Pressure-preserved coring tool, use method, and reservoir analysis method

A reservoir analysis method, comprising:

• S1. drilling out a rock core in a reservoir with a pressure-preserved coring tool which comprises:
• an outer cylinder with an axially extending hollow cavity formed therein, wherein the outer cylinder has a first end and a second end;
• and
• a differential assembly, a downhole rock core cleaning assembly, a pressure-preserving inner cylinder assembly and a seal assembly that are arranged from top to bottom in the hollow cavity in series, wherein the pressure-preserving inner cylinder assembly as an inner cylinder assembly for accommodating a rock core, the inner cylinder assembly comprises a glass fiber tube and an upper joint and a lower joint respectively connected to two ends of the glass fiber tube, the upper joint and the lower joint are non-ferromagnetic alloy parts,
• wherein the downhole rock core cleaning assembly is arranged to clean the rock core contained in the inner cylinder assembly by injecting a cleaning solvent into the inner cylinder assembly when driven by the differential assembly, and moves the pressure-preserving inner cylinder assembly toward the first end of the outer cylinder after completing cleaning, the seal assembly is arranged to close an accommodating space of the inner cylinder assembly at the second end of the outer cylinder after the pressure-preserving inner cylinder assembly moves toward the first end of the outer cylinder;
• S2. taking out the pressure-preserving inner cylinder assembly and the seal assembly integrally from the pressure-preserved coring tool, while preserving the pressure in the accommodating space of the inner cylinder assembly;
• and
• S3. placing the pressure-preserving inner cylinder assembly and the seal assembly in combination in a nuclear magnetic resonance analyzer for testing.