Methods and apparatus for collecting and preserving core samples from a reservoir

A method of analyzing a core sample collected from a reservoir, comprising:

• providing a pressurized vessel comprising the core sample, the pressurized vessel sealed downhole in a wellbore extending into a reservoir after collecting the core sample from the reservoir
• reducing, in one or more steps, a pressure of the pressurized vessel to atmospheric pressure, each step comprising:
• releasing an amount of a gas, an amount of a fluid or any combination thereof, to reduce the pressure of the pressurized vessel by a pressure value;
• and
• determining the released amount of the gas, the released amount of the fluid, or any combination thereof;
• determining, after reducing the pressure of the pressurized vessel to atmospheric pressure, a total amount of the gas released and a total amount of the fluid released;
• and
• calculating a hydrocarbons-in-place value based on the total amount of the gas released and the total amount of the fluid released.