METHODS OF EVALUATING ROCK PROPERTIES WHILE DRILLING USING DOWNHOLE ACOUSTIC SENSORS AND A DOWNHOLE BROADBAND TRANSMITTING SYSTEM

• US 20130075161A1
• Filed: 07/20/2012
• Published: 03/28/2013
• Est. Priority Date: 09/26/2011
• Status: Active Grant

• Current Assignee: Saudi Arabian Oil Company (Government of Saudi Arabia)
• Original Assignee: Saudi Arabian Oil Company (Government of Saudi Arabia)
• Inventors: Yang, Yunlai
• Granted Patent: US 10,180,061 B2
• Time in Patent Office: Days
• US Class Current: 175/50
• CPC Class Codes: E21B 49/00 Testing the nature of borehole walls; Formation testing; Methods or apparatus for obtaining samples of soil or well fluids, specially adapted to earth drilling or wells

Abstract

Methods of identifying rock properties in real-time during drilling, are provided. An example of such a method includes connecting a downhole sensor subassembly between a drill bit and a drill string, operably coupling acoustic sensors to a downhole data interface, and operably coupling a surface computer to the downhole data interface. The method can also include receiving raw acoustic sensor data generated real-time as a result of rotational contact of the drill bit with rock during drilling, transforming the raw data into the frequency domain, filtering the transformed data, and deriving a plurality of acoustic characteristics from the filtered data. This can be performed by a petrophysical properties analyzing program stored in memory of the computer. The method can also include deriving petrophysical properties from the filtered data utilizing a petrophysical properties evaluation algorithm employable to predict one or more petrophysical properties of rock undergoing drilling.

Claims

1. A method of analyzing properties of rock in a formation in real-time during drilling, the method comprising the steps of:

sending sampling commands to a surface data acquisition unit in communication with a downhole data interface through a surface data interface and a communication medium extending between the surface data interface and the downhole data interface, the downhole data interface operably coupled to a plurality of acoustic sensors carried by a downhole sensor assembly, the raw acoustic sensor data representing an acoustic signal generated real-time as a result of rotational contact of a drill bit with rock during drilling;

receiving, by a computer, digitized raw acoustic sensor data from the surface data acquisition unit;

transforming the raw acoustic sensor data into the frequency domain;

filtering the transformed data; and

performing, by the computer, one or more of the following processing steps;

deriving a plurality of acoustic characteristics from the filtered data, the plurality of acoustic characteristics including mean frequency and normalized deviation of frequency, and

deriving petrophysical properties from the filtered data utilizing a petrophysical properties evaluation algorithm employable to predict one or more petrophysical properties of rock undergoing drilling.

2. A method as defined in claim 1, wherein the one or more processing steps comprise deriving the plurality of acoustic characteristics from the filtered data, the method further comprising the steps of:

comparing the mean frequency and the normalized deviation of frequency for the rock undergoing drilling with mean frequency and normalized deviation of frequency for a plurality of rock samples having different lithologies; and

identifying lithology type of the rock undergoing drilling responsive to the step of comparing.

3. A method as defined in claim 2, wherein the mean frequency and normalized deviation of frequency are examined together as part of the step of comparing to thereby determine an amount of correlation of the acoustic characteristics associated with the rock undergoing drilling and the acoustic characteristics associated with the rock samples.

4. A method as defined in claim 2,

wherein the step of comparing further includes employing mean amplitude, normalized deviation of amplitude, and apparent power as part of the comparison to further enhance accuracy of the lithology determination;

and

wherein the mean frequency and the mean amplitude are examined together to determine an amount of correlation of the acoustic characteristics associated with the rock undergoing drilling and the acoustic characteristics associated with the rock samples.

5. A method as defined in claim 2, wherein the one or more petrophysical properties comprise:

lithology type, porosity, water saturation, and permeability of rock undergoing drilling.

6. A method as defined in claim 1, wherein the one or more petrophysical properties comprise:

presence of hydrocarbons in rock undergoing drilling when existing and presence of fractures in the rock undergoing drilling when existing.

