Paris basin

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Figure 1: Map depicting the location of the Paris basin

The Paris Basin is an intracratonic basin that is located in Northern France. It is a saucer-shaped basin that has a maximum thickness of more than 3 km. Tertiary erosion and uplift in the Eastern part have caused the basin to be slightly asymmetric. In terms of the stratigraphic column there’s about 150m of Tertiary, 1000m of Cretaceous, 1500m of Jurassic and 500m of Permo-Triassic sediments. The prominent oil-bearing formations are the Middle Jurassic Dogger carbonates, the Upper Triassic Keuper sandstones and the Lower Creataceous and Upper Triassic sandstones. As shown in Figure 2, the blue area represents where the most hydrocarbons are found.

Figure 2: The Geological Cross-Section of the Paris basin

History of the basin

The Paris Basin, in France, constitutes the lowland area around Paris. Geologically, it is in an area of structural depression that goes between the Armorican Massif (west), the Massif Central (south) and the Vosges, Ardennes and Rhineland (east). The basin is an oval feature of about 140,000 km squared in size. The area consists of flat valleys and plateaus that lie less than 100 meters above sea level. The Paris basin consists of conventional and unconventional reservoirs and is estimated to hold over 222 million barrels of unconventional oil.

Production History

Exploration in the Paris basin started in the early 1950’s with a maximum density of wells located in the central part of France, just east of Paris. First discoveries were made in the Jurassic Dogger carbonates and the Cretaceous Necomian sandstones. As shown in Figure 3, exploration peaked in the 1960’s followed by a brief pause in the 1970’s.

Figure 3: The yearly total production in the Paris basin

There was a revival of exploration in the 1980’s due to new discoveries in the Triassic Keuper sediments. In 1982, the Chaunoy oil field had already produced 10 million tons of petroleum by the end of 2000. In the Paris basin, only 7% of total production is gas of which 63% comes from a single field. Furthermore, 30% of gas production consists of coalbed methane coming from the Poissonniere field. The four main oil-bearing zones are the Cretaceous Necomian sandstones, the Middle-Jurassic Dogger sandstones and the Upper Triassic sandstones.[1]

Geologic Setting and Risks

The key geological considerations deal with the hydrocarbon charge and maturation. The subsurface of the Paris basin has produced less hydrocarbons than investors thought. Another issue deals with extracting unconventional resources and fracking is required. The only issue is that the parliament in France put into place a ban on fracking in 2011. To make matters worse, France will ban all exploration and production of oil and natural gas by 2040.[2]

Petroleum Elements

Reservoir

The main reservoirs in the basin are composed of Triassic sandstones, the Middle Jurassic Dogger carbonates and the Lower Cretaceous sandstones. The reservoir has a low amplitude with a structural nose dipping towards the northwest. The reservoir quality is inversley related to depth. As shown in Figure 4, the reservoir is composed of shales, sandstones, and carbonates.

Figure 4: Stratigraphic column through the Mesozoic showing shales (green), sandstones (yellow) and carbonates (blue).

Trap and Seal

The trapping is stratigraphic with porous micritic and concentric oolithis, about 8-18% porosity, that is being replaced by radial oolite types that do not have a lot of reservoir quality. The seal of the Middle Jurassic carbonate reservoirs is the wide spread Callovian shales. By having a very extensive shale interval, it explains why it is possible that there is no major oil accumulation above it.[3]

Source and Migration

The principal source rocks are several layers of lower Jurassic Toarcian and Hettangian black shales. The Hettangian shales have generated more oil due to them being buried deeper while covering a larger area. In terms of migration, marine sedimentation began in the Permian and continued into the Tertiary. A little more than 3000 m of sedimentary rocks have formed the basin center. The Paris basin is an extensional basin which evolved to a compressional one as of today.

Future Petroleum Potential

In 2015, the U.S Geological survey assessed the potential to find recoverable oil and gas in the Paris Basin. Since the 1950’s, over 35 conventional oil and gas fields have been discovered. The USGS used four assessment units in effort to find undiscovered oil. They assessed that there’s a potential 222 million barrels of oil, 2,092 billion cubic feet of unconventional gas, 18 million barrels of conventional oil and 47 billion cubic feet of conventional gas that could be liberated. By using the assessment input data, the USGS estimated that a mean of 6,400 hydraulically fractured wells would be needed in order to capture the remaining oil and gas.[4]

Petroleum and facility engineering aspects

In the Paris basin, one third of wells are undergoing severe exploitation problems. Furthermore, these problems have not only affected the injection wells but also the producing ones. This damage is caused by a thermochemical formation fluid with a low gas liquid ratio and it results in casing corrosion. In an effort to restore initial well injectivities, operators have succeeded by casing cleaning and open hole jetting. However, other alternatives have come about like implementing a workover technique that uses a high pressure and flexible coiled tubing.[5]

References

  1. Wendebourg, J. “Estimating the Ultimate Recoverable Reserves of the Paris Basin, France.” Oil and Gas Science and Technology, Jun. 2002, https://pdfs.semanticscholar.org/87fe/79eca0bae6c1971942cf5b7fe6bc0b04a692.pdf./>
  2. Jolly, David. “France Upholds Ban on Hydraulic Fracturing.” International Business , 11 Oct. 2013, https://www.nytimes.com/2013/10/12/business/international/france-upholds-fracking-ban.html./>
  3. Karlsson, Tore. “Paris Basin – the geological foundation for petroleum, culture and wine.” Geo ExPro , Jun. 2004, https://assets.geoexpro.com/legacy-files/articles/Geotourism%20The%20Paris%20Basin.pdf./>
  4. Schenk, Christopher. “Assessment of Undiscovered Oil and Gas Resources of the Paris Basin, France, 2015.” National and Global Petroleum Assessment Project, 13 Apr. 2015, https://pubs.usgs.gov/fs/2015/3016/pdf/fs2015-3016.pdf./>
  5. Turon, R. “Geothermal Well Damage in the Paris Basin: A Review of Existing and Suggested Workover Inhibition Procedures.” One Petro , 8 Feb. 1988, https://onepetro.org/SPEFD/proceedings-abstract/88FD/All-88FD/SPE-17165-MS/67672./>

External Links [edit source]

https://www.searchanddiscovery.com/pdfz/documents/2012/10384monticone/ndx_monticone.pdf.html

https://iclg.com/practice-areas/oil-and-gas-laws-and-regulations/france

https://en.wikipedia.org/wiki/Paris_Basin