System and methods for well data compression

• US 7,805,247 B2
• Filed: 03/05/2007
• Issued: 09/28/2010
• Est. Priority Date: 09/09/2002
• Status: Active Grant

• Current Assignee: Schlumberger Technology Corporation (Schlumberger NV)
• Original Assignee: Schlumberger Technology Corporation (Schlumberger NV)
• Inventors: Hsu, Kai, Pop, Julian J.
• Primary Examiner(s): Kundu; Sujoy K
• Application Number:
  US11/682,023
• Publication Number:
  US 20070198192A1
• Time in Patent Office: 1,303 Days
• Field of Search: 702 6- 18, 367/76, 367 81- 83, 367/87, 367/95, 367/101
• US Class Current: 702/6
• CPC Class Codes: E21B 47/12 Means for transmitting measuring-signals or control signals from the well to the surface, or from the surface to the well, e.g. for logging while drilling
• CPC Class Codes: G01V 11/002 Details, e.g. power supply systems for logging instruments, transmitting or recording data, specially adapted for well logging, also if the prospecting method is irrelevant means for transmitting well survey signals E21B47/12; signal transmission systems in general G08C; transmission in general H04B
• CPC Class Codes: H03M 7/30 Compression speech analysis-synthesis for redundancy reduction G10L19/00; for image communication H04N; Expansion; Suppression of unnecessary data, e.g. redundancy reduction
• CPC Class Codes: H04L 67/12 specially adapted for proprietary or special-purpose networking environments, e.g. medical networks, sensor networks, networks in vehicles or remote metering networks

Abstract

Systems and methods in which data compression techniques are utilized to fill a predetermined channel capacity are shown. According to one configuration, event data points within test data are selected for communication via the data communication channel and a data decimator is utilized to identify other data points within the test data to fill or substantially fill the predetermined channel capacity. The foregoing data decimator may employ one or more variables for selecting data for communication, wherein one or more of the variables are preferably adjusted in decimator iterations to select an optimum or otherwise desirable subset of data for communication. Data decimators may additionally or alternatively implement a suitable “growth” function to select the particular data for communication and/or the amount of data communicated.

Claims

1. A method for generating a well log from a downhole tool positioned in a wellbore penetrating a subterranean formation, said method comprising:

determining a data transmission bandwidth associated with said wellbore available to said downhole tool;

identifying a plurality of events in a data stream of said downhole tool;

determining values associated with said plurality of events;

determining a portion of said data transmission bandwidth to be available for data transmission after a bandwidth for transmission of values associated with said plurality of events is deducted from said data transmission bandwidth;

selecting data points from said data stream, said data points being selected as a function of said portion of said data transmission bandwidth to be available for data transmission;

determining values associated with the selected data points;

transmitting to a surface system the values associated with said plurality of events and with said selected data points; and

incorporating the transmitted values into the well log.

2. The method of claim 1, wherein said selecting data points as a function of said portion of said data transmission bandwidth to be available for data transmission comprises:

maximizing the amount of selected data points for consuming said portion of said data transmission bandwidth with values associated with said selected data points.

3. The method of claim 2, wherein maximizing the amount of selected data points comprises solving a discrete optimization problem.

4. The method of claim 1, wherein said selecting data points as a function of said portion of said data transmission bandwidth to be available for data transmission comprises:

identifying candidate data points as a function of said values associated with said plurality of events using a growth function.

5. The method of claim 1, wherein said selecting data points as a function of said portion of said data transmission bandwidth to be available for data transmission comprises:

selecting at least one parameter threshold;

identifying candidate data points using said at least one parameter threshold;

determining if values for said candidate data points would consume said portion of said data transmission bandwidth to be available for data transmission.

6. The method of claim 5, further comprising:

iteratively performing said selecting, identifying, and determining to converge on a selection of candidate data points to provide a maximum amount of said values for consumption.

7. The method of claim 6 wherein said iteratively performing said selecting, identifying, and determining comprises adjusting said at least one parameter threshold.

8. The method of claim 7 wherein said adjusting said at least one data parameter change threshold comprises:

determining if said values would exceed said data transmission bandwidth to be available for data transmission; and

increasing said at least one parameter threshold.

