Patent ID: 9103926
Filing Date: 2015-08-11
Classification: E21B,G01V

Abstract:
1. A method of determining a porosity of a formation surrounding a borehole, the method comprising the steps of: injecting a drilling fluid that penetrates a distance into the formation as a function of time: obtaining a first porosity measurement and a second porosity measurement, wherein the first porosity measurement is a first type apparent porosity measurement and the second porosity measurement is a second type apparent porosity measurement, wherein the first and second porosity measurements provide different porosity measurement values in a presence of a gas having a known characteristic; wherein obtaining the first porosity measurement and the second porosity measurement comprises obtaining the first porosity measurement and the second porosity measurement, both taken at a first time and at a second time; and wherein the first and second porosity measurements are selected to have substantially the same depth-of-investigation into the formation and are affected approximately proportionally by the gas; and determining the porosity of the formation using the first and second porosity measurements and the known gas characteristic, wherein determining the porosity of the formation comprises determining the porosity of the formation from an intersection point between a line connecting two data points representing the first and second porosity measurements respectively taken at the first and second times and a line representing formation porosity values in an absence of the gas.