High pressure rheological properties of methane hydrate slurries entail the high-pressure rheometer that can deliver a suitable mixing to form in situ methane hydrate from the multiphase system. However, the hydrate formation was extremely challenging in conventional cup and bob geometry due to its plane surface. In this work, modified Couette geometry has been used in a high pressure rheometer to study in situ formation and dissociation of methane hydrate slurries formed from multiphase water-hexane (C₆H₁₄), water-heptane (C₇H₁₆) and water-decane (C₁₀H₂₂), with varying water-to-liquid hydrocarbon ratios (50:50, 30:70 v/v). Rheological properties such as viscosity, flow curve measurements, viscoelastic properties have been measured during hydrate formation and dissociation. Transient viscosity measurements are carried out at 10 MPa and 275.15 K at a shear rate of 1000 s⁻¹. It was observed that the viscosity increases significantly during hydrate induction. Viscosity profile has shown bobbing behavior during the course of hydrate formation indicating in situ morphological changes (agglomeration and breakage of hydrate crystals) during hydrate formation. Flow curves indicate strong shear thinning behavior. Viscosity profile of methane hydrate slurries were also observed for each case during the hydrate dissociation using thermal stimulation. The peak in the viscosity has been identified near hydrate equilibrium condition during dissociation. Dynamic viscoelastic properties indicate solid behavior of methane hydrate slurries. The present study provides significant contribution on the rheology of methane hydrate slurries formed from multiphase systems in the context of flow assurance applications.