Precious water

As the oil and gas industry continues to expand, so does the demand for new desalination and water reuse technologies, used to produce high-quality water (mainly for crude processing and cooling towers) and reclaim contaminated water. In addition to having to find new and innovative ways to secure a steady source of water for daily operational use, plants also face ever-increasing financial, environmental and regulatory challenges.

Becoming operationally-efficient is not an easy task. Plants are expected to meet increasingly stringent environmental regulation when it comes to water usage and effluents discharge, and at the same time maintain profitability while implementing practical water treatment methods. From construction to operation, desalination systems that are not properly set-up or managed are cost-intensive, some processes within plants are becoming more energy-consuming, and industrial effluents discharge that is not handled properly can have a significant environmental impact. Wastewater treatment in refineries is growing at a rate of more than 10% annually, and as a result, reusing water and minimising discharge are one the most important factors when dealing with industrial water treatment (IWT) solutions. Typical technologies include membrane-based desalination such as reverse osmosis (RO) and nano-filtration (NF), thermal distillation such as mechanical vapour compression (MVC), multi-effect distillation (MED) and forced circulation evaporator (FCE), but can also be a combination of these and other technologies. Which technology is ideally suited for the unique needs of this industry? That depends on the type of oil and gas application, plant location, amount of effluent discharged, specific water characteristics such as temperature and water chemistry, and of course, local regulations and budget constraints.

IWT has progressed significantly in the past several years, particularly with respect to the oil and gas sector. Ongoing developments and innovative technologies have introduced considerable operational improvements, and are paving the path for IWT solutions to become more cost-effective and energy-efficient. In addition to advancements in RO and NF, plenty of R&D is carried out around membrane pre-treatment such as ultrafiltration and microfiltration for total dissolved solids (TDS) levels of below 70 000 ppm, as well as thermal solutions such as MVC and FCE for TDS ranges of 100 000 – 250 000 ppm.²

When incorporating desalination technologies, especially in recent years, there is a particularly strong focus on addressing aspects such as pre-treatment, pressure recovery, low-temperature sources of energy, as well as comprehensive solutions that enable zero-liquid discharge (ZLD). On the business side, plants are concerned with optimising costs, both CAPEX and OPEX wise, improving yields, and complying with water and effluent regulations, the latter proving to be an ever-growing challenge.

The bottom line

As the scope of the oil and gas industry grows, unconventional oil explorations – shale gas and coal bed methane – are rapidly gaining momentum. Globally, energy demand is on the rise and environmental regulation is tightening, creating the need for more efficient and economical IWT solutions than ever before. The heavy oil sector is making significant investments in recycling produced water for steam enhanced oil recovery (EOR), as is the case with Canada’s oil sands, one of the largest oil reserves in the world, which speaks volumes on the importance of robust water reuse solutions:

• Depending on quality, it is estimated that more than 90% of industrial wastewater could be reused by applying advanced treatment technologies such as RO.
• Zero liquid discharge solutions can meet the most stringent regulations and minimise environmental impact.
• Modular water treatment solutions can dramatically simplify installation and reduce civil works and local site risks, leading to reduced erection costs.
• Water reuse combined with proper water management procedures can enable plants to save up to 40% of their daily freshwater intake.

SWRO and brackish water reverse osmosis (BWRO), thermal desalination and water reuse solutions for industrial effluents, are ideally suited for the oil and gas sector in terms of their operational, regulatory and economical needs. Advanced IWT solutions to address effluents discharge challenges, take a comprehensive, integrated, end-to-end approach in order to meet the unique requirements of the sector. These are essential for maintaining growth while securing efficiency, sustainability and cost-effectiveness in the long-term.

The Wintershall story

Overview of the project

• Company: Wintershall Holding GmbH (BASF group).
• Location: Emlichheim Oil Field, North Germany.
• Industry: Oil and gas.
• Capacity: 2 x 600 m³/d.
• Technology: Mechanical vapour compression (MVC).
• Product: Produced water evaporators.
• Division: Industrial water treatment (IWT) solutions.
• Project type: Engineering procurement construction (EPC).
• Commissioned: 1990, 1991.

Wintershall Holding GmbH, a BASF subsidiary and Germany’s largest crude oil and natural gas producer, has been producing oil at its Emlichheim production facility on the German-Dutch border since 1943. The company explores and produces oil and gas in Europe, North Africa, South America, Russia, the Caspian Sea region, and the Middle East. Active for almost 80 years, Wintershall has a workforce of more than 2000 employees.

