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. © 2019 Elsevier B.V.