Synthesis Of Hyperbranched Polymer And Its Application In Oilfield Chemistry

Hyperbranched polymers have received the extensive attention of various research fields due to their unique 3D topological structure,a large number of modifiable terminal functional groups,and good rheological properties.Besides,they have also made certain study progress in the field of oilfield chemistry.In this paper,in view of the oil exploitation difficulties encountered by oilfields in the later stages of production,unconventional oil and gas reservoirs and old oilfields,we design and develop modified hyperbranched polyamidoamine and modified hyperbranched polyethyleneimine,and respectively research its practical application in low permeability reservoir drag reduction and crude oil demulsification,which has a profound impact on sustainable development of the oilfield.(1)Synthesize hyperbranched polymers with different substituents and different molecular weights to reduce water injection pressure in unconventional oil and gas reservoirs,a series of hyperbranched polyamide amines(h PAMAM)with ethylenediamine and methyl acrylate as raw materials were synthesized by adjusting the ratio of ethylenediamine and methyl acrylate based on the"one-pot method"and temperature-programmed reaction method.Afterwards,epoxy propyl dodecyl dimethylammonium chloride(SE-LH)and epoxy propyl tetradecyl dimethylammonium chloride(SL-LH)with N,N-dimethyl dodecyl amine/N,N-dimethyl tetradecyl amine and epichlorohydrin as raw materials were developed,which is employed as a cationic monomer for modification.Furthermore,a series of modified hyperbranched polyamide amines(h P-SE-LH/h P-SL-LH)were obtained through the modification of h PAMAM end groups by SE-LH and SL-LH.Finally,h P-SE-LH and h P-SL-LH with suitable degree of substitution were preferred as drag-reducing agents through structural characterization and physical and chemical properties.The performance evaluation was carried out from three aspects:core permeability,injection concentration and injected PV number.The results showed that compared with conventional drag-reducing agents,h P-SE-LH and h P-SL-LH indicated eminent pressure reduction performance,especially h P-SL-LH-9 dispalyed the most prominent effect.When the injected PV number is 2,the injected concentration is 2 g·L^-1,and the measured permeability of the core is 0.07 m D,the pressure reduction efficiency is 44.46%.In order to explore pressure reduction mechanism,interfacial tension and wettability of h P-SE-LH and h P-SL-LH were measured.The results showed that,on the one hand,the unique hyperbranched structure of the hyperbranched polymer can be adsorbed on the rock surface to form a film,which can effectively reduce the capillary force and reduce the amounts of drag-reducing agents.On the other hand,the unique rheology and high interface activity of drag-reducing agents can change the wettability of the rock surface and effectively increase the amount of water injected.(2)Synthesize hyperbranched polymer demulsifiers with different degrees of substitution(DS)for demulsification of oil-in-water(O/W)emulsions in old oilfields.A series of water-soluble modified hyperbranched polyethyleneimines(CHPEI)with hyperbranched polyethyleneimine(HPEI)and palmitoyl chloride as raw materials through control the DS value to be less than 0.35.CHPEI with a suitable DS value is preferred as the demulsifier through optimization of structural characterization.The influence of demulsifier concentration,sedimentation time and temperature on demulsification effect were investigated to give a clear view of CHPEI-based demulsification.The results indicated that the demulsifier displayed short sedimentation time and low addition amount compared with traditional demulsifiers,and the oil removal efficiency reached 91%through adding 80mg?L^-1 of CHPEI with sedimentation time of 30 min.Furthermore,to better acquire the mechanism of demulsification,the oil-water interfacial tension of CHPEI demulsifiers in aqueous phase,the real-time size changes of oil droplets and transmittance of the emulsions were both recorded.The results showed that hyperbranched polymer with highly branched structure and high interfacial activity can replace the original interface film of the emulsion and effectively reduce the interface strength,which is beneficial to the coalescence and sedimentation of the oil droplets.These combined results indicated that the demulsification mechanism is flocculation-coalescence and replace-substitution.