Blend of Pre-Treated Lignocellulosic Biomass and Bentonite As Water-Based Drilling Fluid: Preparation, Characterization and Testing

Products from lignocellulosic materials have the potential to be used as substitutes for (or complement to) some of the oilfield chemicals. This study reports the outcome of a preliminary study of their effects on the performance of water-based drilling fluids containing bentonite.

Methodology

Date pit was used as a representative lignocellulosic material. Pretreatment was performed by dispersing 4g of the pit in 20ml of concentrated HCl (38%) at 35^oC under constant stirring of 500rpm for 5hours. The resulting sample was then used for drilling fluid preparation. Tap water (350ml), commercial bentonite (22.5g) and 1-20wt% of the pre-treated lignocellulose was used for the preparation. Filtration, density, and rheological properties of the formulations were evaluated using the API test procedure. Physico-chemical properties were also studied using TGA, SEM, XRD, size analyzer, and FTIR.

Results and Observations

Physico-chemical analysis of the pretreated additive showed that the chemical structure of the material is still intact. However, the pretreatment loosens up the structure of the material by distrupting its crystalline regions. In the case of filter cake removal with enzymes, the de-crystallization will increase the surface area and the porosity of the lignocellulose making it more available for attack by the enzyme. The sample containing 20wt% of the lignocellulose material has filter cake thickness of 0.167cm (compare to 0.192cm of the commercial bentonite) and filtrate volume of 14mL/30min (which is less than the API recommended maximum filtrate loss of 15mL/30min).

Conclusions

This work presents a new lignocellulose-based additive with a unique property that makes it a good candidate for facilitating filter cake removal, mitigate formation damage, and make drilling fluid less toxic. The additive can be made from cheap locally available resources. It could, therefore, serve to minimize the oil production costs that are associated with drilling fluids.