Methods To Characterize Underground Formation

Abstract

A method for determining a characteristic of an underground formation with a fluid is described. The method includes providing a sample material of the underground formation; measuring the permeability and the porosity of the sample material; performing a drainage test on the sample material using the fluid; estimating the threshold pressure of the sample material from the drainage test, the permeability and the porosity measurements; and determining the receding contact angle of the fluid on the sample material from the threshold pressure. The sample material can be disaggregated material.

1 - 18 . (canceled) 
     
     
         19 . A method for determining a characteristic of an underground formation comprising:
 a. providing a sample material of the underground formation;   b. determining the threshold pressure of the sample material from a drainage test;   c. computing the average saturation of the sample material using a measured irreducible saturation and the saturation at the threshold pressure;   d. determining the average threshold pressure of the sample material from the average saturation;   e. determining the threshold pressure at the irreducible saturation of the underground formation from the average threshold pressure, the average saturation and the measured irreducible saturation.   
     
     
         20 . A method for enhancing hydrocarbon recovery from a low-permeability formation comprising:
 causing at least one treating fluid to contact the underground formation such that the at least one treating fluid is imbibed by the formation, thereby increasing hydrocarbon recovery, wherein the at least one treating fluid is selected based at least in part on the determination of the receding contact angle of the treating fluid on the underground formation.   
     
     
         21 . A formation treating fluid for enhancing hydrocarbon recovery from an underground formation comprising at least one constituent selected based at least in part on a quantitative determination of the permeability and the porosity of the underground formation and a drainage test carried out on the sample of the underground formation and the at least one constituent. 
     
     
         22 . A formation treating fluid according to  claim 21 , wherein the drainage test comprises determination of the receding contact angle of the at least one constituent on the sample of the underground formation. 
     
     
         23 . A formation treating fluid according to  claim 21 , wherein the sample of the underground formation comprises disaggregated material. 
     
     
         24 . A method for determining the effect of a fluid on a rock formation comprising:
 a. determining the permeability and the porosity of the rock formation;   b. saturating the rock formation with the fluid;   c. determining the threshold pressure of the rock formation imbibed with the fluid from a drainage test, the permeability and the porosity of the rock formation;   d. determining a cleanup ratio of the fluid for the rock formation using the ratio of the threshold pressure and the maximum threshold pressure wherein the maximum threshold pressure is the threshold pressure for a perfectly wetting fluid.   e. determining the effect of the fluid on the rock formation from the cleanup ratio.   
     
     
         25 . A method according to  claim 24 , further comprising determining the receding contact angle of the fluid on the rock formation from the threshold pressure. 
     
     
         26 . A method according to  claim 24 , further comprising performing an imbibition test on the rock formation prior to the drainage test. 
     
     
         27 . A method according to  claim 26 , wherein the imbibition test includes an estimation of the advancing contact angle on the rock formation. 
     
     
         28 . A method according to  claim 24 , further comprising repeating steps (a) to (e) for at least a second fluid and comparing the effect of first and second fluids on the rock formation using the clean-up ratio of the first and second fluids respectively. 
     
     
         29 . A method according to  claim 24 , further comprising the step of disaggregating the rock formation to form a disaggregated rock formation sample and performing steps (a) to (e) on the disaggregated rock formation sample. 
     
     
         30 . A method of selecting a treatment fluid for enhancing hydrocarbon recovery from an underground formation, the method comprising:
 a. determining permeability and porosity of a first sample material of the underground formation;   b. imbibing the first sample material with a first candidate fluid;   c. testing the first sample material for drainage characteristics for the first candidate fluid;   d. repeating the determining of permeability and porosity and testing drainage characteristics for each of one or more subsequent sample materials from underground formation and each of one or more subsequent candidate fluids; and   e. selecting a candidate fluid based at least in part on the drainage testing, the selected candidate fluid forming at least part of the treatment fluid.   
     
     
         31 . A method according to  claim 30  wherein each testing for drainage characteristics includes an estimation of the receding contact angle for each sample material and candidate fluid, each estimation of receding contact angle being based in part on the determination of permeability and porosity of the sample material, and step of selecting a candidate fluid being based in part on the estimations of receding contact angle. 
     
     
         32 . A method according to  claim 30 , wherein the sample material comprises disaggregated material from the underground formation. 
     
     
         33 . A method according to  claim 30 , wherein the candidate fluid is imbibed in the sample material to reach complete saturation. 
     
     
         34 . A method according to  claim 30 , further comprising performing an imbibition test on the sample material prior to the drainage test. 
     
     
         35 . A method according to  claim 34 , further comprising selecting a candidate fluid based at least in part on the fact that, with the candidate fluid, the reduction of the drainage contact angle on the sample material is less than the reduction of the advancing contact angle on the sample material. 
     
     
         36 - 37 . (canceled)