Design Of Chemical Flooding Formulations For Crude Oil With Different TAN In Jiangsu Oilfield

The D3 and D5 sections,subordinate to Jiangsu oilfield,are ordinary heavy oil reservoirs initially exploited by water flooding,but the water flooded recovery efficiency is relatively low.Both sections are exceedingly deep,and thermal recovery is not suitable for such kind of reservoirs due to high energy consumption.In this thesis,the chemical flooding formulation applicable to D3 and D5 sections are proposed by evaluating the alkali/surfactant/crude oil interfacial tension,emulsification capacity and oil recovery efficiency.Considering the limitations such as obscure inflection point and poor reproducibility of a generally used Total Acid Number?TAN?measurement method,GB/T18609-2001,an improved TAN method was proposed in this thesis.The degree of accuracy can be significantly improved by adding stearic acid called‘spiking solution'into the blank solution and using TBAOH as titrant.Moreover,a much more evident inflection point can be obtained by using this‘spiking method'and its reproducibility can also be significantly improved.Aiming to meet the challenges such as high bicarbonate concentration and,equally important,to solve the scaling problem,a compound scale inhibitor was developed.No scale was formed when the scale inhibitor was mixed with D5 and D3 injection water and 3%Na₂CO₃,provided that the mass fraction of scale inhibitor is larger than 0.05%.As for D5 crude oil with high TAN,the alkali/crude oil interfacial tension with different alkali candidates were investigated.It was found that both ultralow IFT and good emulsification capacity could be achieved by using 1.5%Na₂CO₃.More importantly,the incremental oil recovery on core flooding experiment by 1.5%Na₂CO₃ after water flooding was 34.79%.Then,1.5%Na₂CO₃ was consequently selected.As for D3 crude oil with relatively lower TAN,an alkali/surfactant process is proposed and ultralow IFT can also be achieved with the optimized alkali/surfactant formulation.The displacement efficiency of C3crude oil by polymer flooding,alkali/surfactant flooding,alkali/polymer flooding and alkali/surfactant/polymer flooding are evaluated and compared by core flooding experiments.The results reveal that incremental oil recovery by alkali/surfactant flooding is not promising,by merely 6.04%after water flooding,while the incremental oil recovery by alkali/polymer flooding and alkali/surfactant/polymer flooding are 17.97%and 20.00%,respectively.To summarize,optimized chemical flooding formulations for Jiangsu heavy oil with disparate TAN were studied in this thesis,which may provide guidance to the design of chemical flooding process for analogical reservoir.