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 ?