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The Ice Age and the Giant Bakken Oil Accumulation

The USGS estimated (2013) that the Late Devonian to Early Mississippian Bakken Formation holds in excess of 7 billion barrels (~1.1 billion m3) of recoverable oil, making it one of the top 50 largest oilfields in the world. Most of the production comes from shallow-marine sandstones of the Middle Bakken Member that are directly over- and underlain by extremely organic-rich shale source rocks (Upper and Lower Bakken Shale members respectively). Although not oil-productive everywhere, the Middle Bakken forms a relatively sheet-like unit that covers an area of over 200,000 square miles (~520,000 km2) of the intracratonic Williston Basin.

The vertical juxtaposition of shallow-marine reservoir and more distal source rocks over such a large area, without intervening transitional facies, is unusual from a stratigraphic perspective. One possible explanation would require global fluctuations of sea level to drive geologically rapid and extensive shoreline movements in this relatively stable basin. Forced regression associated with falling sea level could explain the lack of transitional facies (e.g., inner shelf) between the distal Lower Bakken Shale and the overlying Middle Bakken (a sharp-based shoreface). Subsequent sea-level rise would have caused rapid and extensive transgression, leading to the observed stratigraphic relationships between the Middle and Upper Bakken members. But what could have caused the changes in sea level?

A considerable body of evidence points to a Late Devonian-Early Mississippian ice age that covered portions of Gondwana (e.g., parts of present-day Brazil) that were situated close to the paleo South Pole. This ice age consisted of more than one glacial/interglacial cycle and was probably triggered by massive removal of CO2 from the atmosphere by land plants and organic-rich shales. Some evidence indicates that at least 100 m of sea-level drop took place during one of the Famennian glaciations, which would have effectively drained the Williston Basin and induced major shoreline progradation. Melting of the ice sheets would have caused transgression and reflooding of the basin and deposition of the Upper Bakken Shale. Other basins around the world record similar evidence for glacioeustacy near the Devonian-Mississippian transition. The glacial/interglacial cycles are expressed differently from basin to basin, reflecting the interplay between fluctuations of global sea level and each basin’s history of subsidence and sediment supply.

Show more American Association of Petroleum Geologists (AAPG)
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Five Things Geophysicists Should Know About Shale Plays

The Shale Revolution caught geophysicists off guard. Shales had been studied for a variety of reasons (e.g., relationships between velocity, compaction and pore pressure) but not as low-porosity reservoirs that show vertical heterogeneity at all possible scales. Consequently, many geophysicists have framed shale-play imaging problems using inappropriate tools and paradigms. In this presentation, I present five characteristics of shale plays that should enable improved geophysical analyses.

  1. The term “shale play” has become meaningless. Originally intended to describe gas production from fine-grained source rocks (“source-rock reservoirs”), the term is now applied almost indiscriminately to production from many types of low-permeability rock (e.g., shaly sandstones, carbonates).
  2. Source-rock reservoirs aren’t clay dominated. Hydraulic fracturing is needed to establish commercial production from these rocks. Clays make the rocks ductile and harder to fracture. As such, the clay content of shale plays is generally less than 50%. The remainder of the rock is usually composed of fine-grained calcite and/or quartz, organic matter and other minerals.
  3. Links between VTI anisotropy and clay or organic content are not straightforward in source-rock reservoirs. Scanning electron microscopy often reveals textures that are incompatible with the conceptual models used to develop mathematical models of shales.
  4. HTI anisotropy is complicated by natural fracture geometries. Aligned natural fractures generally combine with bedding to produce systems that are best described as orthorhombic. In some cases, multiple fracture orientations produce systems that are effectively isotropic.
  5. Integration of geophysical and geological data and concepts is needed to significantly advance geophysical research on shale reservoirs. This effort will allow geophysicists to define, for a specific shale, which assumptions are reasonable, which analogs are appropriate, what appropriate ranges of properties are, etc.
Show more American Association of Petroleum Geologists (AAPG)
Desktop /Portals/0/PackFlashItemImages/WebReady/dl-bruce-hart-five-things-geologists-should-know-about-shale-plays-hero.jpg?width=100&h=100&mode=crop&anchor=middlecenter&quality=75amp;encoder=freeimage&progressive=true Five Things Geophysicists Should Know About Shale Plays
 

In a recent EXPLORER, Marlan Downey lamented that he had not fully appreciated the idea that source rocks could serve as reservoir rocks for oil and natural gas. He was not alone.

