Diagenesis and Pore Formation Evolution of Continental Shale in the Da’anzhai Lower Jurassic Section in the Sichuan Basin

As an unconventional oil and gas reservoir, the diagenesis evolution of continental shale controls formation occurrence inorganic organic pores. In order to quantitatively characterize pore characteristics a reservoir their influence on stage, types in Da’anzhai section lower Jurassic Ziliujing Formation were identified by means X-ray diffraction mineral composition analysis argon ion polishing scanning electron microscope measurements observations, control stage development its clarified. The results show following: ① matter pores are developed large quantities, including asphalt matrix kerogen; minerals very rich, main linear between clay minerals, intergranular (intergranular) pores, intragranular corrosion microcracks also developed. ② When affected compaction diagenesis, decrease with increase burial depth degree. ③ is 2000–3000 m middle diagenetic A, number dissolved develop at this depth, meaning that total porosity increases significantly. 3000–4000 B, where kaolinite other dehydrated converted into illite, brittleness increased, interior subject external stress, causing form. late when buried more than 4000 m, secondary cracking hydrocarbon generation, again, due compaction. conclusion, we found factor for microfractures reservoirs; caused affecting case 3500 which B. Inorganic reduced, increased. deep thermal high, methane generated conducive shale.