Abstract: Drilling operations in the Yolot area, Turkmenistan have encountered two problems, difficulties in controlling the properties of the drilling fluid because of high pressure formation water invasion and salt/gypsum interbeds, and mud losses. Studies have been conducted on high density drilling fluid formulations and mud loss control and prevention based on the geological and engineering characteristics of the high pressure saltwater zones and the salt/gypsum interbeds. Analyses were conducted on the difficulties in maintaining and controlling the properties of the drilling fluid as well as controlling and preventing mud losses at high drilling fluid densities, high temperatures and high calcium contamination. A high density saturated saltwater base drilling fluid was modified by introducing calcium-resistant shale inhibitors and other selected additives, giving birth to a high temperature high density drilling fluid containing high concentrations of calcium ions. Laboratory study and field practice showed that the modified drilling fluid was able to resist the effects of high temperatures to 140 ℃ and calcium contamination to 40,000 mg/L. Use this drilling fluid, calcium contamination from long section of salt/gypsum interbeds was successfully resolved. By reducing circulation pressure loss of the high density drilling fluid and using the techniques of mud loss control while drilling, combined with high concentration bridging lost circulation material slurries, drilling problems such as mud losses and narrow safe drilling window were satisfactorily resolved.