7. A method as defined in claim 1,

wherein the plurality of acoustic characteristics further include mean amplitude, normalized deviation of amplitude, and apparent power;

wherein the one or more processing steps comprise deriving the plurality of acoustic characteristics from the filtered data; and

wherein the method further comprises the steps of;

comparing the mean frequency, the normalized deviation of frequency, the mean amplitude, and the normalized deviation of amplitude, and the apparent power for the rock undergoing drilling with mean frequency, normalized deviation of frequency, mean amplitude, normalized deviation of amplitude, and apparent power for a plurality of rock samples having different known lithologies to thereby determine an amount of correlation of the acoustic characteristics associated with the rock undergoing drilling and the acoustic characteristics associated with the rock samples, and

determining a location of a formation boundary encountered during drilling responsive to the step of comparing.

8. A method as defined in claim 1, wherein the one or more processing steps comprise deriving the petrophysical properties from the filtered data utilizing a petrophysical properties evaluation algorithm, wherein the petrophysical properties evaluation algorithm is a bit-specific petrophysical properties evaluation algorithm, the method further comprising the steps of:

collecting petrophysical properties data describing one or more petrophysical properties of rock contained in a data set and correspondent acoustic data for a preselected type of drill bit;

processing the collected acoustic data to produce filtered FFT data;

determining one or more relationships between features of the filtered FFT data and correspondent one or more petrophysical properties of rock for each type of drill bit; and

coding the determined relationships into computer program code defining the petrophysical properties algorithm; and

wherein the step of deriving the petrophysical properties includes employing the petrophysical properties evaluation algorithm to predict one or more petrophysical properties of the rock undergoing drilling real-time responsive to filtered data associated with raw acoustic sensor data produced in response to the drilling.

9. A method as defined in claim 8, wherein the collected petrophysical properties data describes petrophysical properties of a plurality of samples taken from the formation undergoing drilling operations.

10. A method as defined in claim 1, wherein the one or more processing steps comprise deriving the petrophysical properties from the filtered data utilizing a petrophysical properties evaluation algorithm, wherein the petrophysical properties evaluation algorithm is a bit-independent petrophysical properties evaluation algorithm, the method further comprising the steps of:

collecting petrophysical properties data describing one or more petrophysical properties of rock and correspondent acoustic data for a plurality of different types of drill bits;

processing the collected acoustic data to produce filtered FFT data;

determining bit-type independent features of the filtered FFT data;

determining one or more relationships between the bit-type independent features of the filtered FFT data and correspondent one or more petrophysical properties of the rock; and

coding the determined relationships into computer program code defining the petrophysical properties algorithm; and

wherein the step of deriving the petrophysical properties includes employing the petrophysical properties evaluation algorithm to predict one or more petrophysical properties of the rock undergoing drilling real-time responsive to filtered data associated with raw acoustic sensor data produced in response to the drilling.

11. A method as defined in claim 10, wherein the collected petrophysical properties data describes petrophysical properties of a plurality of samples taken from the formation undergoing drilling operations.

12. A method of analyzing properties of rock in a formation in real-time during drilling, the method comprising the steps of:

receiving, by a computer, raw acoustic sensor data from a surface data acquisition unit in communication with a downhole data interface through a surface data interface and a communication medium extending between the surface data interface and the downhole data interface, the downhole data interface operably coupled to a plurality of acoustic sensors; and

performing, by the computer, one or more of the following processing steps;

deriving a plurality of acoustic characteristics from the raw acoustic sensor data, the plurality of acoustic characteristics including mean frequency and normalized deviation of frequency, and

deriving petrophysical properties from the raw acoustic sensor data utilizing a petrophysical properties evaluation algorithm employable to predict one or more petrophysical properties of rock undergoing drilling.

13. A method as defined in claim 12, further comprising the steps of sending sampling commands to the data acquisition unit, and deriving a frequency distribution of the acoustic data from the raw acoustic sensor data, the step of deriving a frequency distribution comprising the steps of:

transforming the raw acoustic sensor data into the frequency domain; and

filtering the transformed data.

