Overview

Last year, this section opened with a statement that tubulars were being asked to do more and more. This was ever apparent at last year’s SPE High-Pressure/High-Temperature (HP/HT) Sour-Well-Design Advanced Technology Workshop in that tubulars are being used in deeper, hotter, and more-challenging environments. In fact, we are trying to do more and more with less and less: drilling with casing, using thinner-walled tubulars downhole, and using less weight offshore.

As a relatively new engineer in this industry, I am still exploring and still asking questions. What fatigue life can we get out of the threaded connection? What materials really are required for the HP/HT application? We need to ask the questions not only for product development, but also for product implementation.

Understanding the fundamentals is an important aspect of all our endeavors, especially if we are trying to achieve “more with less.” There is an appropriate systematic process to evaluate the appropriate use of tubular technology for each application. This process requires not only taking advantage of the modeling and experimental tools available to us, but also an understanding of the mechanics of the application. For example: Are the proper equations or models being used to describe the anticipated behavior?

The papers presented on the following pages and in the additional reading take a step back to help us understand and explore these fundamentals. Materials selection is a key aspect in the tubular-design process, especially in a sour or otherwise challenging environment, and it often requires a balance between longevity and economics. Fatigue arises in nearly every well, from drillstem vibrations to thermal-cycle loading. These two situations also represent different regimes of fatigue behavior: high-cycle (low-stress amplitude) and low-cycle (high-stress amplitude). Other loading scenarios, such as wear, collapse, burst, and buckling, are examined in detail in the additional reading.

Cyclic Mechanical and Fatigue Properties of OCTG Materials
Premium-Connection Design
An Integrated Approach to Accurate Corrosion Prediction

David A. Baker, SPE, is a senior research engineer at ExxonMobil Upstream Research Co. He has worked almost exclusively with tubular technology and has been involved in a variety of projects ranging from thermomechanical to threaded-connection analysis. Baker holds a BS degree in mechanical engineering from the U. of California-Berkeley, an MS degree in applied mechanics from the U. of California-San Diego, and a PhD degree from the U. of California-Berkeley. He serves on the JPT Editorial Committee.

Overview

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