9. The method of claim 1, further comprising:

quantizing said values for transmission.

10. The method of claim 9, wherein said quantizing comprises:

selecting at least three data points along a path defined by said data stream;

defining a first interval between a first and second values associated with a first and second data points of said at least three data points;

defining a second interval between the second value and a third value associated with a third data point of said at least three data points;

determining a transform from the first and second intervals;

applying the transform to at least one of said values for transmission; and

dividing the transformed value by a quantization accuracy.

11. The method of claim 10 wherein said transform provides a multi-linear function which compresses one of said first and second intervals with a linear function with the slope less than 1.

12. The method of claim 10 wherein said selecting, defining, determining, applying, and dividing comprise a quantizing operation operable to allocate a largest portion of bits to said first interval and a smallest portion of bits to said second interval.

13. The method of claim 1, wherein said plurality of events comprise at least one event selected from the group consisting of:

a drawdown start event;

a drawdown pressure reached event;

a buildup pressure approximated event;

a beginning of a pretest investigation phase event;

an ending of a pretest investigation phase event;

a beginning of a pretest measurement phase event;

an ending of a pretest measurement phase event;

a final formation pressure reached event; and

a mud cake breached event.

14. The method of claim 1, wherein said data points are disposed in said data stream between at least two events of said plurality of events.

15. The method of claim 1, where said plurality of events are associated with the operations of the downhole tool.

16. The method of claim 1, wherein said determining values associated with the data points comprises:

selecting a portion of the data stream about the data points;

smoothing the values associated with the portion of the data stream; and

determining said values from the smoothed values associated with portion of the data stream.

17. The method of claim 1, further including decoding the transmitted values at the surface.

18. The method of claim 17, wherein decoding includes at least one of restoring with a reverse compander, unwrapping, dequantizing and reconstructing the transmitted values.

19. A method for generating a well log from a downhole tool positioned in a wellbore penetrating a subterranean formation, said method comprising:

acquiring data associated with an operation of said downhole tool;

identifying a plurality of events associated with the operation of said downhole tool;

selecting data points for transmission by said downhole tool, said data points being selected as a function of said plurality of events and a growth function;

determining values associated with said plurality of events and said data points for transmission by said downhole tool;

transmitting to a surface system said determined values; and

incorporating the transmitted data into the well log.

20. The method of claim 19, wherein selecting data points comprises:

selecting a maximum amount of data points capable of being transmitted to the surface as values.

21. The method of claim 20, further comprising:

quantizing said determined values for transmission.

22. The method of claim 21, wherein said quantizing comprises:

selecting at least three data points in a portion of the acquired data;

defining a first interval between a first and second values associated with a first and second data points of said at least three data points;

defining a second interval between the second value and a third value associated with a third data point of said at least three data points;

determining a transform from the intervals;

applying said transform to at least one of said determined values for transmission; and

dividing the transformed value using a quantization accuracy.

23. The method of claim 22 wherein said transform provides a multi-linear function which compresses one of said first and second intervals with a linear function with the slope less than 1.

24. The method of claim 22 wherein said selecting, defining, determining, applying, and dividing comprise a quantizing operation operable to allocate a largest portion of bits to said first interval and a smallest portion of bits to said second interval.

25. The method of claim 19, wherein said growth function is selected from the group consisting of:

a linear progression;

a logarithmic progression;

an exponential progression;

a spherical progression; and

a geometric progression.

26. The method of claim 19, further comprising:

determining a growth factor for said growth function to provide selection of a maximum amount of said data points capable of transmission as values.

27. The method of claim 26 where the determining is performed within the tool acquiring the data.

28. The method of claim 19, wherein said data points comprise data points disposed in said data stream between at least two events of said plurality of events.

29. The method of claim 19, wherein said acquired data define a curve.

30. The method of claim 29, further comprising smoothing at least a portion of the curve and wherein said determined values comprises values associated with the smoothed portion of the curve.

31. The method of claim 30, wherein smoothing at least a portion of the curve comprises filtering the portion of the curve.

32. The method of claim 19, further including decoding the transmitted values at the surface.

33. The method of claim 32 wherein decoding includes at least one of restoring with a reverse compander, unwrapping, dequantizing and reconstructing the transmitted values.