**Injection and Efficiency**

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[52] Olson, J. E, & Wu, K. Sequential versus simultaneous multi-zone fracturing in hori‐ zontal wells: Insight from a non-planar, multi-frac numerical model. SPE Hydraulic Fracturing Technology Conference, Paper No: SPE PP, February 6-8 (2012). The

[53] Cruikshank, K. M, Zhao, G, & Johnson, A. M. Analysis of minor fractures associated with joints and faulted joints. Journal of Structural Geology (1991). , 13(8), 865-886.

San Francisco, CA, USA., 08-327.

770 Effective and Sustainable Hydraulic Fracturing

Woodland, TX, USA., 152602.

**Chapter 38**

**Secondary Fractures and Their Potential Impacts on**

Outcrop studies have revealed the presence of abundant cemented fractures in many low permeable formations. Recovered cores have also revealed the opening of some of these smaller size fractures on the wall surface of main hydraulic fractures. Furthermore, earlyproduction well-testing analysis in some of these cases provide estimates for hydraulically induced fracture surface areas which are much larger than the fracture dimensions estimat‐ ed in fracturing design. Re-opening of these small-size fractures could be a possible reason for this discrepancy. In this paper, we show how and to what extent tensile stresses induced by temperature difference between fracturing fluid and formation fluid or plastic unloading of the formation rock could provide a large enough driving force to open a portion of these small cemented natural fractures laying on the surface of hydraulic fractures. Our thermo‐ elastoplasticity analysis reveals the effect of net pressure, stratigraphy and also temperature of the fracturing fluid on the number of activated microfractures. Accordingly, potential dis‐ tributions of activated micro-fractures are estimated. At the end, through an example, we show that the activation of only a small portion of cemented microfractures can increase the total formation contact surface considerably, and consequently increase the initial produc‐

Hydraulic fracturing has been recognized as the most effective technique for economic recovery in tight oil and gas formations in North America [30], [36]. Hydraulically induced fractures increase well-reservoir contact area enormously; hence well productivity improves

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© 2013 Taleghani et al.; licensee InTech. This is an open access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

© 2013 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution,

**Hydraulic Fractures Efficiency**

Arash Dahi Taleghani, Milad Ahmadi and J.E. Olson

Additional information is available at the end of the chapter

http://dx.doi.org/10.5772/56360

**Abstract**

tion by many folds.

**1. Introduction**
