عنوان مقاله [English]
The drilling fluids play a significant role in the drilling of oil and gas wells. Bentonite is one of the consumable components of the drilling fluid which is used to reduce the fluid loss. The production of high quality bentonite resources which are suitable for drilling is declining in our country, Hence it is necessary to improv the quality of available bentonites. Using polymer additives is a conventional method for improving the quality of bentonites which has attracted the attention of researchers. However, some disadvantages of these compounds such as expensive production procedures and formation damages motivate researchers for developing some new improving methods to reach the high quality drilling fluids. The main aim of this research is to improve the quality of poor bentonites through amencling water absorption capability and increasing the rheological properties. The Properties of 12 types of bentonite were investigated and two compounds B9 with the lowest quality and B6 with the highest quality were selected for further investigations. Carbon ate and magnesium base chemical substances were then added to such compounds and their properties were investigated, too the results showed that adding Carbonate and magnesium compounds could result in a quality improvment of bentonites which satisfied the API RP 13-A standard requirements. The modified bentonite showed about 6.5 times better rheological properties and 2-5 folds lower fluid loss as compared to the untreated sample. The results also showed that the modified bentonite could be a good choice for replacement of the conventional carboxymethyl cellulose and starch in the polymeric drilling fluids, based on their 2.5 to 4 times better rheological properties.