Two methods to help contain treatment costs are to field-manage the water quality and to supervise the concentrations of the downhole chem used.

Four Steps to Quickly Evaluate Produced Water Reuse Option Viability

After it has been determined what waste water reuse options are physically possible and affordable, the viability determination isn't over until the regulatory, environmental, and social impacts have been determined.

Produced water management can be a burdensome task to a producer. Some estimates suggest water management is up to 25 percent of the expense of a well in its lifetime. It often requires trucking through populated areas, exposure of employees or contractors to hazardous chemicals, and it generates public suspicion. In some areas of the United States, but not for all, water disposal through injection is an expensive, ineffective method. There are fields in the United States where disposal by injection is a very limited option due to seismicity concerns or capacity issues. Pennsylvania has only 11 permitted produced water wastewater disposal wells in 2017.

The American Geosciences Institute (AGI) reports 90 percent of produced water volume is disposed of by injection well. This is a potential resource that the industry should consider viewing as an asset instead of a waste. In order to do so, produced water reuse options warrant an occasional viability review, even if produced water disposal by injection is available and affordable.

Produced water reuse and recycling options have become more economic, available, and necessary. This is driven by four factors: more open political climate allowing reuse, the need to restrict fresh water use, the prohibition or over-capacity issues of disposal by injection in some areas, and the advancing technologies available for both water treatment and possible reuse in completions fluid formulas.

Periodic assessment of produced water reuse options is a valuable economic tool with sustainable resource benefits. It is important to know what reuse is locally available, what the requirements are to meet the reuse, and what water quality is available in the field. These parameters are ever-changing, so periodic evaluation of reuse viability is a smarter option than permanent dismissal of a reuse idea.

To begin a viability assessment, it is important to start with an accounting of the entire life-cycle: resources used, material processed, transportation costs, human factors, and waste produced. Start to develop any possible products that can be derived. The AGI estimates that less than 1 percent of produced water is used outside the oilfield, yet there are significant industrial needs for large water volumes in many industries—be open to any new reuse idea and try to look for the potential benefit. Once an outline of potential reuse options is developed, the viability assessment can begin.

Step One: Evaluate the Waste Water
In order to evaluate the types of possible reuse, the waste water characteristics must be determined: water volumes, physical water characteristics, and chemical water characteristics. Begin a sampling plan throughout the field. Collect produced water samples from every type of source in the field: flowback, at the tanks, at SWDs, etc., ideally after the water has settled.

Make sure to sample at multiple periods in a well's lifespan. The intention is to have a solid idea of waste water patterns, both chronologically in a well's lifespan and geographically in the field. Make sure physical water characteristics (temperature, density, etc.) are collected in addition to chemical composition. Lab results are an essential component to the success of a recycling/reuse program.

Determine accurate volume data from your wells. Compare multiple sources of where the volumes are reported (SCADA tank level measurements, separator meters, water hauling receipts, injection receipts). On occasion, the volumes reported by the water hauler are not as accurate as the measurements pulled from SCADA tank readings. Take the time to compare the two. Again, measure at multiple times during wells' life span to develop predictive patterns as wells age.  Seasonal trends may also be apparent after the data collection.

Step Two: Evaluate the Options
Review the water quality results and determine a list of reuse options, starting with a list of what can be reused with minimum treatment: evaporation beds, crop or golf course irrigation, dust control, watering for pad reclamation, rangeland restoration, livestock watering.

If the water quality is too high in contaminant concentration, reuse options will require treatment before use. These usually have a more industrial application: cooling tower water, pulp and paper mill water use, cement and concrete mixing, mining flood fluids, and soluble-mineral extraction fluids.

The production company will receive the most economic benefit if there is a reuse application that can be used directly on site: drilling mud fluid additive, hydraulic fracturing fluid components, ten-pound brine (heavy brine) for workovers, enhanced oil recovery (EOR) fluids in waterfloods or steamfloods, soil cement fluids for pad construction. Exact treatments required to reach usable water quality will vary considerably but start with settling and filtration. The water chemistry will dictate what treatment is necessary.

