Study On Synthesis And Performance Of Branched Heavy Oil Viscosity Reducer

Heavy oil is an important oil and gas resource,which plays an increasingly important role in the world oil supply.However,in many cases,the low fluidity of heavy oil and pipeline blockage caused by the deposition of wax or asphaltene make it difficult to transport.At present,many methods have been proposed to reduce the viscosity of heavy oil to facilitate transportation.Among all the viscosity reduction methods,chemical viscosity reduction method is considered to be the most promising method because of its economic,technical feasibility and cost rationality.Aiming at the problem of offshore heavy oil exploitation,we designed and synthesized a series of water-soluble viscosity reducers,and conducted a series of discussions on their viscosity reduction effect and mechanism.In this paper,different types of dendrimers were synthesized to reduce the viscosity of heavy oil:(1)Two generations of polyamide amines(G0.5-G2.0)were synthesized from ethylenediamine and methyl acrylate,the ends of the full-products were neutralized and modified by different organic acids(acetic acid,butyric acid,hexanoic acid,oleic acid)or acrylamide morpholine.The series of polyamide amines(D0.5-D2.0,T0.5-T2.0)were also synthesized from diethylenetriamine and tetraethylene pentaamine.The ends of all polyamide amines are connected with long-chain hydrophobic alkyl groups(ethyl acrylate,butyl acrylate and hexyl acrylate)to increase their hydrophobicity.The structure of the product is characterized by IR,1H NMR spectra and MS,and their surface activity was studied by surface tensiometer.The results showed that the introduction of hydrophobic alkyl chain could increase the surface activity of polyamide-amine.(2)All of the above polyamide-amines and modified products were used as viscosity reducers to test the viscosity reduction effect of Bohai heavy oil.The viscosity reduction rate of the viscosity reducer was characterized by viscosity meter.The dehydration process of the emulsion was characterized by the stability analyzer.The dispersity of the viscosity reducer to heavy oil was observed by optical microscope,the distribution ratio of the viscosity reducer in the oil phase and the water phase after dehydration was tested by an ultraviolet spectrophotometer.The mechanism of viscosity reduction was discussed by Rheometer and scanning electron microscope.The results show that G2.0 and G1.0 controlled by hexanoic acid have the best viscosity reduction effect of heavy oil.When the concentration is 200 mg/L,the viscosity reduction rate can reach 96%,Moreover,G2.0 regulated by hexanoic acid can increase the stability of emulsion and has good dispersibility to heavy oil.D2.0 and T2.0 with higher branching degree can also show good viscosity reduction performance of heavy oil without adding organic acid;polyamide modified by hydrophobic alkyl chain can increase the clarity of dehydration.Viscosity reduction mechanism shows that they mainly reduce the viscosity of heavy oil by disassembling the association structure of asphaltenes(3)The intermediate monomer N,N-dihydroxyethyl-3-aminopropionic acid methyl ester(DM)was synthesized by Michael addition reaction of methyl acrylate and diethanolamine,and then transesterification reaction of DM with triethanolamine in different proportions was carried out to synthesize hydroxy-terminated polyester with different branching degrees.The structure of DM was characterized by IR,1H NMR spectra and MS.The viscosity reduction evaluation showed that the viscosity reduction rate could reach more than 95%when the concentration was 800 mg/L in pure water,and the viscosity reduction rate had good salt resistance.The distribution coefficient shows that most of the viscosity reducer is distributed in the water phase after viscosity reduction.The mechanism exploration show that the viscosity reducer has dispersibility to the asphaltene and resin in heavy oil.