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Results of the downhole microseismic monitoring at a pilot hydraulic fracturing site in Poland; Part 1, Event location and stimulation performance

Wojciech Gajek, Jacek Trojanowski, Michal Malinowski, Marek Jarosinski and Marko Riedel
Results of the downhole microseismic monitoring at a pilot hydraulic fracturing site in Poland; Part 1, Event location and stimulation performance
Interpretation (Tulsa) (August 2018) 6 (3): SH39-SH48

Abstract

A precise velocity model is necessary to obtain reliable locations of microseismic events, which provide information about the effectiveness of the hydraulic stimulation. Seismic anisotropy plays an important role in microseismic event location by imposing the dependency between wave velocities and its propagation direction. Building an anisotropic velocity model that accounts for that effect allows for more accurate location of microseismic events. We have used downhole microseismic records from a pilot hydraulic fracturing experiment in Lower-Paleozoic shale gas play in the Baltic Basin, Northern Poland, to obtain accurate microseismic events locations. We have developed a workflow for a vertical transverse isotropy velocity model construction when facing a challenging absence of horizontally polarized S-waves in perforation shot data, which carry information about Thomsen's gamma parameter and provide valuable constraints for locating microseis mic events. We extract effective epsilon , delta and V (sub P) 0, V (sub S) 0 for each layer from the P- and SV-wave arrivals of perforation shots, whereas the unresolved gamma is retrieved afterward from the SH-SV-wave delay time of selected microseismic events. An inverted velocity model provides more reliable location of microseismic events, which then becomes an essential input for evaluating the hydraulic stimulation job effectiveness in the geomechanical context. We evaluate the influence of the preexisting fracture sets and obliquity between the borehole trajectory and principal horizontal stress direction on the hydraulic treatment performance. The fracturing fluid migrates to previously fractured zones, while the growth of the microseismic volume in consecutive stages is caused by increased penetration of the above-lying lithologic formations.


ISSN: 2324-8858
EISSN: 2324-8866
Serial Title: Interpretation (Tulsa)
Serial Volume: 6
Serial Issue: 3
Title: Results of the downhole microseismic monitoring at a pilot hydraulic fracturing site in Poland; Part 1, Event location and stimulation performance
Affiliation: Polish Academy of Sciences, Institute of Geophysics, Warsaw, Poland
Pages: SH39-SH48
Published: 201808
Text Language: English
Publisher: Society of Exploration Geophysicists, Tulsa, OK, United States
References: 45
Accession Number: 2019-007345
Categories: Economic geology, geology of energy sourcesApplied geophysics
Document Type: Serial
Bibliographic Level: Analytic
Annotation: From a special section on Characterization of potential Lower Paleozoic shale resource play in Poland, prefaced by Marfurt, Kurt
Illustration Description: illus.
N49°00'00" - N54°45'00", E14°15'00" - E24°15'00"
N52°00'00" - N68°00'00", E10°00'00" - E31°00'00"
Secondary Affiliation: University of Bristol, GBR, United Kingdom
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2019, American Geosciences Institute.
Update Code: 2019
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