Noise characterization in formation testing

Abstract

Herein are described methods and systems for characterizing noise and noise level during downhole pressure testing and/or sampling operations. Methods and systems may identify and quantify the noise level of a formation pressure testing and/or sampling operations by measuring pressures with the probe pressure sensor and the tool pressure sensor with and without extension of the dual probe and closing the bubble point valve that connects the probe fluid passageway to the tool fluid passageway.

What is claimed is: 
     
         1 . A method comprising:
 disposing a tool into a borehole, the tool disposed on a drill string or a conveyance, wherein the tool comprises:
 one or more probes that extend into a formation; 
 a probe fluid passageway to connect a fluid from the formation through the one or more probes; 
 a bubble point valve that connects the probe fluid passageway to a tool fluid passageway; 
 a probe pressure sensor disposed on the probe fluid passageway; 
 a tool pressure sensor disposed on the tool fluid passageway; 
   taking a first pressure measurement at the probe pressure sensor;   closing the bubble point valve;   taking a first pressure measurement at the tool pressure sensor;   opening the bubble point valve;   extending the one or more probes into an inner surface of the borehole;   taking a second pressure measurement at the probe pressure sensor;   closing the bubble point valve;   taking a second pressure measurement at the tool pressure sensor; and   calculating a noise, wherein the noise comprises a sum of:
 a difference between the second pressure measurement at the probe pressure sensor and the first pressure measurement at the probe pressure sensor; and 
 a difference between the second pressure measurement at the tool pressure sensor and the first pressure measurement at the tool pressure sensor. 
   
     
     
         2 . The method of  claim 1 , wherein the noise comprises a common system noise, operational noise, or formation-related noise. 
     
     
         3 . The method of  claim 2 , wherein the common system noise is from a tool vibration, a gauge-related noise, or another tool. 
     
     
         4 . The method of  claim 2 , wherein the operational noise is from a mud pump rate, a pulser, a depth, and a bit position. 
     
     
         5 . The method of  claim 2 , wherein the operational noise is from a mud thickness and mobility of the formation. 
     
     
         6 . The method of  claim 1 , further indicating the one or more probes are not in fluid communication with the formation when the difference is null. 
     
     
         7 . The method of  claim 1 , further identifying a type of fluid within the tool fluid passageway based on pressure drop during drawdown. 
     
     
         8 . A method comprising:
 disposing a tool into a borehole, the tool disposed on a drill string or a conveyance, wherein the tool comprises:
 one or more probes that extend into a formation; 
 a probe fluid passageway to connect a fluid from the formation through the one or more probes; 
 a bubble point valve that connects the probe fluid passageway to a tool fluid passageway; 
 a probe pressure sensor disposed on the probe fluid passageway; 
 a tool pressure sensor disposed on the tool fluid passageway; 
   taking a first set of pressure measurements at the probe pressure sensor;   closing the bubble point valve;   taking a first set of pressure measurements at the tool pressure sensor;   opening the bubble point valve;   extending the one or more probes into an inner surface of the borehole;   taking a second set of pressure measurements at the probe pressure sensor;   closing the bubble point valve;   taking a second set of pressure measurements at the tool pressure sensor; and   calculating a noise, wherein the noise comprises a sum of:
 a difference of a pressure distribution at the probe pressure sensor before and after closing the bubble point valve; and 
 a difference of a pressure distribution at the tool pressure sensor before and after closing the bubble point valve. 
   
     
     
         9 . The method of  claim 8 , wherein the noise comprises a common system noise and formation-related noise. 
     
     
         10 . The method of  claim 9 , wherein the formation-related noise is from a mud thickness and mobility of the formation. 
     
     
         11 . The method of  claim 8 , wherein the noise comprises a common system noise and operational noise. 
     
     
         12 . The method of  claim 11 , wherein the common system noise is from a tool vibration, a gauge-related noise, or another tool. 
     
     
         13 . The method of  claim 8 , further indicating the one or more probes are not in fluid communication with the formation when the difference is null. 
     
     
         14 . The method of  claim 8 , further identifying a type of fluid within the tool fluid passageway based on pressure drop during drawdown. 
     
     
         15 . A method comprising:
 disposing a tool into a borehole, the tool disposed on a drill string or a conveyance, wherein the tool comprises:
 one or more probes that extend into a formation; 
 a probe fluid passageway to connect a fluid from the formation through the one or more probes; 
 a bubble point valve that connects the probe fluid passageway to a tool fluid passageway; 
 a probe pressure sensor disposed on the probe fluid passageway; 
 a tool pressure sensor disposed on the tool fluid passageway; 
   taking a first set of pressure measurements at the probe pressure sensor;   closing the bubble point valve;   taking a first set of pressure measurements at the tool pressure sensor;   opening the bubble point valve;   extending the one or more probes into an inner surface of the borehole;   taking a second set of pressure measurements at the probe pressure sensor;   closing the bubble point valve;   taking a second set of pressure measurements at the tool pressure sensor; and   calculating a noise, wherein the noise comprises a sum of:
 a difference of a standard deviation at the probe pressure sensor before and after closing the bubble point valve; and 
 a difference of a standard deviation at the tool pressure sensor before and after closing the bubble point valve. 
   
     
     
         16 . The method of  claim 15  wherein the noise comprises a common system noise and formation-related noise. 
     
     
         17 . The method of  claim 16 , wherein the formation-related noise is from a mud thickness and mobility of the formation. 
     
     
         18 . The method of  claim 15 , wherein the noise comprises a common system noise and operational noise. 
     
     
         19 . The method of  claim 18 , wherein the common system noise is from a tool vibration, a gauge-related noise, or another tool. 
     
     
         20 . The method of  claim 15 , further identifying a type of fluid within the tool fluid passageway based on pressure drop during drawdown.