American Association of Petroleum Geologists (AAPG)
Desktop /Portals/0/PackFlashItemImages/WebReady/a-retrospective-on-source-rocks-as-reservoir-rocks-hero.jpg?width=100&h=100&mode=crop&anchor=middlecenter&quality=75amp;encoder=freeimage&progressive=true A Retrospective on Source Rocks as Reservoir Rocks
 

In 1965, G.T. Philippi, a Shell geochemist, made the novel proposal that petroleum was generated from organic matter in sediments that had been buried deeply enough to be exposed to warmer earth temperatures, converting the organic matter, with heat and time, to petroleum.

American Association of Petroleum Geologists (AAPG)
Desktop /Portals/0/PackFlashItemImages/WebReady/source-rock-as-a-reservoir-a-personal-odyssey-hero.jpg?width=100&h=100&mode=crop&anchor=middlecenter&quality=75amp;encoder=freeimage&progressive=true Source Rock as a Reservoir: A Personal Odyssey
 

How does diagenesis affect rock physics? What is the relationship of the burial history to the rock physics? Both have a dramatic impact on the rock physics properties of not only the reservoir, but also the source and seals. Welcome to an interview with Per Avseth, who discusses rock physics and quantitative seismic interpretation. He also talks with us about how developing an effective rock physics model requires the integration of geological, geophysical, geochemical, and petrophysical information.

Show more American Association of Petroleum Geologists (AAPG)
Desktop /Portals/0/PackFlashItemImages/WebReady/blog-learn-interview-per-avseth-2016-herov2.jpg?width=100&h=100&mode=crop&anchor=middlecenter&quality=75amp;encoder=freeimage&progressive=true Innovators in Geosciences Series Exploring the Link between Burial History and Rock Physics Properties: Interview with Per Avseth
 
Desktop /Portals/0/PackFlashItemImages/WebReady/dl-arctic-and-marine-gas-hydrate-production-testing-lessons-learnedp-hero.jpg?width=100&h=100&mode=crop&anchor=middlecenter&quality=75amp;encoder=freeimage&progressive=true Arctic and Marine Gas Hydrate Production Testing – Lessons Learned
 

Four lectures, of about 45 minutes each, cover grain assemblages and diagenesis (compaction, cementation, organic maturation, and fracturing) in the dominant rocks of the sedimentary record.

American Association of Petroleum Geologists (AAPG)
Desktop /Portals/0/PackFlashItemImages/WebReady/dl-abstract-mudrocks-shales-mudstone-hero.jpg?width=100&h=100&mode=crop&anchor=middlecenter&quality=75amp;encoder=freeimage&progressive=true Half-day Short Course on the Micro- to Nano-scale Features of Mudrocks
 

The fine-grained sediments and rocks that constitute most of the sedimentary record have received tremendous research attention in the past decade. This talk reviews some of the technologies that have supported these advances and summarizes current knowledge of the diagenetic processes that drive the evolution of bulk rock properties of mud in the subsurface.

American Association of Petroleum Geologists (AAPG)
Desktop /Portals/0/PackFlashItemImages/WebReady/dl-abstract-mudrocks-shales-mudstone-hero.jpg?width=100&h=100&mode=crop&anchor=middlecenter&quality=75amp;encoder=freeimage&progressive=true Mudrocks (shales, mudstones) at the Scale of Grains and Pores: Current Understanding
 
Desktop /Portals/0/PackFlashItemImages/WebReady/dl-gas-hydrate-petroleum-system-analysis-in-marine-and-arctic-permafrost-environments-hero.jpg?width=100&h=100&mode=crop&anchor=middlecenter&quality=75amp;encoder=freeimage&progressive=true Gas Hydrate Petroleum System Analysis in Marine and Arctic Permafrost Environments
 
Desktop /Portals/0/PackFlashItemImages/WebReady/dl-integrated-seismic-and-well-log-analysis-of-gas-hydrate-prospects-hero.jpg?width=100&h=100&mode=crop&anchor=middlecenter&quality=75amp;encoder=freeimage&progressive=true Integrated Seismic and Well Log Analysis of Gas Hydrate Prospects
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In-Person Training
Robin Hood's Bay North Yorkshire United Kingdom 18 October, 2017 20 October, 2017 40473 Desktop /Portals/0/PackFlashItemImages/WebReady/ice-2017-field-trip-7-hero.jpg?width=100&height=100&mode=crop&anchor=middlecenter&quality=75amp;encoder=freeimage&progressive=true Member, Geochemistry and Basin Modeling, Source Rock, Sedimentology and Stratigraphy, Carbonates, ICE 2017, Field Trips, Conventions, Post-Convention
 
