fax 01-972-952-9435. AbstractEconomical development of deep oil and gas wells in the Marlow field in Southern Oklahoma requires efficiently drilling a complex geological structure with faulted and highly dipping formations. Operators typically employ conventional motor directional systems to keep inclination to a minimum in the 8-3/4" vertical hole section. While this type of bottom hole assembly (BHA) has improved directional control, it still leads to unacceptable angle building tendencies/dogleg severity and poor vertical hole quality resulting in additional directional issues in subsequent hole sections. In addition, the conventional directional assembly increases well costs due to multiple deviation correction runs with different BHA configurations resulting in more flat time, lower cumulative bit penetration rate, and more bits/runs per section.To address these issues, the service company studied drilling performance, mud logs and wireline data from offset wells. The resulting analysis detailed the key problems and led the operator to set new objectives for the 8-3/4" vertical hole section of achieving the highest possible rate of penetration (ROP) while maintaining a near-vertical wellbore. An implementation strategy was outlined that had two main components including a sophisticated vertical drilling system (VDS) with a new polycrystalline diamond compact (PDC) bit technology.This approach has been utilized to drill the 8-3/4" hole section on two wells with the following results: Reduced inclination from 22º to 1.5º (VDS) and reduced dogleg severity (DLS) from 4º/100ft to just 1º/100ft (VDS). The new system has also reduced torque/drag and delivered a smooth quality wellbore and totally eliminated costly correction runs. The increased wellbore quality has allowed the operator to log, then set 5 ½" casing without incident. The operator has experienced increased performance when kicking off below a section drilled with the new BHA (VDS/bit) improving directional control and aiding geosteering to the target reservoir.

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.

fax 01-972-952-9435. AbstractEconomical development of deep oil and gas wells in the Marlow field in Southern Oklahoma requires efficiently drilling a complex geological structure with faulted and highly dipping formations. Operators typically employ conventional motor directional systems to keep inclination to a minimum in the 8-3/4" vertical hole section. While this type of bottom hole assembly (BHA) has improved directional control, it still leads to unacceptable angle building tendencies/dogleg severity and poor vertical hole quality resulting in additional directional issues in subsequent hole sections. In addition, the conventional directional assembly increases well costs due to multiple deviation correction runs with different BHA configurations resulting in more flat time, lower cumulative bit penetration rate, and more bits/runs per section.To address these issues, the service company studied drilling performance, mud logs and wireline data from offset wells. The resulting analysis detailed the key problems and led the operator to set new objectives for the 8-3/4" vertical hole section of achieving the highest possible rate of penetration (ROP) while maintaining a near-vertical wellbore. An implementation strategy was outlined that had two main components including a sophisticated vertical drilling system (VDS) with a new polycrystalline diamond compact (PDC) bit technology.This approach has been utilized to drill the 8-3/4" hole section on two wells with the following results: Reduced inclination from 22º to 1.5º (VDS) and reduced dogleg severity (DLS) from 4º/100ft to just 1º/100ft (VDS). The new system has also reduced torque/drag and delivered a smooth quality wellbore and totally eliminated costly correction runs. The increased wellbore quality has allowed the operator to log, then set 5 ½" casing without incident. The operator has experienced increased performance when kicking off below a section drilled with the new BHA (VDS/bit) improving directional control and aiding geosteering to the target reservoir.

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