Abstract:  Four kinds of drilling fluid systems commonly used in offshore drilling are briefly described in this paper. Among them, the improved PEC drilling fluid system has the characteristics of soft inhibition, low viscosity and high cut, which is suitable for the upper and middle strata of offshore drilling. The PEM drilling fluid system has the characteristics of inhibition, anti-collapse, lubrication and temperature resistance, which is suitable for the middle and deep strata of offshore drilling and the extended displacement and horizontal wells. EZFLOW drilling fluid system has the characteristics of strong sand carrying ability, good reservoir protection and strong anti-pollution ability, which is suitable for large displacement wells, horizontal wells and oil reservoir protection in offshore drilling. The invisible acid completion fluid system has the characteristics of strong reservoir protection and corrosion resistance, which is suitable for the completion of offshore drilling. The paper also introduced the effects achieved by these four drilling fluid systems in offshore drilling applications.

Key words:  drilling fluid, PEC, PEM, EZFLOW, invisible acid