An Aggressive Approach to Reducing Failure-Driven Non-Productive Time in Onshore Drilling Operations
Authors: Everage Jeffery Martin , Altizer Shawn , Roberts Geoffrey Kevin , Kellow Fred 
Published: March 2009

Abstract
In determining the necessity of drill string quality assurance initiatives, an operator must answer two primary questions:What is the probability of failure; andWhat would be the impact, financial or otherwise, of a failure event?
Typically, balancing the answers to these questions with the expense of additional quality management measures has presented a challenge to onshore operators. However the switch to drilling 100% horizontal wells in recent years has served to make it economical to implement a robust quality assurance program. Some of the drivers are:The increase in stress placed on drill string components while drilling horizontal wellsThe increased cost of directional BHAs over vertical BHAsThe increase in day rates for all servicesAvailability of suitable drill string components.
Referencing the questions posed earlier, both the probability and impact of failure events have significantly increased.
To address this issue, an operator drilling in the Barnett Shale region implemented an aggressive quality management plan to reduce risks and expenses resulting from drill string failures. The operator first established a baseline for non-productive time due to drill pipe and HWDP failures, and then tracked the changes in NPT over a two-year period as the quality program was developed and implemented. The primary work scope of the quality consulting company was to ensure that industry-accepted standards (API, Standard DS-1®, etc.) were followed with respect to inspection methods, procedures, and acceptance criteria. Initial quality audits on machine shops, hardbanding applicators, and inspection companies allowed formal documentation of quality gaps and development of individual quality plans for the respective vendors. The program evolved to include an in-house project manager and multiple field technicians for third-party witnessing of inspection, machine shop and hardbanding processes.
At the end of the two-year period, non-productive time due to drill pipe and HWDP failures had been reduced by 47%, with a trend to negligible NPT in the final two quarters of the measurement period. Analysis indicated a significant net savings to the operator when comparing the decrease in non-productive time with the investment in the quality program.

Introduction
In January 2006, Devon Energy's Fort Worth Basin group was experiencing excessive non-productive time (NPT) due to normal weight and heavyweight drill pipe fatigue failures. The failures presented as both tube washouts (Figure 1.a) and tube twist-offs (Figure 1.b), and resulted in significant expense due to additional trip times, side track requirements, and equipment loss. The drilling program initially consisted of seventeen rigs with expectations that the rig fleet would double in size by the end of 2007. The projected increase in activity coupled with the history of failures motivated the operator to consider aggressive approaches to reducing non-productive time and associated costs. With well depths spanning 6,200 to 12,800 feet and spread rates ranging from ﹩30,000 - ﹩70,000 USD per day, any changes implemented needed to balance delivery cost with impact to maximize benefit for the drilling program.