Research On The Low-temperature Oxidation Process Of Heavy Oil By Air Injection And Its Influence On Enhanced Oil Recovery

Low temperature catalytic oxidation air injection is a new EOR technology to improve the performance of steam injection in heavy oil reservoirs.It has some advantages,such as no regional restriction,low investment cost,strong adaptability and high recovery in heavy reservoirs.However,the risk of explosion of air injection is closely paid attention,especially when the oxygen breakthrough in the production wells.In this thesis,reaction reactivity of different crude oil,low temperature catalytic oxidation of ChenBei heavy oil and the recovery of ChenBei heavy oil by air injection have been studied.The reaction order and reaction activation energy of Huizhou light oil,Chengbeiheavy oil and Lukeqinextra-heavy oil were 0,0,1 and 77.279,59.670,53.276kJ/mol,respectively.With the increase of the viscosity of crude oil,the reaction order of crude oil changed from zero-order reaction to first-order reaction and the reaction activation energy decreased.With the increase of the content of heavy components(resins and asphaltene)of crude oil,the reaction activity increased.Meanwhile,low temperature oxidation(LTO)was an exothermal reaction,the higher concentration of heavy component of crude oil,the more heat would release during LTO.Although heavy oil had strong reaction activity,the reaction rate was still low.Therefore,five organic metal salts was used to catalyze the LTO of Chenbei heavy oil and the catalytic activity was MnL<NiL<ZnL<CuL<FeL.On the condition of 120℃、8MPa and 1.5%FeL,the content of oxygen in the effluent gas decreased from 14.36%to 4.52%after 24h reaction,which could ensure the safety of air injection.The concentration of light component(saturate and aromatic)of oxidized oil increases and the acid value of oxidized oil also increased.FeL could catalyze the oxidation reaction and the cleavage reaction of heavy oil.The results of kinetics analysis indicate that the reaction order changed from zero-order reaction to first-order reaction and the Arrhenius activation energy decreased from 59.670 to 47.007 kJ/mol,decreased by 21.22%at the present of FeL.FeL could also improve the heat generation during LTO,which is beneficial for EOR during air injection.Single-tube displacement experiments showed that the recovery of water flooding,nitrogen injection and air injection are 32.97%,48.86%and 60.25%,respectively.The reaction heat of crude oil during air injection could make the temperature of sand tube increase about 12℃.Meanwhile,a slug of high viscosity oxidized oil would be formed during air injection,due to the effect of gravity segregation,which could blockthe high penneability channel.What’s more,double-tube displacement experiments showed that the recovery of high-permeability tube and low-permeability tube increased from 32.33%,19.41%to 60.72%,36.72%,increased by 28.39%and 17.31%,respectively.Total recovery of heterogeneous model increased from 26.08%to 49.11%,increased by 23.03%.Air injection has the capability to increase the water-flooded heavy oil reservoirs,which could be a significant technology for tertiary oil recovery of heavy oil reservoirs.