Injection Fall-off Testing
The DFIT Test (a.k.a., DFIT Test, Pre-Frac, Injection Fall-off, Data Frac or Mini Frac) has become the dominate pressure transient test for DRC and the SPIDR in the domestic USA marketplace. Because conventional Gulf Coast and offshore shelf Gulf of Mexico gas drilling has decreased dramatically and has been replaced largely by tight gas (sand /shale) horizontal, multi-stage stimulation jobs, the DFIT has moved to the top of the list in transient testing in.
What is the DFIT or Injection Fall-Off Test
The DFIT (Diagnostic Fracture Injection Test) is an acronym coined by Halliburton. Schlumberger calls their equivalent test a MFO (Mini Fall-off), other operators and service companies may refer to it variously as a Data Frac or Mini Frac but is defined as:
a short duration, small volume fracturing operations where a small amount (<100 BBLS) of KCL water is pumped until fracture initiation. At that point the wing or frac valve is closed allowing the well’s pressure to fall-off naturally over the course of 24 to 48 hrs. (or longer).
The Role of the SPIDR in Injection Fall-Off testing
The SPIDR provides a high resolution and high frequency quartz transducer to collect this fall off information at 1 second intervals over the entire duration. Because the analysis takes the pressure data into derivative analysis, quality of the data is extremely important and can mean the difference between providing the customer with reservoir parameters or not being able to use the file for analysis. Failure to provide quality data and analysis means that the major expense of performing the high pressure pump is lost and the actual frac design must be guessed at rather than specific for the actual reservoir properties. A major operator in the USA has determined, via simultaneous comparisons with downhole pressure gauges, that the SPIDR Dual crystal quartz gauge provides equivalent data quality to downhole pressure gauges without the RISK and a fraction of the cost. If the fluid density is known and the well does not go on a vacuum during the fall-off the SPIDR is the recommended gauge of choice.
The SPIDR as Secondary Monitoring
Many operators and service companies also appreciate the ability of the SPIDR gauge to capture pump rate information (rate and cumulative volumes) during the pumping of the DFIT. Because the volume of fluid pumped is critical to the analysis, having a secondary high resolution method of verifying that information along with high frequency, high resolution pressure data on the same data file….is proving to be a nice feature that our customers value and appreciate.
DRC also has the ability to analyze the DFIT data set via our Meyer MinFrac software package if the client needs a primary or a backup analysis to his own.