Application of New Impregnated Diamond Bit Technology Saves Operator $2 Million Drilling Southern Oklahoma Well

Abstract

Abstract Economic development of deep gas wells, such wells in the Carter-Knox field in Stephens and Grady Counties, Oklahoma, depends on the effectiveness and efficiency of the drilling program. Many costly challenges are encountered while drilling the deep, high compressive strength, abrasive sandstone and interbedded shale in this geologically complex area with high-angle beds, faults, fractures, and depleted formation pressures. Improvements in bit technology have expanded the variety of formations that can be drilled with impregnated bits at penetration rates equivalent to roller cone bits. This technology has helped reduce the risk in drilling operations while improving well economics. A recent well in the Carter-Knox field utilized three new impregnated bits to drill the interval from the third Bromide sandstone (15,000 ft) through the Arbuckle limestone and dolomite (18,700 ft) in 51 days improving well construction time by 35% over the best offset. Previous offset wells required 18 to 20 roller cone, natural diamond and traditional impregnated bits to drill the same interval in 78 to 155 days. The operator reached total depth 21 days ahead of the AFE and $2.07 million under budget. Reducing the dry hole cost more than 30% has positively impacted the development plans for the Carter-Knox field. The operator and a bit manufacturer cooperatively applied new bit technology to an optimized well program to reduce drilling costs. Attention focused on using recently developed impregnated bits that drill shale at penetration rates equivalent to rollercone bits without loss of performance in the hard abrasive sandstone formations. This technology combined with changes in drilling practices has increased the overall average penetration rate, kept the bit drilling on bottom, and replacing multiple bits. The longer bit runs also reduced the number of bit trips limiting potential problems associated with tripping operations through depleted and sensitive formations. Introduction Since the mid 1990's Marathon Oil Company drilled four deep wells in the Carter-Knox field in southern Oklahoma. The operator and a bit manufacturer applied lessons learned from the first three wells to the latest well that reached total depth (TD) in February 2003. A team based approach identified opportunities to aggressively apply recent advancements in impregnated bit technology targeted at: staying on bottom drilling for longer periods of time, drilling the deeper Simpson sand intervals at higher rates of penetration, and reducing the total number of bits and bit trips required to complete the well. When the team implemented the drilling program, drilling time and costs were substantially reduced. The operator reached TD 50 days faster than the best offset well and was over $2 million under the original budget. Field History The Carter-Knox field is located 30 miles west of Pauls Valley, Oklahoma (see Figure 1). Shallow production was first discovered in this field in 1924. In February 1956, the British American Oil Producing Company penetrated the deep Simpson sandstone and completed the first Bromide gas well drilled in the Carter-Knox field. The Simpson sandstone interval consists of multiple sandstone formations: the first, second, and third Bromide sandstone, the McLish sandstone, and the Oil Creek sandstone. The Harrison No. 2 was the deepest producer at the time in Oklahoma, drilling to 15,310 ft in 244 days1. The operator made it through the first, second, and third Bromide sandstone formations without penetrating the McLish and Oil Creek sandstone. By 1957, two additional Bromide wells had been drilled and two more were underway. The Sally Krieger well reached total depth of 17,484 ft. This well drilled through the third Bromide sandstone, the McLish sandstone, the Oil Creek sandstone, and into the Arbuckle dolomite. The operator reached the third Bromide in 220 days and finished the well in the Arbuckle in just over 300 days requiring 256 drill bits.