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Abstract: Membrane Technology For the Treatment of Produced
Water
The disposal cost of wastewater from oilfield operations is steadily
rising in the state of Texas. The oil and gas industry must dispose
of approximately 6.3 million barrels of water per day at a cost
exceeding $2 billion annually. At the same time, the availability of
fresh water for oilfield operations continues to be a concern,
particularly in areas of concentrated activity such as the Barnett
Shale Trend of Central Texas. As these trends continue, there is a
need in the oil and gas industry for a reliable technology to purify
wastewater in order to reduce disposal cost and increase fresh water
supply.
A consortium of oil producers and service companies led by the Texas
A&M University Global Petroleum Research Institute (GPRI) has been
working on this problem for the past five years, and has developed a
unique pretreatment and reverse osmosis (RO) process that is
specifically adapted to oilfield wastewater purification. Regulatory
agencies such as the Texas Railroad Commission and the Ground Water
Protection Council have been involved since the project’s
origination.
Texas A&M/GPRI has licensed the fresh water recovery technology to
GeoPure Water Technologies, LLC of College Station, TX, in order to
commercialize the process. GeoPure is installing and supporting the
desalination systems for oil and gas operators, as well as service
providers throughout the United States.
The RO pilot system has been put through extensive testing in the
Texas A&M laboratory as well as 12 separate field locations in
Texas, and results show that dissolved solid levels up to about
50,000 mg/L can be reduced to the level of fresh water. Chloride
levels are low enough that the fresh water may be discharged, or
used as a base for fracturing fluid, drilling fluid, or oilfield
chemicals. The process uses a uniquely staged pre-filtration
approach to remove suspended solids and macromolecules before the
stream is fed through the final RO filtration stage. This
pre-filtration approach prolongs system life and performance, and
reduces cost. The RO process paves the way for surface discharge of
fresh water under a TRRC permit, or the sale of fresh water to
end-users.
GeoPure has installed a 200 gallon-per-minute commercial system in
the Barnett Shale Trend of Central Texas, which has been
successfully recovering fresh water from fracturing fluid flow-back
for an oil and gas operator since January 2007. The pretreatment
process reduces suspended solids, metals and some salts to a level
where the processed water can be effectively processed by the
GeoPure RO system. Comparative results from raw feed water and final
RO permeate are shown in the table below.
GeoPure has recently completed engineering of their
second-generation system, which contains new features such as
automated controls and safety shutoffs, in-place cleaning
capability, and output conductivity monitoring. The technology is
scalable, allowing for small or large volume throughput. The pilot
unit has been deployed to an area on the U.S. west coast where an
operator is purifying wastewater from coal bed methane operations.
A chemical comparison of raw flow-back fluid vs. fluid treated with
the RO process
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Barnett Shale Fracturing Fluid Testing |
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Analyte |
Untreated Water |
Final RO Permeate |
|
|
(mg/L) |
(mg/L) |
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Alkalinity, Total as CaCO3 |
160 |
4.69 |
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Bicarbonate as HCO3 |
195 |
5.72 |
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pH |
6.86 |
6.28 |
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Solids, Total Suspended TSS @ 105 C |
4200 |
<4 |
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Potassium |
39.3 |
1.13 |
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Magnesium |
43 |
0.094 |
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Calcium |
472 |
0.662 |
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Sodium |
2934 |
63.6 |
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Boron |
6.5 |
3.18 |
|
TPH |
0.59 |
<1.1 |
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Total Dissolved Solids |
13,400 |
191 |
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Chloride |
7830 |
105 |
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Sulfate |
396 |
1.2 |
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Bromide |
77 |
1.33 |
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Phosphorus |
56 |
<0.1 |
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Iron |
173 |
0.017 |
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Manganese |
3.7 |
0.0023 |
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Aluminum |
106 |
<0.03 |
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Barium |
936 |
0.0007 |
David Crowe
GeoPure Water Technologies, LLC
May 2007
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