Rock Physical Experiment And Theoretical Study On Broadband Dispersion Attenuation Of Rocks In Heavy Oil Reservoirs

Heavy oil is an important unconventional reservoir type.Its reserves are basically equivalent to conventional reservoirs that can be exploited.Its characteristics are that with the increase of temperature,the viscosity will gradually decrease,showing the characteristics of Newtonian fluid at high temperature and non-Newtonian fluid at low temperature.The viscosity of glycerol is also very sensitive to temperature.The viscosity of glycerol will decrease by about one order of magnitude when the temperature increases by 20℃.With the temperature,Octadecane can realize the mutual conversion of solid and liquid states.Therefore,glycerol and Octadecane are ideal heavy oil substitutes under laboratory conditions.In this thesis,a series of cross band rock physical experiments of glycerol and Octadecane saturated rock samples are carried out to explore the influence of heavy oil on the elastic properties of sandstone at different temperatures,frequencies and pressures,and establish a cross band rock physical model suitable for heavy oil rock samples.Firstly,through a series of calibration experiments,it is proved that the cross band rock physics measurement system can accurately measure the elastic parameters of rock.Then a series of systematic and comprehensive ultrasonic experiments were carried out on the rock samples containing heavy oil.It was found that the P-wave velocity of saturated glycerol rock samples was higher at low pressure and lower than that of drying at high pressure.Solid Octadecane increases the stiffness of the rock sample,so the P-wave velocity increases greatly.Liquid Octadecane and distilled water have similar effects on the velocity of rock samples.Then a series of systematic and comprehensive rock physical experiments are carried out on the rock samples containing heavy oil in the seismic frequency band.It is preliminarily concluded that the decrease of temperature increases the viscosity of heavy oil,increases the young’s modulus of saturated heavy oil core,weakens the dispersion and attenuation,and the attenuation characteristic frequency moves towards low frequency,which means that the squirt flow occurs in lower seismic frequency band,and high pressure has a good inhibitory effect on the frequency dependence of Young’s modulus.Finally,considering the experimental results,the aspect ratio distribution of soft pores,the squirt flow between hard pores,soft pores and intermediate pores,a three pore solid squirt(TSS)model suitable for heavy oil samples is established.The model fits well with the results of cross band rock physical experiments of heavy oil rock samples,and can explain the influence of pore filled with heavy oil and other similar solids on the elastic properties of rock samples.