Evaluation of local bentonitic clay as oil well drilling fluids in Nigeria

Rheological and filtration tests were carried out on bentonitic samples obtained from Pindiga Formation in Borno Basin and the commercial Wyoming bentonite using a Rheometer and API Filter Press respectively. This is to evaluate the performance of the local clays for drilling operations in Nigeria.The free swell volume, gel strength, filtration and rheological properties of Pindiga mud improved as clay concentration increased with optimum concentration observed at 80 g/350 ml. However, when beneficiated at 40 g/350 ml with Na2CO3, potash and starch, there was an increase of 64% in free swell volume with Na2CO3, 750% and 3000% in plastic viscosity and yield point respectively with 12.5% Potash while there was a reduction of 35% and 32% in filtrate loss and 55% and 33% in mud cake thickness with 12.5% Starch and Potash respectively. This study shows that beneficiated Pindiga clay gives a good promise for drilling purposes at optimum clay and additives concentrations.