Patent ID: 8005618
Filing Date: 2011-08-23
Classification: E21B,G01V

Abstract:
1. A logging while drilling method, comprising: drilling a wellbore within an earth formation; circulating a fluid within said wellbore and injecting it inside said earth formation under pressure; taking a first measurement of said earth formation using a well logging instrument having a selected type of formation sensor thereon, the selected type of sensor generating signals corresponding to a physical property of the earth formation, as altered by said fluid within said earth formation, during an initial stage of drilling said wellbore, said initial stage taking place while drilling the wellbore; taking a second measurement of said earth formation using a well logging instrument having the selected type of formation sensor thereon, as altered by said fluid within said earth formation, during a later stage after said initial stage of drilling said wellbore; determining a zero-time state measurement of said earth formation, from a combination of said first measurement and said second measurement, wherein said zero-time state measurement represents the physical property of said earth formation prior to drilling said wellbore; and determining an infinite-time state measurement of said earth formation, from a combination of said first measurement and said second measurement, wherein said infinite-time state measurement represents the physical property of said earth formation as altered by said fluid within said earth formation assuming said fluid injection has continued indefinitely, wherein said first measurement and said second measurement are simultaneously inverted in a system of equations wherein said first measurement comprises a resistivity measurement and said second measurement comprises a resistivity measurement, and wherein said first and second measurements are simultaneously inverted to produce a zero-time state resistivity, an infinite-time state resistivity, an initial-stage depth-of-invasion and a later-stage depth-of-invasion.