Benchmarking Roller Cone Drill Bit Performance in Prudhoe Bay Directional Wells
Authors: Brown L.A. , Stoltz D.S. , Nims D.G. 
Published: December 2007

A simple approach to analyzing bit performance in directional and horizontal wells has been applied successfully on the Prudhoe Bay Unit of Alaska's North Slope. This paper presents a methodology that has enabled Shared Services Drilling (BP and ARCO) to establish performance benchmarks that have resulted in optimizing the bit selection process in North America's largest oilfield. The approach has resulted in a cumulative cost savings of more than $5 million over the past two years, when compared to the prior year.

Optimizing drilling performance was seen as critical to lowering the development cost per barrel in this mature field. More specifically, the operators recognized that developing a standard approach to evaluate bit performance could play a significant role in meeting that objective. Previously it was difficult to accurately compare bit runs in the field, because of the numerous variables that effect performance in directional applications, thus everyone had their own opinion of which type of bit was working the best. Variables such as the direction the well was drilled into the dipping formations, the amount of directional work required, the type of motor used and whether the rotor of the motor bit was jetted with a nozzle, made it difficult to quantify which bit/s were yielding the best performance. By setting Performance Benchmarks from bit records, enhanced with TVD data, the authors were able to quantify the present level of performance. The authors will present and analyze the methods used to evaluate bit performance data in directional wells. Further, the procedure used to challenge the benchmark to facilitate continuous improvement will be discussed in detail.

Introduction

Shared Services Drilling (SSD) is a consortium of BP Exploration Alaska and ARCO Alaska. Since its formation in 1992, SSD has been responsible for all rotary drilling engineering and supervision in Alaska's Prudhoe Bay Unit (PBU), North America's largest field (Fig. 1). Various alliance partners, as well as independent consultants, supplement the drilling staff consisting of BP and ARCO personnel.

The fashioning of alliances is an integral part of SSD's wide-ranging efforts to lower development costs on the mature North Slope. Industry-wide, alliances have become universally accepted vehicles for improving the drilling process. Lowering recovery costs per barrel is the ultimate objective of any alliance, and as several authors stress, improving processes is the first step toward achieving that goal. Accordingly, much emphasis has been placed on continuously improving all aspects of the drilling process. A starting point is the establishment of performance benchmarks. Be it producing automobiles or drilling wells, benchmarking processes and performance and establishing guidelines for exceeding the accepted standards are essential to the continuous improvement process. With that in mind, SSD initiated a standardization process, aimed at setting performance benchmarks to guide the selection and application of drill bits used in the Prudhoe Bay Unit.

Bit costs relative to the base costs of drilling a well represent a minimal expenditure. Yet, their performance can significantly impact final well economics, as evidenced by a recent analysis of more than 100,000 bit runs worldwide. The analysis, representing all manufacturers, concluded that up to 36% reductions in overall drilling costs can be attributed directly to the performance of contemporary bit designs.

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