Porosity estimator for formate brine invaded hydrocarbon zone

A system for estimating a property of an earth formation comprising hydrocarbon and non-hydrocarbon components, the system comprising:

• a carrier configured to be conveyed through a borehole penetrating the earth formation;
• an NMR instrument disposed at the carrier and configured to perform nuclear magnetic resonance (NMR) measurements on fluid in the formation to provide total NMR measurement data that includes a combination of hydrocarbon-resultant NMR measurement data and non-hydrocarbon-resultant NMR measurement data;
• and
• a processor configured to separate the total NMR measurement data into the hydrocarbon-resultant NMR measurement data and the non-hydrocarbon-resultant NMR measurement data, scale a portion of the non-hydrocarbon-resultant NMR measurement data based on a correction factor to obtain scaled non-hydrocarbon-resultant NMR measurement data, and estimate the property based on the hydrocarbon-resultant NMR measurement data and the scaled non-hydrocarbon-resultant NMR measurement data.

A non-transitory computer-readable medium configured to store instructions that, when processed by a processor, cause the processor to perform a method of estimating a property of an earth formation comprising hydrocarbon and non-hydrocarbon components, the method comprising:

• receiving total NMR measurement data based on fluid in the earth formation from an NMR instrument disposed at a carrier conveyed through a borehole penetrating the earth formation, the total NMR measurement data including a combination of hydrocarbon-resultant NMR measurement data and non-hydrocarbon-resultant NMR measurement data;
• separating the total NMR measurement data into the hydrocarbon-resultant NMR measurement data and the non-hydrocarbon-resultant NMR measurement data;
• scaling a portion of the non-hydrocarbon-resultant NMR measurement data based on a correction factor to obtain scaled non-hydrocarbon-resultant NMR measurement data;
• and
• estimating the property based on the hydrocarbon-resultant NMR measurement data and the scaled non-hydrocarbon-resultant NMR measurement data.