The current focus of many US land drilling programs is on major unconventional gas shale plays. In this paper, the authors will discuss the challenges posed by and effective solutions developed for wells drilled in one of these plays: the Marcellus Shale. In response to the economic, real-estate, water disposal, and regulatory challenges the Marcellus Shale presents, multiwell pads have become a common approach. Historically, the Marcellus and Appalachian Basin has been developed using inexpensive, vertical wells drilled using the latest technologies and techniques. While some of these options are still viable, changing conditions make proper surveying and anticollision monitoring imperative. The pad design, surveying, preplanning, and execution of successful multiwell pad drilling require extensive collaboration between service providers and operators, a process that will be addressed in this paper.

Inconsistent roller cone/PDC bit performance drilling horizontally through the hard/abrasive Granite Wash reservoir in western Oklahoma has resulted in low ROP, increased operating days, and escalating drilling costs. The difficult Marmaton age wash formation is encountered at 11,000-13,000ft TVD and has unconfined compressive strength (UCS) in excess of 30,000 psi. The typical well requires drilling a curve to horizontal, then 4,000 ft of 6-1/8-in lateral borehole. Offsets analysis revealed that 1-4 RC/PDC bits are required to drill the curve in addition to 1-13 bits to finish the lateral. The operator required a technological solution to minimize bit consumption/trips to lower well construction costs while achieving directional requirements. An analysis of the most troublesome wells was conducted and a mathematical-based predictive analysis software identified the changes required to efficiently deliver the directional objectives. The study indicated that using a 4¾-in high-power steerable turbodrill, with two bends and a specific stabilization setup coupled with an application-specific 6 1/8-in diamond impregnated bit would significantly increase BHA performance and enhance section economics. The operator's drilling team studied the recommendation and concluded the BHA had the potential to increase reliability and reduce operating costs drilling the difficult Marmaton Wash. This new turbodrill/impregnated bit BHA was run in several Washita and Beckham County wells with outstanding results. In one well the BHA drilled 4,040ft of 6 1/8-in lateral hole section in a single-run saving the operator eight drilling days and $348,000USD vs plan. The assembly required steering only 17% of the time. The borehole was completed in 589hrs at an average ROP of 6.9ft/hr. This performance set several new world drilling records. The authors will present case histories that illustrate performance achievements in the horizontal section and provide details that contributed to the success of the unique BHA.