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OilOilFlowsFlows

Hydraulic PressureHydraulic PressureFractures RockFractures Rock

FRACKING=HYDRAULIC FRACTURINGFRACKING=HYDRAULIC FRACTURING

Sand lodgesSand lodgesin fracturesin fractures

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The Marcellus Shale Formation:

• Large Area• Shallow Depth• Lots of Gas

Thin formation• Tight Rock• Jointed formation

http://geology.com/articles/marcellus-shale.shtml

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Marcelus and Utica Shale are Tight Marcelus and Utica Shale are Tight RocksRocks•

• Marcellus shale is “tight”, meaning not many small cracks between joints, so the gas trapped in the rock needs help to be released to the surface: artificial fracture is the solution.

• Open joints using “hydraulic fracturing” or fracking.

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““Horizontal” Drilling and Fracturing Horizontal” Drilling and Fracturing

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~ 3500 feet

~ 100 feet Pay zone

Cap rock

Cap rock

Not to scale

A Typical Drilling PadA Typical Drilling Pad

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Drill Rig

Drilling MudLagoon

Pumps and Power

Injection Water and Flowback Lagoon

http://www.glossary.oilfield.slb.com/

Let’s watch a movie to see what happens from such a site

More Than One Well per PadMore Than One Well per Pad

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many 1000’s of feet

Well (6 here)~100’s of feet

Pad

Not to Scale

Hydraulic fracture

Geology controls the arragement

Direction of max horizontal stress

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Ideal Ideal Arrangement of Spacing UnitsArrangement of Spacing Units

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Example: Dallas/Fort Worth Airport Property, Example: Dallas/Fort Worth Airport Property, Barnett Shale PlayBarnett Shale Play

• 53 pads on 18,076 acres

• Almost complete coverage

• Patchwork, mostly ideal units

• One developer

Some chemicals used in the procedureSome chemicals used in the procedure

Proppant: Particles, like sand, transported into the fractures to keep them open after fracturing pressure release.

Gelling Agents: Increase fluid viscosity to help proppant transport.

Biocides: Kill bacteria that harm the gelling agents.Breakers: Decrease viscosity of the fracturing fluid, after the

fracturing process, to improve flowback.Anti-Corrosives: Protect metallic elements in the well.Friction Reducers: Allow high pressures and flow rates.Acid : Clean out perforations, well, fractures

11http://www.epa.gov/OGWDW/uic/pdfs/cbmstudy_attach_uic_ch04_hyd_frac_fluids.pdfhttp://www.earthworksaction.org/hydfracking.cfm

Additives to Fracturing FluidsAdditives to Fracturing Fluids

From NYS DEC’s SGEIS, 2009

• When the fracturing process is completed, the pressure is released, and much of the fracturing fluid backflows to the wellhead*.

• The backflow is: highly saline; contain some heavy metals (e.g. barium, strontium); Toxic fluid additives;

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PROBLEM

FLUID Recycling can ameliorate this problem but more research is needed to achieve good results

Contamination of ground water and surface water by fracturing fluids Water leaks Gas leaks Interconnection of aquifers produced by fractures and alteration of the

underground rock layers Destruction of the confining nature of common confined aquifers in SE Ohio. Lack of good models to predict expected impacts, more research is needed to

understand water and gas circulation during and after exploitation. For zones that are impacted (contaminated water wells, etc.), for how long are

they going to be impacted? Who is going to supply clean water to the affected users after exploitation ends?

Potential Problems