An Environmentally Friendly Oil Base Mud

Abstract

Mineral oils and several oil base mud additives presently in use are highly biologically toxic and the discharge of oil base muds formulated with them are prohibited or limited. To minimize the toxicity of oil base muds, an environmentally friendly oil base mud was formulated with a weakly biologically toxic base oil, a high efficiency low-toxicity all-in-one emulsifier, a new modified high-gel organophilic clay and other additives developed. The concentrations of these additives were optimized to obtain an oil base mud with satisfactory performance. The oil base mud has LC50 of greater than 15,000 mg/L and is biologically degradable. The oil base mud has good rheology, and its electrical stability is at least 800 V. The HTHP filtration rate is less than 6 mL. This oil base mud is resistant to contamination from 5% gypsum or 5% drilled cuttings or 15% salt water. The oil/water ratio of the mud can be adjusted between 60/40 and 90/10, and the density can be controlled between 1.25 g/cm3 and 2.0 g/cm3. This oil base mud has good high temperature stability, it functions normally at 220 ℃. These properties can satisfy the needs of drilling in wells penetrating complex formations and in area with stringent environment protection requirements.