Improvement Of Equipment For Oil Separation And Filtration And Application In Oilfield Wastewater Treatment

Most oilfields in China have entered into the third oil exploitation stage. Largeamount of oily wastewater was produced from primary oil/water separation process. Ifthe oily wastewater without treatment was discharged into the aquatic environment, itwould damage the environment, and cause economic losses. As the development ofpolymer flooding technique, the content of polymer in the oilfield wastewater isincreasing, which brings more difficulties to wastewater treatment, the traditionaltechnology of the sewage treatment equipment in use process is difficult to play itsoriginal design of efficacy.At present our country oilfield sewage treatment is generally used is floating inaddition to oil, coalescence except oil or oil removal combination+walnut, quartzsand filter medium or more. In the actual application process the oil removalefficiency is low, the coalescence material pollution is serious, water quality is bad,the filter performance is instable, the pressure reverse wash is high, filter materialloss and so on a series of problems arise.This topic in view of the above questions, aims to solve the problems oftreatment of wastewater containing polymers through the improvement andoptimization of oil remover’s internal structure, as well as developing filters suitablefor oilfield sewage treatment. At the same time, the micro flocculation technology andnew oil removal device and low voltage reverse wash filter are combined to form anew sewage treatment process, which can make the oil field water after level2treatmentmeet the low permeable reservoirs reinjection water standard. Based on thistechnology the oil fields wastewater treatment station is reformed, and the removalefficiency of the new type transverse flow oil separator and the oilfield wastewaterpurification efficiency of the low-pressure steady flow backwashing filter withinbackwashing period are investigated..The following conclusions are obtained:1. Based on the analyzes of the transverse flow oil separator and conventionalfilters, the main problems and their causes mainly lie in the existence of polymers,which increase the adhesion strength between oil and suspended substances,coalescence as well as filter materials, decrease the density of light coalescencematerials and filter materials relatively. The expansion rate of the filter materials ishigh under the effect of big reverse wash flow, which causes the blockage of waterdistributor’s sieve tube. It is also found that polymer flooding sewage is easy to causethe hardening of the filter materials, and causes pressure increase in the backwashingprocess, damage of sieve tube and loss of filter materials, etc. In view of the abovequestions, the internal structure of existing equipment is redesigned, new types of transverse flow oil separator and low-pressure steady flow backwashing filter aredeveloped.2. The actual application results of the new sewage treatment equipment showthat, the oil removal rate and impurity separating rate of the new transverse flow oilseparator has respectively reached nearly80%and60%, almost30%higher comparedwith the conventional transverse flow oil separator. The oil removal rate and impurityseparating rate of the new low-pressure steady flow backwashing walnut shell filterare respectively80%and55%, which are35%and15%higher than the conventionalwalnut shell filter. The oil removal rate and impurity separating rate of thelow-pressure steady flow quartz sand filter are79%and74%, which are respectively40%and20%higher than the conventional quartz sand filter. And in the long termrunning process, the treatment effects of the new sewage treatment devices are morestable, with no great fluctuation.3. The micro flocculation technology for the treatment of wastewater containingpolymers is studied. Through the indoor experiment the SPX flocculant is determinedto have the best effect. According to the on-site application effect experiment, theSPX is further determined to be the best flocculant, and the optimal dosingconcentration is determined to be3mg/L.4. Based on the application of the sewage treatment equipment, traditionaltechnology is improved. The micro flocculation technology is used in the process ofoil wastewater treatment to increase the removal rate of micro-sized suspendedparticles from sewage. According to the test on the new process, in the out flow aftertreated, the oil content is less than1mg/, the suspended particles content is less than3mg/L. The removal rates of oil and suspended particles are more than99%and95%respectively. The effect of the new treatment process is better than the traditionalprocess, and the cost is lower. The outflow quality completely meets the lowpermeable reservoirs reinjection water standard.