What is MINI-FRAC?

A mini-frac test is simply an injection/fall-off test performed using a reservoir compatible fluid. Mini-fracs provide better estimation of reservoir properties in tight/low permeability formations and in formations where fluid inflow is severely restricted by formation damage compared to conventional tests.

What is the objective of a MINI-FRAC?

The main purpose of a mini-frac is to break down the formation to create a small fracture and observe the pressure respond before and after fracture closure. The short fracture establishes a better communication between the wellbore and true formation.
A geothermic power station.
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How to perform a MINI-FRAC with DST string?

Packers are set above or straddling the test interval to isolate the zone of interest (pay zone). The drill pipe and DST string are filled with injection fluid and a pumper is rigged in to inject additional fluid to break down the formation and create a short fracture. The well is then shut-in to observe the closure of the fracture and monitor the after-closure falloff response, see Figure 1. Northstar uses pressure-temperature downhole gauges to monitor the progress of the test in real time (Northstar Live) as well as a downhole shut-in valve to decrease the effect of wellbore storage and observe more rapidly the onset of reservoir dominated flow.

Why MINI-FRAC Test?

Minifrac test are conducted to obtain fracture design parameters (fracture closure, fracture gradient, fluid leakoff and fluid efficiency) and reservoir characterization parameters (formation permeability, reservoir pressure, flow regimes, flow capacity). Pre-Closure Analysis (PCA) is used to determine fracture design parameters (flow is governed by the fracture). PCA is performed with injection and time data collected until fracture closure.  It uses a G-function derivative analysis to determine fracture closure and fluid leakoff, see Figure 2.
A geothermic power station.
Image 1

Figure 1. Modified Mini-frac test overview – Northstar Real Time Recording Data [1].

After-Closure Analysis (ACA) is used to estimate reservoir characterization parameters. ACA is performed with pressure data collected after fracture closure (flow is governed by the reservoir) and a similar approach to traditional pressure transient analysis (PTA), see figure 3.

Figure 2. Modified Fekete G-function Semilog Plot to Estimate Fracture Design Parameters [2].

After-Closure Analysis (ACA) is used to estimate reservoir characterization parameters. ACA is performed with pressure data collected after fracture closure (flow is governed by the reservoir) and a similar approach to traditional pressure transient analysis (PTA), see figure 3.
Image 2
Image 3

Figure 3. Soliman ACA Derivate Analysis and Conventional Injection/Falloff Derivative Analysis to Estimate Reservoir Pressure and Permeability [3].

Benefits

References

[1] HIS Markit Ltd. “Minifrac”. WellTest 2019.1. 2021, Minifrac (ihsenergy.ca). Revised: November 9, 2021.

[2] Fekete Associates Inc. “Mini-frac (DFIT) Analysis for Unconventional Reservoir using F.A.S.T WellTestTM”. Petroleumengineer.ru. Microsoft PowerPoint – Mini-frac Analysis for Unconventional Reservoirs using FAST WellTest_Updated 16-Aug-2013 (petroleumengineers.ru). Revised: August 16, 2013.

[3] Ewens, S. Idorenyin, E. O’Donnell, P. Bruneer, F. and Santo, M. “Executing Minifrac Tests and Interpreting After-Closure Data for Determining Reservoir Characteristics in Unconventional Reservoirs”. OnePetro. https://doi.org/10.2118/162779-MS. Published: October 30, 2012.

What is the objective of a MINI-FRAC?

The main purpose of a mini-frac is to break down the formation to create a small fracture and observe the pressure respond before and after fracture closure. The short fracture establishes a better communication between the wellbore and true formation.

How to perform a MINI-FRAC with DST string?

Packers are set above or straddling the test interval to isolate the zone of interest (pay zone). The drill pipe and DST string are filled with injection fluid and a pumper is rigged in to inject additional fluid to break down the formation and create a short fracture. The well is then shut-in to observe the closure of the fracture and monitor the after-closure falloff response, see Figure 1. Northstar uses pressure-temperature downhole gauges to monitor the progress of the test in real time (Northstar Live) as well as a downhole shut-in valve to decrease the effect of wellbore storage and observe more rapidly the onset of reservoir dominated flow.

Why MINI-FRAC Test?

Minifrac test are conducted to obtain fracture design parameters (fracture closure, fracture gradient, fluid leakoff and fluid efficiency) and reservoir characterization parameters (formation permeability, reservoir pressure, flow regimes, flow capacity). Pre-Closure Analysis (PCA) is used to determine fracture design parameters (flow is governed by the fracture). PCA is performed with injection and time data collected until fracture closure.  It uses a G-function derivative analysis to determine fracture closure and fluid leakoff, see Figure 2.

