Increasing BHA and wellbore complexity create a need for case specific engineering modeling software. Hence, mathematical modeling of the mechanical and dynamical behaviour of BHAs under various downhole conditions such as different wellbore curvatures has become routine. This paper discusses an advanced engineering model and the verification of its predictions with downhole measurements. First the mathematical model and the downhole dynamics measurement sub are introduced. Next, three examples comparing measured and predicted steady state bending loads are presented. While the predicted and measured results match well, detail and accuracy of input parameters such as wellbore curvature are proven essential. Lateral natural frequencies of the model are compared to the peaks in the measured frequency spectrum. In conclusion, the general validity of the model regarding bending loads and vibrations is evaluated. Backward whirl dynamics is evaluated by comparing downhole measurements with time domain model simulations. The predictions meet the downhole measurements both in frequency and magnitude. Introduction The benefits of applying mathematical models to analyze the mechanical behaviour of bottom hole assemblies (BHAs) in the design phase prior to actual drilling operations are obvious. A multitude of different downhole scenarios can be investigated very efficiently leading to an optimized bottomhole assembly design which is not susceptible to mechanical failures related to high static or dynamics forces exceeding the specifications of the downhole equipment. However, this approach will only be successful if the model can be trusted and its predictions are accurate. As such, the verification of a mathematical model with field measurements and observations are a key requirement. In the past, surface dynamics measurements were used to verify model predictions[1,2,3]. However, the problem with surface measurements, in particular in the case of lateral vibration problems, is that the measurements are taken at a huge distance away from the point where the vibrations actually occur. As such, the accuracy and applicability of these measurements for verification purposes are limited mostly to axial and torsional vibration problems. Earlier publications have shown that the verification process can be significantly improved if surface and downhole measurements are available[6,7]. Today, advanced downhole dynamic measurement subs are routinely used in drilling operations[4,5]. These subs measure the actual downhole forces including the downhole bending loads and provide an ideal data source for the verification of mathematical BHA models. This paper focuses on an advanced mathematical model capable of predicting the bending load of a BHA and its verification with downhole bending moment measurements. The paper starts with an introduction of the mathematical model and its application modes: static load prediction, natural frequency analysis and detailed time domain simulation. A short overview introduces the downhole measurement sub with focus on the downhole bending moment measurement. In the main part of the paper several examples are presented where the model predictions are compared with equivalent downhole measurements. The accuracy of the model predictions, the source of observed disagreements and the limitations of the mathematical models are discussed. Mathematical Model The theory behind the mathematical model used in this paper is described in detail in reference 8. The model is based on the finite element method utilizing a geometrically nonlinear three dimensional beam element. This beam element is character-ized by its outer and inner diameter, its length, its modulus of elasticity and its density. More complex cross sections can be modeled by defining equivalent stiffness and mass correction factors.

The paper shows that a downhole bending moment measurement combined with a simple mathematical model can provide a good estimate of the wellbore curvature, matching the results obtained from survey data analysis quite well. In addition, the bending moment measurement delivers wellbore curvature information at a much higher resolution than the standard Minimum Curvature method, which assumes a constant curvature between the survey stations. The paper presents numerous examples of downhole bending moment data measured in deployments with both rotary steerable and steerable motor BHAs and compares the dogleg severity estimates from the bending moment data with the dogleg severity derived from the survey measurements. Accuracy and limitations of the measurement and the model predictions are discussed. The paper also introduces a new method of analyzing cyclic hole effects applying FFT techniques to the depth-based bending data. Introduction Any drilling bottom hole assembly (BHA) in a directional wellbore is subjected to bending moments due to side forces acting on the BHA. These side forces may be caused by gravity, by dynamic effects, or by wall contacts of the BHA in curved wellbore sections. In the past, mathematical models have been developed5 to predict the side forces, bending moments and stresses that are introduced into a BHA in a given borehole curvature profile, usually derived from measured survey data. This paper discusses the application of mathematical models in the opposite direction: to predict the borehole curvature from measured bending moment data. The bending moment data have been acquired with a recently introduced drilling dynamics tool3 in a variety of different applications and tool configurations including rotary steerable systems (RSS) and steerable motor BHAs. The bending moment data can be both transmitted to the surface while drilling and recorded in on-board memory for post-run processing and detailed analysis. Bending moment data recorded during directional drilling operations have been published in 1989 by Cook et al.6; however, their analysis was limited to some qualitative statements. Hood et al.7 demonstrated recently how real-time bending information can successfully reduce the risk when drilling hard interbedded formations with an increased tendency to develop high local doglegs at the formation interfaces. Dogleg Severity The drilling industry uses the term dogleg severity (DLS) to describe the total curvature of a directional wellbore. The dogleg severity is derived from the directional survey data as explained in detail in Appendix A. All DLS calculations from survey data in this paper are based on the Minimum Curvature method. Here, the well path between two survey stations is assumed to be a circular arc with constant curvature, i.e. constant dogleg severity. Appendix B shows that the bending moment data constitute a measurement of the curvature of the BHA at the point of the bending moment sensors. With the assumption that the curvature of the BHA does not differ significantly from the curvature of the wellbore the BHA is in, an estimate of the wellbore curvature is obtained. The goal of this paper is to demonstrate the validity of this assumption for a variety of cases and to discuss the influencing parameters. The examples in the next section compare the DLS calculated from the survey data with the DLS estimated from the bending moment data. For better readability, the terms survey DLS and bending DLS are used from hereon. A sensitivity analysis in the section after next illustrates the influence of various factors on the accuracy of the bending DLS estimate.

