Effect of injected chemical density on hydrate blockage removal in vertical pipes: Use of MEG/MeOH mixture to remove hydrate blockage

One of the problems with natural gas production in the pipes is gas hydrate formation which can lead to blockage. Although there are options to inhibit hydrate formation e.g. thermodynamic hydrate inhibitors and kinetic hydrates inhibitors, hydrate blockage can occur in some cases, e.g. underestimation of water cut production, unplanned shut-in, inappropriate inhibitor injection method or failure of inhibitor delivery. There are a number of remediation methods for hydrate blockage removal such as depressurization, chemical injection e.g. methanol and MEG, mechanical, and thermal methods. In the case of chemical useage in vertical pipes, density plays an important role and needs to be considered. In this work, the effect of chemical density on removing hydrate blockage in the vertical pipes was assessed using a long window rig. The use of methanol/MEG mixtures in removing hydrate blockage in vertical pipes could be more efficient than methanol or MEG alone. The results indicate that a mixture of methanol/MEG with a density of 1 g/cc could remove hydrate blockage successfully and efficiently. The hydrostatic pressure of aqueous phase due to chemical injection could be reduced by using methanol/MEG mixture, because the amount of methanol/MEG mixture required for removing plug could be less than methanol or MEG alone. In addition, ice formation during hydrate dissociation due to its endothermic nature should be taken into consideration during chemical injection. (C) 2017 Elsevier B.V. All rights reserved.