Fracture geometry

A fluid loss additive is described [1849] that helps achieve a desired fracture geometry by lowering the spurt loss and leak-off rate of the fracturing fluid into the surrounding formation by rapidly forming a filter-cake with low permeability. The fluid loss additive is readily degraded after the completion... 

Lee, W.S. and Daneshy, A.A. "Fracture Geometry and Proppant-Transport Computation for Multiple-Fluid Treatment," SPE Prod. Eng. J.. (November 1987) 257 266. 

Ahmed, U., et al. "Effect of Stress Distribution on Hydraulic Fracture Geometry A Laboratory Simulation Study in One Meter Cubic Blocks," SPE/DOE paper 11637, 1983 SPE/DOE Symposium on Low Permeability, Denver, March 14 16. 

Settari, A. and Cleary, H.P. "Development and Testing of a Pseudo-Three Dimensional Model of Hydraulic Fracture Geometry," SPE Prod. Eng,. July 1986, 449-466. 

The mechanical properties of rapidly polymerizing acrylic dispersions, in simulated bioconditions, were directly related to microstructural characteristics. The volume fraction of matrix, the crosslinker volume in the matrix, the particle size distribution of the dispersed phase, and polymeric additives in the matrix or dispersed phase were important microstructural factors. The mechanical properties were most sensitive to volume fraction of crosslinker. Ten percent (vol) of ethylene dimethacrylate produced a significant improvement in flexural strength and impact resistance. Qualitative dynamic impact studies provided some insight into the fracture mechanics of the system. A time scale for the elastic, plastic, and failure phenomena in Izod impact specimens was qualitatively established. The time scale and rate sensitivity of the phenomena were correlated with the fracture surface topography and fracture geometry in impact and flexural samples. 

Smith, L., and F.W. Schwartz. 1984. An analysis of the influence of fracture geometry on mass transport in fractured media. Water Resour. Res. 20 1241-1252. 

Fracture geometry and extension during treatment depend largely on the rheological characteristics of the clean viscous fluid and suspensions or slurries prepared with viscous carrier fluids. Particle settling and distribution in the fracture also are affected significantly by suspension properties. 

In the early days of fracturing treatments, proppant concentrations were 1-6 lb/gal, but now concentrations of 14 and 16 lb/gal are not uncommon. The effect of proppant on fluid viscosity (under laminar flow in the fracture) at low solid concentrations is not significant but is at higher solid concentrations. With recent advances in placement of high proppant concentrations and the desire to predict fracture geometry and extension accurately, it has become important to include the effect of proppant concentration on the viscosity of fracturing fluids in the currently available fracture design simulators. 

The main limitations of current capability of modeling coupled HM processes in fractured rocks are a lack of knowledge about fracture geometry and uncertainty in in situ properties. 

The variation of the permeability distribution can be used for the analysis of the dispersion behaviour by ergodic hypothesis. The degree of the variation is dependent on the fracture geometry. In this study, the effect of the fracture geometry on the flow regime in the coupled behaviour is examined by considering some different fracture systems. 

To investigate the effect of fracture geometry on the scale effect of the permeability, some parametric study is carried out. Table 1 shows the parameters examined for this aim. Case 1 is the reference case in which the original measured data at Sella-field are used. Case2 is the case to examine the effect of uncertainty on the fracture density, in which the density is defined by Eq. (6). Thus the number of fracture in this case is about 4 times that in Case 1. Case 3 is related to the uncertainty on the... 

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... 

McIntyre RC Jr, Bensard DD, et al. (1993) Pelvic fracture geometry predicts risk of life-threatening hemorrhage in children. J Trauma 35 423-429 Montana MA, Richardson ML, et al. (1986) CT of sacral injury. Radiology 161 499-503... 

Physical meaning of f(x). We digress to consider several properties of f(x). An understanding of f(x) and its relationship to local velocity helps to improve numerical formulations for more complicated fracture geometries and assists in posing and solving fracture problems governed by other boundary conditions. Let us return to the expression for pressure in Equation 2-10 and differentiate it with respect to the vertical coordinate y normal to the fracture. 

Figure 8.5 Fracture under a blunt indenter (a) cone fracture sequence on loading (+) and unloading (-) (b) cone fracture geometry (according to Lawn, 1993).

Unfortunately, as complex and rigorous as the modeling and prediction of fracture geometry and final conductivity can be, all is meaningless if the greatest unknown, leak-off, is not accurately estimated—and it is rare that it can be. Defining the leak-off properties of a reactive acid—which is changing in viscosity, density, and temperature, in a fracture and formation with unknown leak-off characteristics— is not realistic. 

In naturally fractured carbonates, propped fracturing may not be appropriate because of the difficulty in placing necessary amounts of proppant. The tortuous paths often present and complex stress properties can result in fracture geometry that is convoluted that it becomes impossible to maintain proppant injection. 

Viscous fingering is a method in which the formation is first hydraulically fractured with a nonreactive, high-viscosity gel, normally cross-linked gelled water. This is used to create the desired fracture geometry (i.e., length, height, and width) and to cool the formation to slow subsequent reaction of the acid injected. Next, lower-viscosity acid (HCl or an HCl-organic acid blend) is pumped into the created fracture. 

Muller-Huber (2013) investigated low porous carbonate rocks from Austria. Figure 2.23 shows a plot of permeability versus porosity. The measured permeabilities range from slightly less than 0.05 up to 1190 md. In elastics, permeability depends strongly on porosity, fri craitrast, the permeability of carbonates is controlled not solely by porosity, but also by the pore and fracture geometry. 

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