Drilling efficiency must be improved, in order to drive down operational costs. This requirement must not be viewed in isolation, considering the vast number of activities that determine a drilling program's success. In most instances, discussions relating to drilling efficiency have centered on rate of penetration (ROP)1,2. As a result, ROP is either equated to drilling efficiency, or seen as the parameter that establishes drilling efficiency. These positions, in addition to being flawed, are highly inconsistent with field results. ROP must not be equated to drilling efficiency. Rather, ROP needs to be seen as one of several parameters that influence drilling efficiency. The industry's most common performance quantifying metrics - cost per foot (CPF), feet per day (FPD), mechanical specific energy (MSE)3,4, etc - are strongly influenced by ROP. These relationships complicated earlier efforts that sought to establish the appropriate dependencies, between drilling efficiency and ROP. To drive down operational costs, while continuing to push drilling activities into harsher and more challenging environments, emphasis must clearly be placed on drilling efficiency. Thus, in order to achieve this goal, drilling efficiency and ROP must both be defined. In addition, the factors influencing ROP and drilling efficiency must be identified. Most importantly, drilling efficiency's different influencing factors5, which include but are not limited to ROP, must always be analyzed based on specific project objectives. This paper, in addition to addressing the issues listed above, will also establish a clear distinction between drilling efficiency and ROP. In addition the contributions and impact of both ROP and drilling efficiency, as it relates to value creation will be discussed. The positions, to be presented and argued, will be supported with field and operational data.

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Deepwater Gulf of Mexico wells are generally deep and they may incorporate casing designs that provide only a single-casing barrier between the wellbore and the formation. These aspects present unique issues and risks in regard to casing wear. The extreme depths (>30,000 ft) of many wells in the Gulf of Mexico create the potential for high side loads imparted by the drillstring to the casing, even with low doglegs (1.0°/100 ft or less) in the upper part of the well. This, combined with potentially high rotating hours, particularly on exploration wells with sidetracks, creates the potential for casing wear that exceeds allowable limits. In order to proactively manage and mitigate casing wear during drilling operations, Chevron has developed a Casing Wear Monitoring standard operating practice (SOP). Deployment and application of this SOP has proven effective. Application of this SOP indicates that casing wear can be predicted, managed, and/or mitigated with proper planning and execution. This paper illustrates a casing wear event on a Chevron well and provides an overview of the Chevron Deepwater Casing Wear Monitoring SOP. Additionally, the paper highlights some casing wear processes, well control issues, and environmental risks that are unique to deepwater wells. Application of the casing wear prediction and monitoring procedures outlined in this paper help to ensure that the integrity of the casing is maintained during drilling operations, thereby reducing the risk of a health, safety and environment event or loss of the well due to excessive casing wear.

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Downhole drilling tools1,2, continue to see improvements in reliability, leading to extended mean times between failures (MTBF). Drive systems, specifically positive displacement motors (PDM), rotary steerable tools (RSS), and turbines have seen extensive improvements in MTBF. Consequently, technical successes on directional drilling programs, where such drive systems are commonly used have also improved. However, these gains do not always translate into meaningful operational success4, which is needed to drive down drilling costs. This situation is caused by some of the industry's perceptions and approach to drilling system design. Additionally, it is influenced by how projects are analyzed, and sometimes interpreted, with regards to performance drilling expectations. This paper will discuss three types of success – technical, mechanical, and operational. It will also identify and discuss the reasons why gaps still exist between technical and operational success. In addition, evaluation processes developed to bridge the gap between technical and operational success will be discussed. Multiple case histories, highlighting the impact of the concepts and evaluation processes to be discussed in the paper, will be presented.