Hydrothermal Systems as Analogs for Breached hdtraps and Subsurface Healing: Outcrop and Subsurface Examples and Escape Mechanisms

Transcription

1 Hydrothermal Systems as Analogs for Breached hdtraps and Subsurface Healing: Outcrop and Subsurface Examples and Escape Mechanisms David Bowen, David Lageson, Lee Spangler (Montana State University) Bryan Devault, Herbert Mosca (Vecta Oil and Gas) David Eby (Eby Petrography) Natural Releases of CO 2 Workshop Maria Laach, Germany November 2 4, 2010

2 ZERT is funded by US-DOE Fossil Energy under grant DE-42262

3 Research Conundrum Research value of studying a breached sequestration trap would be high Funding and public acceptance of a designed breach would be difficult to obtain So How as scientists do we understand the physical and chemical response of reservoirs and seals? What pathways and geometries do we use to model the behavior of fluids when a breach occurs? Analogs but what is analogous?

4 Not all modern leaks are analogs for breached traps (volcanoes, oceanic vents, lake muds over lava, major earthquake zones) Not all breached traps will leak at the surface and thus are not easily observed

5 Soda Springs, Idaho Natural Leakage Analogue through h Basalt (McCling this conference)

6 Crystal Geyser, Utah Breached Confined Aquifer, Wellbore

7 Study the Rocks Natural processes have breached reservoirs and seals throughout geologic time at similar scales and with similar mechanisms to simulate the circumstance of a breached sequestration reservoir. The evidence remains in the rock record to be studied at surface outcrops and in the subsurface.

8 Ongoing Hydrothermal Research Projects

9 Outcrops Small scale geometries Geochemistry Dissolution effects Precipitation effects Timing

10 Subsurface Large scale three-dimensional morphologies and attributes (principally the realm of geophysics)

11 What geologic systems are analogous?

12 Hydrothermal Systems as Analogs for Breached Traps and Subsurface Healing Schematic Models and Published Examples Ancient Surface Exposures Eroded to Various Levels of Observation Ancient Subsurface Examples Display 3-D Geometries with 2-D and 3-D Seismic and Sampled by Core Data

13 Hydrothermal Reservoir Systems

14 Major Aquifer Systems Separated by Major Aquacludes Partition Sedimentary Basins

15 Hydrothermal System (modified from Davis and Smith, 2006)

16 After breach of sandstone aquifer seal hydrothermal fluids spread out below secondary top seal, lose energy and heat, and often, system self-heals (modified from Davis and Smith, 2006)

17 After Breach of Sandstone Aquifer Seal Hydrothermal Fluids spread out Below Secondary Top Seal Lose Energy and Heat and often, System Self-Heals (modified from Davis and Smith, 2006)

18 Movement of Hydrothermal Fluids away from Igneous Centers

19 Idealized Cross-section of Hydrothermal System

20 Outcrop and subsurface examples show: Continuous process from breach, through reservoir enhancement, reservoir degradation, and finally to healing

21 Surface Example Central Montana Geologic Map Location Outcrop Scale Hand Samples Collected from Outcrop Photo-micrographs from thin sections

22 Hydrothermal System Emplaced along Wrench Fault Zone, Western Big Snowy Mountains Montana

23 Breach Auto-Brecciation in Madison Fm. Hydrothermal Plume, Big Snowy Range, MT

24 Vertical Fractures Autobrecciation in Hydrothermal Chimney

25 Auto-Brecciated Limestone Clasts from Hydro-Fracturing in Hydrothermal Chimney Breach

26 Vuggy Dissolution Porosity and Vertical Fractures Associated with Hydrothermal Chimney Reservoir Enhancement

27 Dissolution along Fractures, Dolomite Re-Precipitation, High-Temperature Quartz Crystal Growth, Sulfide Precipitation, Hydrothermal Chimney, Madison Fm., Big Snowy Mountains Montana Reservoir Enhancement

28 Dissolution along Fractures, Dolomite Re-Precipitation, High-Temperature Quartz Crystal Growth, Sulfide Precipitation, Hydrothermal Chimney, Madison Fm., Big Snowy Mountains Montana Reservoir Enhancement

29 Secondary Dolomite with Bitumen (black specks) Reservoir Enhancement

30 Thin-section of hydrothermal dolomite zone in Lodgepole Fm. Reservoir Enhancement

31 Healed Fractures from Carbonate Re-Precipitation Reservoir Degradation/Plugging

32 Occlusion of Dissolution Vuggy Porosity by Re-Precipitaion of Carbonate Minerals Reservoir Degradation/Plugging

33 Other examples Utah Gallatin Canyon, Montana Montana Disturbed Belt

34 Hydrothermal Breccia Pipe Eastern Utah

35 Hydrothermal fluids introduced along a fracture zone Madison Fm. Gallatin Canyon Montana

36

37

38 Hydrothermal expansion plume Gallatin Canyon, Montana

39

40 Hydrothermal reservoir features Montana Disturbed Belt

41 Sub-Surface Examples Central Seismic Data Core Data Montana

42 What are shear waves? vector v. scalar waves excited by horizontal vibrators shaking both inline and crossline 3-component geophones * 3 component sources = 9-C data matrix inherently richer dataset than P-waves, so common sense would suggest greater information content Fractures Oriented N45 E Time Delay Source Oriented NE-SW Slow Shear Component N45 W Fast Shear Component N45 E

43 Hydrothermal Chimney Subsurface Central Montana

44 Shear waves are much more sensitive to the presence of fracturing than conventional P-wave seismic data..time-delay splitting gives Shear waves measure fracture robust estimate t of fracture orientation directly, intensity if fractured interval is unlike conventional seismic thick enough...and S1/S2 amplitude differences give independent, highresolution estimate of fracture intensity

45 Amsden Reservoir

46 NOTE BRECCIA w/ Bitumen Linings USGS B017 USGS B017, Carter 2 H.O. White, 6166 ft.

47 Hydrothermal auto- brecciated zone in Amsden Fm. subsurface core sample central Montana, additional hydrothermal indicators include sulfide minerals, bitumen, hightemperature quartz crystals, and saddle dolomite

48

49 Late Stage Diagenetic Characteristics LCM Filling Vug Sulfides, Saddle Dolomite, High-Temp. Quartz, Dissolution Porosity

50 Thin-section of hydrothermal brecciated zone in Amsden Fm.

51 ARCO RALPH HARVEY: Amsden ~6940 ft.

52 Healed Brecciated Zone

53 Healed Brecciated Zone

54 Horse tail fractures as energy is lost and precipitation of minerals occludes porosity, Jurassic Piper Fm., subsurface core sample, central Montana

55 Oil Reservoir in Hydrothermal Dolomite Seal above Dolomite Reservoir has Healed to Allow Trapping of Re- Migrated Oil (modified from Davis and Smith, 2006)

56 Conclusions Hydrothermal intrusions can cause breaches Many systems have areas of brecciation, reservoir enhancement After hydrothermal plume expands energy loss reduces fracture propagation and systems typically self heal (even for large systems) Thick primaray and / or secondary seals are a major safety factor (modified from Davis and Smith, 2006)