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Injection Fall-off (IFO) testing


Injection Fall-off (IFO) testing Related Terms

Injection Fall-off (IFO) testing, DFIT, Frac Monitoring, Surface Pressure Transient Testing

Injection fall-off (IFO) testing typically refers to testing done in either Water disposal wells or injector wells for pressure maintenance or secondary/tertiary recovery methods.  

They are most often employed when either a new wells is drilled and completed for this purpose or more commonly a pre-existing production well is converted into a disposal/injection well.  The IFO is the mirror image of a Pressure Build-Up (PBU) on a producing well and analysis can derive the same types of fundamental wellbore/reservoir information on an injector well that you can with a producing, permeability and reservoir pressure.  The main interest in the IFO is to understand skin and its affect on your injector.  Because you are limited to 0.5 psi/ft. on injection surface pressures, an increasing skin will require ever higher injection pressures to maintain the same injection rates.  At some future point you will be limited by the surface injection pressure limitation, as set by the state, not mentioning the increased cost of fueling your injection pumps.  If the well in question is a Saltwater Disposal (SWD) well, which often have less stringent separation/filter requirements for the injected fluid, skin accretion can happen quickly.  Knowing your "original" wellbore condition before injection begins and then testing periodically thereafter or when you notice increasing injection pressures,  would be a good idea. 

There is ever increasing scrutiny being placed upon these injector wells and especially so near population centers or even in rural areas if water is being pulled from wells for consumption and use.  Better to have performed tests and be able to demonstrate, via documentation, that your wells are operating normally and within state guidelines.

As mentioned previously on this website, if your disposal/injector well can hold a column of fluid without going on a vacuum, then performing the test via surface measurements to keep costs low and RISK FREE is the recommended way to go and yields virtually identical values as you would obtain by running wire and pressure gauges downhole.

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