New hard formation roller cone bit technology improves economics of abrasive Travis Peak, Cotton Valley wells

The typical gas wells drilled in heavily explored Panola County of East Texas encounter the highly abrasive Travis Pcak and Cotton Valley formations at around 6.300 ft. The Travis Peak is normally reached at 6,300 - 6.500 ft, followed by the Cotton Valley from 8,0000-8,3000 ft to TD. The Travis Pcak and Cotton Valley are each about 1,700-2,000 ft in length. Until recently, the extremely abrasive sections in these formations severely limited the life of the IADC Class 537 through 737 roller cone bits used to drill these wells. Between severe gauge and cutting structure wear. the bits run previously were normally pulled after about 600 ft of drilling. The shortened life meant six to 10 bits were required to complete the two intervals. This paper describes the design and application of new hard formation rock bits that are drilling up to 50% more footage than the 627 and 737 types run previously. The new IADC Class 647 and 747 roller cone bits incorporate new inscrt geometries and quantities. along with improved carbide grades and diamond-enhanced gauge protection. Today, the Travis Peak and Cotton Valley are being drilled with four bits, averaging more than 850 ft per bit. Along with the new bits, a revised mud program consisting of low-solid polymers contributed to the improved performance realized in recent Panola County wells. The authors will review the design process of the new bits, as well as presenting case studies of typical Travis Peak and Cotton Valley wells in Panola County and elsewhere in East Texas.