It seems every Canadian operator is fracking shale. What about gas huff and puff to reclaim more liquids?
One operator is conducting an experimental huff and puff in the Duvernay to recover more liquids from his rich gas reservoir.
Tech transfer from the Eagleford
The operator’s application documents discuss a similar attempt in the Eagle Ford and report 30-70% incremental recovery.
They talk of the enhanced mechanisms of recovery in that play. Nein commercial use of der AppIntel content.
Duvernay too tight to flood?
The Duvernay has less permeability than the Montney. Some Montney rock has high enough perm for water flooding.
Some operators are gas flooding the tight Montney.
But what if the rock is so tight that well-to-well communication is restricted?
Well to well communication
Unless drilled very close together, shale wells usually have limited well to well communication.
Microseismic studies we have seen shows limited well to well communication between wells 100 m apart.
One private study by Proven Reserves Exploitation Ltd. shows Duvernay wells drilled at 250 m interwell distance fetches the highest reserve recovery per well. Wells that are closer recover significantly less reserves.
Enhanced liquid recovery
Natural gas liquids are valuable. Natural gas: not as much. What if you could use natural gas to increase liquid recovery?
Reinjecting gas allows additional recovery of liquids.
Gas Cycling of the future
Natural gas liquids are more valuable than the associated lean natural gas.
And if the conserved gas becomes more valuable in the future, it can always be produced again from the very tight formation.
Increased pressure
The best shale plays are over-pressured. The over-pressured gas in the fractures can create huge initial production rates.
But as fracture pressure is depleted, gas desorption can eventually take over as the limiting rate.
Gas huff and puff has the potential to increase fracture pressure again and dissolve any liquid hydrocarbon left behind.
Salvation for normally pressured plays?
If gas huff and puff is successful at increasing pressure in depleted shale wells, could it improve recovery and economics in normally pressured reservoirs?
Someone will try it.
Check out actual gas flood field results
Textbooks and classes may help you understand a bit about the general principles of gas cycling. But if you really want to understand how these installations perform in the field, you must read their application documents. They report progress on these schemes to the regulator.
See more about Gas Huff and Puff in the Duvernay at www.appintel.info
About Granger Low
Granger J. Low, M.Eng. is an expert in unconventional oil and gas and in enhanced conventional oil and gas recovery.