| In the 21st century and even in the future,the low permeability reservoir is the important resource base of the oil reserves and production increasing.It is even more,the Extra-low permeability fractured reservoir is the field which needs more key technology to further research.PGL block C6 reservoir is a typical "3 lows" reservoir,developing artificial fracturing fracture and micro fracture,having the strong inner layer and interlayer heterogeneity,with the phenomenon of the injected water breakthrough along the high permeability,having the difficult of production stable and the high formation water salinity.Polymer/surfactant flooding technology is a method witch display fully the polymer and surfactant with their respective advantages and synergies to enhance oil recovery.At present,the technology is mainly used in low temperature and low salt sandstone reservoir witch's permeability is greater than 50mD and has a medium heterogeneity.This paper uses the methods of experimental research to identify whether the technology has a flooding and blocking effect on PGL block with the extra low permeability fractured reservoir and achieving purpose of enhancing oil recovery.Firstly,this paper has expounded the general characteristics,seepage characteristics and development characteristics of extra low permeability fractured reservoir.Then it has researched and summarized the S/P flooding examples and the present development situation at home and abroad.It also has summarized the current development situation of physical simulation technology.Secondly,the geologic development characteristics of PGL block have been analyzed,especially the crack's situation of PGL block was analyzed in the paper.Finally,this paper has put forward the problems existing in this development plan.It also has a preliminary discuss in adaptability of Polymer/Surfactant flooding technology in the target reservoir.It has refined the formula problems which need to be solved.This paper gets the optimization and evaluation method for P/S system formula mainly through the experimental method.In this experiment we need to chose one S/P formula which is suitable for the target reservoir from 4 kinds of polymer and 4 kinds of surfactants.There are some polymer performance which need to be emphasized,such as improving oil displacement efficiency characteristics,injection pressure,aging stability,salt resistance properties,shear properties,adsorption,a matching relationship with the pore throat,etc.There are some surfactant performance which also need to be emphasized,such as reducing the interfacial tension properties,adsorption,etc.Mix X4 polymer of 2000 mg/L and Y1 petroleum sulfonate surfactants of 1500 mg/L which has been chosed,and then evaluate the performance of S/P system such as injection,adsorption,aging stability and so on.These studies indicate that the S/P system as a driving-agent to improve oil recovery in the extra low permeability fractured reservoir in block PGL is completely feasible,it has the following advantages:?The moderate injection pressure can reduce the influence of the Low Speed non-Darcy seepage,improve the tonguing phenomenon so that it is helpful to be used in low permeability field.?It has good salt resistance,shearing resistance,aging resistance and lower adsorption.?It is matching the matrix porosity.Three indoor physical simulation experiments of small core diameter(2.5cm)oil displacement for comparison have been made to the polymer flooding,surfactant flooding and S/P flooding.Finally,we take natural outcrop from mine and make the 3D physical model according to the principle of similar,design the core parallel experiment scheme of 3D model,use the patent of our laboratory equipment and high temperature and high pressure 3D physical model of large scale to do displacement experiments.According to the analysis of experimental results,the S/P flooding in PGL block of extra low permeability fractured reservoir is feasibile and it can improve the recovery by 6.5%.But it is must be applied prudently. |
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