Influences of the Diagenetic Evolution of Aluminosilicate Minerals on the Formation of the Transitional Zone Gas

The formation of oil and gas is not a simple process of the transformation among organic matters. In other words, it is a result of the interaction between organic- inorganic matters which take place at the early diagenetic stage. The essence of this process is the elastic aluminosilicate mineral dissolution and diagenetic evolution of clay minerals during diagenesis in the transitional zone. In general, sandstone undergoes a series of diagenesis including compaction, cementation, dissolution, replacement and formation of authigenic minerals, while mudstone mainly changes its clay mineral composition by way of the M→I/M→I and M→C/M→C transformation which could produce proton acid when organic acid dissolves sandstone and replaces Si⁴⁺ in montmorillonite with Al³⁺ in pore water. The proton acid plays an important role in catalysis for the formation of the transitional zone natural gas.