Overbalanced Drilling of Extended Horizontal Sections with Potassium Formate Brines

Abstract

Interbedding of hard shale and sandstone sequences across the Lower Permian ‘Unayzah and Jauf formations of Saudi Arabia which usually occur between 12,900 to 14,600 ft tvd, present unique drilling fluid density requirements such that 90-102 pcf (12.0-13.6 ppg) drilling fluids are often required to mechanically stabilize the shales while only 66-89 pcf (8.8-11.9 ppg) is needed to balance the ‘Unayzah and Jauf reservoir pressures.Review of offset wells drilled with similarly high overbalances indicated that the differential sticking forces effected drilling 5-7/8