Development and Evaluation of Novel Loss Prevention Materials for Oil-Based Drilling Fluids

In complex wells drilling, oil-based drilling fluids has been one of the best solutions to overcome high-temperature stability and wellbore instability problems, but lost circulation is more prone to occur when drilling with oil-based drilling fluids compared to water-based drilling fluids. It is difficult to deal with this problem on the drilling site for lack of high-efficiency loss prevention materials. In order to solve this technical problem, the principles of pressure resistance plugging technology of oil-based drilling fluids were firstly investigated according to the force-chain theory of granular matter mechanics. Based on the principle above, novel loss prevention materials were finally developed for oil-based drilling fluids by use of the Permeability Plugging Test, and rigid bridging particles, elastic packing particles, micro fibers and softening particles could synergistically form fracture tight sealing zones with strong force-chain network to strengthen the lost circulation prevention ability of oil-based drilling fluids. Experimental evaluation results showed that novel loss prevention materials could be compatible with other components of oil-based drilling fluids, and the lost circulation prevention ability of oil-based drilling fluids was significantly improved after adding novel loss prevention materials with a low PPT filtration of 11.4 mL.