Shale Swelling Inhibition Properties of (Carboxymethyl)trimethylammonium chloride (CTAC) in Water-based Drilling Fluids

One of the most important challenges during drilling an oil or gas well is dealing with shale formations and the sub-sequent shale swelling. In this study, we utilized Carboxymethyl Trimethyl Ammonium Chloride (CTAC) to inhibit shale swelling, representing a novel application for this particular cationic surfactant. Several experiments were carried out to assess the effectiveness of CTAC in preventing shale swelling and to gain insights into the underlying mechanisms. Moreover, based on the results, CTAC is highly effective at low concentrations and can be used with other common additives. Furthermore, the contact angle in the presence of CTAC, cetyltrimethylammonium bromide (CTAB), and potassium chloride (KCl) at 1 wt.% in the bentonite mixture was 77°, 75°, and 38°, respectively. Also, by adding CTAB, total shale recoveries in simple and complete drilling muds increased by 5.53% and 0.94%, respectively. Meanwhile, In the presence of CTAC, the increase was equal to 12.37% and 6.43%, respectively. In addition, CTAC and CTAB in the complete drilling mud reduced the swelling by 9.94% and 4.2%, respectively. Ultimately, comparative studies show that CTAC performs better as a new inhibitor than CTAB and KCl as conventional inhibitors.