Abstract
During fracturing operations, conventional and unconventional wells require from 50,000 to more than 200,000 barrels of water per well, which generates a strain on fresh water supplies. In areas where fresh water is scarce, water quality is not consistent, or delivering water to a location is logistically complex, the strain intensifies. Therefore, having capabilities to reuse produced or flowback water for fracturing applications is a cost-attractive option, especially when major savings in produced water disposal costs and reduced treatment requirements are achievable.
This paper summarizes the proven benefits of using a bi-polymer crosslinking system 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. 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 therefore create 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, which is a major environmental breakthrough in fresh water preservation. The new fluid system consists of a specially formulated bio-polymer crosslinking system that is not affected by produced or inconsistent water quality typically associated with fracturing applications.
The fracturing fluid system can tolerate 100% untreated produced or flowback water with salt concentration in excess of 300,000 parts per million (ppm), between 5,000 and 30,000 ppm of divalent ions, and more 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. Rheological profiles illustrate that the fracturing fluid system yields higher viscosities compared to 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 those of a traditional crosslink system. Permeability tests demonstrate the non-damaging nature of the new system and actual field data demonstrates enhanced scale tendency reduction.
In summary, this paper comprehensively reviews the benefit of using a robust fracturing fluid that can use 100% produced water or flowback instead of fresh water for fracturing operations. The paper indicates that use of produced water or flowback for fracturing should become the norm as we move into a more environmentally friendly paradigm.
