Drilling a shale formation is one of the challenges faced by the petroleum industry. Designing the drilling fluid, that reduces the interaction with shale, is important for safe and efficient drilling. This study investigates the new cationic surfactant as a shale inhibitor for the drilling fluid. The main objective of this study is to block the water penetration into the clay layers using the new shale inhibitor and evaluate its performance with commercial shale inhibitors.

To assess the performance of new cationic surfactant two reliable clay sources were considered. The first source is from unconventional Qusiba (Kaolinite) formation in Saudi Arabia and the second is a commercial Bentonite. The effect of new cationic formulation on preventing clay swelling were tested using API dynamic swelling meter at reservoir condition.

Further, X-ray diffraction and SEM analysis were performed to ensure clay stability before exposing it to WBM and after exposure for cation exchange phenomenon, shape and size of the particle and efficacy of water penetration blockage. The results were also compared with commercial shale inhibitor.

The results show that the new cationic surfactant can act as a shale inhibitor as well as water blocking agent. It also showed acceptable performance compare with common shale inhibitors used in the industry, the performance can be further improved by optimizing the percentage of surfactant addition to the drilling fluid. This study provides the new cationic surfactant and proved to have good feature for oilfield applications and the cationity which is helping to reduce the water shale interactions.

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