Biodegradable Shale Inhibitors for Water Based Fluids

Abstract

Swelling of shale formations is the main challenge may be encountered during the drilling operations. To address this challenge, the potassium chloride (KCl) is traditionally added as an inhibitor to the drilling mud for controlling its chemical reaction with the shale formations. However, environmental concerns surrounding the non-biodegradability and detrimental effects of chloride ions necessitate the exploration of alternative solutions. This study focuses on evaluating the efficiency of biodegradable and environmentally friendly additives in mitigating the shale swelling. Potassium sorbate, potassium citrate, and potassium bicarbonate are the selective additives with different concentrations (1%-7%). Different tests, including X-ray diffraction and X-ray fluorescence, were conducted to characterize the shale type and determine its chemical composition or the major mineral abundances. Additionally, scanning electron microscopy was employed to analyze the microstructure of shale cuttings and identify the small-scale pore features. Furthermore, cation exchange capacity measurements were performed to ascertain the shale samples' ion exchange capabilities. The effectiveness of the additives was evaluated using the Linear Swell Test. The results revealed that potassium sorbate exhibited a remarkable performance in reducing shale swelling, its consistently yielding the lowest swelling percentage compared to other tested materials. A concentration of 4% of potassium sorbate demonstrated the lowest reduction in swelling that reaches to 3.938%. Additionally, potassium citrate and potassium bicarbonate exhibited swelling rates close to those observed with KCl. The lowest swelling percentage achieved at different concentrations of potassium citrate (4% and 5%) was 12.019%. In contrast, a 11.819% of swelling percent was observed when 5% concentration of potassium bicarbonate was added to the drilling mud. This research introduces innovation biodegradable materials added to the drilling mud for mitigating the shale swelling.