This study adopts dynamic evaluation method to screen composite kinetic inhibitors, evaluate KHIs and its combinated inhibitors with thermodynamic hydrate inhibitors(THIs) in field gas system. The main points are summarized as follows:First, screening composite kinetic inhibitors—HYs by dynamic evaluation method. HYs was prepared by PVCap(main agent) and diethylene glycol monobutyl ether(synergistic agent). Results showed that HY14 was the best composite kinetic inhibitor among HYs, which has the longest induction time on both CH4 and CH4 / CO2 hydrate. HY14’s preparation method is: PVCap mixes with diethylene glycol monobutyl ether by 1:4(quality).Second, ealuating KHIs’(HY1, ISP501 and HY14) inhibition performance on field gas hydrate by dynamic method. Results showed that HY14 was better than commercial inhibitor ISP501 and HY1. HY14 has the highest durable supercooling degree, which means strongest adaptability in the low-temperature environment. In the dynamic evaluation experiment at 14.5 ℃ supercooling degree, HY14’s induction time was longer than ISP501 and HY1: when liquid concentration was 2.0 wt %, HY14’s induction time was 17.3 h, while ISP501 and HY1 were both 6.8 h; when liquid concentration was 3.0 wt %, HY14’s induction time was 24.5 h, while ISP501 and HY1 were 10.1 h and 8.2 h.Finally, ealuating inhibition performance of combinated inhibitors of KHIs(HY1, ISP501 and HY14) and MEG on field gas hydrate by dynamic method. Results showed that KHIs and MEG have excellent synergistic inhibition effect; when combinated with MEG, HY14’s performance is better than ISP501 and HY1. Combinated inhibitors’ s durable super-cooling degree in A-gas system ranted: HY14/MEG > HY1/MEG > ISP501/MEG, and found that while MEG increase 10.0 wt %, durable super-cooling degree will increase about 2℃. In the dynamic evaluation experiment at 19℃ supercooling degree, combinated inhibitors’ s induction time ranted: HY14/MEG > HY1/MEG > ISP501/MEG, that means when combinated with MEG, HY14’s inhibition performance is better than ISP501 and HY1 in A-gas field. Combinated inhibitors which induction time above 48 h was 3.0wt %HY14/30.0wt %MEG(49.4h), 3.0wt%HY14/40.0wt%MEG(>72h), 5.0wt%HY14/20.0wt %MEG(50.5h) and 5.0wt %HY14/30.0wt% MEG(> 72h). All of these were prepared by HY14 and MEG,which means HY14/MEG is likely to be fit in A-gas hydrate prevention and control. It is worth considering to test HY14/MEG’s effect in drilling and transmission of A-gas, so as to determine whether HY14/MEG can be put into field application.