Keeping it clean

Marc Bellanger, Bosque Systems, USA, shows how integrated water treatment solutions can result in increased operator efficiencies.

Water is an essential component for oil and natural gas production during both the drilling and hydraulic fracturing processes. Most of this water comes from surface water sources such as area lakes, ponds, rivers and municipal supplies. The industry’s thirst for water has revealed challenges in sourcing a sufficient amount to sustain the level of completion activities. Alternatives have been growing such as brackish water where available or reuse/recycling programs we have observed in the past year, especially in Texas. Technologies for water treatment and management also have come a long way, and now more affordable solutions are readily available in the market place to ensure better efficiencies to operators. It becomes possible thanks to a wider range of fracturing fluid’s compatibility with various water quality. In this article, Bosque Systems explains how additional value is being offered to operators, with new technologies, integration of services, and lean management of operational processes.

Bosque Systems has recently combined the efficacy of its chlorine dioxide based biocide (DIONIX™) with a scale inhibitor (ScaleStop™) to provide a more complete surface water treatment before it goes downhole for fracturing. The biocide uses chlorine dioxide which is the most effective biocide that reacts within seconds, and is recognised by the EPA as an environmentally friendly biocide. It is less corrosive than chlorine and superior for the control of legionella bacteria outside of the oilfield. One of the primary benefits of using chlorine dioxide is that it reacts less with organic matter present in the water, thus minimising the formation of trihalomethanes. The biocide’s two precursor system is a safe way to generate chlorine dioxide on-site. Having mobile water treatment units allows integration with the fracturing crew, allows for a small footprint on site, and moves seamlessly from job to job.

Biocide benefits:

  • Effective, fast-reacting biocide that is environmentally friendly and has a longer residual than traditional bleach-based biocides.
  • Process is the safest way of generating chlorine dioxide on site, with numerous safety shutdown components and procedures.
  • Two precursor chemical design utilises less harmful chemicals and is more cost-effective than traditional solutions and other chlorine dioxide systems.
  • Convenient and mobile 30 ft trailer allows for small footprint on pad site.
  • Also available as a stationary unit for treating saltwater disposal facilities and reserve pits.
  • Redundancy: The system has two chlorine dioxide generators for redundancy and maximum generation of chlorine dioxide.
  • Monthly report reviewed with customers to validate results (KPI).

Scale inhibitors work by preventing the particles of carbonates, sulfates, and other matter to form larger deposits during the blending process of a fracturing job. If a scale inhibitor is not used, deposits will plug equipment such as pumps and pipelines, which will affect and delay operations. Bosque Systems’ scale inhibiting technologies help eliminate buildup of calcium carbonate and other matter that occurs along the production tubing and equipment due to the pressure and temperature changes as oil is produced. ScaleStop works to inhibit the crystallisation of mineral scales which if left untreated, will agglomerate.

Scale inhibitor benefits:

  • Superior scale treatment from a leader in the oil and gas water management and water treatment industry.
  • Superior tagged polymer scale inhibitor for maximum protection of the formation an wellbore.
  • Rapid residual analysis for flowback monitoring.
  • High thermal stability capable of withstanding temperatures up to 375°F.
  • Mounted on a trailer for mobility.
  • Ease of deployment and management through a single point of contact.

Case study

By combining the biocide and scale inhibitor solutions, operators can make further savings by making use of a single operation crew for multiple services, an advantage versus separate treatments. With the price of oil going down, companies are looking for creative solutions such as this. The combination is unique to the industry and provides a one-stop shop for the operators’ bacteria and scaling issues. The following is a case study that demonstrates the system’s success with an operator who combined the two solutions and was able to reduce bacteria and scale while reducing cost and increasing efficiencies in their operations.A Fort Worth - based independent oil and gas exploration and production company with operations in New Mexico and the Permian Basin areas of the United States was experiencing high levels of bacteria counts in their water. The company’s operations in New Mexico were being affected due to bacteria going downhole at the injection site causing corrosion all the way to the sourcing well.

Solution

After evaluating the operator’s results and issues, Bosque Systems offered DIONIX to produce chlorine dioxide on-site and eliminate bacteria in source water, stop H2S production, and plugging of the formation/equipment due to iron sulfide and biofilm. In addition to the biocide, the company decided to use the scale inhibitor solution as well, benefiting from a single crew, saving from the use of both solutions.

