Proppant Selection: The Key to Successful Fracture Stimulation
- C.T. Montgomery (Dowell Schlumberger) | R.E. Steanson (Dowell Schlumberger)
- Document ID
- Society of Petroleum Engineers
- Journal of Petroleum Technology
- Publication Date
- December 1985
- Document Type
- Journal Paper
- 2,163 - 2,172
- 1985. Society of Petroleum Engineers
- 4.1.2 Separation and Treating, 5.5 Reservoir Simulation, 3 Production and Well Operations, 5.2 Reservoir Fluid Dynamics, 2.4.3 Sand/Solids Control, 2.5.2 Fracturing Materials (Fluids, Proppant), 3.2.3 Hydraulic Fracturing Design, Implementation and Optimisation, 4.6 Natural Gas
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Many proppants and mesh sizes are available for the design of a fracture stimulation treatment. When proppants-sand (Ottawa, Texas Mining, Unisil), proppants-sand (Ottawa, Texas Mining, Unisil), bauxite, intermediate-strength proppants (ISP), resin-coated sand (RCS), precured resin-coated sand (PRCS) and Z prop-are considered, the principal questions seem to be, prop-are considered, the principal questions seem to be, "Which one do I select"" and "How should I use it?" Maximized, adequate, long-term productivity in low-permeability reservoirs depends on fracture penetration and fracture conductivity. How to obtain deeply penetrating fractures that are contained and adjacent to the porous penetrating fractures that are contained and adjacent to the porous interval is one of the questions that challenge the industry. Another is how to obtain sufficient fracture conductivity to use the deep penetration effectively. This is a state-of-the-art paper that attempts to bring the current technology on proppants together. This paper discusses how to determine and to obtain sufficient fracture conductivity. Fracture conductivity is a function of the proppant properties (i.e.. strength, roundness, and fines content), closure stress, drawdown rate, formation properties (i.e., proppant embedment conditions), and properties (i.e., proppant embedment conditions), and resultant propped fracture width. The engineering, principles involved in the selection of- the proper type and principles involved in the selection of- the proper type and amount of proppant are supported with a case history.
As we explore for reserves at depths exceeding- 10.00ft 13,048 in], the tendency is to find reservoirs that have low permeability and contain natural gas. Because of the low permeability of the formation, the natural rate of production and the drainage area are often too low to provide a commercial well. provide a commercial well. Propped hydraulic fracture-stimulation treatments that create deeply penetrating, highly conductive flow channels can be used to increase both the rate of production and the drainage area. Four factors control improvements in productivity (i.e., the productivity index) provided by hydraulic fracturing. 1. Propped fracture area (sq ft). This is the area of the fracture adjacent to the porous interval that has been propped (length times height). All the fracture area propped (length times height). All the fracture area adjacent to the porous interval that is created have not be propped, and only the fracture area adjacent to the propped, and only the fracture area adjacent to the productive porosity that is propped is considered an effective productive porosity that is propped is considered an effective area. 2. Conductivity of the propped fracture (md-ft). This is a measurement of how well the propped fracture conducts the produced fluids. In addition to the effect of closure stress on the permeability of the proppant, factors such as embedment. proppant distribution, and resultant fracture width must be considered to determine the conductivity of the fracture at reservoir producing conditions. 3. Reservoir permeability. This value is used to determine the fracture conductivity required to use the proposed fracture penetration effectively. proposed fracture penetration effectively. 4. Drainage radius. This value is used, as is reservoir permeability, to determine the length of fracture needed. permeability, to determine the length of fracture needed. A long, fracture is needed if the well spacing is large and the reservoir permeability is low.
To show how the principles that are described in this paper work, we will use a typical gas well with the properties described in Table 1.
Effect of Reservoir Permeability on Fracturing. In deep, hot, low-permeability sandstone reservoirs, development of deeply penetrating fractures with adequate conductivity is important. Once reservoir permeability is known, it is important to optimize the fracture length and conductivity by comparing treatment cost to expected production. The pressure drop along a propped fracture that production. The pressure drop along a propped fracture that has an insufficient flow capacity will limit the production from a well. A fracture with excessive fracture capacity is not effective.
Fig. 1 can be used as a guide in the selection of the desired effective fracture length based on reservoir permeability. When the reservoir permeability is greater than permeability. When the reservoir permeability is greater than about 0.1 md, the desired fracture lengths are generally 1,000 ft 1305 mi or less. In low-permeability reservoirs (kg, less than 0.1 md), production can be almost directly proportional to fracture length before boundary conditions are proportional to fracture length before boundary conditions are reached. With adequate fracture flow conductivity, the longer the fracture, the higher the producing rate. For example, in very-low-permeability reservoirs (i.e., 0.001 to 0.0001 md), fracture half-lengths of 2.500 to 4,000 ft 1762 to 1220 nil can be used to increase production effectively. Fig. 1 shows that in the typical well example with a permeability of 0.03 md. a 1,300-ft [396-m] fracture half-length should be created and propped to achieve maximum production.
Effect of Fracture Conductivity and Fracture Length on Production. Fig. 2 was generated with a reservoir simulators and shows the effect of fracture conductivity (Cf) and fracture half-length on production in dimensionless terms.
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