Assessing the impact of an ionic liquid on NaCl/KCl/polymer water-based mud (WBM) for drilling gas hydrate-bearing sediments

Abstract

Herein, 1-methyl-3-octylimidazolium tetrafluoroborate (OMIM-BF4) was tested as a potential additive to enhance the rheological and hydrate inhibition properties of polymer water-based muds (WBMs) for drilling natural gas hydrate sediments. API standards were adopted for the mud testing with and without OMIM-BF4, while the hydrate study was conducted using a high-pressure reactor at 8 MPa and −2 °C. The presence of OMIM-BF4 efficiently improved the rheological properties of the PAC and XGUM based muds by decreasing their flow behavior index by 4.97% and 47.77% and increasing their consistency index by 96.00% and 33.63%, respectively. The XGUM based mud system exhibited efficient rheological properties suitable for drilling hydrate reservoir compared with the PAC based mud system with and without OMIM-BF4. The Hershel-Bulkley model best predicted the rheological properties of all the mud systems by exhibiting less Mean Percentage Error (MPE) values in the range of 1.39% – 24.71%. Furthermore, the presence of OMIM-BF4 greatly inhibited methane hydrate formation in both PAC and XGUM water-based mud systems due to its kinetic inhibition efficiency mainly arising from its long alkyl chain hydrophobic adsorption activity on the hydrate crystals.