Holistic Fracture Diagnostics: Consistent Interpretation of Prefrac Injection Tests Using Multiple Analysis Methods
- Robert D. Barree (Barree & Associates) | Valencia L. Barree (Barree & Associates) | David Craig (Halliburton)
- Document ID
- Society of Petroleum Engineers
- SPE Production & Operations
- Publication Date
- August 2009
- Document Type
- Journal Paper
- 396 - 406
- 2009. Society of Petroleum Engineers
- 5.2 Reservoir Fluid Dynamics, 5.3.2 Multiphase Flow, 3 Production and Well Operations, 5.6.5 Tracers, 5.1 Reservoir Characterisation, 2.5.1 Fracture design and containment, 5.6.4 Drillstem/Well Testing, 4.1.5 Processing Equipment, 5.6.9 Production Forecasting, 4.1.2 Separation and Treating, 2.4.5 Gravel pack design & evaluation, 3.2.3 Hydraulic Fracturing Design, Implementation and Optimisation, 5.1.5 Geologic Modeling, 5.6.1 Open hole/cased hole log analysis
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Since the introduction of the G-function derivative analysis, prefrac diagnostic injection tests have become a valuable and commonly used technique. Unfortunately, the technique is frequently misapplied or misinterpreted, leading to confusion and misdiagnosis of fracturing parameters. This paper presents a consistent method of analysis of the G-function, its derivatives, and its relationship to other diagnostic techniques including square-root(time) and log(?pwf)-log(?t) plots and their appropriate diagnostic derivatives.
Four field test examples are given for the most common diagnostic curve signatures. These show how multiple analysis methods can be applied to consistently interpret closure pressure and time, as well as pre- and post-closure flow regimes and reservoir properties from the test data. The cases include normal constant-area and constant permeability leakoff, pressure dependent fissure leakoff, fracture tip extension, and variable fracture storage. In some cases conventionally accepted analysis methods, such as the Sqrt(time) plot, can lead to misleading interpretations. A single consistent approach to analysis is described for each case. The example cases can be used to build a foundation for consistent and less ambiguous analysis of any complex fracture injection/falloff test.
Prefrac diagnostic injection test analysis provides critical input data for fracture design models, and reservoir characterization data used to predict post-fracture production. An accurate post-stimulation production forecast is necessary for economic optimization of the fracture treatment design. Reliable results require an accurate and consistent interpretation of the test data. In many cases closure is mistakenly identified through misapplication of one or more analysis techniques. In general, a single unique closure event will satisfy all diagnostic plots or methods. All available analysis methods should be used in concert to arrive at a consistent interpretation of fracture closure.
Relationship of the pre-closure analysis to after-closure analysis results must also be consistent. To correctly perform the after-closure analysis the transient flow regime must be correctly identified. Flow regime identification has been a consistent problem in many analyses. There remains no consensus regarding methods to identify reservoir transient flow regimes after fracture closure. The method presented here is not universally accepted but appears to fit the generally assumed model for leakoff used in most fracture simulators.
Four examples are presented to show the application of multiple diagnostic analysis methods. The first illustrates the expected behavior of normal fracture closure dominated by matrix leakoff with a constant fracture surface area after shut-in. The second example shows pressure dependent leakoff (PDL) in a reservoir with pressure-variable permeability or flow capacity, usually caused by natural or induced secondary fractures or fissures. The third example shows fracture tip extension after shut-in. These cases generally show definable fracture closure. The fourth example shows what has been commonly identified as fracture height recession during closure, but which can also indicate variable storage in a transverse fracture system.
|File Size||1 MB||Number of Pages||11|
Barree, R.D. 1998. Applicationsof Pre-Frac Injection/Falloff Tests in Fissured Reservoirs--Field Examples.Paper SPE 39932 presented at the SPE Rocky Mountain Regional/Low- PermeabilityReservoirs Symposium, Denver, 5-8 April. DOI: 10.2118/39932-MS.
Barree, R.D. and Mukherjee, H. 1996. Determination of Pressure DependentLeakoff and its Effect on Fracture Geometry. Paper SPE 36424 presented atthe SPE Annual Technical Conference and Exhibition, Denver, 6-9 October. DOI:10.2118/36424-MS.
Castillo, J.L. 1987. ModifiedFracture Pressure Decline Analysis Including Pressure-Dependent Leakoff.Paper SPE 16417 presented at the Low-Permeability Reservoirs Symposium, Denver,18-19 May. DOI: 10.2118/16417-MS.
Cinco-Ley, H. and Samaniego-V., F. 1981. Transient Pressure Analysis forFractured Wells. J. Pet Tech 33 (9): 1749-1766.SPE-7490-PA. DOI: 10.2118/7490-PA.
Cinco-Ley, H., Kuchuk, F., Ayoub, J., Samaniego-V., F., and Ayestaran, L.1986. Analysis of Pressure TestsThrough the Use of Instantaneous Source Response Concepts. Paper SPE 15476presented at the SPE Annual Technical Conference and Exhibition, New Orleans,5-8 October. DOI: 10.2118/15476-MS.
Craig, D.P. and Blasingame, T.A. 2006. Application of a NewFracture-Injection/Falloff Model Accounting for Propagating, Dilated, andClosing Hydraulic Fractures. Paper SPE 100578 presented at the SPE GasTechnology Symposium, Calgary, 15-17 May. DOI: 10.2118/100578-MS.
Hagoort, J. 1981. Waterflood-induced hydraulic fracturing. PhD thesis, DelftTechnical University, Delft, The Netherlands.
Koning, E.J.L. and Niko, H. 1985. Fractured Water-Injection Wells: APressure Falloff Test for Determining Fracture Dimensions. Paper SPE 14458presented at the SPE Annual Technical Conference and Exhibition, Las Vegas,Nevada, USA, 22-25 September. DOI: 10.2118/14458-MS.
Nolte, K.G. 1979. Determinationof Fracture Parameters from Fracturing Pressure Decline. Paper SPE 8341presented at the SPE Annual Technical Conference and Exhibition, Las Vegas,Nevada, USA, 23-26 September. DOI: 10.2118/8341-MS.
Settari, A. 2000. Coupled Fracture and Reservoir Modeling. Presented at theWorkshop on Three Dimensional and Advanced Hydraulic Fracture Modeling, FourthNorth American Rock Mechanics Symposium, Seattle, Washington, USA, 29 July.
Talley, G.R., Swindell, T.M., Waters, G.A., and Nolte, K.G. 1999. Field Application of After-ClosureAnalysis of Fracture Calibration Tests. Paper SPE 52220 presented at theSPE Mid-Continent Operations Symposium, Oklahoma City, Oklahoma, USA, 28-31March. DOI: 10.2118/52220-MS.