Environmentally Friendly Water-Based Drilling Fluid for Drilling of Water-Sensitive Formations

Drilling of shale and clay-rich geological formations are always challenging because of their instability and water sensitivity. Oil-based drilling fluids (OBDF) are widely used in drilling operations, especially in highly technical wells. OBDF systems perform much better than water based drilling fluid (WBDF) in borehole stabilization and they allow faster penetration rates. Additionally, one of the most important features of OBDF is its high lubricity especially for deviated wells. Although OBDF prevents many problems of drilling the shale formations, they have negative impacts on the environment. So, there are many efforts to replace them by a water based and environmentally friendly drilling fluid. In this research, by investigation of drilling history and according to the results of studies accomplished on Iranian shale formations, a water-based and environmentally friendly drilling fluid has been developed. This fluid has improved properties such as high filtration control, reduced formation damages, diminished clay activities, stability against high temperature, cutting stability, acidity alteration and compatibility with any contaminations which may be entered to the drilling fluid during the drilling operations. Lubrication and cutting (shale cuttings) removal of this developed fluid are superior. New additives containing meshed solid particles, inhibitive agents and synthesized polymers were used to develop this fluid