Paper on cyclic soft stimulation at Pohang EGS

I co-authored paper in Geophysical Journal International by Hannes Hofmann discussing the cyclic soft stimulation campaign performed in August 2017 at Pohang EGS system. The paper is available to download from journal website. The analysis performed by Hannes was a part of activities performed within DESTRESS DEmonstration of Soft Stimulations Treatments of Geothermal Reservoirs project.

 

Reference:

Hofmann, H. et al. (2019). First field application of cyclic soft stimulation at the Pohang Enhanced Geothermal System site in Korea, Geophys. J. Int. 217, no. 2, 926–949, doi 10.1093/gji/ggz058.

Abstract:

Large-magnitude fluid-injection induced seismic events are a potential risk for geothermal energy developments worldwide. One potential risk mitigation measure is the application of cyclic injection schemes. After validation at small (laboratory) and meso (mine) scale, the concept has now been applied for the first time at field scale at the Pohang Enhanced Geothermal System (EGS) site in Korea.From 7 August until 14 August 2017 a total of 1756 m³ of surface water was injected into Pohang well PX-1 at flow rates between 1 and 10 l s–1, with a maximum wellhead pressure (WHP) of 22.8 MPa, according to a site-specific cyclic soft stimulation schedule and traffic light system. A total of 52 induced microearthquakes were detected in real-time during and shortly after the injection, the largest of Mw 1.9. After that event a total of 1771 m³ of water was produced back from the well over roughly 1 month, during which time no larger-magnitude seismic event was observed. The hydraulic data set exhibits pressure-dependent injectivity increase with fracture opening between 15 and 17 MPa WHP, but no significant permanent transmissivity increase was observed.The maximum magnitude of the induced seismicity during the stimulation period was below the target threshold of Mw 2.0 and additional knowledge about the stimulated reservoir was gained. Additionally, the technical feasibility of cyclic injection at field scale was evaluated. The major factors that limited the maximum earthquake magnitude are believed to be: limiting the injected net fluid volume, flowback after the occurrence of the largest induced seismic event, using a cyclic injection scheme, the application of a traffic light system, and including a priori information from previous investigations and operations in the treatment design.

EPSL paper on slow earthquake in the Sea of Marmara

We recently published a paper in Earth and Planetary Science Letters entitled “Slow strain release along the eastern Marmara region offshore Istanbul in conjunction with enhanced local seismic moment release”.

The paper was quite widely commented in a GFZ press release, as well as in the Science Daily and Phys.org.

Full reference:

Martínez-Garzón, P., M. Bohnhoff, D. Mencin, G. Kwiatek, G. Dresen, K. Hodgkinson, M. Nurlu, F. T. Kadirioglu, and R. F. Kartal (2019). Slow strain release along the eastern Marmara region offshore Istanbul in conjunction with enhanced local seismic moment release, Earth and Planetary Science Letters 510, 209–218, DOI: 10.1016/j.epsl.2019.01.001.

Abstract:

We analyze a large transient strainmeter signal recorded at 62.5 m depth along the southern shore of the eastern Sea of Marmara region in northwestern Turkey. This region represents a passage of stress transfer from the Izmit rupture to the Marmara seismic gap. The strain signal was recorded at the Esenkoy site by one of the ICDP-GONAF (International Continental Drilling Programme – Geophysical Observatory at the North Anatolian Fault) strainmeters on the Armutlu peninsula with a maximum amplitude of 5 microstrain and lasting about 50 days. The onset of the strain signal coincided with the origin time of a MW 4.4 earthquake offshore Yalova, which occurred as part of a seismic sequence including eight MW ≥3.5 earthquakes. The MW 4.4 event occurred at a distance of about 30 km from Esenkoy on June 25th 2016 representing the largest earthquake in this region since 2008. Before the event, the maximum horizontal strain was subparallel to the regional maximum horizontal stress derived from stress inversion of local seismicity. During the strain transient, we observe a clockwise rotation in the local horizontal strain field of about 20°. The strain signal does not correlate with known environmental parameters such as annual changes of sea level, rainfall or temperature. The strain signal could indicate local slow slip on the Cinarcik fault and thus a transfer of stress to the eastern Marmara seismic gap.

Paper on SHEER project database within EPOS system

Some months ago Szymon Cielesta has published a paper that presents the development of SHEER database and its implementation in EPOS TCS Anthropogenic Hazard system.

Reference:

Cielesta, S., B. Orlecka-Sikora, M. Staszek, P. Urban, D. Olszewska, E. Ruigrok, S. Toon, M. Picozzi, G. Kwiatek, S. Cesca, J. A. López Comino, C. Isherwood, N. Montcoudiol, and J. Jarosławski (2018). SHEER “smart” database: technical note. Acta Geophysica. DOI: 10.1007/s11600-018-0205-3

Abstract:

The SHEER database brings together a large amount of data of various types: interdisciplinary site data from seven independent episodes, research data and those for the project results dissemination process. This concerns mainly shale gas exploitation test sites, processing procedures, results of data interpretation and recommendations. The smart SHEER database harmonizes data from different fields (geophysical, geochemical, geological, technological, etc.), creates and provides access to an advanced database of case studies of environmental impact indicators associated with shale gas exploitation and exploration, which previously did not exist. A unique component of the SHEER database comes from the monitoring activity performed during the project in one active shale gas exploration and exploitation site at Wysin, Poland, which started from the pre-operational phase. The SHEER database is capable of the adoption of new data such as results of other Work Packages and has developed an over-arching structure for higher-level integration.