1 / 22

Ekofisk Seismic Event of May 7, 2001: Understanding Induced Earthquakes

Learn about the seismic event at Ekofisk on May 7, 2001, its causes, mechanisms, and implications. Explore how human activities trigger earthquakes and the challenges faced in resolving causal relations with production.

sthelen
Télécharger la présentation

Ekofisk Seismic Event of May 7, 2001: Understanding Induced Earthquakes

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. EKOFISK SEISMIC EVENT OF MAY 7, 2001 Lars Ottemöller (BGS, UK)Hardy Hartmann Nielsen (PhillipsConoco, Norway)Jochen Braunmiller (ETHZ, Switzerland) Kuvvet Atakan, Jens Havkov (University of Bergen, Norway)

  2. (from Fejerskov and Lindholm, 2000)

  3. Date 07.05.2001; Time 09:43:34Loc. 56.565 N / 3.182; RMS=1.1; Mb=4.4; MS=4.6

  4. Strike: 356Dip: 85Rake: -92 Mw: 5.1

  5. Natural: Earthquakes caused by purely tectonic stresses • Triggered: Earthquakes caused by tectonic stresses that are initiated by human activity • Induced: Earthquakes caused by stresses that can be traced directly to human activity

  6. Basic mechanisms • Local fluid injection decreases effective normal stress and induces seismic cracks M<3 within the reservoir • Fluid withdrawal causes pore pressure to decrease within reservoir, stresses are transferred to surrounding region where M<5 occur above or below reservoir • Isostatic compensation after load removal through hydrocarbon recovery can cause M>6 at larger distance (after Grasso, 1992)

  7. Ekofisk facts • Started production in 1971 • Chalk reservoir at depth of ~3 km • Production now is ~340000 barrel oil and ~11*106 m3 gas per day • Total of more than 8 m subsidence • Water flooding program started early 1990s, led to increase in pore pressure and reduced subsidence • Drill cuttings re-injection into overburden started 1996 after extensive risk and cost evaluation • Induced micro-earthquakes on reservoir level, about 100 per day • Causal relation between seismicity and production not resolved

  8. Bathymetric Difference Map 1999-2001

  9. (From Segall, 1989)

  10. Conclusions • Event induced • Located in the overburden • Cause is unintended water-injection into overburden • Event was sudden compaction of overburden

More Related