Enhancing the shale inhibition performance of low-melting mixture solvents utilizing DTAB in water-based drilling fluids
Wellbore instability issue is a common occurrence in the development of clean energy sources such as shale gas. Low-melting mixture solvents (LoMMSs), as a novel and environmentally friendly liquids material, are anticipated to be utilized to address this issue. In this work, a novel shale inhibitor (LoMMSs-2) was formulated through introducing a cationic surfactant with a long hydrophobic chain, dodecyl trimethyl ammonium bromide (DTAB), into a commonly used choline chloride/glycerol LoMMSs. Inhibition assessment results indicated that the swelling height of bentonite in LoMMSs-2 solutions decreased by 53.46 %, and shale recovery rate reached as high as 89.51 %, demonstrating superior hydration inhibition compared to commercial inhibitors. The mechanism for inhibiting hydration in LoMMSs-2 was explored through tests involving zeta potential, particle size, interlayer spacing, shale wettability, and surface tension, etc. The findings revealed that choline cations and quaternary ammonium cations in LoMMSs-2 could tightly adsorb to the clay surface. The exposed long alkyl chains made the rock more hydrophobic, increasing the water contact angle from 22.49° to 65.26°. Subsequently, more interlayers water in the clay was expelled, leading to a significant reduction in adsorbed water. Additionally, the lower surface tension and stronger hydrophobicity corresponded to a smaller capillary force, further minimizing water infiltration into shale. Therefore, introducing hydrophobic groups into LoMMSs was a promising approach for developing efficient shale inhibitors to address wellbore instability issue in shale gas drilling.
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