Robin Hood's Bay, North Yorkshire, United Kingdom
18-20 October 2017

We will visit sections of organic-rich, Lower Jurassic, mudstone-dominated strata where depositional, diagenetic and structural processes can be examined in the context of shale resources, and Zechstein (Upper Permian) lagoonal, reefal and lower slope carbonates which act as tight, fractured reservoirs from the North Sea to Poland.

Marrakech Morocco 01 November, 2017 04 November, 2017 37903 Desktop /Portals/0/PackFlashItemImages/WebReady/gtw-afr-the-paleozoic-hydrocarbon-potential-of-north-africa-past-lessons-and-future-potential-2017-17apr17-hero.jpg?width=100&height=100&mode=crop&anchor=middlecenter&quality=75amp;encoder=freeimage&progressive=true Engineering, Development and Operations, Production, Infill Drilling, Geochemistry and Basin Modeling, Petroleum Systems, Source Rock, Thermal History, Geophysics, Clastics, Sedimentology and Stratigraphy, Conventional Sandstones, Sequence Stratigraphy, Structure, Compressional Systems, Extensional Systems, Tectonics (General), Deep Basin Gas, Stratigraphic Traps, Structural Traps
 
Marrakech, Morocco
1-4 November 2017

This workshop provides the opportunity to learn and discuss the latest knowledge, techniques & technologies applied to petroleum reservoirs in the Paleozoic of North Africa which can be utilized to explore for and develop these reservoirs. The workshop will provide a set-up for networking, interacting & sharing expertise with fellow petroleum scientists interested in developing and producing hydrocarbon resources within the Paleozoic of North Africa.

Marrakech Morocco 03 November, 2017 04 November, 2017 41272 Desktop /Portals/0/PackFlashItemImages/WebReady/gtw-afr-the-paleozoic-hydrocarbon-potential-of-north-africa-past-lessons-and-future-potential-2017-17apr17-hero.jpg?width=100&height=100&mode=crop&anchor=middlecenter&quality=75amp;encoder=freeimage&progressive=true Structure, Geochemistry and Basin Modeling, Sedimentology and Stratigraphy, Geophysics, Engineering, Compressional Systems, Tectonics (General), Extensional Systems, Source Rock, Petroleum Systems, Thermal History, Sequence Stratigraphy, Clastics, Development and Operations, Production, Structural Traps, Deep Basin Gas, Stratigraphic Traps, Conventional Sandstones, Infill Drilling
 
Marrakech, Morocco
3-4 November 2017

Location: Atlas; Anti-Atlas of Marrakech and Ouarzazate areas of Morocco**
Field Trip Leader: Abdallah Aitsalem (ONHYM) & Lahcen Boutib (ONHYM)
Field Trip Fee: USD575 *

* Field trip pricing covers accommodation, feeding and transportation for the duration of the Trip. Seats are limited and will be confirmed on a first come first served basis.

Day 1 Departure from Marrakech to Ouarzazate

The Atlas Mountains of Marrakech extend more than 250 km East-West and 50 km North-South. They record the highest mountainous peaks in North Africa with altitudes exceeding 4,000 meters (Toubkal 4,165m and Ouenkrim 4,089m). Northward and southward, they rise hundreds of meters above the Marrakech plain (Haouz plain) and Imini syncline, respectively. The recently incised mountain valleys, created during the last inversion of the Atlas, form the crossing ways of the massif, as is the case of the main road that connects Marrakech to Ouarzazate passing via the Tizi n'Tichka Pass. They also provide the opportunity to view multiple breathtaking landscapes and contain outcrops that shed light on the geological evolution of the mountain from the Precambrian to the present. Day 1 of the field trip will allow participants to view Paleozoic outcrops through the Tizi n'Tichka Pass, which displays a complete Cambrian to Devonian succession and contains several organic-rich intervals. Mesozoic and Cenozoic deposits, which are exposed on the borders of the massif, will also be viewed briefly.

