Hydraulic fracturing transport

Clark, P.E. and Quadir, J.A. "Prop Transport in Hydraulic Fractures A Critical Review of Particle Settling Velocity Equations," SPE/DOE paper 9866, 1981 SPE/DOE Low Permeability Symposium, Denver, May 27-29. 

Daneshy, A.A. "Numerical Solution of Sand Transport in Hydraulic Fracturing," J. Pet. Technol.. January, 1978, 132 140. 

We discuss the suspensions used in well stimulation and hydraulic fracturing processes. The following sections pertain to various types of suspensions used in well stimulation and fracturing processes, their rheological characterization and hydraulic properties, behavior of suspensions in horizontal wells, a state-of-the-art review of proppant settling velocity and proppant transport in the fracture, presently available measurement techniques for suspensions and their merits, and, finally, a summary and conclusions on the use of suspensions in well stimulation. Future industry needs for better understanding of the complex behavior of suspensions are also mentioned in this section. 

To design a successful hydraulic fracturing treatment for horizontal wells, accurate information on the transport properties of slurry in horizontal pipe is required. One must know the critical deposition and resuspension velocities of various fluids in horizontal pipe flow. 

One of the most important factors in the effectiveness of the hydraulic fracturing treatment is the ability to predict the settling velocity of proppant under fracture conditions. The transport of proppant and the final distribution of proppant in the fracture highly depends on the accurate estimation of settling velocity of proppant. The length of the propped fracture, the conductivity of the propped fracture, and height of the propped fracture are consequently affected by the settling velocity. 

In order to perform the large scale hydraulic flow and transport simulations using a continuum media based model, the first step is to examine the possibility of approximating hydraulic fracture network flow as continuum media at some small scale [Long et al. (1982) and Cacas et al. (1992)]. 

Many shale gas service companies use groundwater pumped directly from the formation or treated water for their fracturing jobs. In some well stimulations, proppants are not needed to prop fractures open, so simple water or slightly thickened water can be a cost-effective substitute for an expensive polymer of foam-based fracturing fluid with proppant (Ely, 1994). Hydraulic fracturing performance is not exceptional with plain water, but, in some cases, the production rates achieved are adequate. Plain water has a lower viscosity than gelled water, which reduces proppant transport capacity. 

The sensitivity of the hydraulic conductivity and other transport properties of discontinua (fractured media) to normal stress is typically substantially greater than that of continua (unfractured media). The stress-sensitivity has been demonstrated in numerous studies of fracture flow (e.g.. Gale, 1982). Natural fractures are a suspected cause of anisotropic water-flooding with a maximum rate of flood front advance approximately in the direction of the maximum horizontal stress (Heffer and Dowokpor, 1990). Natural fractures were recognised as significantly contributing to Clair well productivity (Coney et al., 1993). These fractures are aligned with the present day direction of the maximum horizontal stress in at least one of the wells in the Clair Field. 

In our approach a detailed hydraulic analysis is carried out, where the flow and transport properties at the small scale are analysed by means of the fracture network software FracMan, Derschowitz et al. (1998), and MAFIC, Miller et al. (1999), that handle complex fracture geometries and fracture transmissivity distributions. The approach is probabilistic. A large number of network... 

Aquifers with high hydraulic conductivity can transport contaminants at high velocity over great distances, e.g., solution limestones, highly fractured rocks or gravel deposits. 

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