A Study On The Relationship Between Porosity And Velocity Of Unconsolidatod Sediments

Exploration of marine hydrocarbon resources is increasingly important. One of problems to face first is velocity of unconsolidated sediments below the sea floor. The seismic wave propagation velocity is a necessary parameter during the time-depth conversion. Unless we know the value of velocity we can not determine the depth, angle of inclination and location of formation that produce a reflection or refraction. Velocity is closely related to lithology,porosity,pressure and other petrophysical parameters . It is indispensable in reservoir parameter prediction.In this dissertation, we analyze the porosity's effect on interval velocity and root mean square velocity of unconsolidated sediments below the sea floor. That is,we use software to generate a group of random number as high-frequency components of porosity. Then analyze effect of background porosity and high-frequency components of porosity on interval velocity and RMS velocity. The concrete steps are: we build a theoretical rock physics model. Furthermore, using the porosity from 70% to 20% as the background porosity and Gassman equation, we acquire compressional and shear wave velocities and analyze effect of the background porosity on P and S wave velocities. Using Dix equation, we acquire root mean square velocities of P and S wave and analyze effect of the background porosity on RMS velocities of P and S wave. Subsequently, we use software to generate two groups of random number which will not exceed ten percent of 60% (value of porosity) and thirty percent of 60% (value of porosity) as high-frequency components of porosity. Then we analyze effect of the two groups on P and S wave velocities and on RMS velocities of P and S wave. Finally, we analyze effect of porosity (equals background porosity add high-frequency components of porosity) on P and S wave velocities and on RMS velocities of P and S wave.