Figure 1. Modified Mini-frac test overview – Northstar Real Time Recording Data [1].

After-Closure Analysis (ACA) is used to estimate reservoir characterization parameters. ACA is performed with pressure data collected after fracture closure (flow is governed by the reservoir) and a similar approach to traditional pressure transient analysis (PTA), see figure 3.

Figure 2. Modified Fekete G-function Semilog Plot to Estimate Fracture Design Parameters [2].

After-Closure Analysis (ACA) is used to estimate reservoir characterization parameters. ACA is performed with pressure data collected after fracture closure (flow is governed by the reservoir) and a similar approach to traditional pressure transient analysis (PTA), see figure 3.

Figure 3. Soliman ACA Derivate Analysis and Conventional Injection/Falloff Derivative Analysis to Estimate Reservoir Pressure and Permeability [3].

Benefits

References

[1] HIS Markit Ltd. “Minifrac”. WellTest 2019.1. 2021, Minifrac (ihsenergy.ca). Revised: November 9, 2021.

[2] Fekete Associates Inc. “Mini-frac (DFIT) Analysis for Unconventional Reservoir using F.A.S.T WellTestTM”. Petroleumengineer.ru. Microsoft PowerPoint – Mini-frac Analysis for Unconventional Reservoirs using FAST WellTest_Updated 16-Aug-2013 (petroleumengineers.ru). Revised: August 16, 2013.

[3] Ewens, S. Idorenyin, E. O’Donnell, P. Bruneer, F. and Santo, M. “Executing Minifrac Tests and Interpreting After-Closure Data for Determining Reservoir Characteristics in Unconventional Reservoirs”. OnePetro. https://doi.org/10.2118/162779-MS. Published: October 30, 2012.

What is the objective of a MINI-FRAC?

The main purpose of a mini-frac is to break down the formation to create a small fracture and observe the pressure respond before and after fracture closure. The short fracture establishes a better communication between the wellbore and true formation.

How to perform a MINI-FRAC with DST string?

Packers are set above or straddling the test interval to isolate the zone of interest (pay zone). The drill pipe and DST string are filled with injection fluid and a pumper is rigged in to inject additional fluid to break down the formation and create a short fracture. The well is then shut-in to observe the closure of the fracture and monitor the after-closure falloff response, see Figure 1. Northstar uses pressure-temperature downhole gauges to monitor the progress of the test in real time (Northstar Live) as well as a downhole shut-in valve to decrease the effect of wellbore storage and observe more rapidly the onset of reservoir dominated flow.

Figure 1. Modified Mini-frac test overview – Northstar Real Time Recording Data [1].

Why MINI-FRAC Test?

Minifrac test are conducted to obtain fracture design parameters (fracture closure, fracture gradient, fluid leakoff and fluid efficiency) and reservoir characterization parameters (formation permeability, reservoir pressure, flow regimes, flow capacity).

Pre-Closure Analysis (PCA) is used to determine fracture design parameters (flow is governed by the fracture). PCA is performed with injection and time data collected until fracture closure.  It uses a G-function derivative analysis to determine fracture closure and fluid leakoff, see Figure 2.

Figure 2. Modified Fekete G-function Semilog Plot to Estimate Fracture Design Parameters [2].

After-Closure Analysis (ACA) is used to estimate reservoir characterization parameters. ACA is performed with pressure data collected after fracture closure (flow is governed by the reservoir) and a similar approach to traditional pressure transient analysis (PTA), see figure 3.

Figure 3. Soliman ACA Derivate Analysis and Conventional Injection/Falloff Derivative Analysis to Estimate Reservoir Pressure and Permeability [3].

After-Closure Analysis (ACA) is used to estimate reservoir characterization parameters. ACA is performed with pressure data collected after fracture closure (flow is governed by the reservoir) and a similar approach to traditional pressure transient analysis (PTA), see figure 3.

Benefits

References

[1] HIS Markit Ltd. “Minifrac”. WellTest 2019.1. 2021, Minifrac (ihsenergy.ca). Revised: November 9, 2021.

[2] Fekete Associates Inc. “Mini-frac (DFIT) Analysis for Unconventional Reservoir using F.A.S.T WellTestTM”. Petroleumengineer.ru. Microsoft PowerPoint – Mini-frac Analysis for Unconventional Reservoirs using FAST WellTest_Updated 16-Aug-2013 (petroleumengineers.ru). Revised: August 16, 2013.

[3] Ewens, S. Idorenyin, E. O’Donnell, P. Bruneer, F. and Santo, M. “Executing Minifrac Tests and Interpreting After-Closure Data for Determining Reservoir Characteristics in Unconventional Reservoirs”. OnePetro. https://doi.org/10.2118/162779-MS. Published: October 30, 2012.