Shale-Fluid Sensitivity for an Unconventional Shale Formation

Abstract

Abstract Shale instability is a major problem for drilling operation. Shales make up over 75% of drilled formations and are responsible for 90% of wellbore instability problems. There are many problem associated with shale drilling such as wellbore instability, cuttings dispersion, stuck pipe, and bit balling. Shales used to be the problematic formations that needed to drill through with the minimum number of problems, lowest possible lost time and generally the shortest possible open-hole time to minimize fluid sensitivity issues. However, with the advancement in drilling and production techniques, some shale formations are now the target for hydrocarbon production, meaning that much longer periods of open-hole are required for horizontal drilling, logging and completion meaning fluid sensitivity is an increasingly important question.. In this paper, we evaluate the shale-fluid sensitivity of a target unconventional shale formation. A total of 20 samples from 6 different wells were used in this study. The mineralogy of all 20 samples were analyzed using XRD. Then two shale-fluid sensitivity tests (dispersion test and capillary suction time test) were run on the samples using four different water based fluids (7% KCl, 3% KCl, 3% NaCl, and 5% NH4Cl) in addition to fresh water and diesel which were used to establish bounding parameters. Overall, all inhibitors performed well, with 7% KCl and 3% KCl being the best performing inhibitors for drilling shale formations of this composition followed by 5% NH4Cl and lastly 3% NaCl.