Abstract
Conventional and unconventional well designs require 50,000 to more than 200,000 barrels of water per well during fracturing operations, generating a strain on fresh water supplies. The strain intensifies in areas where fresh water is scarce, water quality is inconsistent, or it is logistically complex to deliver water to a location. Therefore, having capabilities to reuse produced or flowback water for fracturing applications is a cost-effective option, especially when major savings in produced water disposal costs and reduced treatment requirements are achievable.
This paper comprehensively summarizes the proven benefits of using a bi-polymer crosslinking system that can be used in environments where water quality cannot be guaranteed. In addition, to the cost advantages of using a crosslink system that uses a conventional gelling agent, this paper also demonstrates the yielded cost savings per well that are achievable when reusing 100% produced and or flowback water for hydraulic fracturing operations. The costs cited in this paper are in US dollars.
Produced water typically contains large amounts of dissolved monovalent and divalent salts and other types of ions. Some of the ions present in produced water interfere in the formulation of traditional crosslinking fracturing fluids, and that creates a need in certain systems to mix produced with fresh water in specific percentages. The guar-based system discussed in this paper allows for 100% produced water reuse without filtering or treatment, representing a major environmental breakthrough in fresh water preservation. The new fluid system is a specially formulated bio-polymer crosslinking system that is not affected by produced or inconsistent water quality normally associated with fracturing applications.
The proven robust fracturing fluid system can process 100% untreated produced or flowback water with salt concentration in excess of 300,000 parts per million (ppm), between 5,000 to 30,000 ppm of divalent ions, and greater than 400 ppm of boron and 185,000 ppm of chlorides. The thermal stability of the system is proven to be unaffected by bottomhole temperatures ranging from 120°F to 300°F. The rheological profiles presented illustrate the performance of the fracturing fluid system: It yields higher viscosities than an equivalent traditional borate crosslink fluid system in fresh water. Well treatment results indicate that the bi-polymer system can be accelerated or delayed with proppant carrying/suspending properties comparable to a traditional crosslink system. Permeability tests demonstrate the benign non-damaging nature of the new system that directly represent actual field data with enhanced scale tendency reduction.
In summary, this paper comprehensively reviews the benefits of a robust fracturing fluid that can use 100% produced or flowback instead of freshwater for fracturing operations; that should become the norm as we move into a more environmental friendly paradigm.
