High-Impact Reservoirs
Roger Barton True Oil LLC Casper, Wyoming, USA
Ken Bird
US Geological Survey Menlo Park, California, USA
Jesús García Hernández PEMEX Villahermosa, Tabasco, Mexico
José M. Grajales-Nishimura Gustavo Murillo-Muñetón Mexican Petroleum Institute Mexico City, Mexico
Ben Herber Paul Weimer
University of Colorado Boulder, Colorado, USA
Christian Koeberl University of Vienna Vienna, Austria
Martin Neumaier Oliver Schenk Aachen, Germany
Jack Stark
Continental Resources, Inc. Enid, Oklahoma, USA
Oilfield Review Winter 2009/2010: 21, no. 4. Copyright © 2010 Schlumberger.
For help in preparation of this article, thanks to Judson Ahern, University of Oklahoma, Norman; John Dribus, New Orleans; Gretchen Gillis, Sugar Land, Texas, USA; Alan Hildebrand, University of Calgary, Alberta, Canada; Kenneth J. Kerrihard, Continental Resources, Enid, Oklahoma; Jorge Lopez de Cardenas and Jesus Mendoza Ruiz, Mexico City; Jodie Lowry, Oklahoma City, Oklahoma; Josephine Ndinyah, Cambridge, Massachusetts, USA; Ken Peters, Mill Valley, California; and Matt Varhaug, Houston.
1. Lowman PD Jr: “Extraterrestrial Impact Craters,” in Johnson KS and Campbell JA (eds): Ames Structure in Northwest Oklahoma and Similar Features: Origin and Petroleum Production (1995 Symposium). Norman, Oklahoma, USA: Oklahoma Geological Survey, Circular 100 (1997): 55–81.
Buthman DB: “Global Hydrocarbon Potential of Impact Structures,” in Johnson KS and Campbell JA (eds): Ames Structure in Northwest Oklahoma and Similar Features: Origin and Petroleum Production (1995 Symposium). Norman, Oklahoma: Oklahoma Geological Survey, Circular 100 (1997): 83–99.
2. “Hazards, Impacts in Our Future?” American Museum of Natural History, Arthur Ross Hall of Meteorites,
http://www.amnh.org/exhibitions/permanent/meteorites/ impacts/
hazards.php (accessed September 7, 2009).
Geologic processes and events shape the Earth and determine the location and quality of petro- leum reservoirs. Many geologic processes, including erosion, mountain building, sediment deposition, continent breakup and ocean spreading, occur over tens of millions of years. These gradual pro- cesses are often punctuated by distinct events— earthquakes, landslides and volcanic eruptions— that are instantaneous on a geologic time scale. Another type of sudden event, and one that is
seldom mentioned in petroleum geology discus- sions, is asteroid impact. Although relatively rare, a collision between the Earth and a large extrater- restrial object dramatically alters surface and sub- surface rock properties and can have lasting effects over large areas. Equipped with a better understanding of the consequences of an asteroid strike, explorationists can exploit the isolated basins and fractured rock left in the aftermath. This article describes the processes that
accompany impact and the roles they play in creating or destroying petroleum source rocks,
reservoirs and traps. Case studies from the USA provide evidence of current oil and gas produc- tion from ancient impact structures. An example from Mexico shows how a massive impact con- tributed to the formation of some prolific reser- voirs. In a case from Alaska, USA, inclusion of impact effects increased the reliability of the basin and petroleum system model.
Sustaining Impact For billions of years the Earth has been bom- barded by comets, asteroids and meteoroids. Comets are composed of ice, dust and rock and have diameters up to 20 km [12 mi]. In our solar system they typically have long elliptical orbits about the Sun and rarely impact the Earth or other terrestrial planets. Asteroids can be larger, up to 900 km [560 mi] in diameter, and are formed of rocky matter. Most asteroids orbit the Sun in the asteroid belt, which lies between Mars and Jupiter, but some—the so-called Earth- crossing asteroids—come closer to the Earth.
To the surprise of many in the E&P industry, the impact of an extraterrestrial mass may bring about conditions conducive to the formation of petroleum reservoirs. Conversely, these Earth-shattering events can also disrupt hydrocarbon accumulations.
Every year
Once a century
Every 10,000 years
Every million years
Every 100 million years
4 20 90 400 Impactor diameter, m
> Frequency of impact. Impact frequency is inversely proportional to impactor size. [Adapted from Short N: “The Remote Sensing Tutorial, Section 18: Basic Science II: Impact Cratering,”
http://rst.gsfc.nasa.gov/ (accessed December 10, 2009).]
2,000 9,000
14
Oilfield Review
Impact interval
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