Applications Based On Fluid Properties Measured Downhole

Abstract

Downhole drilling fluid measurements are made as a function of time or as a function of depth. A change in the downhole drilling fluid measurements is correlated to a feature of a formation penetrated by a drill bit or to a feature of fluids in the formation. The downhole drilling fluid measurements may include density, photoelectric factor, hydrogen index, salinity, thermal neutron capture cross section (Sigma), resistivity, slowness, slowing down time, sound velocity, and elemental composition. The feature may include fluid balance, hole-cleaning, a kick, a shallow water flow, a formation fluid property, formation fluid typing, geosteering, geostopping, or an environmental correction. A downhole system has a measurement-while-drilling tool or a logging-while-drilling tool and a processor capable of obtaining the downhole drilling fluid measurements and correlating the change in the downhole drilling fluid measurements.

What is claimed is: 
     
         1 . A method, comprising:
 obtaining downhole drilling fluid measurements as a function of time or as a function of depth; and   correlating a change in the downhole drilling fluid measurements to a feature of a formation penetrated by a drill bit or to a feature of fluids in the formation.   
     
     
         2 . The method of  claim 1 , wherein the downhole drilling fluid measurements are selected from a group consisting of density, photoelectric factor, hydrogen index, salinity, thermal neutron capture cross section (Sigma), resistivity, slowness, slowing down time, sound velocity, and elemental composition. 
     
     
         3 . The method of  claim 1 , wherein the feature is used in an application selected from a group consisting of determining fluid balance, monitoring a hole-cleaning process, recognizing a kick, determining shallow water flow, determining a formation fluid property, determining a formation fluid type, determining a formation lithology type, geosteering, geostopping, and determining an environmental correction. 
     
     
         4 . A method, comprising:
 obtaining downhole drilling fluid measurements as a function of time or as a function of depth; and   monitoring a drilling process based on the downhole drilling fluid measurements.   
     
     
         5 . The method of  claim 4 , further comprising making one or more drilling-decisions based on information obtained from the monitoring of the drilling process. 
     
     
         6 . The method of  claim 5 , wherein the one or more drilling-decisions are made in real-time. 
     
     
         7 . A method, comprising:
 obtaining downhole drilling fluid measurements as a function of time or as a function of depth; and   inferring one or more formation properties based on the downhole drilling fluid measurements.   
     
     
         8 . The method of  claim 7 , wherein the inferring comprises identifying a formation fluid type. 
     
     
         9 . The method of  claim 8 , wherein the formation fluid type is selected from a group consisting of water, oil, and gas. 
     
     
         10 . The method of  claim 8 , wherein the identifying the formation fluid type comprises examining a measured mud density in light of a rate of penetration and a drilling fluid flow rate, and inferring a density of the fluid contained within the formation. 
     
     
         11 . The method of  claim 8 , wherein the formation fluid is flushed.