Previous practice to determine the source mechanism of microseismic events associated with hydraulic fracture typically includes only far-field terms in moment tensor inversion. The intermediate-field terms and near-field term are normally ignored because of increased complexity in the calculation. Source-receiver distances in hydraulic fracturing are usually 1000 ft and the effects of near and intermediate-field terms are still unknown. We perform a study to improve the precision of the source mechanism by including the intermediate-field term in moment tensor inversion.
We find that the intermediate-field term contributes 1/3 of the signal amplitude when the source-receiver distance is 1000 ft. The intermediate-field term contributes 1/20 of the signal amplitude when the source-receiver distance is 6700 ft. Note that "1/20" is at the noise level. Thus, when source-receiver distance is less than 6700ft, we need to consider the intermediate-field term. Especially, when the distance is 1000ft, the intermediate-field term becomes significant. Similarly, near-field terms contribute less than 1/20 of the signal amplitude when distances are larger than 300 ft. In our case, we confirm that the near-field term can be ignored in microseismic analysis.
Our results indicate that the intermediate-field terms can improve moment tensor inversion by 2% to 40% at source-receiver ranges less than 1000 ft. When distances are larger than 6700, the improvement is limited to 1%. In the presence of noise, the intermediate-field terms help to improve the moment tensor inversion (15% improvement with noise present vs 3% improvement without noise).
Our study provides a foundation for using intermediate-field terms in moment tensor inversion in the studies of hydraulic fractures.
| Identifer | oai:union.ndltd.org:LSU/oai:etd.lsu.edu:etd-01162014-150947 |
| Date | 08 May 2014 |
| Creators | Fan, Chennu |
| Contributors | Dahi Taleghani, Arash, Lorenzo, Juan, Sears, Stephen O., Smith, John Rogers |
| Publisher | LSU |
| Source Sets | Louisiana State University |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.lsu.edu/docs/available/etd-01162014-150947/ |
| Rights | unrestricted, I hereby certify that, if appropriate, I have obtained and attached herein a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to LSU or its agents the non-exclusive license to archive and make accessible, under the conditions specified below and in appropriate University policies, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
Page generated in 0.002 seconds