Hydraulic Fracture Treatments

Created by pumping above the pressure needed to fracture the rock.

Propped Fracs:

To prevent closure, hydraulic fracture is propped open by pumping a slurry of sand. At greater depths high strength proppant is used.

• Substantially increases production from low permeability formations (less than 10mD).
• Bypassses skin damage over a wide range of permeabilities.
• Careful design essential or fracture may grow out of zone resulting in water and unwanted gas production.

Acid Fracs:

• Only used in carbonates.
• Conductive path along fracture created by acid "etching" fracture walls.
• Etched formation must be strong enough to withstand closure forces.

Matrix Treatments:

Fluid pumped below the fracture pressure.

Matrix Acidization:

• Acid is injected to dissolve formation damage or else bypass it by dissolving the rock.
• Significant productivity increases only obtained if damage is present.

Carbonates (limestone, chalk, dolomites):

• Most carbonate reservoirs are acidized with HCl, although not suitable for high porosity (>35%) chalk.
• Acid bypasses damage and links up with nearby vugs and natural fractures.
• Careful design essential or acid may create a high conductivity path to nearby gas or water zones.

Sandstones:

• Careful design essential or acidizing can damage the permeability of some sandstones.
• Hydrochloric acid (HCl) most easily used but formation damage must be soluble in HCl or carbonate content of reservoir must be >15%.
• Mud acid (HCl/HF) can dissolve damaging siliceous material such as clay minerals.

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