(646a) Treatment Approaches for Produced Water Re-Use and Surface Discharge

Treatment Approaches for Produced
Water Re-use and Surface Discharge

Madison Wenzlick, Alexandra Hakala, Nicholas
Siefert

Nearly all
methods for extracting oil and gas resources produce a high salinity brine
byproduct [1]. Half of the high salinity brines produced
in the U.S. are currently managed by injection into salt water disposal
wells, which is a practice that has been linked to increased seismicity and has
prompted new regulatory policies. One option for reducing the amount of
reinjected brine is to remove fresh water from the brine, which allows for
development of a tailor-made brine of a desired density or TDS [2]. These
near-saturation NaCl brines could be sold as a
feedstock to the chemical manufacturing industry. For example, saturated NaCl brines are called “10-lb brines” and are a tradeable
commodity in parts of the U.S, particularly in Texas and Louisiana. Dewatering
produced brines from oil & gas wells creates both a concentrated,
lower-volume brine and fresh water.

Figure 1: Relative locations of formations and basins,
chemical plants, as well as locations of known salt dome collapses.

 Base map from eia.gov

The main
commercially available technology for concentrating brines is mechanical vapor
recompression (MVR). However, typically the energy usage and cost of this
technology are high and there is still limited data available on applying MVR
to oil and gas produced brines.

In this
presentation, the following topics will be covered. First, we will discuss the
region (TX & LA) and shale formations chosen for this analysis. Second, we
will present a geochemical analysis of the brines produced in the formations in
this region. The analysis will include geographic considerations of brine
concentration, determination of necessary pretreatment and chemical use,
transportation, and potential benefits from reuse. Next, we will present a
baseline techno-economic analysis of concentrating these brines into 10-lb
brines while generating fresh water for surface discharge. The baseline case is
a process using commercially-available treatment technologies, such as MVR.

Figure 2: The baseline process flow diagram for the centralized water
treatment process

Next, we
present results from a sensitivity analysis around a number
of the assumptions in the model, such as the cost of pretreatment
chemicals, electricity costs, and brine disposal fees. Finally, we present an
advanced case in which we model advanced membrane processes for both the
pretreatment and brine concentrating steps of the process. Preliminary results
from the baseline case suggest that, for those brines with low concentrations
of divalent cations (Ca⁺², Mg⁺², Sr⁺²), there
is a positive rate of return on investment for dewatering oil and gas produced
brines in TX & LA into 10-lb brine and fresh water.

Figure 3: Advanced
case process flow diagram

References

[1]  J. Veil, "U.S. Produced Water Volumes
and Management Practices in 2012," 2015.

[2] J. T. Arena, J. C. Jain,
C. L. Lopano, J. A. Hakala, T. V. Bartholomew, M. S. Mauter and N. S. Siefert,
"Management and dewatering of brines extracted from geologic carbon
storage sites," International Journal of Greenhouse Gas Control, no.
63, pp. 194-214, 2017.