Synergy Between Poly Vinyl Alcohol and Bentonite in Drilling Fluid Formulation: An Experimental Study

The formulation of a drilling fluid is mostly defined by the type of formation to drill. Ensuring drilling mud's effectiveness before throughout a drilling process implies monitoring its physico–chemical properties, including cake filtration. Cake filtration of a drilling mud can be either good or poor (loss filtration or fluid drag effect) depending on the mud swelling efficiency. A drilling mud made of bentonite (or Barite) still needs the assistance of appropriate additives to carry it to its optimum performance. The present study aims at monitoring the cake filtration of a water-based drilling mud using polyvinyl alcohol (PVA), which is known and used for its swelling abilities. The mud samples were formulated by blending two different types of PVAs (standard & synthetic PVAs) with deionized water at various concentrations (0.0%–0.3%) and 7% of bentonite. pH and density of muds were measured before filtration tests. The cake filtration was evaluated by injecting 10 mL of mud samples at constant pressure into a stainless steel Millipore sigma filter holder 90 mm at a constant pressure of 1.2 MPa. Results show that the addition of PVA increases the mud's acidity with the concentration of polyvinyl alcohol. The observed higher reliable content of the samples with standard PVA was confirmed by their higher density values, leading to lower filtrate productions than the muds samples with synthetic PVA.