Oilfield Produced Water Management

Nov. 24, 2014
The global oil industry is emerging as a surprisingly fertile arena for the development of a growing number of innovative water treatment technologies.
Recent advances in hydraulic fracturing also requires large quantities of fresh water and produce large volumes of high salinity wastewater.

The global oil industry is emerging as a surprisingly fertile arena for the development of a growing number of innovative water treatment technologies. One US-based start-up has invented a new process that is capable of cleaning the very briny water that emerges from oil wells. How are other global technology providers stepping up to provide solutions for this industry?

By Andrew Williams

Estimates suggest that for every barrel of oil brought to the surface in North America, so are eight barrels of water. Although challenging to treat, produced water – highly saline and contaminated – has become a focus of companies to innovate and develop new treatment technologies.

One of these companies is Massachusetts-based Gradiant Corporation, formed as a spin-out company by Massachusetts Institute of Technology (MIT) alumni Anurag Bajpayee and Prakash Govindan. As co-founder and CEO Bajpayee explains, the company's water treatment technology is based on its proprietary carrier gas extraction (CGE) technology, used in conjunction with a range of other "complementary technologies and innovations".

"CGE was invented by [us] at MIT to handle the most challenging water treatment problems," he adds. "It was commercialised by the company working closely with oil and gas industry partners. We are currently focused on treating produced and flowback water from oil and gas operations and converting every drop of the influent into re-usable water streams," he adds.

According to Professor John H. Lienhard, director of the Center for Clean Water and Clean Energy at Massachusetts Institute of Technology (MIT), the technology works by causing water vapour to evaporate from a wastewater stream into a moving airstream and then "condensing the vapour out of the airstream in another location".

"The system uses relatively advance thermodynamic principles to recovery energy effectively and lower the required energy consumption," he says.

The technology has been commercialised by Gradiant Corporation and is currently treating water that is produced during unconventional gas extraction in West Texas.

"The results have been excellent," adds the professor. "It can be applied to a very wide range of industrial wastewaters," he adds.

In Lienhard's view, the key advantage of the new technology is that, "unlike many other newly proposed technologies," it is "very robust and does not depend upon the invention of new membranes, new liquids, or new materials".

"It includes a highly innovative direct-contact condenser that minimizes hardware while maximizing thermal effectiveness," he adds.

Avoiding pitfalls
The main motivation for the creation of the new technology was the need to develop an effective means of treating the water that emerged as a by-product of oil drilling, which Bajpayee says contains "high levels" of oil, grease, suspended solids and volatile organic compounds and "very high levels of dissolved solids," often two to six times that of seawater, that are "very difficult to overcome using existing technologies".

He adds: "The presence of oil and grease creates operational issues with membrane based techniques and so do the harsh thermo-physical properties of high salinity water. The presence of volatile compounds which have similar distillation temperatures as water creates operational issues for conventional thermal desalination techniques. The high levels of contamination also makes the water extremely corrosive to metals and other usual materials of construction," he adds.

For Bajpayee, Gradiant's novel method of decontaminating water by using a carrier gas helps the CGE system to "steer clear of many of these pitfalls". He also points out that operation at lower temperatures and ambient pressures makes it possible to "use simpler materials of construction and avoids the need for exotic metals" - meaning that the proprietary primary treatment system, used in combination with CGE, helps to "eliminate pitfalls caused by the presence of oil and grease and scaling ions"

Hot wheels: GE's Mobile Evaporator system has been designed for the onsite treatment of high salinity wastewater. It has been continuously operated for over one year at a metal refining facility in Nevada.

"Gradiants' technologies are already deployed industrially and the company is successfully operating a 12,000 bpd (barrels per day) commercial plant in Midland, Texas for the treatment of oilfield produced water. Our customers are happy with the operation and the performance of the system, as well with our service teams' competence, professionalism, and attention to safety detail," adds Bajpayee.

The company is also currently in discussions relating to the deployment and operation of additional plants with several other customers. Bajpayee foresees most of the future growth in the company's operations being in the North American oil and gas industry but is also in "active discussions" with international customers about potential future industrial wastewater applications.

Hydraulic fracturing water technologies
A number of recent advances in natural gas and oil drilling and recovery operations, such as horizontal drilling and hydraulic fracturing - or ‘fracking' - also require large quantities of fresh water and produce large volumes of high salinity wastewater.

