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Analysis of BHA Configuration for Deviated Well to Investigate their Response to the Bit during Well Trajectory Development

Leedham, Robert

Engineering Honours Degree 2007

University of Adelaide


With today's climate in the drilling industry we are again appreciating the importance of sound Bottomhole assembly (BHA) analysis techniques. Borehole trajectories are becoming more and more complex and the need for these trajectories to be increasingly accurate but also flexible is one of the driving factors behind the need for advancements in the understanding and development of BHA analysis. Other current climatic factors such as "the current market's high prices for drilling units and sophisticated directional and formation assessment services, low systems reliability or poor directional performance in the execution of complex wells (Extended Reach Drilling (ERD), High Pressure and High Temperature (HPHT) conditions, Deep water Applications) can spell costly Non Productive Time (NPT) for operators, (Studer, 2007). These factors are all motivating the push for an increase in the reliability and accuracy of BHA analysis, and hence a change in the approach to directional control of the BHA.

This paper is an attempt to present a logical progression from the factors that impact on the steerability and directional tendencies of a BHA to the methods that allow these factors to be calculated and then used in the industry.

This paper is primarily based around an in depth literature survey designed around forming the basis of what a suitable method for analysing the BHA should contain and what it should supply to the user. The literature survey leads into findings concerning the various methods used for the analysis of the BHA and their suitably given the benchmarks that the industry currently has.

An appreciation can be gained for the multitude of considerations that are needed for a proper BHA analysis, and hence the required complexity of an extensive BHA model. I have also attempted to demonstrate the ease at which a simple model for BHA analysis can be constructed using simple modelling methods in Microsoft Excel. A brief investigation into a method presented by Jiazhi has provided the understanding that even an amateur can construct a simple BHA model that can allow the user to get an understanding of the directional tendencies of various BHA with varying operational conditions on them. On the contrary though, the value of the simple BHA model that can give the user the directional tendencies of the BHA is small in comparison to an in depth program that can give the user the exact direction, location and projected location of the wellpath.

A brief glance at where the industry currently stands in terms of its directional drilling programs and technologies was also conducted in order to gain an appreciation for where the industry has progressed from and where it currently stands. This has helped to provide a basis for the reasoning and ideas behind the methods in use today and their origin. Through this brief investigation, trends in the industry have become apparent.

It can be recognised that if all factors are considered and the proper modelling is undertaken then an Ideal Performance can be hoped for. Ideal performance can be regarded as reaching all objectives in relation to successfully modelling the BHA and gaining all the required outputs to act on the models analysis. An interactive, computationally efficient and accurate BHA analysis program that is able to supply suitable BHA setups for a given wellpath would be the ultimate result of a well thought out BHA model.

I personally see that the natural progression of attempting to find a suitable method for BHA analysis leads into creating suitable programs for the industry that rely on these methods. Without this in mind we can lose appreciation for the benefits that are gained from each different method. Throughout the reading it is demonstrated that by having the proper methodology, or combined methodology, the final model/program can be very valuable when implemented in field applications.

Australian School of Petroleum



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