Optimization of Water Based Drilling Fluid Produced Using Modified Nigerian Bentonite and Natural Biopolymers: Reduced experiment and Response Surface Methodology

Research has shown that many Bentonite in Nigeria are unsuitable for oil well drilling in their natural states. Their modification and blends with some additives could increase the yield and boost their suitability. Many indigenous polymers have become very popular due to environmental friendliness and their ability to modify rheology of clay suspension. However, the common natural polymers are characterized with excessive fluid loss, low gel strength at typical reservoir conditions. The aim of this study is therefore to examine the influence of selected polymers on the physicochemical and rheological properties of Nigerian clay-water suspension. Mud samples were prepared with polymers according to mud formulations currently used in the wells drilling with properties varied and optimized in a Reduced Central Composite Design (RCCD). The physico-chemical (pH, mud weight), rheological (plastic viscosity, yield point) and fluid loss were measured out on the studied muds. The results show that, the rheological characteristics of studied muds (PV (19.4 ± 1.50 cp) and Yp (21.5 ± 0.79 lbf/100ft2), the Fluid loss (10.12 ± 0.45 ml/30 minutes/100 psi) and 10 min and sec Gel value (4.6 ± 0.05 and 5.1 ± 0.01 lb/100ft2) were clearly improved. However, the mud weight values recorded (8.6 – 8.9 lb) though satisfied the minimum 8.6 lb/gal ceiling value but was due to the local barite that this study evaluated. The barite is characterized with low specific gravity and we recommend its modification prior to use to avoid high sand content.