The Preparation Of Boron Polymerization Silicon Aluminium Sulfate Iron And Performance Evaluation

A large amount of wastes were produced during oil and gas exploitation process, including drilling wastewater, waste drilling mud, flow-back fracturing and the wastewater from tertiary oil recovery. Many kinds of chemical agents were added into working-fluid, so the oilfield wastewater had the traits of high concentration of pollutants, complicated composition and bad bio-degradation performance. Besides, oil and gas exploitation is a systemic project, the properties of wastewater were different from different stages. Due to the present coagulants were hard to treat the changeable and complicated oilfield wastewater, preparation of a novel and effective coagulant which could adapt to changeable oilfield wastewater has significant meaning.This paper analyzed the defects of present coagulants for oilfield waste water and prepared boron-polymerization-silicon-Al-Fe(BPSAF). The polymerization of Al/Fe sulfate and polymerization of silicic acid’s conditional preparation technologies were organism combined to prepare BPSAF in this paper. Sodium borate was used as stabilizing agent, so the stable coagulant was prepared.The optimum preparation technologies were gained in this paper. The preparation technologies of PBS were as follows:3.75%of SiO2, activation pH of1.5, activation temperature was normal atmospheric temperature. The preparation conditions of PAFS were:0.42mol/L of basifier(Na2CO3), Al/Fe=5:2, reaction temperature was70℃, reaction time was2h. BPSAF was prepared in different ratios of (Al+Fe)/Si and found that any was the BPSAF prepared in appropriate ratio, the BPSAF had good coagulation performance. When the (Al+Fe)/Si was10:3, the stability of BPSAF was the best. After12h aging, BPSAF had the best coagulation performance and stable time was60d, the coagulation performance became worse as aging time went by. So the BPSAF preparation condition was gained.The results of treatment for drilling wastewater, flow-back fracturing and waste drilling mud proved BPSAF had nice decolour function and high removal rate of SS and CODcr, besides, BPSAF had good performance of gel-breaking for waste drilling mud. As to the polymerization of silicic acid in BPSAF, it could promote solidification of waste drilling mud.The experimental results of FTIR、XRD and SEM illustrated complex Fe/Al or Al/Fe(Ⅲ) were connected with Si by chemical bond of Al/Fe-Si and Al/Fe-O-Si. The complexation of complex Fe/Al or Al/Fe(Ⅲ) with OH changed microcosmic structure of BPSAF, BPSAF has no crystal form structure. Cotton structure was formed after chemical reaction, so the BPSAF had larger specific surface.