When evaluating the reuse options, don't disregard the water's physical characteristics. Produced water with a sufficient density can be a viable reuse of heavy brine water, once disinfected properly. Additionally, produced water can come up-hole at temperatures near boiling (200º F). This available energy can be used as heat during distillation, field evaporation, steam production, and electric generation.

Don't forget to evaluate the physical inputs of the technology: How will it be powered, will it work remotely, what volumes can it handle, is it robust, will wells need to be shut-in if something fails? Work through the large possibilities of actual operation.

Step Three: Evaluate the Costs
Determining the costs for reuse is the most difficult part, because the water volumes and chemistry will vary. It is hard to budget for the considerable variation of nature. Start with the costs of fresh water sourcing. Water supply costs are often a driving factor of a reuse/recycling plan. Research the costs of the current disposal plan: treatment, transport, storage. Are there any contractual minimum volume requirements? Check with accounting to see how the fresh water purchasing and wastewater disposal fees are distributed among the lease and partners. Determine your company's actual cost.

Two methods to help contain treatment costs are to field-manage the water quality and to supervise the concentrations of the downhole chem used. After considering the results of the chemical sampling program of the wells, manage your gathering system by directing the water to where there is one available "cleaner" source of produced water. Instruct the gathering system or water haulers to load one of your storage facilities with less heavily contaminated produced water to use as your source material for the reusable water. Also, manage the wells' downhole paraffin thinners and descaling fluids so that it is not fouling the "better" produced water collection. If sample results are exceptionally high in methanols (or other constituents of your downhole chem), reduce the rate or load. The results are showing it is just coming back up hole unspent.

Step Four: Evaluate the Reality
After it has been determined what waste water reuse options are physically possible and affordable, the viability determination isn't over until the regulatory, environmental, and social impacts have been determined. Will the regulators buy in? Is this going to require a year-long permitting process? Does the treatment process use combustion to provide clean water? Will the process itself require an additional air permit? Will the limits of the air permit be achievable? (NAAQS lb./hr. is a tough standard to meet for some sources of combustion). What other air, water, or wastes issues will be generated? Are there measurable social impacts due to the recycling—noise, traffic, explosive atmospheres in close proximity to neighborhoods, etc.?

Fortunately, as more reuse is put into place, expenses will begin to lower due to economies of scale. It is reported by the Global Petroleum Research Institute that half of the produced water in Texas is less than 10,000 ppm TDS. That is a significant useable resource. However, once produced water has an economic benefit, there are mineral rights owner issues that may need to be contractually addressed prior to use, so plan ahead.

Preparing the Study Pays Dividends
There are many more decisions to make to refine the type of reuse possible for an operator (such as disinfection), but this four-step process outlines a good start to determine what process warrants further scrutiny. Of course, economics is usually the basis of any reuse decision, but preparing a reuse viability study in advance of a fresh water shortfall or a disposal issue will give the operator an advantage when it is necessary to react to change.

References
1. Allison, E. 2018. Petroleum and The Environment
American Geosciences Institute, https://www.americangeosciences.org/critical-issues/petroleum-environment (accessed April 20, 2019).
2. Matthews, C. 2018. The Next Big Bet in Fracking: Water. Wall Street Journal, 22 August 2018, https://www.wsj.com/articles/the-next-big-bet-in-fracking-water-1534930200 (accessed Nov. 14, 2018).
3. Burnett, D. 2018. Potential for Beneficial Use of Oil and Gas Produced Water, https://www.researchgate.net/publication/237345333_Potential_for_Beneficial_Use_of_Oil_and_Gas_Produced_Water (accessed Nov. 14, 2018).

This article originally appeared in the June 2019 issue of Occupational Health & Safety.

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