Lag calculation with caving correction in open hole
A gas analyzer system that can detect atmospheric air gasses in drilling mud is used to calculate an actual lag time in a well. The calculated lag time and a theoretical lag time may be compared to estimate a caving percentage in an open hole section of the well.
1. A method of estimating an amount of caving in an open hole drilling well, comprising:
calculating by a gas analyzer system an actual lag for a well by detecting a predetermined component of atmospheric air in a drilling fluid with a gas analyzer probe, comprising:
detecting a connection event;
detecting a change in an amount of the predetermined component of atmospheric air in the drilling fluid corresponding to the connection event;
determining a first quantity of mud pump strokes at an end of the connection event;
determining a second quantity of mud pump strokes at a beginning of the change in the amount of the predetermined component of atmospheric air in the drilling fluid corresponding to the connection event;
determining a third quantity of down strokes of the mud pump; and
calculating the actual lag by subtracting the second quantity and the third quantity from the first quantity;
calculating by the gas analyzer system a theoretical lag for the well; and
calculating by the gas analyzer system a caving amount by comparing the actual lag and the theoretical lag.
2. The method of claim 1 , wherein the component of atmospheric air is nitrogen gas.
3. The method of claim 1 , repeating the acts of calculating an actual lag, calculating a theoretical lag, and calculating a caving amount for a plurality of connection events.
4. The method of claim 3 , further comprising:
calculating a trend in a borehole caving over time.
5. The method of claim 3 , further comprising:
calculating a trend in a borehole caving corresponding to location.
6. The method of claim 3 , further comprising:
correlating the actual lag, theoretical lag, and caving amount for a plurality of connection events with data from other sources to indicate a state of a borehole.
7. The method of claim 3 , wherein the plurality of connection events is every connection event for the well.
8. The method of claim 3 , further comprising:
identifying specific downhole locations where deviations from a nominal borehole occurred.
9. The method of claim 3 , further comprising:
storing the actual lag in a database.
10. The method of claim 3 , further comprising:
storing the caving amount in a database.
11. A gas analyzer system, comprising:
a gas analyzer probe, configured to detect and measure a predetermined component of atmospheric air in a drilling fluid; and
a gas analyzer system unit, coupled to the gas analyzer probe, comprising:
a processor;
instructions for execution by the gas analyzer system unit, comprising instructions that when executed by the processor, cause the processor to:
calculate an actual lag for a well by detecting the predetermined component of atmospheric air in the drilling fluid, comprising instructions that when executed cause the processor to:
detect a connection event;
detect a change in an amount of the predetermined component of atmospheric air in the drilling fluid corresponding to the connection event;
determine a first quantity of mud pump strokes at an end of the connection event;
determine a second quantity of mud pump strokes at a beginning of the change in the amount of the predetermined component of atmospheric air in the drilling fluid corresponding to the connection event;
determine a third quantity of down strokes of the mud pump; and
calculate the actual lag by subtracting the second quantity and the third quantity from the first quantity;
calculate a theoretical lag for the well; and
calculate a caving amount by comparing the actual lag and the theoretical lag.
12. The gas analyzer system of claim 11 , wherein the predetermined component of atmospheric air is nitrogen gas.
13. The gas analyzer system of claim 11 , wherein the instructions further comprise instructions that when executed by the processor cause the processor to repeat the acts of calculating an actual lag, calculating a theoretical lag, and calculating a caving amount for a plurality of connection events.
14. The gas analyzer system of claim 13 , wherein the plurality of connection events is every connection event for the well.
15. The gas analyzer system of claim 13 , further comprising:
a database, coupled to the gas analyzer system unit,
wherein the software further comprises instructions that when executed by the processor cause the processor to:
store the actual lag in the database.
16. The gas analyzer system of claim 13 , further comprising:
a database, coupled to the gas analyzer system unit,
wherein the software further comprises instructions that when executed by the processor cause the processor to:
store the caving amount in a database.
17. A non-transitory machine-readable storage media, containing instructions that when executed by a gas analyzer system unit cause the gas analyzer system unit to:
calculate an actual lag for a well by detecting a predetermined component of atmospheric air in a drilling fluid, comprising instructions that when executed cause the gas analyzer system unit to:
detect a connection event;
detect a change in an amount of the predetermined component of atmospheric air in the drilling fluid corresponding to the connection event;
determine a first quantity of mud pump strokes at an end of the connection event;
determine a second quantity of mud pump strokes at a beginning of the change in the amount of the predetermined component of atmospheric air in the drilling fluid corresponding to the connection event;
determine a third quantity of down strokes of the mud pump; and
calculate the actual lag by subtracting the second quantity and the third quantity from the first quantity;
calculate a theoretical lag for the well; and
calculate a caving amount by comparing the actual lag and the theoretical lag.