Field Trials of the New DFIT-Flowback Analysis (DFIT-FBA) for Accelerated Estimates of Closure and Reservoir Pressure and Reservoir Productivity
- Behnam Zanganeh (University of Calgary) | Christopher R. Clarkson (University of Calgary) | Alexander Cote (Origin Energy) | Brenton Richards (Origin Energy)
- Document ID
- Unconventional Resources Technology Conference
- SPE/AAPG/SEG Unconventional Resources Technology Conference, 20-22 July, Virtual
- Publication Date
- Document Type
- Conference Paper
- 2020. Unconventional Resources Technology Conference
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- 126 since 2007
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A new Diagnostic Fracture Injection Test (DFIT) procedure and analysis method was recently introduced whereby flowback data, obtained immediately after pump shut down, is analyzed for closure pressure (pc), reservoir pressure (pr) and reservoir productivity (well productivity index). The test is referred to as ‘DFIT-FBA’ to highlight the importance of flowback analysis (FBA) in the interpretation of the data. A proof-of-concept field trial of DFIT-FBA in a low-permeability reservoir demonstrated that the modified test design can significantly accelerate estimates of pc and pr compared to a conventional (pump-in/falloff) DFIT. The current study demonstrates repeatability of DFIT-FBA, improved analysis methods, and its critical importance for guiding an exploration program.
The DFIT-FBA procedure consists of two steps: 1) injection at about 3 to 6 bbls/min to initiate and propagate a mini hydraulic fracture and 2) immediate flowback of the injected fluid on surface at less than 5% of the injection rate using a choke management system. The well flowing pressure and flowback rates are monitored throughout the flowback period. Rate-transient analysis (RTA) methods are then applied to the flowback rates and pressures, including flow-regime identification plots to identify flow regimes and estimate reservoir pressure, and straight-line analysis to derive mini-fracture and reservoir properties. A unique set of field trials of DFIT-FBA are presented where vertical layers in the frontier unconventional reservoirs of the Beetaloo Basin are tested for pc and pr.
The DFIT-FBA procedure was successfully implemented for this exploration program. Flow regimes observed during the tests included before-closure wellbore/fracture storage and after-closure linear flow and boundary-dominated flow (BDF). Reservoir pressure (pr) was obtained from the start of the after-closure BDF period. Straight-line analysis applied to the after-closure flow regimes, assumed to be associated with flow through a fluid bank adjacent to the mini-fracture, was used to estimate productivity index. The new DFIT-FBA design enabled estimates of pc, pr and productivity index for each reservoir layer in just a few hours. In contrast, the conventional DFIT design would have required several days or weeks to estimate pr, which would not have met the key decision timelines for the operator’s exploration program.
This work engages both the completions and reservoir engineering communities. The results can be used for hydraulic fracture stimulation treatment design and for predicting the production performance of the reservoir.
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