On Water... Treating Flowback and Produced Water Part 1
A severe criticism leveled at industry (and me frankly) has been that the water resources used in hydraulic fracturing where not being treated and are difficult if not impossible to economically treat. In response to these criticisms I felt that it was important to lay out to the readers some of the issues related to frack water and the types of treatment that are NOW being used in the field. This is a voluminous subject so I will break it down into the constituent parts and take on each section in a post. The key contaminants in frack water are:
Total Dissolved Solids (essentially, salt)
Free hydrocarbons (natural petroleum like substances in very low concentrations)
Dissolved hydrocarbons (same as above, but actually dissolved in the water)
Heavy Metals (low concentrations of naturally occurring metals in the geologic formation brought up by hydraulic fracturing)
Frack Chemicals (those chemicals added in VERY low concentrations to aid in the fracturing of the shale)
Suspended Solids (sand and fine particulate matter)
For today, let's deal with TDS.
The problem with the level of TDS in Marcellus Shale water can be boiled down to a single word: concentration. The TDS levels in most Marcellus Shale flowback waters are extremely high and near that of concentrated brine (from 100,000 to 250,000 parts per million, or 10 to 25%). This is obviously very high and not conducive for treatment using typical technologies such as filtration or even reverse osmosis.
But, the high concentrations are somewhat advantageous in that some crystalization and or evaporation technologies work more efficiently at high concentrations (i.e. less water to drive off). As such, a number of firms in the shale are testing and utilizing these technologies right now. Since no definitive discharge concentrations have been released by the regulators, no standard of treatment has yet to be determined.
The crystalizer or evaporator works as easily as it sounds, energy is consumed to drive off the water and the salt material is left behind, either has a solid or as a dramatically reduced brine that can be recycled. In some cases the water is collected or recovered, therefore the facility has zero air emissions. NGInnovations of Charleston WV has patented this technology and early trials are promising. There are a number of firms performing this work both on-site and free standing facilities located throughout the Appalachian Basin, including 212 Resources, Intevras, Fountain Quail and others.
Energy is a key component of the cost to recovery the brine, but as of this writing those technologies appear to be within the market price of water disposal. One ideal synergy is often that the gas from the well or an adjoining well can be used as the energy source, thus reducing the overall cost to treat the flowback water.
It should be noted however that many E&P firms have begun programs to begin reusing existing flowback water for additional hydraulic fracturing projects. This recycling reduces the net water needs in the Marcellus shale and takes trucks off of the roads (those trucks that would take the water for disposal and bring back fresh). Some water treatment must still be done, but at a greatly reduced price if the TDS is allowed to remain in tact.
The issue of high TDS is one that once again the industry is up to solving. A combination of recycling and treatment (both on-site and off) will allow for future development in the Marcellus Shale.
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Comment
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Comment by Deborah Goldberg on May 26, 2010 at 7:21am
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Where are on-site or free-standing evaporation/crystalization facilities operating in Pennsylvania? Why would there be zero air emissions when water is recovered, if there are volatile chemicals such as hydrocarbons in the flowback?
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Comment by Michael Havelka on May 25, 2010 at 2:26am
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The next item of importance are the suspended solids, the "dirt" if you will that is present in the water. These particles can range from 1000 microns the size of course sand down to sub-micron particle size. These particles are particularly damaging to equipment when the water is to be pumped or recycled therefore it is in the best interest of the driller to remove as much suspended solid as possible prior to discharge.
Even if the water is to be disposed at a WWTP off-site, the removal of these suspended solids is important as often these particles will clog filters and cause interferences in the treatment system. The technology to remove suspended solids has been around for a long time, typically a type of mechanical filter is used. We have seen bag filters, solid element filters, sand and diatomaceous earth and even plate and frame type filters to remove heavy solids.
This key to removal is doing so in a way that maximizes the removal efficiency while minimizing the cost. Some technologies do well removing the larger particles (>50 microns), whereas others are best for particles below 10 microns. The key is to have analyzed the water for your particle size distribution (inexpensive test at a contract analytical lab), so that the system is sized properly.
For most shale applications where recycling is the focus, a much more robust and well defined filtration system should be designed. Knowing the type of solids, the sizes and the amount (total concentration) will aid in designing an effective removal system that protects pumps and other equipment during the recycling of the water. Often overlooks, suspended solids have been the focus on several projects in the Marcellus whereby water handling equipment was damaged. For such an inexpensive fix, it is best to take a second look before you leap. Next... free and dissolved hydrocarbons.
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Thanks Josephine... Right now the solutions are as diverse as the problems. The fixed base brine treatment plants upgrades are not in place so it is unclear what technology they will employ. Needless to say nearly nobody is talking about TDS treatment in public. We do know that NONE of the plants are conventional WWTP's, rather they all take on the concept of crystalliation or evaporation in some manner or the other.
As for the recycling of the water on-site for refracturing, that is also an evolutionary step and lots of treatment technologies are being evaluated to determine WHAT technology exactly is required and then how the high TDS water works in re-fracking the well. We will see more about this subject in the coming months.
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Comment by Josephine Sabillon on May 20, 2010 at 4:40pm
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Excellent article Michael! Keep it coming! What to do with the flowback seems to be the holy grail right now w/i unconventional gas play at large. I was in attendance at the Easter Gas Compression Roundtable and everyone wanted to know what was being utilized or at least vetted in the field or spoke of companies they worked with that were experimenting with technology that was trying to remediate frac water enough that it could be re-used more than what is done currently in order not to corrode the well-bores....preferably on site to reduce transport costs and subsequent road damage of course. I have heard of brine treatment plants being built this year, although unclear as to where, however if not based on conventional waster water treatment plant models given the high salinic content then are you familar with what applications they are using? Or are they ending up with TDS' and relegating them for road use? (I had read that municipal WWTPs were instructed not to continue to accept frac water and not to use as road brine since the true chemical composition was unknown and run off would propogate further pollution). .....while at the same conference I heard from those in the field that Schlumberger and Halliburton's scientists were fervently trying to find an answer...
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Kind of breaking news. The DEP's new regulations on TDS discharge as proposed is going to be 2,000 ppm for existing discharges (everyone but natural gas drillers) and 500 ppm for drillers. Doesn't seem fair to me but there had to be allowances made as 500 ppm across the board would devastate industry. See the link below:
http://www.timesleader.com/news/Official__Seek_upgraded_water_prote...
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There are many ways to drive it off, typically using a heat exchanger of some type. Please follow the link below, the Intevras solution using waste heat and it could be a good option for a fixed facility that already generates some waste heat.
http://www.intevras.com/evras.html
Others require direct firing, natural gas the most common fuel. The water is either driven off and collected or allowed to escape as water vapor.
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Comment by Keith Mauck (Site Publisher) on May 20, 2010 at 2:20am -
Do have a picture of one of these evaporators? How is the water driven off?
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