Dagang Sheep Miki Oilfield Alkali / Polyethylene Binary System Viscosity Stability

As one of the most important EOR techniques,AP flooding uses polymer to reduce mobility ratio and alkali to decrease interfacial tension,therefore,enhances both the sweep efficiency and the microscopic displacement efficiency.Considering AP flooding pilot test of Yangsanmu oilfiled had produced incremental oil,Dagang Oilfield Co.decided to further implement expanding test.To ensure that expanding test goes with a swing,it is necessary to solve the serious problems exposed during pilot test;①viscosity loss of AP system is heavy;②interfacial tension between AP system and crude oil is high.This study based on reservoir conditions and injection water quality of expanding test area.Taking low IFT,weak scaling and low alkali consumption as alkali screening targets, while viscosifying ability and compatibility with alkali as polymer screening targets,obtain AP system—NPS-2/HTP;at 63℃,the IFT of 1.25%NPS-2+1500mg/LHTP arrives 4.1×10^-3mN/m, and the viscosity reaches 25.6mPa·s.However,owing to the effects of alkali,oxygen,metallic ions,shear action,temperature and so on,viscosity stability of AP system is poor,and incapable of having favorable mobility control.Exerting the theory of intermolecular interaction as well as macromolecule entanglement,and taking advantage of macromolecule hydrogen bond compound viscosity stabilization effect,polyelectrolyte compound viscosity stabilization effect,clay minerals viscosity stabilization effect together with alcohols viscosity stabilization effect,carried out viscosity stabilization experiments on ten kinds of chemical agent.The results show that they can enhance viscosity stability of AP system in varying degree,but still can't meet the expanding test design requirements.On the basis of mechanism analyses in viscosity stabilization experiments,utilizing the interaction between phenols and AP system,develop GH compound viscosity stabilizers—GH-01 and GH-02. Therm-oxygen aging experiments were conducted to examine the long-term therm-oxygen stability of GH—AP system and the compatibilities of GH with different alkali-polymer proportion AP systems.The results show that GH possess long-term and highly effective viscosity improvement abilities which adapt with different alkali-polymer proportion AP systems(including polymer solution);after aged 6 months at 63℃,viscosity retention of GH-01-AP system archive over 50%(50.4%～61%),while that of GH-02—AP system approache even surpass 100%(91.7%～135.9%).What's more,field appraisal experiment acquired preferable viscosity improvement effect of GH-02 to laboratory experiment.Pendent drop apparatus and rheometer were employer to measured the ITF,rheological properties and viscoelastic properties of GH—AP system.The results show that GH keep the ultra-low IFT (10^-3mN/m)along with pseudoplastic rheology characteristics of AP system,further more, endow it stronger elasticity.According to the physical chemistry function of GH—AP system, incorporating their structure and micromorphologic analyses presented by infrared spectrometer and scanning electron microscope,probed the viscosity stabilization mechanisms of GH.Core flooding tests were performed to determine the oil displacement efficiency of GH—AP system.The results show that GH can effectively enhance oil recovery of AP flooding;if GH-01—AP system and GH-02—AP system which experienced aging of 30 days at 63℃are injected after water cut were 98%,the oil recovery are enhanced by 12.8% and 18.5% respectively; if they are injected when water cut were 50%,the oil recovery can enhanced by 32.5% and 45.9% respectively.In a word,GH compound viscosity stabilizers possess excellent performances,and are the ideal viscosity stabilizers for Yangsanmu oil field AP system.This study has practical application value for AP flooding of Yangsanmu,Dagang and guidance meaning for research on viscosity stability of oil displacement agents.