Multi-probe pressure test

Abstract

A method and device for determining a formation gradient. The device comprises probes that are a set distance apart, disposing the device into a wellbore and measuring formation pressure with the probes provides formation pressures that can be correlated with the set distance. The measured pressures and correlated set distance is used to determine the formation gradient.

1 . A method of evaluating a formation gradient comprising:
 sampling the formation pressure at locations a set distance apart; and   calculating the formation gradient based on the sampled formation pressure and the set distance.   
   
   
       2 . The method of  claim 1  wherein the step of sampling is conducted with probes. 
   
   
       3 . The method of  claim 1 , wherein the step of calculating the formation gradient comprises taking the ratio of the change in pressure at the locations a set distance apart. 
   
   
       4 . The method of  claim 2 , wherein the probes comprise two probes. 
   
   
       5 . The method of  claim 2 , wherein the probes comprise a multiplicity of probes. 
   
   
       6 . The method of  claim 1 , wherein the set distance is constant. 
   
   
       7 . The method of  claim 1 , wherein the set distance varies. 
   
   
       8 . The method of  claim 1  further comprising sampling fluid from within the formation. 
   
   
       9 . The method of  claim 7  further comprising analyzing the sampled fluid. 
   
   
       10 . The method of  claim 1 , wherein the set distance between adjacent locations from about 0.5 feet to about 5 feet. 
   
   
       11 . The method of  claim 1 , wherein the set distance between adjacent locations ranges from about 1 foot to about 2 feet. 
   
   
       12 . The method of  claim 1 , wherein the set distance between adjacent locations is about 1 foot. 
   
   
       13 . The method of  claim 2 , wherein the probes are on a downhole tool configured for connate fluid sampling. 
   
   
       14 . The method of  claim 1  further comprising identifying a formation compartment. 
   
   
       15 . The method of  claim 1  further comprising determining fluid properties within a formation compartment. 
   
   
       16 . A method of sampling subterranean formation fluid comprising:
 drawing a first amount of connate fluid from the formation, thereby creating a clean region in the formation; and   drawing a second amount of connate fluid from the clean region of the formation.   
   
   
       17 . The method of  claim 16 , wherein the step of drawing amounts of connate fluid is performed with probes. 
   
   
       18 . The method of  claim 17 , wherein the probes are adjacently disposed. 
   
   
       19 . The method of  claim 17  wherein the probes comprise cleaning probes disposed on opposite sides of a sampling probe. 
   
   
       20 . The method of  claim 16 , wherein the step of creating a clean region comprises drawing particulate matter entrained within the formation fluid. 
   
   
       21 . A fluid sampling system comprising:
 probes disposed apart a set distance; and   an analyzer configured to calculate subterranean formation gradient based on a fluid pressure measurement of the probes and the set distance.   
   
   
       22 . The fluid sampling system of  claim 21  further comprising a body on which the probes are located. 
   
   
       23 . The fluid sampling system of  claim 21 , wherein the probes are configured to pierce the wall of a wellbore and sample fluid from a formation adjacent the wellbore. 
   
   
       24 . The fluid sampling system of  claim 21  further comprising a pump in fluid communication with the probes. 
   
   
       25 . The fluid sampling system of  claim 21  wherein the set distance varies. 
   
   
       26 . The fluid sampling system of  claim 21  wherein the set distance is substantially same. 
   
   
       27 . The fluid sampling system of  claim 21  wherein the set distance ranges from about 0.5 feet to about 5 feet. 
   
   
       28 . The fluid sampling system of  claim 21  wherein the set distance ranges from about 1 foot to about 2 feet. 
   
   
       29 . The fluid sampling system of  claim 21 , wherein the analyzer comprises an information handling system. 
   
   
       30 . The fluid sampling system of  claim 21  further comprising surface equipment. 
   
   
       31 . A connate sampling system comprising:
 a sample probe; and   a cleaning probe.   
   
   
       32 . The connate sampling system of  claim 31  further comprising a pump in fluid communication with at least one of the probes. 
   
   
       33 . The connate sampling system of  claim 31  further comprising a second cleaning probe. 
   
   
       34 . The connate sampling system of  claim 31  further comprising a body. 
   
   
       35 . The connate sampling system of  claim 31  wherein said cleaning probe is configured to selectively draw contaminated connate fluid. 
   
   
       36 . The connate sampling system of  claim 31  wherein said sample probe is configured to selectively draw clean connate fluid. 
   
   
       37 . The connate sampling system of  claim 31  further comprising an information handling system.