The Rock Physics Characteristics Experimental And Modeling Research Of Longnaxi Formation Shale Gas Reservoir

With the rising attention to Longmaxi shale gas in China, research on enrichment conditions of shale gas is constantly advancing. However, the experiment data on the elastic properties of Longmaxi shale gas reservoir are rare. This paper collected dozens of samples, the compression and shear wave velocity were determined by the measurement of ultrasonic transmission method, and made the composition analysis and microstructure analysis of part of the samples.In the research, TOC content was found to have a positive correlation with quartz content while it has a negative correlation with clay content, for which was mostly decided by the sedimentary environment. Through the observation of SEM and nano CT, find that the main pore type is organic matter pore and intragranular pore.The samples shows characteristics of low Vp/Vs and low impedance as the result of the high content of quartz and TOC. As we found two different types of ultrasonic speed change, we regard as the change of the micro cracks inside shale.In this paper, the static test for some samples were taken, and we found the Longmaxi shale mainly failure in the splitting way. We find static elastic anisotropy from different direction has different static mechanical parameters, and the static elastic anisotropy is greater than the dynamic elastic anisotropy.By all the results mentioned above, we constructed rock physical template for Longmaxi shale. The relationship between the elastic properties and the brittle shale and kerogen content was calculated using the template, and the template was verified using the well data, successfully pointed out the sweet spot of Longmaxi shale gas reservoir.