The conditions and requirements that forged this project

In the past, because oil in the Emlichheim deposit has an extremely viscous texture, the Wintershall facility had to resort to experimenting with various techniques to ensure stable, uninterrupted operation. The company opted to employ increasingly sophisticated EOR methods – hot water in the late 1960s, boiler feed water (BFW) generation in 1981 – but its conventional steam injection oil recovery method did not meet the company’s business, operational or environmental goals.

Wintershall sought a cost-effective, eco-friendly alternative for oil recovery. The solution needed to maintain high levels of oil production while avoiding the risks presented by steam injections, namely:

• Contamination of potable ground water.
• Contamination and shutdown of ground water wells, due to a rise in the water table driven by pressure.
• Irreversible changes in underground locked crude pockets, potentially damaging future oil exploration.

In the early 1990s, the use of horizontal drilling was introduced, leading to an increase in oil recovery rates of more than 40%. One of the keys to its success is the use of two 600 m³/d MVC evaporators furnished by IDE Technologies.

Smart deployment of MVC for IWT

IDE provided Wintershall with two MVC units, which enabled an enhanced oil recovery via closed water cycle treatment processes. These MVC units allowed Wintershall to recycle produced water – wastewater that is generated with the oil – into distillate. This distillate is then used to produce 300°C steam that is injected into the formation ground at a pressure of 100 bar (1450 psi), as part of the enhanced oil recovery process. In addition to improving oil production, the ability to recycle wastewater eliminated the need for an ongoing freshwater supply.

IDE’s MVC evaporators are able to concentrate produced water from a salinity of 7 – 8% to about 13% in a single-effect MVC unit at a temperature of 65°C. Each unit produces approximately 26 m3/hr of distillate at an energy consumption of 10 – 12 kWh/m³, which requires no further polishing prior to being used as feedwater for the once-through steam generators (OTSG). Although the MVC units can be designed with top temperatures of up to 105°C, the units supplied for Emlichheim are operated at a lower temperature in order to reduce the likelihood of scaling.

Since its installation almost 30 years ago, the Wintershall facility has demonstrated remarkable stability, delivering 100% of the designed capacity and ensuring a smooth, steady and more efficient oil production. The MVC units have been operating continuously since 1991 at 98% availability, with chemical cleaning performed every two years during a planned shutdown. Innovative technologies such as these, which optimise production while maximising oil recovery, not only extend the life of existing oil fields, but also reduce the industry’s environmental impact.

This project also has a low environmental impact as no additional water resources are required and the system uses a closed-loop water treatment with 25% lower energy consumption.

Technological highlights

The Wintershall Project has a robust horizontal falling film design that was optimised to meet the needs of the facility. What is more, the proprietary design of the MVC – incorporated inside the MVC vessel – is also highly efficient. Cost-effective and high-quality construction materials were also incorporated into this project for durability, inherent stability and automated control. This reduced the need for labour and maintenance, while providing constant high availability.

Conclusion

Refineries are continuously looking for more effective ways to meet their water needs, while managing the total heat balance of the plant in the most effective manner. Water consumers in a refinery include, among others, BFW, cooling tower makeup, potable water, service water, desalter makeup, coker quench water and coke cutting water. While these consumers require different water qualities, the first two (BFW and cooling tower makeup) require very high-quality water.

IDE Technologies has extensive experience in designing, building and operating plants that are particularly suited for generating high-quality water by means of desalination, either through RO or MED, which have been successfully installed and operated in multiple locations around the world.

According to each refinery’s needs, IDE designs a tailor made solution that may also include other water treatment solutions, such as lime softening, ion exchange, electrodeionisation, various filtration methods, biological treatments, etc.

IDE’s MVC offers a robust horizontal design that is optimised for customer needs, including high-grade material selection. The MVC is also designed with environmental sensibility; wastewater volume is reduced with low use of chemicals, and overall energy consumption is lowered by ~25%. The MVC is easy to operate with inherent stability and automated control reducing the need for labour and maintenance, while maintaining high availability of the system. The MVC also meets strict BFW quality requirements.

References

1. COPE, G., ‘Waste not want not’, Hydrocarbon Engineering, Vol. 17, No. 6, (June 2012), pp. 26 – 32.
2. HADDAWAY, A., ‘Desalination Trends in the Oil and Gas Industry’, WaterWorld, (April 2015), https://www.waterworld.com/industrial/article/16211374/desalination-trends-in-the-oil-and-gas-industry

Written by Tomer Efrat, IDE Technologies, Israel.

Read the article online at: https://www.hydrocarbonengineering.com/special-reports/23122019/precious-water/