Seismic measurements while drilling
Measurements are made continuously with a seismic while drilling (SWD) system and the measured data are stored in a working memory of a downhole processor along with quality control (QC) measurements. The QC data are analyzed and based on the analysis, portions of the data in working memory are recorded in permanent memory for retrieval. Alternatively, QC measurements are made substantially continuously predictions are made when data quality for SWD measurements are likely to be good. Recording of SWD data are then started based on the prediction.
1. A method for making measurements during drilling of a borehole, the method comprising:
(a) making measurements continuously with a formation evaluation (FE) sensor on a bottom hole assembly (BHA);
(b) concurrently making quality control (QC) measurements while said FE measurements are being made, said QC measurements including at least one measurement not related to motion of said BHA;
(c) storing samples of said FE measurements in a working memory of a processor on said BHA;
(d) analyzing said QC measurements; and
(e) based on said analysis, storing selected samples of said FE measurements in a permanent memory of said processor.
2. The method of claim 1 wherein said FE sensor comprises at least one hydrophone responsive to a seismic signal from a surface source.
3. The method of claim 1 wherein said FE sensor comprises at least one geophone on a non-rotating sleeve of said BHA, said at least one geophone responsive to a seismic signal from a surface source.
4. The method of claim 1 wherein said at least one QC measurement is selected from (i) a weight on bit (WOB), (ii) flow rate of a fluid in said borehole, (iii) a level of a tube wave in said borehole, (iv) a level of motion of a non-rotating sleeve on said BHA, and (v) a measurement made by a near bit accelerometer.
5. The method of claim 1 wherein said QC measurements further comprise a measurement of motion of said BHA.
6. The method of claim 1 wherein said FE sensor comprises an accelerometer responsive to a signal from a surface source.
7. The method of claim 1 wherein said FE sensor comprises an acoustic sensor responsive to a signal from a source in another borehole.
8. The method of claim 1 wherein said FE sensor comprises an acoustic sensor responsive to a signal from a source at at least one of (i) a surface location, and, (ii) in another borehole.
9. The method of claim 1 wherein said acoustic sensor is one of (i) a hydrophone, (ii) a geophone, and, (iii) an accelerometer.
10. A method of making measurements during drilling of a borehole, the method comprising:
(a) making quality control (QC) measurements using a sensor on a bottom hole assembly BHA during drilling of said borehole, said QC measurements including at least one measurement not related to a motion of said BHA;
(b) analyzing said QC measurements;
(c) using the results of the analysis for predicting an initial time when measurements made by a formation evaluation (FE) sensor on said BHA are expected to be of acceptable quality; and
(d) making measurements with said FE sensor over a time interval that starts earlier than said initial time; and
(e) recording the amendments made with the FE sensor.
11. The method of claim 10 wherein said predicting is based at least in part on measurements made by an axial accelerometer on the BHA.
12. The method of claim 10 wherein said predicting is based at least in part on monitoring of a mud flow in said borehole.