Benefits:

  • The combination was used on a total of 35 wells in the New Mexico region (April to December 2014), including 608 stages of fracturing, for a total of 2.9 million bbls of treated water.
  • Extensive cost savings using a combination of services, both sharing a highly trained crew of technicians.

Results:

Evaluating Well 1, treated between August 3 and August 8, 2014, the source water analysis shows significant bacteria concentration. Fresh water is the source for this example; as shown below it still contains a significant amount of bacteria. The concentration of acid producing bacteria (APB) and sulfate reducing bacteria (SRB) is measured in ‘bottle turns’, which is a recognised API method (API RP 38) of bacteria counts in the water. This method is described in Annex 1, along with the results observed on Well 1.

Annex 1

Inoculation of serial dilution vials*

  1. Arrange 2 rows of 6 vials of APB and SRB solution.
  2. Remove metal tab from top of vial, being sure not to damage the rubber seal, and wipe surface with alcohol swab.
  3. Using a disposable syringe, inoculate the first APB vial with 1 ml of the sampled water and mix thoroughly.
  4. Withdraw 1 ml from the first vial. Inoculate the second APB vial and mix thoroughly.
  5. Repeat step 4 until all APB vials have been inoculated.
  6. Repeat steps 3 through 5 for SRB vials with a fresh syringe.

*API dilution method are shown at 1, 15, and 30 days from inoculation.

Well 1 results:

Based on the data, it has been observed that the pretreat water (source water) were ‘turning’ five bottles (APB) and 1 (SRB) respectively at 15 and 30 days after incubation. However, after treatment with DIONIX at the tank level, there is no indication of bacteria in the water after the treated point and at the tank. Chlorine dioxide acts within seconds after injection within the main water transfer line. In a recycling project, flowback water will need to be treated again to ensure that only bacteria-free water will be reintroduced into the formation.

Objectives of treatment and observations:

  • Maintain consistent ClO2 residual in the tank to ensure sterilisation of the water.
  • Bosque Systems’ analyser automatically adjusted (set point) the delivery of ClO2 on a demand basis to maintain the target residual.
  • This is helps with operations and safety on site.
  • Fluctuations were observed in the delivery rate of ClO2 and has a direct correlation with the bacteria concentrations observed in the water.
  • The system reacts in real time.
  • On stage 1, treatment is higher at the set point to sterilise the tanks.
  • When a large delta is shown between the analyser set point and the residuals measured, in most cases means the inlet water was temporarily ‘dirtier’ than previous stages.
  • All points of measurement are monitored every 15 minutes to ensure a cost effective use of ClO2.
  • Chlorine dioxide has no significant impact on the pH of the fracturing fluid; it is important because a high or low pH may disrupt the efficacy of the fluid.
  • Limited to no effect on pH of the fracturing fluid.
  • ClO2 is pH tolerant and kills organisms at pH 2 as well as at pH of 10.

Scale inhibitor results:

ScaleStop 54 was used as the scale prevention treatment in New Mexico. The treatment uses nucleation and crystal modification to prevent scaling, and can be used at temperatures up to 375°F downhole. Given the scaling tendencies for this particular water, specifically the calcite potential, a minimum of 8 ppm residual of the phosphonate tag was required. This residual is measured at 30 days after production start to ensure a longer term of treatment efficacy and could be prolonged as long as the operator needs. In this case, a continuous treatment can be observed after 30 days.

Conclusion

Many operator’s budgets are being revisited and scaled back for 2015 while vendors are working hard to increase water management and treatment efficiencies to support continued completion activities. With water solutions and services such as those offered by Bosque Systems, producers are provided numerous cost effective solution systems for all their water initiatives. Chlorine Dioxide, while being the most effective biocide, is also price-competitive, especially when combined with other solutions such as scale treatment, from one support system and crew. The oil and gas industry has experienced those cycles in the past and is well versed to seizing opportunities during hard times, reinforces its structure, and comes out stronger when activities will pick back up. Because it will.

Edited from source by David Bizley

Published on 26/03/2015


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