Numerical Analysis of the Source of Excessive Na+ and Cl– Species in Flowback Water From Hydraulically Fractured Shale Formations
Fracture fluid comprises fresh water, proppant, and a small percentage of other additives, which support the hydraulic fracturing process. Excluding situations in which flowback water is recycled and reused, total dissolve solids in fracture fluid is limited to the fluid additives, such as potassium chloride (1-7 weight percent KCL), which is used as a clay stabilizer to minimize clay swelling, and clay particle migration. However, the composition of recovered fluid, especially as it relates to the total dissolve solids (TDS), is always substantially different than the injected fracture fluid. The ability to predict flowback water volume and composition is useful when planning for the management or reuse of this aqueous byproduct stream. In this work, an ion transport and halite dissolution model was coupled with a fully implicit, dual porosity, numerical simulator, to study the source of the excess solutes in flowback water, and to predict the concentration of both Na+ and Cl- species seen in recovered water. The results showed that mixing alone, between the injected fracture fluid and concentrated in situ formation brine, could not account for the substantial rise in TDS seen in flowback water. Instead, the results proved that halite dissolution is a major contributor to the change in TDS seen in fracture fluid during injection and recovery. Halite dissolution can account for as much as 81% of Cl- and 86.5% of Na+ species seen in 90-day flowback water; mixing, between the injected fracture fluid and in situ concentrated brine, accounts for approximately 19% Cl- and 13% Na+.
- Research Organization:
- National Energy Technology Lab. (NETL), Pittsburgh, PA, and Morgantown, WV (United States). In-house Research
- Sponsoring Organization:
- USDOE
- OSTI ID:
- 1435761
- Report Number(s):
- NETL-PUB-20026
- Journal Information:
- SPE Journal, Vol. 21, Issue 05; ISSN 1086-055X
- Publisher:
- Society of Petroleum Engineers (SPE)
- Country of Publication:
- United States
- Language:
- English
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