Study On The Oil/Water Seperation Flocculant/Coagulant Of Polymer Flooding Produced Oily Water

Polymer flooding has been widely adopted in Daqing Oilfield toenhanced oil recovery. In 2001, 8 million metric ton crude oil was producedby polymer flooding. With the application of polymer flooding, the stabilityof the inverse oil/water emulsion in produced oily water of Daqing Oilfieldhas been significantly increased. The tight oil/water emulsion of oily water inpolymer flooding has significantly reduced the treating ability of some oldoily water treating facilities. What is worse is that the treated oily water fromsome oily water treating facilities is seriously out of specification. Thereaction between the residual anionic polyacrylamide in the produced oilywater and the state-of-the-art cationic flocculant and coagulant has lead tosignificant increase of flocculant/coagulant dosage, plugging of oily waterfilters and worse quality of the treated oily water.Stabilization of inverse crude oil emulsion of oily water in polymerflooding of Daqing oilfield was investigated through water quality analysis,interfacial active particle separation and tests on oil-water separation of bothartificial and genuine polymer flooding produced oily water. The enhancedstability of inverse crude oil emulsion in polymer flooding produced oilywater primarily results from adsorption of colloidal particles on oil dropletswhich presents steric hindrance to oil droplet coalescence and decreases thedensity difference between the oil droplet and the water phase. Residualpolymer in polymer flooding produced oily water enhances its stability bypromoting deposition of colloidal particles on oil droplet surface andincreasing water phase viscosity, leading to lower oil droplet floatingvelocity.An oil/water separation agent, formulated mainly with nonionic andanionic active components, was developed for polymer flooding producedliquid and oily water. The novel oil/water separation agent developed workswell both as demulsifier for o/w type polymer flooding produced crude oilemulsion and as flotation agent for polymer flooding produced oily water.With the dosage of the novel flocculant at 20mg/L, polymer floodingproduced liquid can undergo well phase separation after 1h 45℃ thermalsettling, resulting in only 2.88% water in the oil phase and 651.1 mg/L oil inthe water phase. With the dosage of the newly formulated flocculant at20mg/L, the oil content of polymer flooding produced oily water can belowered from 827mg/L to 23.9mg/L after 6min induced air flotation. Basedon the performance of the newly developed flocculant, a thermo-chemicalsettling – flocculation process, in which the newly developed oil/waterseparation agent is injected into polymer flooding produced liquid upstreamof free water knock-out, was proposed for the oil/water separation of polymerflooding produced liquid and oily water.