Study On Geological And Geochemical Features Of Mudstone And Shale In Dongying Depression And Zhanhua Depression

Due to the increased pressure of energy, unconventional shale gas resources begin to cause more and more attention while conventional oil and gas resources can’t meet the needs. Some countries such as America have achieved great success in terms of exploration and exploitation of shale gas. At present, we focus on the exploration of the south marine black shale gas and achieve a certain development, but there is relatively weak research for the shale in eastern continental faulted lake basin. We select the Paleogene shale in Dongying and Zhanhua depression, eastern Bohaibay basin, North East China as research target. The study include the distribution of shale, element geochemical characteristics, mineralogy characteristics, microscopic pore characteristics and adsorption characteristics, aiming to find out the geological inorganic heterogeneity and guide the future exploration and exploitation of the shale gas.The study was based on the methods and results from the previous research that is related to the shale gas. Abudant data was collected including the data from drilling, well log, logging, stratigraphic, element and mineral. Furthermore, many samples were tested in this study to obtain scientific and convincing information.The shale samples from Dongying depression were conducted in numerous experiments such as N2 adsorption experiments, methane adsorption experiments, X-RD whole rock identification experiments, sweep surface electron microscopy experiments.The results suggest that the shale can be divided into clay rock, calcareous mudstone, calcareous shale, oil shale, marlstone according to differences of the mineral compositions in Dongying and Zhanhua depressions. The mudstones and hales have good development and stronge heterogeneity in distribution. In view of elements and minerals that were measured and predicted, different types of mudstones and shales show heterogeneous distribution in their enrichment characteristics vertically or horizontally which are subjected to the differences of depositional environment possibly. Mineral test shows lower clay mineral content and higher carbonate minerals content. Shale has complex microscopic pore structure which is given priority to the ink bottle pore, which is beneficial to gas reservoir. Tests show higher specific surface area and pore volume, and lower pore diameter which is given priority to micro porous and mesoporous. The types of microscopic pore can be divided into the organic pore, the pore in the particle, the pore between the particle and microcracks. There are many factors affecting the shale adsorption. Tests show that specific surface area and pore volume have positive correlations with adsorption gas content while pore diameter shows negative correlation with adsorption gas content. In terms of pore structure, the adsorption from the ink bottle pore structure is higher than that from the parallel plate pore structure. Clay mineral and illite have positive correlations with adsorption gas in content while carbonate mineral such as calcite have negative correlation with adsorption gas in content.