Drilling mud is one of the important components in deep drilling of oil wells. Drilling muds consist of two phases: liquid phase (i.e. sweet water, salt water, seawater) and solid phase (such as clay minerals). Rheological characteristics of ordinary muds change in deep wells under high pressure and temperature therefore the mud is unable to perform its duties, specially transportation of the cuttings. Different methods are used for modification of these properties. One of these methods incorporates using of polymers in drilling mud. The present study investigates the properties of polymeric muds under conditions present in drilling operation in Iranwith the aim of eliminating the problems and poor efficiency of traditional muds.
In this study the effects of two kinds of polymers (PHPA and XC) on the physical and rheological behavior of liquid base mud and also the effects of two kinds of pollutants (CaSO4 and MgSO4) on the behaviors and properties of polymeric muds is investigated. The results demonstrate that polymer based mud can improve rheological and thixotropic properties of the mud, decreasing of water loss, and has no effect on PH balance. Also the obove mentioned polymers become viscose when exposed to saturated salt water and are resistant to other ionic pollutants. They keep the initial specifications and viscosity in high shear rates. Increasing of temperature results in increasing of shear stress for bentonite and decreasing of shear stress for XC and PHPA polymers, Also increasing the tempreature ( of bentonite based mud ) results in increasing of yield point, viscosity and thixotropic properties, but increased temperature will have a reverse effect on mud containing XC and PHPA polymers.