Calculation Model of Shale Reserves Considering the Adsorption Layer Based on Molecular Simulation

Area of Science:

• Geochemistry
• Materials Science
• Chemical Engineering

Background:

• Shale gas reservoirs contain methane (CH4) adsorbed within nanopores.
• Accurate estimation of shale gas reserves requires understanding CH4 occurrence and adsorption behavior.
• Existing models may not fully capture the complexities of gas-molecule interactions in nanopores.

Purpose of the Study:

• To simulate the occurrence state and distribution of CH4 molecules in shale nanopores using molecular simulation.
• To investigate the influence of temperature, pressure, and pore width on CH4 distribution and adsorption layer characteristics.
• To develop a calculation model for shale gas reserves that incorporates adsorption effects.

Main Methods:

• Construction of nanopore models using organic matter, montmorillonite, and quartz.
• Molecular simulation to analyze CH4 molecule distribution and adsorption layer properties.
• Development and application of a new shale gas reserve calculation model.

Main Results:

• CH4 molecules exhibit non-uniform distribution in shale nanopores, with distinct peaks near pore surfaces.
• Adsorption layer thickness and density are significantly affected by pressure and temperature.
• The appearance and intensity of distribution peaks increase with rising pressure.
• Ignoring the adsorption layer in reserve calculations can lead to errors of approximately 26%.

Conclusions:

• Methane adsorption in shale nanopores is a critical factor influencing reserve estimations.
• The proposed model, considering adsorption, provides a more accurate assessment of shale gas reserves.
• Accurate reserve calculations necessitate understanding the pressure and temperature-dependent nature of methane adsorption layers.