Engineered Bottom Hole Assembly Design and Equipment Selection Criteria Prove To Be Key Factors in a Challenging Drilling Environment
Authors: Stronach Graham R. , Voden Gerre S. , Hubbard Jeffrey S. , Ming C. Michael , Northcutt J. Craig 
Published: December 2007

Abstract
In a technically challenging deep well in the Anadarko Basin, the importance of engineered bottom hole assemblies (BHA) and "fit for purpose" drilling equipment were key factors in achieving project success. This paper will discuss the BHA analyses carried out prior to the start of the well, including prediction modeling and contingency considerations. Establishing a unique formation deviation control index for the well bore is demonstrated to be an important element in the decision making process of BHA design. Post-well analysis results are also discussed as are the lessons learned. The importance of establishing and maintaining consistent standards for equipment selection and the subsequent results are discussed. To manage a large amount of data gathered during drilling operations, a new system of data management was employed to ensure that the data gathered was in a useable format, and could be used for concurrent and future operational improvements. The results of field data, computer prediction modeling and the system of data management are discussed in this paper.

Introduction
A non-directional well with a total depth of approximately 25,000 feet to intersect the Hunton formation was planned in the South West New Liberty field of Beckham County, Oklahoma. Twelve previous wells drilled by five different operators in this area were reviewed as part of the planning process for this well. Numerous technical challenges were identified including casing design, completion requirements and well bore instability. Two additional challenges that were identified are the primary areas of focus in this paper, namely:Control of well bore deviation and minimizing dogleg severity. This was a critical concern in particular for the 11–7/8 inch intermediate casing. The control of deviation and dogleg severity was also identified as important factors in minimizing casing wear as the well depth increased.Avoidance of down hole drill stem failures including both drill pipe and BHA components.
Both of the above factors were noted to be serious and costly problems in the offset wells studied. Therefore, the following specific processes were developed and utilized to address these concerns.A model was established for assisting in the prediction of BHA performance. This formed the basis for the decision making process of BHA configuration.Criteria were also established for assessing the suitability of equipment to be used in the drill stem. All drill stem equipment, regardless of the supplier, was assessed in accordance with common and stringent criteria.Equipment evaluation was carried out on location at periodic intervals to review its condition and to determine if changes to its design and inspection criteria were required.Rig site personnel were also given scheduled awareness training, both before and during drilling operations.A data management process was also initiated to capture drilling data and equipment evaluation results during operations. This allowed optimizations to be made concurrent with drilling operations.