A packer or annular fluid includes a hydrocarbon fluid; and a gelling agent; wherein the packer fluid is a yield power law fluid. A method for preparing a packer fluid includes preparing a mixture of a hydrocarbon fluid, and a gelling agent; heating the mixture to a selected temperature; and shearing the mixture. A method for emplacing a packer fluid into an annulus includes preparing the packer fluid that includes a hydrocarbon fluid and a gelling agent, wherein the packer fluid is a yield power law fluid; and pumping the packer fluid into the annulus.