Resaerch On Fracturing Fluid Preparation Using Oilfeild Swage In Da Niudi Gas Feild

In the exploration of oil and gas, a lot of oilfield sewage will be produced. If discharged arbitrarily, it will make a series pollution to the environment. And it would damage the formation, effecting the exploration of oil and gas, if injected into formation. Therefore, oilfield swage is a key link which restricts the development of oil and gas development in China, and oilfield sewage treatment should be an important part in the process of oilfield production. In view of fracturing wastewater in Da Niudi gas field, deep treatment of sewage was carried out in this paper, and a comparison of fracturing fluid was made which was prepared by sewage and sewage that has been treated, respectively.Combination method of sodium carbonate and sodium hydroxide or physical adsorption method of 13 A zeolite had been used to remove the calcium and magnesium ions in sewage, because there is a high content of calcium and magnesium ions in the sewage of Da Niudi gas field. It was found out that calcium and magnesium ions can be removed effectively when the adding amount of sodium carbonate and sodium hydroxide is 45% of the amount of substance of calcium and magnesium ions, respectively. And 13 A zeolite can remove calcium and magnesium ions effectively, too. But it is hard to revive in oilfield. Experiment of reducing COD value using Fenton reagent has been carried out due to a high COD value in the sewage, finding out the optimum condition of reducing COD is: pH=3.5, initial concentration of H2O2 is 0.095mol/L, mole ratio of Fe2+/H2O2 is 2:10, mass ratio of H2O2/COD is 1:1, reaction time is 60 min, respectively. Finally, residual organic compounds is 71mg/L;A high content of oil existing in the sewage, the oil removal experiment had been carried out using cationic polyacrylamide. It has been found that the optimum condition of removing oil is: the adding amount of flocculant is 70mg/200 mL, and the reaction temperature is 80℃, respectively. And the best oil removal rate is 96%. Complex polymeric ferrum oxydatum phosphate can also be used removing residual oil because the F e( O H) 3 gel formed by complex polymeric ferrum oxydatum phosphate can effectively absorb the residual oil and the oil removal rate can reach at 90.6%. At the same time, it has been found out that the sewage that had been modified by complex polymeric ferrum oxydatum phosphate can exist at least 3 days in the formation temperature of 30℃~90℃.Additionally, comparison and evaluation of performances between two kinds of fracturing fluids and base fluids which were prepared by sewage that had been treated and distilled water, respectively, had been made. It has been found that the fracturing fluid which was prepared by treated sewage had a higher temperature and shearing resistance; and its gel breaking is complete, having a higher flowback rate. In addition, it made a lower damage to formation through dynamic filtration damage experiment, meeting the requirements of fracturing.