Abstract

Drilling mud is a working fluid which consists of a water and different added additives and is used during drilling of wells. By circulating through the wellbore, it ensures continuous cuttings removal, required pressure to stop the influx of reservoir fluid in wellbore, lubrication of drilling tools and maintaining wellbore stability while drilling through various types of formations. Since the well is often drilled through water-soluble rocks, which are mostly consisted of clay minerals, the penetration of the filtrate (water) into such rocks can lead to their destabilization, so the industry is considering the application of new types of additives because conventional additives, due to their size, can not enter in pores of rocks which has very low permeability, plug them and thus reduce further penetration of the filtrate. In recent years, scientists have paid great attention to the testing of nanoparticles (most tests are carried out with SiO2 nanoparticles) for drilling through low permeability rocks. Nanoparticles are particles whose diameters range from 1 to 100 nanometers so they can enter into the pores and create a high-quality mud cake, thereby reducing the filtrate invasion and increasing the wellbore stability. This paper describes a laboratory test carried out with SiO2 nanoparticles which average particle size was 20 and 60 nm added in concentrations of 1 and 3 wt% to water-based muds. Special emphasis was put on rheological and filtration properties. By
optimizing the concentration and size of the used nanoparticles, the rheological and filtration properties of the used drilling muds were improved.