Frac-and-Pack Stimulation: Application, Design, and Field Experience
- L.P. Roodhart | P.A. Fokker | D.R. Davies | Jacob Shlyapobersky | G.K. Wong
- Document ID
- Society of Petroleum Engineers
- Journal of Petroleum Technology
- Publication Date
- March 1994
- Document Type
- Journal Paper
- 230 - 238
- 1994. Society of Petroleum Engineers
- 2.4.3 Sand/Solids Control, 1.2.3 Rock properties, 4.3.4 Scale, 1.14 Casing and Cementing, 4.1.2 Separation and Treating, 5.2 Reservoir Fluid Dynamics, 2.4.6 Frac and Pack, 2.5.2 Fracturing Materials (Fluids, Proppant), 3 Production and Well Operations, 2.4.5 Gravel pack design & evaluation, 4.6 Natural Gas, 3.2.3 Hydraulic Fracturing Design, Implementation and Optimisation, 5.6.4 Drillstem/Well Testing, 2.5.1 Fracture design and containment, 2.2.2 Perforating, 1.8 Formation Damage, 5.6.8 Well Performance Monitoring, Inflow Performance
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Paper first presented at the 1993 SPE Annual Technical Conference andExhibition held in Houston, Oct. 3-6. Combined with SPE 26563 and published inthe Journal of Petroleum Technology, March 1994.
A relatively short, highly conductive fracture created in a reservoir ofmoderate to high permeability will breach near-wellbore damage, reduce thedrawdown and near-wellbore flow velocity and stresses, and increase theeffective wellbore radius. Fracturing treatments of this type have two stages:fracture created, terminated by tip screen out, and fracture inflation andpacking. Such a two-stage treatment is the basis of a number of newwell-completion methods, collectively known as "frac-and-pack." Thistechnique has been successfully applied, with a range of fracture sizes, tostimulate wells in various reservoirs worldwide.
This paper discusses the criteria for selecting wells to be frac-and-packed.We show how a systematic study of the inflow performance can be used to assessthe potential of frac-and-packed wells, to identify the controlling factors,and to optimize design parameters. We also show that fracture conductivity isoften the key to successful treatment. This conductivity depends largely onproppant size; formation permeability damage around the created fracture hasless effect. Appropriate allowance needs to be made for flow restrictionscaused by the presence of the perforations, partial penetration, and non-Darcyeffects. We describe the application of the overpressure-calibrated hydraulicfracture model in frac-and-pack treatment design, and discuss some operationalconsiderations with reference to field examples.
The full potential of this promising new completion method can be achievedonly if the design is tailored to the individual well. This demandshigh-quality input data, which can be obtained only from a calibrationtest.
This paper presents our strategy for frac-and-pack design, drawing onexamples from field experience. We also point out several areas that theindustry needs to address, such as the sizing of proppant in soft formationsand the interaction between fracturing fluids and resin in resin-coatedproppant.
The idea of combining sand control and well stimulation in a singletreatment was first practiced in Venezuela some 30 years ago. The treatmentconsisted of perforating the pay zone, then applying a small-scale fracturingtreatment with a viscous crude (10 to 20 cp) and sand sizing to controlformation sand. Ball sealers were used in long intervals to promotedistribution across the entire section. A screen was washed down through thegravel remaining inside the casing after the fracture treatment, and additionalsand was placed around the screen where necessary. This technique yieldedrelatively high production rates because of low skin and adequate sandcontrol.
This treatment was later extended to consist of a small, propped fracturedesigned to bypass the skin around wells completed in well-consolidated sandsthat were severely impaired. In this case, the screen was not run and thegravel was not topped up. A typical job for a 100-ft interval would consist of500 to 800 bbl of crude oil (18 API) with some 40,000 lbm of 10- to 20-meshsand. This propped minifracture typically yielded a two- to three-fold increasein production rate.
Though it received considerable publicity, to the best of our knowledge, thetechnique was never applied widely outside Venezuela. Nevertheless, thetechnology in this area has now developed to the point where the theoreticalunderstanding of the processes involved has greatly improved, proven treatmentdesign tools are available, and vastly improved mixing and pumping equipmenthas been developed for both gravel packing and propped hydraulicfracturing.
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