January 2019
Columns

Water management

May you live in interesting times
Mark Patton / Hydrozonix

Produced water management has evolved significantly in the last few years from needing to treat, to discharge quality, to the minimal treatment used today with more produced water-tolerant completion fluids. This transition has changed dramatically the way that we treat produced water for reuse, and this evolution to simpler and less treatment has resulted in very low-cost produced water recycling or reuse programs.

Recycle vs. Reuse. I often use “recycle” and “reuse” interchangeably, but there is a difference. If I take any empty bottle and rinse it out and use it again, I am reusing. If I send the same bottle to a recycling plant, and it is processed into a new bottle, I am recycling it. Reuse implies no change, and I’m finding another purpose for the product in question; recycling implies processing and sometimes making a material change to the product.

So, when it comes to minimum treatment that we do today for produced water, are we recycling or reusing? Good question—if my produced water is going to disposal, and I’m dropping out solids, removing oil, providing bacteria control, then I’m not recycling, I’m going to disposal. If I redirect this water from the disposal well to a pit for storage, aren’t I just reusing this water? I really believe there is a gray area here, because you may still provide some additional bacteria control in storage with aeration or adding an oxidizer as pre-treatment, because you need a little more treatment for bacteria and iron than you normally would consider for disposal. I think an argument can be made for minimum treatment being reuse, and also one for it being recycling. I often get this question, and there really isn’t a clear-cut answer. It depends on how you define your produced water reuse or recycling system/program.

Now that I have gotten that out of the way, let’s get back to interesting times. Whether you call it reuse or recycling, produced water has become an uncomplicated process of oxidation for bacteria, iron and sulfide control, and dropping out solids instead of filtration. This low-cost program has driven produced water recycling/reuse below that of disposal. So that’s good news for reuse but not the whole picture. There is a tremendous excess of produced water, even if you reused 100% in completions, and 100% reuse is not practical. So, you need a balance between disposal wells and recycle/reuse. Completion programs aren’t consistent, so you can’t always rely on reuse as a completion fluid, which complicates the recycle/reuse program. So, you need balance between reuse and disposal, but that’s not entirely the answer either, and here’s where it gets interesting.

New RRC rules. On Dec. 5, 2018, the Railroad Commission (RRC) announced they are considering new restrictions on disposal wells. There has been some confusion as to the meaning. The RRC also imposed some changes recently that are already in effect, which require a review of earthquake activity within a 100-mi2 radius of a disposal well, while giving the RRC the latitude to change an existing permit to limit capacity or pressure at the wells in question. Gone are the days that you are grandfathered in with a permit. The existing amendment is unclear on how they define earthquake activity, some say magnitude 2.0 and greater, but TexNet reports 1.5 and greater, and I’m sure that will be argued. TexNet is Texas’s earthquake monitoring system, which began recording in 2017. They have over 20 fixed locations, as well as many portable stations. So, now that the data will be readily available, how will this change disposal practices or permitting? We’ve already seen New Mexico impose stricter standards.

This all comes after reports of a tripling in the number of 2.5-size earthquakes in the Permian to over 60. Now, this isn’t anywhere as extreme as what happened in Oklahoma, where we saw 3.0-sized earthquakes go from two events to almost 900. Nonetheless, the RRC is paying attention and so is New Mexico. In Oklahoma, the events were studied, and they found a correlation before they acted, but specifically in the Delaware basin, there are no studies I’m aware of that have found the same correlation.

I mention the Delaware, because that appears to be an area of concern for the RRC and New Mexico. You can assume from other studies that it is probable, that the volume of produced water injected for disposal has some correlation to earthquake activity, but I’m not big on assumptions. In November, the University of Texas released a report, indicating a link between deeper disposal wells and earthquakes, but it wasn’t specific to the Delaware. Are other studies on the way? In December, it was reported that Stanford University’s Center for Induced and Triggered Seismicity had visited the Permian basin, so I believe the study period is on its way.

So, the theme song for produced water management in the Permian may be “The Times They Are A Changing” for 2019. It’s not just the recent changes coming from the RRC that we have to look forward to—the EPA has been collecting data and should be releasing its findings during the summer of 2019.

Plan C. It’s time for a Plan C. Plan A was disposal wells, Plan B was recycling/reuse, but now it’s time to look at other options, because it appears there may be some restrictions on disposal wells coming during 2019. So, can we get discharge quality under $1/bbl, or, better yet, under $0.50/bbl, or is Plan C forced or enhanced evaporation? Whatever it is, it’s time that we figure it out, because things are about to get interesting, and the times they are changing.

For more on induced seismicity, go to Energy Matters and review their Produced Water Injection Risk Report—great information for all of you produced water nerds like me. wo-box_blue.gif

About the Authors
Mark Patton
Hydrozonix
Mark Patton is president of Hydrozonix and has more than 30 years of experience developing water and waste treatment systems for the oil and gas industry. This includes design, permitting and operation of commercial and private treatment systems, both nationally and internationally. He has seven produced water patents and two patents pending. He earned his B.S. in chemical engineering from the University of Southern California (USC) in 1985.
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