Study On Inhibitors For Fresh-water Drilling Fluids

The corrosion of drill tools is a serious problem in the drilling engineering. It will become even worse when the drill tools have gone deeper and the surroundings have changed, such as temperature, pressure and geologic structure and so on. Drill tools have corroded seriously when they are used in the engineering of oil exploitation by Jiangsu Oil Field. It is concluded by EDS(Energy Dispersive Spectroscopy) analysis on corrosion products of drill tools in drilling fluid that the main component of the corrosion products on local drill tools is Fe2O3. Thus the corrosion of drill tools is mainly caused by the depolarization of dissolved oxygen. Factors on corrosion were studied. Inhibitors that could be used in the practice were selected. Efficiencies of composite inhibitors were improved.Results tested by polarization curves showed that the corrosion rate decreased with the increasing of pH value. The passive current in the anodic area had obviously increased with the increasing of temperature. This proved that it would be more difficultly for the passive film to form with the increasing of temperature. In addition, the corrosion rate increased firstly and then decreased with the increasing of the salt content. The high salt content could hinder oxygen from arriving the metal surface and therefore, there was a decrease in the corrosion rate. It could be inferred from the results the sequence of the effect on corrosion rate is Cl->S2->HCO3->SO42-. The influence of Cl- on the corrosion is the greatest. Results tested by potentiadynamic polarization curves proved that the sensitivity of corrosion partly increased with the increasing of Cl- content. The protective potential and corrosion resistance decreased.Results from the weight loss test showed that the corrosion rate increased with the increasing of the agitating speed, temperature. The corrosion rate increased firstly and then decreased with the increasing of corrosion time and quantity of oxygen. The results indicated the sequence of the effect on corrosion rate is temperature> agitating speed>time> quantity of oxygen.Sodium molybdate, sodium silicate, potassium permanganate, sodium...