Day 2: Departure from Ouarzazate to Tazzarine and back to Ouarzazate **

Day 2 of the field trip crosses the central Anti-Atlas Paleozoic basin and offers spectacular views of the largest oasis in North Africa, along the Draa River, and its majestic ancient Kasbahs. Participants will examine formations ranging in age from Upper Precambrian to Silurian. Discussions will focus on the evolution of their various depositional environments in relation to sea level changes. The well exposed sandstone formations provide the opportunity to view major Paleozoic reservoirsintervals, as well as the organic-rich "hot shales" that source these reservoirs. Rubble from recent water wells and ingenious sub-cropping irrigation systems (Khattara) provide the chance to sample fresh Ordovician and Silurian organic-rich and fossiliferous black shales. In addition, the participants will have perspective views of gentle folding generated during the Hercynian compression and related regional fractures.

Field trip route map
Field trip route map

**Field trip will end in Ouarzazate. All participants to arrange their own transport from Ouarzazate following the conclusion of the field trip.

To register for the field trip please click here.

Online Training
23 April, 2015 23 April, 2015 16809 Desktop /Portals/0/PackFlashItemImages/WebReady/an-analytical-model-for-shale-gas-permeability-hero.jpg?width=100&height=100&mode=crop&anchor=middlecenter&quality=75amp;encoder=freeimage&progressive=true
 
23 April 2015
Recent laboratory studies have revealed previously unknown behaviors in shale gas which unlock secrets of permeability and sweet spots in shale gas reservoirs. The presentation presents the findings and also goes into detail about how the new information can be applied in order to potentially improve recovery in reservoirs.
02 December, 2014 02 December, 2014 11967 Desktop /Portals/0/PackFlashItemImages/WebReady/esymp-multiscale-modeling-of-gas-transport-hero.jpg?width=100&height=100&mode=crop&anchor=middlecenter&quality=75amp;encoder=freeimage&progressive=true
 
2 December 2014

The gas transport in organic-rich shales involves different length-scales, from organic and inorganic pores to macro- and macrofractures. In order to upscale the fluid transport from nanoscale (flow through nanopores) to larger scales (to micro- and macrofractures), multicontinuum methodology is planned to be used.

30 October, 2014 30 October, 2014 11390 Desktop /Portals/0/PackFlashItemImages/WebReady/sc-kerogen-maturity-determinations.jpg?width=100&height=100&mode=crop&anchor=middlecenter&quality=75amp;encoder=freeimage&progressive=true
 
30 October 2014

Cross disciplinary workflows play an important part of successful characterization of shale reservoirs. This course discusses how the artificial kerogen maturity of organic-rich Green River shale affects the petrophysical, micro-structural, geochemical and elastic properties.

28 April, 2011 28 April, 2011 1471 Desktop /Portals/0/PackFlashItemImages/WebReady/oc-es-niobrara-petroleum-system-a-major-tight-resource-play.jpg?width=100&height=100&mode=crop&anchor=middlecenter&quality=75amp;encoder=freeimage&progressive=true
 
28 April 2011

The Niobrara Petroleum System of the U.S. Rocky Mountain Region is a major tight petroleum resource play.

09 December, 2010 09 December, 2010 1466 Desktop /Portals/0/PackFlashItemImages/WebReady/oc-es-bakken-petroleum-system-of-the-williston-basin.jpg?width=100&height=100&mode=crop&anchor=middlecenter&quality=75amp;encoder=freeimage&progressive=true
 
9 December 2010

The Mississippian-Devonian Bakken Petroleum System of the Williston Basin is characterized by low-porosity and permeability reservoirs, organic-rich source rocks, and regional hydrocarbon charge.

11 November, 2010 11 November, 2010 1465 Desktop /Portals/0/PackFlashItemImages/WebReady/oc-es-geochemical-evaluation-of-eagle-ford-group-source.jpg?width=100&height=100&mode=crop&anchor=middlecenter&quality=75amp;encoder=freeimage&progressive=true
 
11 November 2010

This e-symposium is ideal for geologists, geophysicists, engineers and other geoscientists who are involved in gas shale exploration and production.

14 February, 3000 14 February, 3000 7817 Desktop /Portals/0/PackFlashItemImages/WebReady/oc-es-generic-hero.jpg?width=100&height=100&mode=crop&anchor=middlecenter&quality=75amp;encoder=freeimage&progressive=true
 
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