14. A method as defined in claim 12, wherein the plurality of acoustic characteristics further include mean amplitude, normalized deviation of amplitude, and apparent power, and wherein the one or more processing steps comprise deriving the plurality of acoustic characteristics from the raw acoustic sensor data, the method further comprising the steps of:

comparing the mean frequency, the normalized deviation of frequency, the mean amplitude, the normalized deviation of amplitude, and the apparent power for the rock undergoing drilling with mean frequency, normalized deviation of frequency, mean amplitude, normalized deviation of amplitude, and apparent power for a plurality of rock samples having different known lithologies, the mean frequency and normalized deviation of frequency being examined together and the mean frequency and the mean amplitude being examined together to determine an amount of correlation of the acoustic characteristics associated with the rock undergoing drilling and the acoustic characteristics associated with the rock samples, the step of comparing being performed substantially continuously during drill bit steering; and

performing one or more of the following responsive to the step of comparing;

identifying lithology type of the rock undergoing drilling, and

determining a location of a formation boundary encountered during drilling.

15. A method as defined in claim 12, wherein the one or more processing steps comprise deriving the petrophysical properties from the raw acoustic sensor data utilizing a petrophysical properties evaluation algorithm, wherein the petrophysical properties evaluation algorithm is a bit-specific petrophysical properties evaluation algorithm, the method further comprising the steps of:

collecting petrophysical properties data describing one or more petrophysical properties of rock for a plurality of formation samples and correspondent acoustic data for a preselected type of drill bit;

processing the collected acoustic data to produce filtered FFT data;

determining one or more relationships between features of the filtered FFT data and correspondent one or more petrophysical properties of rock describing petrophysical properties of a plurality of formation samples for the preselected type of drill bit; and

coding the determined relationships into computer program code defining the petrophysical properties algorithm; and

wherein the step of deriving the petrophysical properties includes employing the petrophysical properties evaluation algorithm to predict one or more petrophysical properties of the rock undergoing drilling real-time responsive to filtered data associated with raw acoustic sensor data produced in response to the drilling.

16. A method as defined in claim 12, wherein the one or more processing steps comprise deriving petrophysical properties from raw acoustic sensor data utilizing a petrophysical properties evaluation algorithm, wherein the petrophysical properties evaluation algorithm is a bit-independent petrophysical properties evaluation algorithm, the method further comprising the steps of:

collecting petrophysical properties data describing one or more petrophysical properties of rock for a plurality of formation samples and correspondent acoustic data for a plurality of different types of drill bits;

processing the collected acoustic data to produce filtered FFT data;

determining bit-type independent features of the filtered FFT data;

determining one or more relationships between the bit-type independent features of the filtered FFT data and correspondent one or more petrophysical properties of the rock; and

coding the determined relationships into computer program code defining the petrophysical properties algorithm; and

wherein the step of deriving the petrophysical properties includes employing the petrophysical properties evaluation algorithm to predict one or more petrophysical properties of the rock undergoing drilling real-time responsive to filtered data associated with raw acoustic sensor data produced in response to the drilling.

17. A method of analyzing properties of rock in a formation in real-time during drilling, the method comprising the steps of:

receiving, by a computer, raw acoustic sensor data from a surface data acquisition unit in communication with a downhole data interface through a surface data interface and a communication medium extending between the surface data interface and the downhole data interface, the downhole data interface operably coupled to a plurality of acoustic sensors, the raw acoustic sensor data representing an acoustic signal generated real-time as a result of rotational contact of a drill bit with rock during drilling; and

deriving a plurality of acoustic characteristics from the raw acoustic sensor data, the plurality of acoustic characteristics including mean frequency and normalized deviation of frequency.

18. A method as defined in claim 17, further comprising the steps of sending sampling commands to the data acquisition unit, and deriving a frequency distribution of the acoustic data from the raw acoustic sensor data, the step of deriving a frequency distribution comprising the steps of:

transforming the raw acoustic sensor data into the frequency domain; and

filtering the transformed data.

