Assessment of KCl Inhibition Efficiency in Water-Based Drilling Fluids: A Formation-Responsive Approach for Shale Stability
Yasser Ali Abdulhameed, Jagar A. Ali, Lokman A. Abdulkareem
Abstract
High Resolution Image Download MS PowerPoint Slide Drilling activity in the Kurdistan Region of Iraq is challenging because of the swelling behavior, dispersion of particles, and mechanical breakdown of shale, which is subjected to exposure to common water-based drilling fluids (WBDFs). This research examines the role of KCl-based inhibitive-WBDFs through the Gercus, Sarmord, Chia gara, Garagus, Naokelekan (CG-G-N), and Baluti Formations. Inhibitive-WBDFs were developed by mixing several additives in deionized water (DW) along with 1 and 2 wt % KCl, which were subjected to rheological testing, linear swelling measurements (LSM), hot-rolling dispersion, filtrations, and bulk hardness. The results demonstrate that the fluid loss of the drilling fluid containing 2 wt % KCl (WBDF-KCl-2%) used with the Baluti Formation is the lowest compared with other drilling fluids, which are 4.8 and 9 mL for the LPLT and HPHT, respectively. Meanwhile, the Sarmord Formation exhibited the highest filtration rates of 8.5 and 15.9 mL at LPLT and HPHT conditions, respectively. The Gercus Formation, which mostly contains smectite and palygorskite along with a cation exchange capacity (CEC) of 6.5 mequiv/100 g, produced severe swelling of 6.23–6.45% LSM and low bulk hardness of 130–140 psi. Meanwhile, the Baluti Formation, containing the vermiculite and glauconitic clay types with a CEC of 1.75 mequiv/100 g, exhibited the lowest shale swelling rate of 0.16%, 91.51% recovery, and 250 psi bulk hardness when exposed to WBDF-KCl-1%. These results demonstrate that the optimum inhibition depends on fluid formulation, shale mineralogy, and CEC. Although KCl at a low concentration of 1–2 wt% was highly effective in minimizing shale swelling, its role was not universal for all study formations. Thus, it can be stated that the formation response to KCl-based WBDFs affects the inhibition efficiency for swelling prevention, which strongly depends on mineralogy and CEC.