Four Phenomena Observed on Microseismic Data

St-Onge, Andre Maurice

Four Phenomena Observed on Microseismic Data

atmire.migration.oldid	1357
dc.contributor.advisor	Eaton, David
dc.contributor.author	St-Onge, Andre Maurice
dc.date.accessioned	2013-09-13T18:51:58Z
dc.date.available	2013-11-12T08:00:12Z
dc.date.issued	2013-09-13
dc.date.submitted	2013	en
dc.description.abstract	Passive seismic data recorded in observation wellbores for hydraulic fracture monitoring are usually used to detect P- and S-wave arrivals from induced microseismic events. The time arrivals for these events are used to compute source locations to build a fracture location map. Along with these arrivals are a number of other coherent signal and noise events. The primary objective of this thesis is to examine various other types of coherent signal and noise on four microseismic datasets. This thesis is made up of four separate studies. The first study examines numerous coherent low-frequency (<100 Hz) arrivals characterized by conspicuous dispersion and quasi-linear moveout. Their apparent velocities and dispersion characteristics are consistent with Lamb waves, an elastic guided wave that propagates within finite media such as plates or cylindrical casing. Lamb waves may be used for monitoring degradation of casing cement over time. The second study examines two datasets to characterize frequency shifts in discrete narrow passbands caused by wellbore acoustic transmissivity due to geophone clamping. The passbands changed throughout two fracture stimulations in proportion to the hydraulic fracture pressure. Analytical and finite-element models suggest that these temporal variations may be caused by a relative change in geophone clamping force as the pressure external to the wellbore varies. This sensitivity suggests that passive seismic monitoring can be used for downhole detection of relative stress changes. The third study focuses on frequency content variations of 20 high S/N P- and S-wave events. The 20 events were grouped into four clusters based upon a geolocation algorithm and event cross-correlations. Spectral analysis shows variation in the signal within event sets. A 2-D elastic finite-difference simulation using a layered model shows that this variation could be ascribed to path effects associated with propagation of the signal from the source to the receivers. The fourth study examines a potential long-period long-duration (LPLD) seismic event and analyzes the phenomena in detail. LPLD events observed on microseismic data have been likened to deep low-frequency tremor attributed to slow-slip processes along pre-existing fractures or strike-slip regimes at subduction zones. The event may be the result of hydraulic fracture fluid leak-off out of the intended zone into a pre-existing fracture.	en_US
dc.identifier.citation	St-Onge, A. M. (2013). Four Phenomena Observed on Microseismic Data (Doctoral thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca. doi:10.11575/PRISM/26220	en_US
dc.identifier.doi	http://dx.doi.org/10.11575/PRISM/26220
dc.identifier.uri	http://hdl.handle.net/11023/959
dc.language.iso	eng
dc.publisher.faculty	Graduate Studies
dc.publisher.institution	University of Calgary	en
dc.publisher.place	Calgary	en
dc.rights	University of Calgary graduate students retain copyright ownership and moral rights for their thesis. You may use this material in any way that is permitted by the Copyright Act or through licensing that has been assigned to the document. For uses that are not allowable under copyright legislation or licensing, you are required to seek permission.
dc.subject	Geophysics
dc.subject.classification	Geophysics	en_US
dc.subject.classification	Microseismic	en_US
dc.subject.classification	Interpretation	en_US
dc.title	Four Phenomena Observed on Microseismic Data
dc.type	doctoral thesis
thesis.degree.discipline	Geoscience
thesis.degree.grantor	University of Calgary
thesis.degree.name	Doctor of Philosophy (PhD)
ucalgary.item.requestcopy	true