Behrooz Ahmadi - Department of Petroleum Engineering, Sahand University of Technology, Sahand, Iran
Mehdi Bahari Moghaddam - Department of Petroleum Engineering, Petroleum University of Technology, Ahwaz, Iran

Success in drilling operation extremely depends on drilling fluid performance. Depletion of manyoil and gas reservoirs and increase of demand for energy is caused to pay more attention tounconventional reservoirs. Many of usual additives that are used for improving drilling fluidcharacteristics, in high pressure-high temperature (HP-HT) or unconventional conditions are unstableand hardly are applicable in these conditions. Up to now, many researchers have used differentNanoparticles (NPs) for improving drilling fluid characteristics and overcoming drilling operationproblems. In this research, various concentrations of nanosilaca as solid particle and surfactants aswettability alteration of solid particles have been used. Based on the amount of water separated, whichis a sign of instability for emulsion, the optimum concentration of nanoparticles and surfactants andaccordingly the most stable sample has been selected. This sample has been considered for thermalstability at ۱۱۰, ۱۴۰, ۱۶۰ and ۱۸۰ F. According to the average droplet size at these temperatures, it hasbeen shown that till ۱۶۰F, stability of the emulsion is acceptable but at ۱۸۰F, emulsion is unstablecompletely as the droplet size at this condition increases significantly.

Emulsions, Surfactant, nano particles, thermal stability, droplet size