Modified flow rate analysis

Abstract

Methods, systems, devices, and products for estimating a parameter of interest of an earth formation. The method may include using a correction factor to conduct a flow rate analysis on fluid sampled from the formation via a probe contacting a wall of the borehole, wherein the correction factor compensates for total compressibility; determining at least one of: i) the product of formation porosity and total compressibility; ii) system compressibility; and iii) initial formation pressure; or determining a mobility of the formation using a slope of a linear relationship of a time-dependent pressure of the fluid with respect to a formation flow rate. The parameter of interest may be i) formation mobility or ii) formation permeability. The correction factor may be determined using formation compressibility. The correction factor may be determined using at least one of: i) gas saturation; ii) oil saturation; and iii) water saturation.

What is claimed is: 
     
         1 . A method for estimating a parameter of interest of an earth formation intersected by a borehole, the method comprising:
 using a correction factor to conduct a flow rate analysis on fluid sampled from the formation via a probe contacting a wall of the borehole, wherein the correction factor compensates for total compressibility.   
     
     
         2 . The method of  claim 1 , further comprising determining at least one of: i) the product of formation porosity and total compressibility; ii) system compressibility; and iii) initial formation pressure. 
     
     
         3 . The method of  claim 1 , further comprising determining a mobility of the formation using a slope of a linear relationship of a time-dependent pressure of the fluid with respect to a formation flow rate. 
     
     
         4 . The method of  claim 3 , further comprising applying the correction factor to pressure measurements of the sampled fluid to derive the time-dependent pressure. 
     
     
         5 . The method of  claim 4 , further comprising:
 sampling the fluid from the formation;   taking fluid pressure measurements over time;   determining a volume of the sampled fluid as a function of time; and   determining a corresponding draw rate of the formation fluid as a function of time.   
     
     
         6 . The method of  claim 1 , wherein the parameter of interest is at least one of: i) formation mobility; and ii) formation permeability. 
     
     
         7 . The method of  claim 1 , wherein the correction factor is determined using at least one of: i) a complementary error function; and ii) a numerical inversion of a laplace transform. 
     
     
         8 . The method of  claim 1 , wherein the correction factor is determined using estimated formation porosity and at least one of: i) predicted formation permeability; and ii) predicted formation mobility. 
     
     
         9 . The method of  claim 1 , wherein the correction factor is determined using a geometric factor. 
     
     
         10 . The method of  claim 1 , wherein the correction factor is determined using both draw-down and build-up measurements. 
     
     
         11 . The method of  claim 1 , wherein the correction factor is determined using superposition. 
     
     
         12 . The method of  claim 1 , wherein the correction factor is determined using formation compressibility. 
     
     
         13 . The method of  claim 1 , wherein the correction factor is determined using at least one of: i) gas saturation; ii) oil saturation; and iii) water saturation. 
     
     
         14 . An apparatus for estimating a parameter of interest of an earth formation intersected by a borehole, the apparatus comprising:
 a tool body;   a fluid sampling unit associated with the tool body configured to sample fluid from the formation while in the borehole, the fluid sampling unit including a probe configured to contact a wall of the borehole; and   a processor configured to use a correction factor to conduct a flow rate analysis on fluid sampled from the formation by the fluid sampling unit, wherein the correction factor compensates for total compressibility.   
     
     
         15 . The method of  claim 14 , further comprising determining at least one of: i) the product of formation porosity and total compressibility; ii) system compressibility; and iii) initial formation pressure. 
     
     
         16 . The apparatus of  claim 14 , wherein the processor is configured to determine a mobility of the formation using a slope of a linear relationship of a time-dependent pressure of the fluid with respect to a formation flow rate. 
     
     
         17 . The apparatus of  claim 16 , wherein the processor is configured to apply the correction factor to pressure measurements of the sampled fluid to derive the time-dependent pressure. 
     
     
         18 . A method for estimating a parameter of interest of an earth formation intersected by a borehole, the method comprising:
 modeling the formation using an adjusted time-dependent pressure of a fluid sampled from the formation through a probe extending to the formation through a wall of the borehole, wherein the adjusted time-dependent pressure is determined by applying a correction factor compensating for total compressibility to time-dependent pressure measurements of the fluid.   
     
     
         19 . A non-transitory computer-readable medium product having instructions thereon that, when executed, cause at least one processor to perform a method, the method comprising:
 using a correction factor to conduct a flow rate analysis on fluid sampled from the formation via a probe contacting a wall of the borehole, wherein the correction factor compensates for total compressibility.   
     
     
         20 . The non-transitory computer-readable medium product of  claim 19  further comprising at least one of: (i) a ROM, (ii) an EPROM, (iii) an EEPROM, (iv) a flash memory, or (v) an optical disk.