Evaluation of Contribution of Drilling Additives to the COD of Drilling Wastewater and Their Coagulation Effects
常用钻井泥浆处理剂对钻井废水COD值的贡献及其混凝处理效果评价

The COD contribution of six drilling mud additives used in the Jidong Oil Field were determined and correlated. The COD contributions were found to be in the following order: sulfonated phenolic resin>NH4-HPAN> collapse preventing agent>silicon stabilization agent>PAC-141>acylonitrile-acrylamide-potassium. The correlations were used for estimation of COD values of 3 samples of wastewater corresponding to different additive formulations,the estimated values agree well with the measured ones when the dilution was considered. It is indicated that the COD was mainly contributed from additives. Results from coagulation experiments of mixture of drilling fluid additives and drilling wastewater indicate that the residual TOC value is larger than the prediction when the Zeta potential of the mixture system is over 50 mV; conversely, the residual TOC value is less than the prediction. The less the Zeta potential is, the less the removal of TOC is. SMP has the highest Zeta potential among the six drilling mud additives, so its TOC removal is the poorest.