Investigation of Sodium/Potassium Formate Fluid Properties in Drilling Troublesome Shales and Reservoir Section

Drilling troublesome shales is one of the major problems in drilling operations. Borehole instability during drilling of shale layers results in increasing rig time and consequently increased operational cost. Thus, the correct choice of drilling fluid for drilling shale layers reduces drilling time and cost. One of these fluids is formate fluids. Potassium and cesium formate brines are among the best water based shale inhibitor fluids. Formate fluidsaccording to their inherent properties create very good borehole stability. By the use of formate salts, we can design high density fluids with minimum solid content for drilling shale and reservoir sections. The obtained results showed that formate fluids are stable at high temperatures and show very good shale recovery like OBM. The results show that recovery shale of sodium/potassium formate fluid is higher than that of glycol,silicate, and KCl fluids. Formate fluids showed good compatibility with various kinds of polymers. The result of lubricity test showed that lubricity properties of formate fluids are comparable with other WBM. They do not need any lubricants.