Shale-Drilling Fluid Interactions: An Experimental Study to Assess the Impact on Shale Inhibition

The objective of this paper is to discuss shale-fluid interactions while drilling clay-rich shale formations. Shale swelling, dispersion and sloughing are frequently encountered problems that may lead to excessive non-productive time. Comprehensive understanding of the behavior of the shale sample helps in mitigating shale drilling problems. To understand the behavior of a shale sample when exposed to fluids, different types of characterization tests have been conducted starting with mineralogy identification using X-ray diffraction. Testing campaign also included capillary suction time test as well as utilizing nuclear magnetic resonance to study diffusion behavior in shale matrix with and without the presence of shale inhibtors. After carrying out X-ray diffraction and thermogravimetric analyses on shale samples to determine clay content and organic carbon content, a series of shale inhibition and water imbibition tests were conducted using non-inhibitive and inhibitive fluids such as polyamine and potassium chloride brines. This paper provides a review of various factors that influence shale-drilling fluid interactions. It presents a suggested scheme to assess the reactivity of shale in presence of different fluid types. Preliminary results are presented here while it is recommended to conduct further study to validate the use of nuclear magnetic resonance under different conditions to monitor the imbibition/diffusion of water molecules into shale matrix.