Drilling mud is a mixture of water and clay, weighing materials and few chemicals which is called additives to stabilize the wellbore pressure. Drilling fluids, affects drilling operations. The cost of drilling fluid has been a major issue during operation and the effect of salinity on the additives has also resulted into investigation of determine if other additives can be used as a substitute to the predominant used ones. To that effect, this work was focused to determine the effect of salinity on the rheological properties of mud type prepared with Carboxyl-methyl cellulose (CMC) and polyanionic cellulose-regular (PAC-R). From this study, salinity effect shows that as the salinity of drilling mud are increased, the effectiveness of the polymer decreases. This has a negative effect on the rheological properties of drilling mud. Plastic viscosity decreases with increasing temperature and yield point increases with increasing temperature. Also, the thixotropic property (gel strength) of both PAC-R and CMC muds increases with temperature but decreases on the introduction of salt. It can also be deduced that the ability to suspend cuttings for both KCl and CMC mud are unique.

High performance water-based mud, a drilling fluid type used for deepwater drilling is posed with similar challenges faced by the aqueous water-based mud used for onshore drilling. These challenges emanate due to high temperature condition encountered in deepwater formations. The challenges include decrease in density, viscosity and other rheological properties of the drilling mud under high temperature condition which can lead to failure to meet drilling objectives. An experimental investigation was carried out on the high-performance water-based mud designed for drilling in the Niger delta region where clay type kaolinite is predominant. Four mud samples were formulated by varying the concentration of Sodium Chloride (NaCl) ranging from 3%, 5%, 7%, and 9% and increasing the temperature from surface condition to 140°F. The properties of the high-performance water-based mud was observed at different salinity concentration. The study shows that the density and viscosity tend to increase with increasing temperature where the mud has high salinity concentration of 7% to 9%. Other rheological properties of the high-performance water-based mud increases at increasing temperature but decreases above 118°F except for the 9% NaCl sample which increases with an increasing temperature. The conclusion drawn from this experimental study is that the increase in NaCl concentration increases the density, viscosity and other rheological properties of the high-performance water-based mud when drilling through deep-water formations under high temperature condition. This has provided solution to the deep-water drilling changes.