Development of a water-based drilling fluid for chemical enhancement of drilling rate in a dolomite rock sample

The Rate of penetration into the formation being drilled determines the speed of the drilling process and also is an economic indicator, which estimates the operation efficiency. The magnitude of ROP depends on several factors, including drilling fluid properties, rock properties, and drilling operational parameters. Density, rheological characteristics, and solid content of the drilling fluids have a significant effect on ROP. However, the chemical interaction of drilling fluid with rock surface may also improve ROP. In this work, water-based muds were developed to investigate their effect on the chemical enhancement of the drilling process in dolomite rock samples. For this purpose, different properties of dolomite samples, including unconfined compressive strength, contact angle, and fluid absorption were studied. The novelty of the work lies in the more realistic condition in drilling fluid composition selection, where bentonite, as the most common additive of water-based muds, was used. Besides, rock samples were aged in formation water and oil before contact angle measurement, to get more realistic results. Experimental results showed that the addition of surfactants to the mud composition leads to an increase in average fluid absorption inside the rock sample by about 60% and a decrease in rock uniaxial strength by about 34%, which subsequently results in higher penetration rates. Results also confirmed the positive effect of polymer in ROP improvement.