Why is N2 used for hydraulic fracturing?
The use of N2 in hydraulic fracturing fluids is very common within the oil and gas industry. By using N2, the water used in the fracturing fluid can be significantly reduced. With less liquid in the treatment and the high mobility and expansion of the N2, it is much easier and quicker to remove the fracturing fluids from the formation. Replacement of liquids with nitrogen can provide economic and environmental benefits by reducing the liquid volume needed to complete the fracturing treatment.
N2 provides gas saturation to the reservoir fluids improving relative permeability to hydrocarbons. N2 immediately reduces the hydrostatic of the system and, in foamed fluids, provides excellent proppant transport capability.
In many cases, the N2 may be less expensive and provide a cost effective volume, thereby lowering the cost of the treatment. Additionally, the use of N2 with water-or oil-based fracturing fluids can alter the physical properties of the base fluid following the treatment, including reducing the viscosity, minimizing relative permeability effects and lowering surface tension.
In addition to imparting improved physical properties to the base fluid, the dissolved N2 breaks out of solution during drawdown ensuring a gas phase exists in the pore space and energized flow is achieved. These effects result in improved fracturing fluid mobility within the formation pores, improved recovery of the fracturing fluids and greater production of the reservoir fluids.
What are the benefits of N2?
Well drilling and construction:
- Freeing differentially stuck pipe
- Underbalanced drilling
- Reduced cement density with foamed cementing
Completions and workovers:
- Enhance coiled tubing operations
- Lighten liquid columns in wellbores
Stimulation and hydraulic fracturing:
- Commingle with acid to improve treatment penetration
- Nitrify fracturing fluids to improve liquids recovery, minimize liquid loading in the wellbore and speed post-fracturing clean-up
- Foam fracturing liquids to improve fracture fluid viscosity and proppant transport
- Effectively stimulate coal bed methane wells and low pressure reservoirs without reservoir damage
- Substitute N2 for water to meet environmental needs
- Substitute N2 for workover or fracturing oil to reduce costs
Facilities and pipeline:
- Purge facilities and pipelines for safe turnarounds and repairs
- Safely and effectively pressure test facilities and pipelines