Patent ID: 6290000
Filing Date: 2001-09-18
Classification: E21B,G01N

Abstract:
A method for determining the characteristics of fluid in a fluid-containing formation while drilling, the formation of interest being traversed by a wellbore drilled by a drill bit, a volume of mud being circulated down through the bit and returning up the wellbore to the surface with gaseous traces of the formation fluid, comprising the steps of:determining formation drillability characteristics including a rate of penetration (ROP);normalizing the rate of penetration (NROP) to remove drillability characteristics which are other than those inherent in the formation;determining an average NROP over the formation of interest;analyzing a volume of the gaseous traces using a first gas sensor for establishing TG values which increase with increasing concentrations of hydrocarbons;determining a dilution factor which is proportional to the average NROP and the circulated volume of mud and which is inversely proportional to the volume of gaseous traces analyzed by the TG sensor;determining a porosity factor for the drilled formation which is proportional to the dilution factor and inversely proportional to the NROP;normalizing the TG values by the porosity factor for establishing normalized TG values which are indicative of the fraction of the fluids which are hydrocarbons.