Review of PDC Bits Run With Invert-Emulsion Oil Mud in Shallow South Texas Wells

This paper examines 56 polycrystalline-diamond-compact (PDC) bit runs, discusses the evolution of the PDC bit, and recommends guidelines for selecting the most economical bit design for shallow south Texas wells drilled with invert-emulsion oil mud. From March 1981 to April 1984, our South Texas Div. Drilling documented 88 PDC bit runs with invert-emulsion oil mud in shallow south Texas wells. These PDC bits primarily drilled soft Frio formations of sand and shale to less than 12,000 ft (3660 m) total depth (TD). Throughout this time, PDC bit design continually improved, providing progressively greater time and cost savings. Field data indicated that improvements in bit material, body design, cutter placement, and operating procedures have increased rates of penetration (ROP's) and bit life, thus decreasing drilling cost.