Pore-fissures Characteristics Of The Shale/mudstone Reservoirs And Their Influence On Shale Gas Enrichment In Jiangxi Province

This dissertation selects the shale/mudstone reservoirs in Jiangxi as the main object on the basis of geological surveys, drilling cores observation and sampling. Environmental SEM, mercury intrusion, nitrogen adsorption, nuclear magnetic resonance, cathodoluminescence micrography, adsorption isotherms and other methods were used to study the interstice type, pore structure and other physical properties systematically. Based on the above date, influencing factors of pore development and the control action of pore-fissures characteristics on shale gas accumulation were analyzed.1) Organic pore and mineral pore can be founded easily in the shale/mudstone reservoirs in Jiangxi. Organic pore can be divided into original organic pore and hydrocarbon generating organic pore. Mineral pore can be divided into inter-granular pore, intra-granular pore, intra-crystalline pore, dissolved pore.etc. Macroscopic cracks give first place to large shear fractures, developing "X" type conjugate shear fracture.etc. The microfracture can be divided into intra-granular, grain boundary cracks, integrated micro-cracks including hydrocarbon generating organic cracks and shrinkage joint. Interstice has nested, moniliforme, cluster, crowds and the other combination forms.2) The pore system is from the nanometer to the centimeter level continuously with a higher proportion of mesopores. Nanometer pores can be sorted by morphology, including the parallel-plate holes.etc. Mesoporous provides most of the pore volume. Mesoporous and microporous provide more than 95% of the surface area. The reservoirs have a low porosity and permeability with low mobile water saturation, high irreducible water saturation, moderate gas saturations, ultra-low water saturation. The ultra-low water saturation can enhance the ability of seepage and the risk of shale gas development. Factors of pore-fissures development are tectonics, mineral content, magmatic activity, diagenesis,deposition, gas generating fracturing effect.3) The desorbed gas is poor but the theoretic maximum adsorption capacity of adsorption isotherms reaches the requirement of North America. Ability of adsorption and TOC, the specific surface area, pore volume has a positive correlation respectively. It is noteworthy the specific surface area, pore volume of mesoporous, pore volume of macroporous have the same trend, micropores not. The main reason is that adsorption method of methane molecules in microporous and mesoporous surface is in different ways. Van Edward force is overlapping in microporous. Methane molecules arranged irregularly. Methane moleculars absorb in mesoporous in single molecular layer uniformly. The linear relationship between porosity and the theoretic maximum adsorption capacity is not obvious. There are three principal types of passage system of the shale/mudstone reservoirs in Jiangxi. They are fissure type, pore-fissure type, pore belt type.