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Feasibility Assessment of Early Flowback Water ...

SKU: RPSEA - 08122-05.07
Feasibility Assessment of Early Flowback Water Recovery for Reuse in Subsequent Well Completions

Fresh water is critical for natural gas production in the Barnett Shale, where in excess of 3 to 5 million gallons are required for the completion of each gas well. The financial costs, logistical challenges and public relations concerns over the use of fresh water supplies thus impel Barnett gas producers to use less fresh water and to use it more efficiently. The objectives of this work were to develop a simple, empirical modeling approach for characterizing and forecasting flowback water rates and total dissolved solids (TDS) and to use such models to characterize the efficacy of flowback water recycling based on predefined TDS reuse criteria.
Document Type
Report
Report Type
Topical Report
Report Period
October 2011
Author(s)
L. Peter Galusky, Jr., Ph.D., P.E.; Thomas D. Hayes, Ph.D.
Corporate Source
Gas Technology Institute (GTI)
Sponsor
Research Partnership to Secure Energy for America (RPSEA)
Pagination
54p
Product Media
PDF Download (2 MB)
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Feasibility Assessment of Early Flowback Water Recovery for Reuse in Subsequent Well Completions


 

Barnett and Appalachian Shale Water Management and Reuse Technologies


 
RPSEA Report No: 08122-05.07

 
Approximately one third of the fracwater used for a typical Barnett Shale well is recovered from the initiation of blowback until the time that the well produces salable volumes of natural gas. Flowback water production could be efficiently described and modeled using either an exponential or hyperbolic equation; (these are commonly used in forecasting petroleum and natural gas production). Both models were found to be particularly sensitive to the initial flowback rate, which unfortunately tends to be rather erratic during the first few days of flowback production. It is suggested, therefore, that the “initial” value used not necessarily be that of the first day of flowback, but may be averaged among the first three to five days or otherwise adjusted so that the resulting flowback rate and production curves follow a reasonable course.

Flowback chloride and TDS concentrations were efficiently described by a power function of cumulative flowback. The rate of change in flowback TDS concentration reflects the sum effect of exponential (or hyperbolic) decline in flowback rate and the increasing TDS concentration as flowback waters accumulate. Initially TDS rises rapidly because of high flowback rates and rising TDS concentrations. However, although TDS concentrations continue to rise, the precipitous drop in flowback caused TDS accumulation to slow and its rate of change to then begin to drop. The net result is that TDS concentrations begin to level off more or less in parallel with flowback accumulation.

In analyzing flowback water production volumes and TDS concentration using these models for a hypothetical location, it was found that at the field scale that a substantial portion of recovered flowback could be recycled for subsequent well completions across a wide range of TDS reuse thresholds. This finding stems from the observations that: 1.) only a portion (roughly a third) of the fracwater used to complete a well is typically recovered as flowback during the first several weeks following well completion, and 2.) The volume –weighted TDS concentration is low enough so that the recovered flowback can be diluted for effective reuse. Thus, the substantial recovery of a useful fraction of flowback water for reuse is technically feasible and logistically achievable.

The primary benefits of recycling flowback water include a potentially substantial reduction in the volume of freshwater needed to complete future wells as well as a concomitant reduction in the volume of wastewater that must otherwise be disposed.
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