Effects of temperature and pressure rheology of less toxic oil muds

This paper will propose general procedures used in collecting base data concerning oils, laboratory-prepared oil-base muds, and oil-base muds which have been exposed to field use. Some of the trends which have been observed while testing various oil base muds will be noted. This paper is concerned only with establishing a general framework of temperature and pressure relationships. Specific problems should be examined using measured data which pertains to the borehole under inspection. Less toxic oils become more viscous as pressure is increased. Temperature has the greatest effect on the viscosity reduction of oils and oil muds below 200/sup 0/F. The magnitude of viscosity differences between oils tend to decrease with temperature in spite of increased pressure. This indicates the dominant effect of temperature over pressure. The same effect can be seen in oil muds. It is observed from the results that the rheology of less toxic oil muds, over the normal range of field operations, are influenced primarily by temperature, mud density, solids content and chemical treatments. These criteria determine mud rheology significantly more than pressure-induced viscosity.