Method to estimate the influence of pore-size distribution on phase equilibrium of multi-component hydrocarbon systems in unconventional shale gas and oil reservoirs

A system for transforming a property of an earth formation based on estimating liquid and vapor molar fraction of components, liquid mole fraction, vapor mole fraction, liquid saturation, and vapor saturation of a mixture of hydrocarbons in nano-pores in an earth formation, the system comprising:

• a memory having computer-readable instructions;
• a processor for executing the computer-readable instructions, the computer-readable instructions comprising:
• constructing an equation of state (EOS) representing the mixture of hydrocarbons in the nano-pores in the earth formation;
• the EOS comprising a term accounting for capillary pressure in the nano-pores;
• inputting a composition of the mixture of hydrocarbons and a phase pressure of the hydrocarbons into the EOS;
• inputting a pore size distribution of the earth formation into the EOS;
• and
• solving the EOS to estimate the liquid and vapor molar fraction of components, liquid mole fraction, vapor mole fraction, liquid saturation, and vapor saturation of the mixture of hydrocarbons in the nano-pores in the earth formation;
• physical action-related apparatus configured to transform the property of the earth formation by performing a physical action on the earth formation based on at least one of the estimated liquid molar fraction, vapor molar fraction, liquid mole fraction, vapor mole fraction, liquid saturation, and vapor saturation of components of a hydrocarbon in the nano-pores in the earth formation.