Testing and Evaluation Techniques for Drilling Fluids-Shale Interaction and Shale Stability

摘要

Wellbore instability caused by the failure of shale formations represents a major challenge to drilling in the oil and gas industry. Incompatibilities of drilling fluids and shale formations are often the root cause of shale instability or wellbore instability. The most common and effective solution to shale instability is through drilling fluids design and selection, although drilling fluids-shale interaction and shale stability are complex and not well understood. There is no single testing or modeling method to solve this complex shale instability problem. Addressing drilling fluids and shale interaction requires a holistic approach. Geomechanics engineers and mud engineers have the same goal of minimizing shale instability by selecting the optimum mud weight and chemistry, but their methods of addressing shale instability are quite different. This paper highlights and shares with geomechanics engineers some of the important laboratory and well-site testing techniques that are often used by mud engineers for characterizing and remediating drilling fluids and shale interaction. Each testing technique is effective and useful in eliminating or confirming one single attribute of fluids-shale interactions. When these test results are put together, they give a more complete picture and the root cause of shale instability and thus a potential solution options.