In response to the challenge of dealing with this, GE has created its Mobile Evaporator system - which was developed specifically for the onsite treatment of the high salinity wastewater. As William Heins, general manager of the Thermal Products business unit and a produced water evaporator and zero liquid discharge (ZLD) expert for GE Water & Process, explains, the new system not only reduces the volume of water requiring disposal but also produces fresh water for recycling - minimizing the amount of fresh water ‘make-up' required for the facilities to operate.

"The use of membrane distillation, which is a variation to this technology, is also being demonstrated. Membrane distillation will further improve the economics of this technology," he adds.

The Mobile Evaporator itself is a self-contained, trailer mounted, mechanical vapour recompression (MVR) evaporator system. The unit is designed with horizontal heat transfer surfaces, which reduces overhead space requirements, operates at or below atmospheric pressure, is designed to reduce fouling and scaling of heat transfer surfaces, and is ‘designed to minimize energy consumption and other operating costs."

"The Mobile Evaporator was developed to provide on-site treatment of wastewater from drilling operations. It concentrates the high salinity wastewater, thereby reducing transportation costs for off-site disposal.

The unit recovers fresh water, which can be recycled to support on-site operations, thereby minimizing the fresh water make-up requirements for the facility."

For Heins, the key advantages of Mobile Evaporator systems like this are that they are "highly mobile, self-contained systems" designed to ‘minimize the time and costs associated with setup, operation, and decommissioning' and that they have a small footprint - helping to minimises the space requirement for on-site operation.

In addition, he says that the MVR system design "significantly reduces power consumption' and that ‘in-transit and on-site overhead restrictions" and site set up time and complexity are reduced as a direct result of its horizontal heat transfer design.

Following a development process lasting several years, Heins reveals the Mobile Evaporator was demonstrated at full-scale this past year. He highlights the fact that many of the technical and economic challenges that were initially faced have "already been overcome through optimization over the last few years". However, he points out that the continued use of the technology is "primarily dependent on the evolving regulatory climate".

"Increased regulatory restrictions in some regions have generated considerable interest in this technology as it addresses the key issues of minimization of wastewater disposal and fresh water make-up. The economics of the technology are also strong in many regions, especially where wastewater disposal requires hauling of wastes over long distances," he says.

In terms of installations, the technology has already operated successfully in the Permian Basin for the treatment of drilling wastewater, known as flowback. More recently, Heins says that the Mobile Evaporator was ‘continuously operated for over one year' at a metal refining facility in Nevada.

"The [system] demonstrated an on-stream availability of over 98% during operation at this facility. Future activity is planned in all regions where unconventional natural gas and oil drilling operations are being conducted," he adds.

Andrew Williams is a freelance correspondent for WWi magazine, specialising in water and environmental issues. For more information, email: [email protected]


Other Oilfield Wastewater Treatment Technologies

In addition to GE and Gradiant, a number of other companies are also developing, or have already developed, innovative water treatment technologies in this sector. One example is water-engineering outfit Ecosphere, which claims that it has used its patented Ozonix advanced oxidization system to treat over three billion gallons of water in the U.S. hydraulic fracturing industry since 2008. Billed as ‘mobile, self-contained and fully transportable,' a single Ozonix oxidation system is capable of processing up to 3,300 gallons of wastewater per minute ‘to a level that is suitable for re-use.'

Another example is Massachusetts-based firm Clean Membranes, which has developed what it calls a fouling-resistant filtration technology for wastewater treatment. Amongst other applications, the system has already been used for oil and gas wastewater processing and recovery. It can also be used for pre-treatment for seawater desalination and reverse osmosis systems, as well as for wastewater treatment in the food and beverage sector.

Elsewhere, Oasys Water has developed what it describes as a "revolutionary" process that "enables high recovery desalination while using low thermal energy, dramatically reducing cost and complexity."

The system employs a forward osmosis process that features a patented "membrane-based desalination platform that can transform wastewater with up to five times the salinity of seawater into fresh water". A "robust" variation of the technology, known as the Clearflo MBC system, has been specifically designed for oilfield wastewaters - which Oasys reports "can handle variability in feed water while maintaining a constant, reliable feed water quality" and produce a "clean, quality 10 pound brine that can be used for completion or stimulation".

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