CORES WITH DIFFERENT LITHOLOGIES
zones by elastic wave velocity.
Vp/Vs ratio has a nonlinear positive correlation with porosity.
In formations with low porosity, its ratio in gas and water zones
changes slightly. Therefore, porosity’s influence should be considered in identifying reservoir fluid types based on Vp/Vs ratio,
especially in low-porosity formations. The relationship between
elastic wave velocity and density, known as the Gardner function, is an empirical formula that requires regression-formula fit
for other local areas to obtain optimal parameters.
Well logging generally uses electronic and non-electronic
methods. The most common non-electronic method relies
on acoustic and physical properties of rocks to analyze differences in gas zones and water zones determined by the
formation’s elastic wave velocity and velocity ratio.
Early studies observed response characteristics of elastic
wave velocity to different fluids. Focus eventually shifted to
in-depth analyses of influencing factors and physical mecha-
nisms related to elastic wave velocity.
External factors including temperature and pressure influence elastic wave velocity. But the research for this article
focuses on internal factors such as petrology, physical rock
properties, and fluid saturation. 1-9
Elastic wave velocities differ in stone with varying mineral compositions and contents. Research has established
laws of Vp and Vs in different rock types and studies have
proposed a linear relationship between the compression or
P-wave velocity and formation porosity. 3 10-23
Past research primarily focused on clastic and carbonate
rocks. For igneous rock, which is compacted with a complex
lithology, the influence of internal factors on elastic wave
velocity and the carboniferous cores from the Junggar basin needed further study. The experiment measured elastic