The Rock Physics Characteristics Experimental Research Of Longnaxi Shale Gas Reservoir

In spite of the growing interest in Late Ordovician to the Early Silurian Longmaxiblack shale for gas production in the southeast of the Sichuan Basin, little data areavailable on the acoustic properties of these shale reservoirs. Dynamic elastic propertiesof a suite of shales from this formation with different organic matter content weremeasured using the ultrasonic transmission technique at a range of confining pressures.The mineralogical features and reservoir space types were studied with the goal toanalyze their influence on acoustic properties of the shale samples. The TOC (totalorganic content) is found to have a positive correlation with the quartz content and anegative correlation with the clay content. Organic matter pores and inter-crystalmicro-pores are the main pore types. Organic-rich shales show low P-wave impedanceand Vp/Vs due to relatively higher TOC and quartz content; nonetheless, high P-waveimpedance is also observed when the quartz content is very high resulting from thevariation of load-bearing grains. The velocities and anisotropy of different shalesamples show varying pressure dependence. A strong positive correlation is foundbetween the anisotropy and the clay content. Three different types of microfabric can beobserved in the shale samples, giving a qualitative explanation for the correlationbetween the anisotropy and the clay content.