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In today's robust hydrocarbon markets, complexity and volume of drilling and evaluation activity have grown to unprecedented levels. This is driving technology development and new application practices at a record pace. At the same time, the industry is struggling to grow the talent base to manage the increased workload. These issues have resulted in a need to track and ensure application engineer and geoscientist competency levels. To solve this challenge, the company developed a detailed process for individual competency assessment and employee development for various application disciplines. Certification is awarded in set disciplines when the necessary criteria have been met and competence has been successfully demonstrated to a technical experts' review panel. The required competencies for each discipline were developed from the expanded job functions expected of the experienced senior applications engineers and geoscientists, as well as expectations of the services provided in each discipline. From this, a competency assessment and tracking methodology was created. The methodology enables the assessment of an individual engineer's competency level so a tailored development program of training and mentoring can be developed. A formal mentoring system plays a vital role in the certification process. Assigned mentors offer valuable engineering and process guidance. The authors will describe a certification process and a methodology for competency assessment and tracking for application engineers and geoscientists. Finally, the authors will discuss how the program benefits raise the level of the company's technical expertise. Introduction Industry demands for the optimized application of drilling and evaluation technologies have led to challenges in developing and hiring application engineers and geoscientists with suitable competency levels. These challenges are attributable to the limited number of skilled industry professionals and the increased volume of drilling activity. For large companies, there is the added issue of tracking and understanding the skill level of its technical staff. These companies must ensure the knowledge of their application engineers and geoscientists is sufficient to successfully manage the industry's complex technologies. The lack of skilled application engineers and geoscientists affects oil companies and service suppliers. For oil companies, lack of optimization results in higher costs through an increased number of drilling days and/or reduced borehole quality, leading to delayed or reduced production. Service companies, as the suppliers of technical solutions, must ensure their products are used efficiently; otherwise, they run the risk of low performance and poor perception of their technologies. This, in turn, leads to rejection of services, which can be very costly when R&D for failed technologies is taken into account. The limited number of skilled industry professionals is a well-known issue. The Society for Petroleum Engineers (SPE) estimates that between 1980-1998, the industry staffing levels fell to 300,000 from 700,000. As of December 2006, the median age of all SPE members was 47. The industry is expected to experience a 44% attrition rate among petroleum engineers by 2010; more than 200,000 years of cumulative experience and knowledge will be lost in the next 10 years because of retirement. Almost half of the workforce will be new to the industry.1In an attempt to fill staffing gaps, companies are giving application engineering and geoscience disciplines expanded job functions. The complexity of solutions for optimized drilling and evaluation requires a full understanding of the technologies and the total drilling environment in which they can be applied. These professionals must have skill sets that span traditional drilling engineering and oilfield geoscience disciplines.

fax 01-972-952-9435. AbstractIn today's robust hydrocarbon markets, complexity and volume of drilling and evaluation activity have grown to unprecedented levels. This is driving technology development and new application practices at a record pace. At the same time, the industry is struggling to grow the talent base to manage the increased workload. These issues have resulted in a need to track and ensure application engineer and geoscientist competency levels. To solve this challenge, the company developed a detailed process for individual competency assessment and employee development for various application disciplines. Certification is awarded in set disciplines when the necessary criteria have been met and competence has been successfully demonstrated to a technical experts' review panel.The required competencies for each discipline were developed from the expanded job functions expected of the experienced senior applications engineers and geoscientists, as well as expectations of the services provided in each discipline. From this, a competency assessment and tracking methodology was created. The methodology enables the assessment of an individual engineer's competency level so a tailored development program of training and mentoring can be developed. A formal mentoring system plays a vital role in the certification process. Assigned mentors offer valuable engineering and process guidance.The authors will describe a certification process and a methodology for competency assessment and tracking for application engineers and geoscientists. Finally, the authors will discuss how the program benefits raise the level of the company's technical expertise.