shale gaz exploitation water resource
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Communauté de Communes du Grand Pic Saint Loup – 3 mars 2011 1
Shale Gaz Exploitation
Environnemental challenges to preserve
water resource
Example of South‐East France
Prof. Dr. Séverin Pistre Hydrogeologist
Communauté de Communes du Grand Pic Saint Loup – 3 mars 2011 2
The 3 challenges for water resource
Problem with water volumes needed
Problem with indirect water pollution
Problem with direct water pollution
Communauté de Communes du Grand Pic Saint Loup – 3 mars 2011 3
Water volumes needed
Quantity ?
Lubrication and cuttings : ±1000m3 each well
Hydraulic fracturing : 10 000 ‐ 20 000m3 each well
Origin ?
1‐ Surface water : globaly resource is sufficient
problem with transportation/infrastructure (mediterranean areas)
(Flow rate of Rhône = 1800 m3/s)
2‐ Groundwater : exploited aquifers = water use conflicts (drinking water, agriculture..)
non exploited aquifers = Possible but risky if exploited aquifers
nearby (leakage)
Solutions are possible to limit the impact (other fluid ?)
Communauté de Communes du Grand Pic Saint Loup – 3 mars 2011 4
Direct water pollution
Surface pollution (surface waters/groundwaters)
Discharge of recovered fluids (basins leakage)
Industrial liquids leakage (oil, gas…)
Deep pollution
Bad well casing = leakage of products towards crossed aquifers
Fracking uncontroled = leakage of products towards above layers
Fracking uncontroled = reactivation of natural fractures
and leakage of products towards above layers
Abandonment of wells = casing deterioration
= connection between deep layers and upper aquifers
Reduction possible of risksTechnical solutions ± hard depending on geological setting
Communauté de Communes du Grand Pic Saint Loup – 3 mars 2011 5
Indirect water pollution
Surface pollution (surface waters/infiltration)
Leaching of recovered muds containing resident chemical elements
(identical with Mines Acid Drainage problem : sulfurs oxidation...)
Example USA : strong [Ra‐226] Kargbo et al., 2010. Environmental Science and Technology
Hydrosystems recharge with contaminated rain water (from gazeous rejects)
Resident chemical elements : chemical elements in particular metals or radionucleidesnaturally present in target layers (adsorbed or trapped by shales and organic matter).
‐ radioactive elements : Lead‐210, Radium‐226, Thorium‐234,…‐metals: Lead, Thallium,…‐ Arsenic, Selenium,…
Example : Autunien (South of France) = old mines of bituminous Uranium
Possible solutions : rejects treatment and storage of derived products
Source Institut National de Santé Publique du Québec
Communauté de Communes du Grand Pic Saint Loup – 3 mars 2011 6
Indirect water pollution
Deep pollution
Modification of hydrodynamic parameters in target layers
+
Modification of physico‐chemical conditions
(30% to 90% of injected fluid is not recovered)
=
Circulation of resident chemical elements
Possible ascent towards above layers
According to geological conditions (faults, types of rocks)
Risks are directly depending on geological setting Solutions ?
Communauté de Communes du Grand Pic Saint Loup – 3 mars 2011 7
Example South‐East France
Mediterranean climate
dry summers
Karstic aquifers
main drinking water resources
fast pollutions transfersdeep network development
Deep Faults
connection of aquifers
natural fluids ascents (thermal water, CO2)
Communauté de Communes du Grand Pic Saint Loup – 3 mars 2011 8
Montpellier
Karstic aquiferswith strongstrategicinterest
Bakalowicz, 1994
Karstic resources with regional interest
Karstic resources with local interest
French RMC water agency
Communauté de Communes du Grand Pic Saint Loup – 3 mars 2011 9
Aquifers connection
Karstic aquifers separated by thinimpervious layers
but possible connections by fault zones (fracturation => porosity => conduit)
D’après Benedicto, 1996
Lez
Nîmes
Montpellier
Example of the Lez aquiferDrinking water supply for Montpellier400.000 citizen
Communauté de Communes du Grand Pic Saint Loup – 3 mars 2011 10
From Bicalho, 2010and Benedicto, 1996
Hydrodynamic of Lez aquiferdeep water arrivals highlighted by geochemistry
infiltration
Lez spring(pumped)
SENW
Fast recharge
Karstic main aquifer
Deep arrivals
Lirou spring
13%
Communauté de Communes du Grand Pic Saint Loup – 3 mars 2011 11
Geological/hydrogeologic studies specific to each site are necessary to evaluate the risks
Conclusions
Impacts on the quantity of the resource can be limited overall
Follow‐up networks of hydrosystems (surface and subterranean) during and after exploitation are needed
Risks for resource quality : sufficient technical improvements to strongly reduce them ? About chemical resident elements ?
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