**Author details**

Mao Bai1 , Arturo Diaz1 , John McLennan2 and Juan Reyna1

\*Address all correspondence to: mao.bai@halliburton.com

1 Halliburton, Houston, USA

2 University of Utah, Salt Lake City, USA

#### **References**

**Figure 11.** Comparison of two cases of (NL-3 and PDL-2): a) initial linear line and late linear line with a different slope for the P - G relationship with normal leakoff; and b) concave curves for the P – G relationship with pressure-depend‐

Based on past experience in cuttings injection monitoring, it can be concluded that the quality of fracture closure after shut-in has a critical impact on the efficiency of a cuttings injection operation. Cuttings injection is inefficient when the fracture closure cannot be assured as a result of an insufficient shut-in period between batch injection operations. Conversely, cuttings injection becomes efficient when sufficient time is provided between batch injections to allow

The quality of the cuttings injection can be evaluated by analyzing the trend of batch injections. The rising peak batch pressures during injection and slow declining of terminal batch pressures during shut-in are indications of poor pressure maintenance and thus poor cuttings injection management. Rising batch injection pressure usually reveals difficulties in maintaining needed injectivity while slow pressure decline can be the result of insufficient shut-in time in a low permeability disposal domain. The required solutions include but are not limited to: a) mitigating the injection pressure or pump power and ensuring the proper breakdown of the injected formation, b) extending the shut-in period to dissipate injection pressure, and c) adjusting the injected batch volume or injection rate to allow the relevant acceptance of the

ent leakoff.

**5. Conclusions**

804 Effective and Sustainable Hydraulic Fracturing

adequate fracture closure.

disposal formation for the injected cuttings.


**Chapter 40**

**The Fate of Injected Water in Shale Formations**

It is well known that only about a third of water injected for hydraulic fracturing of shales is recovered. It is important to understand the fate of this injected water. The amount of water infiltrating the matrix is determined by a number of parameters such as the pressure differ‐ ential between the fracture and the matrix, the capillary pressure relationships in the frac‐ tures and in the matrix and other petrophysical properties of the formation. In this paper, we provide a breakdown for the various possible water losses depending on the reservoir, fracture and operating parameters. A set of capillary pressure relationships for the forma‐ tion were first created based on the basic mineralogy and the total organic carbon (TOC) content. Fracture capillary pressure also changed depending on the concentrations and types of proppants in the fractures. Two basic end members can be defined – silicistic and dolomitic with different amounts of TOC. The capillary pressure relationships ranged from oil wet, neutral to water wet. Different porosity and permeability combinations were also examined. Amounts of water relative to the total amount injected that would infiltrate the formation were compiled as the operating conditions (pressures) and formation properties changed. This calculation shows that the infiltration due to the various phenomena are not sufficient to account for the water losses if the formations are strongly oil wet. In addition, situations where water blockages occur due to these multiphase flow effects were identified and the loss of productivity due to this phenomenon was quantified both for gas and for oil production. The study was conducted using a discrete-fracture network simulator devel‐ oped at the University of Utah. A realistic (non-orthogonal) representation of a complex fracture network was employed in the study. Realistic representation of distribution and re‐ tention of these aqueous fracturing fluids is essential for optimizing hydraulic fracturing

> © 2013 Jia 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,

> © 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,

distribution, and reproduction in any medium, provided the original work is properly cited.

and reproduction in any medium, provided the original work is properly cited.

Hongtao Jia, John McLennan and Milind Deo

Additional information is available at the end of the chapter

http://dx.doi.org/10.5772/56443

**Abstract**

treatment volumes.