19. A method as defined in claim 17, further comprising the steps of:

comparing the mean frequency and the normalized deviation of frequency of the rock undergoing drilling with mean frequency and normalized deviation of frequency of a plurality of rock samples having different lithologies, the mean frequency and normalized deviation of frequency being examined together to determine an amount of correlation of the acoustic characteristics associated with the rock undergoing drilling and the acoustic characteristics associated with the rock samples, the step of comparing being performed substantially continuously during drill bit steering; and

performing one or more of the following responsive to the step of comparing;

identifying lithology type of the rock undergoing drilling, and

determining a location of a formation boundary encountered during drilling.

20. A method as defined in claim 17, wherein the plurality of acoustic characteristics further include mean amplitude, normalized deviation of amplitude, and apparent power, the method further comprising the steps of:

comparing the mean frequency, the normalized deviation of frequency, the mean amplitude, the normalized deviation of amplitude, and the apparent power for the rock undergoing drilling with mean frequency, normalized deviation of frequency, mean amplitude, and normalized deviation of amplitude of a plurality of rock samples having different known lithologies, the mean frequency and normalized deviation of frequency being examined together and the mean frequency and the mean amplitude being examined together to determine an amount of correlation of the acoustic characteristics associated with the rock undergoing drilling and the acoustic characteristics associated with the rock samples, the step of comparing being performed substantially continuously during drill bit steering; and

performing one or more of the following responsive to the step of comparing;

identifying lithology type of the rock undergoing drilling, and

determining a location of a formation boundary encountered during drilling.

21. A method of analyzing properties of rock in a formation in real-time during drilling, the method comprising the steps of

receiving, by a computer, raw acoustic sensor data from a surface data acquisition unit in communication with a downhole data interface through a surface data interface and a communication medium extending between the surface data interface and the downhole data interface, the raw acoustic sensor data representing an acoustic signal generated real-time as a result of rotational contact of a drill bit with rock during drilling;

and

deriving petrophysical properties from the raw acoustic sensor data utilizing a petrophysical properties evaluation algorithm employable to predict one or more petrophysical properties of rock undergoing drilling.

22. A method as defined in claim 21, wherein the petrophysical properties evaluation algorithm is a bit-specific petrophysical properties evaluation algorithm, the method further comprising the steps of:

collecting petrophysical properties data describing one or more petrophysical properties of rocks for a plurality of formation samples and correspondent acoustic data for a preselected type of drill bit;

processing the collected acoustic data to produce filtered FFT data;

determining one or more relationships between features of the filtered FFT data and correspondent one or more petrophysical properties of rocks describing petrophysical properties of a plurality of formation samples for the preselected type of drill bit; and

coding the determined relationships into computer program code defining the bit-specific petrophysical properties algorithm; and

wherein the step of deriving the petrophysical properties includes employing the bit-specific petrophysical properties evaluation algorithm to predict one or more petrophysical properties of the rock undergoing drilling real-time responsive to filtered data associated with raw acoustic sensor data produced in response to the drilling.

23. A method as defined in claim 21, wherein the petrophysical properties evaluation algorithm is a bit-independent petrophysical properties evaluation algorithm, the method further comprising the steps of:

collecting petrophysical properties data describing one or more petrophysical properties of rocks for a plurality of formation samples and correspondent acoustic data for a plurality of different types of drill bits;

processing the collected acoustic data to produce filtered FFT data;

determining bit-type independent features of the filtered FFT data;

determining one or more relationships between the bit-type independent features of the filtered FFT data and correspondent one or more petrophysical properties of the rocks; and

coding the determined relationships into computer program code defining the bit-independent petrophysical properties algorithm; and

wherein the step of deriving the petrophysical properties includes employing the bit-independent petrophysical properties evaluation algorithm to predict one or more petrophysical properties of the rock undergoing drilling real-time responsive to filtered data associated with raw acoustic sensor data produced in response to the drilling.