Experimental Study for the Influence of Shale Characteristics in Oil-based Drilling Fluid

Oil-based drilling fluid has a good effect in preventing collapse of long open hole section of large-displacement well. To determine if there is a wellbore collapse cycle when using oil-based drilling fluid, in this paper Scratch Test was conducted to study influence of oil-based drilling fluid on uniaxial compressive strength and elasticity modulus of shale. Results showed that if oil-based drilling fluid soaks for a long time, it would reduce uniaxial compressive strength and elasticity modulus of shale. Similar to waterbased drilling fluid, oil-based drilling fluid also has a collapse cycle, which should be considered in the long open hole construction.