Shale Inhibition: What Works?

Abstract

Abstract Understanding the behavior and responses of shale to shale inhibitor additives of drilling and completion fluids has been a challenge for many years because of the numerous and complex chemical and physical variations present in these type of formations. This paper presents the results of laboratory experiments that show how the integration of the geological aspects can help to understand the different responses of the shale to fluids and improve the selection of chemical additives for clay inhibition. Many of the chemical inhibitor additives have been developed in the laboratory through systematic methods with the use of "standard clay-rich rock samples". These rock samples have relatively simple geologic characteristics and predictable behaviors. The responses of these types of rock samples tend to be consistent and appropriate for evaluations where chemistry of the additives is manipulated constantly. However, the application of these additives goes beyond this approach. In the field, applications target formations that can vary significantly in composition and structure, and simplicity is an uncommon condition. Therefore the challenge for clay stabilization is to integrate many more aspects that can influence the response of the shale formation to fluids. The paper will present the preliminary process of analysis and understanding of the geologic characteristics of the rock samples and the importance of this fundamental step to achieve the chemical clay stabilization objectives. The paper will include various cases of the inhibitor selection process for shale samples with different characteristics. Chemistry and geology perspectives will be used to analyze the results of the experiments including cases with typical and atypical responses of shale samples. This approach is used to provide a more comprehensive and meaningful interpretation of the rock structural failures due to rock/fluid chemical interactions and, in the same manner, explain how chemical solutions can be used to minimize and control rock instability.