Inert fluid assays for sealed core recovery

A method of assaying a test fluid for collecting reservoir core samples at reservoir temperature and pressure (RTP) and determining if said test fluid is inert at RTP, said method comprising:

• a) assaying a live oil to generate a first dataset using methods comprising at least one of:
• i) determining a weight contribution of components of said live oil;
• ii) determining a bubble point of said live oil;
• iii) determining a density of a remaining oil when said live oil is flashed to standard temperature and pressure (STP) or ambient conditions;
• iv) determining a weight contribution of gaseous components flashed from said live oil;
• or
• v) determining total acid number (TAN), metal content, viscosity, asphaltene content, C7 content, nitrogen content, water content, carbon content, total contents, wax content, carbon residue content, conductivity, pour point, density at 15° C., salt content, sediment content, specific gravity, light end hydrocarbon content, mercaptan content, hydrogen content, total sulfur, hydrogen sulfide content or vapor pressure of said hydrocarbon phase or said remaining hydrocarbon phase;
• b) assaying said live oil plus a test fluid mixed together and equilibrated at RTP to form hydrocarbon phase and a test fluid phase to generate a second dataset, using methods comprising at least one of:
• i) determining a bubble point of said hydrocarbon phase;
• ii) determining a weight contribution of components of said hydrocarbon phase;
• iii) determining a density of a remaining hydrocarbon phase when said hydrocarbon phase is flashed to STP or ambient conditions;
• iv) determining a weight contribution of gaseous components flashed from said hydrocarbon phase;
• or
• v) determining total acid number (TAN), metal content, viscosity, asphaltene content, C7 content, nitrogen content, water content, carbon content, total contents, wax content, carbon residue content, conductivity, pour point, density at 15° C., salt content, sediment content, specific gravity, light end hydrocarbon content, mercaptan content, hydrogen content, total sulfur content, hydrogen sulfide content or vapor pressure of said hydrocarbon phase or said remaining hydrocarbon phase;
• c) comparing said first dataset and said second dataset, wherein changes in said second dataset compared with said first dataset indicates that said test fluid is not inert, but no changes indicates said test fluid is inert and can be used to collect reservoir core samples at RTP.