Patent ID: 8583377

Claim:
A method comprising: placing a tool within a borehole, the borehole penetrating a formation and the borehole comprising drilling fluid; irradiating the formation with gammas from a source of gammas that resides within the tool, wherein drilling fluid has invaded the formation, and wherein Pe of the drilling fluid that has invaded the formation is greater than Pe of the formation; determining a first value indicative of a parameter of the formation, the first value based on a first set of gammas detected at a first gamma detector; determining a second value indicative of a parameter of the formation, the second value based on a second set of gammas detected at a second gamma detector; determining a third value, the third value determined based on gammas in an energy range different than used in determining the first value; and calculating, using the first, second, and third values, at least one selected from the group consisting of: a standoff; a formation porosity; a formation density prior to invasion by the drilling fluid; and radial depth of invasion of the drilling fluid into the formation.