Proppant Materials

To carry proppant material into the fracture to create a conductive path for produced fluids... 

Intermediate- to high-strength ceramics Proppant material... 

Sand is the simplest proppant material. Sand is cheap, but at higher stresses it shows a comparatively strong reduction in permeability. 

Hydraulic fracturing is a method of stimulating production of oil or gas from rock formations. A fluid is pumped under conditions of high pressure and high rate Into the formation to fracture it. The fluid also carries sand or a similar proppant material into the fractures. When the pumping is stopped and the hydraulic pressure is released at the wellhead, the fracture partially closes on the sand leaving a highly permeable channel for the oil or gas to flow back to the well. 

The materials commonly used as proppants can be grouped into three main categories, listed in Table 10.25. The first proppant material used was rounded silica sand mined from glacial deposits. This material was initially selected owing to both its wide availability near production wells and its low cost, but since the early days several other industrial materials have been selected and used as proppants, and today we observe the increased use of synthetic materials, especially sintered and fused ceramics. The main impetus in focusing on ceramics was driven by the fact that ceramic materials offer suitable properties for use in modern deep wells today. 

A series of crushing resistance tests consists in determining the stress at which the proppant material shows excessive generation of fines. Tests are conducted on samples that have been sieved. Four specific stress levels (i.e., 7.5,10,12.5, and 15 ksi) are used in the recommended practice (see API RP-61). 

Fired ceramic spheroids have been described for use as a well proppant [1051], Each spheroid has a core made from raw materials comprising mineral particulates, silicium carbide, and a binder. The mixture includes a mineral with chemically bound water or sulfur, which blows the mixture during firing. Therefore the core has a number of closed air cells. Each spheroid has an outer shell surrounding the core, comprising a metal oxide selected from aluminum oxide and magnesium oxide. The fired ceramic spheroids have a fired density less than 2.2 g/cm. ... 

It is possible to build within the formation a porous pack that is a mixture of fibers and the proppant. The fibrous material may be any suitable material (e.g., natural or synthetic organic fibers, glass fibers, ceramic fibers, carbon fibers). 

Thermoplastic Films. Recently, thermoplastic film [1342,1343] materials have been developed to reduce the proppant flowback that can occur after fracturing treatments. A heat-shrinkable film cut into thin slivers provides flowback reduction over broad temperature ranges and closure stress ranges... 

Adhesive-Coated Material. The addition of an adhesive-coated material [335] to proppants decreases the flowback of the particulates. Such adhesive-coated materials can be inorganic or organic fibers, flakes, and the like. The adhesive-coated material interacts mechanically with the proppant particles to prevent the flowback of particulates to the wellbore. The consolidation of a proppant also may occur via a polyurethane coating, which will slowly polymerize after the fracturing treatment because of a polyaddition process [1856]. 

A. Khaund. Sintered low density gas and oil well proppants from a low cost unblended clay material of selected composition. Patent US 4668645,1987. 

To optimize processes that are based upon the interaction between microstructure and flow (for example, proppant placement in hydraulic fracture of geologic formations [oil recovery], separations processes for biological materials, mixing and dispersion of additives in blenders, crystal growth and solidification processes). 

A low-bulk-density material leads to the use of less mass of proppant for a given volume of reservoir bed or storage tank to fill. 

All ceramic proppant producers use as feedstock essentially bauxite and, to a lesser extent, other industrial minerals with a high alumina content such as kaolin, nepheline syenite, wollastonite, talc, and feldspars. The final spherical shape is obtained by several processing routes currently used in the ceramics industry for producing beads and other particulate materials. The most common of these processes are pelletizing and sintering, atomization, fire polishing, and flame spraying. 

With hydraulic fracturing, fracture conductivity is maintained by propping open a fracture created with a solid material, such as sand, bauxite, ceramic, and certain lighter-weight materials. When used in hydraulic fracturing, these materials are referred to as proppants. 

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