Activation of Local Bentonitic Clays for Use as Viscosifiers in Water-based Drilling Fluids

Activated locally sourced clay as replacement for imported commercial bentonite for use as viscosifiers was studied. Tests and analyses were performed on local clay samples obtained from five (5) locations: Ini, Ibiono, Ikono, Itu and Uyo Local Government Areas in Akwa Ibom State of Nigeria. The mineralogical composition of the unactivated samples determined using X-Ray Fluorescence (XRF), indicates montmorillonite contents less than the American Petroleum Institute (API) standard, so also are the rheological properties and fluid loss characteristics. The activation of the local clays with soda ash (Na2CO3) resulted in improved montmorillonite content. In addition, the activation process increased the clay yield and swelling power. Mud rheological properties and fluid loss potential improved more in the Ikono and Uyo than other clays. Thus, the activated clays can be classified as sub-bentonite that can be used as drilling mud for medium depth wells. The viscosifying potential of the locally sourced clays in water-based mud for oil well drilling can be exploited. This will reduce importation of foreign bentonite, lower total drilling cost as well as add value to the Nigerian economy.