Improving oil sands production efficiency with modular evaporators

By Yaniv Schmidt | February 19, 2016

Alberta’s oil sands industry is facing a challenging time. The rapid drop in oil prices from $110/barrel to less than $40/barrel is putting a lot of stress on new developments and making it almost impossible to raise capital.

Companies are looking for ways to make new projects viable at current oil prices, not an easy task after the previous project break even at $80/barrel. The market is looking for lower capital investment installation efforts and risks, and shorter project execution time. To make a steam assisted gravity drainage (SAGD) project more cost-effective and competitive in a low oil price environment, it is necessary to reduce capital investment in equipment and maintain maximum site operation availability in order to ensure a steady flow of income.

Developing a new SAGD 10,000 barrels/day project is an approximately $500M – $1,000M high risk operation. The economics are significantly affected by the steam to oil ratio (SOR), as well as the selection and performance of the water treatment equipment. At typical SAGD sites, more than 97% of the produced water is recycled and reused for steam generation, a process mainly carried out by evaporators.

Produced water evaporators are robust process equipment that distill the produced water to pure water, which can then be fed into steam generators. The evaporators are critical elements in the water treatment process, as well as major contributors to capital investment. The market is turning to modular and prefabricated solutions to reduce site construction costs and minimize project risks. Horizontal evaporators, which are making their first steps into the market, are completely prefabricated and can be easily transported to site in small modules.

In order to reduce the operation risk, IDE offers a process demonstration system, which is designed for small scale process simulation and demonstration of produced water treatment. The unit has been installed at the Alberta Innovates Technology Futures (AITF) facility in Edmonton. A 12-month testing program was completed, during which process condition optimization and chemicals usage were developed.

The testing program was composed of several runs, each of which was executed continuously for 30 days. Different water sources from SAGD facilities were shipped to the testing site, and extensive analytical work was performed during each test run.

Process and system description

Produced water is fed to the system from a collection tank. It then flows to the degasifier to reduce the bicarbonate level. Downstream, feed water is mixed with brine from the evaporator sump and is divided into two streams. A small amount of the water flows as blow down to the brine tank. Most of the brine water is circulated and sprayed in the shell of the evaporator. The dropping water creates a horizontal falling film on the heat transfer tubes. Steam that is injected inside the tubes transfers heat to the brine, which evaporates.

When the system operates with the compressor, compression adds ~2oC to the vapour and feeds this to the inner tube side. When the unit operates with external steam, the vapour flows to the condenser and continues to the distillate line. Steam, either from the compressor or from an external source, flows into the tubes, where it condenses and exits the tubes as distillate and is pumped into the distillate tank.

The operator controls conditions such as pH, temperature, production, and chemical dosing rates. Chemicals are injected directly to the recirculation line.

The trial demonstrates actual working conditions at the highest concentration and working temperature (worst case scenario) for brine concentration of the SAGD plant. This facility is used as a risk mitigation tool for new projects, allowing process optimization in a safe environment, instead of doing it on-site where costs can spiral.

Modular horizontal evaporator

IDE has developed a modular evaporator design which reduces installation costs. The modular horizontal evaporator is based on standard prefabricated modules that are easily transported and installed on site. Site installation includes positioning of the modules on piles, connection between them and lifting the evaporator vessel on top.

Modular MVC-1500 m3/day.

The modules and the vessels are designed to fit standard shipping, making the supply chain very flexible. Manufacturing outside of Alberta lowers costs.

The modular design can be suited to different evaporation capacities by adding more modules and more vessels, as well as increasing the capacity of the vapour compressor.

The modules are placed on piles driven into the muddy ground, which saves expensive concrete work. They are designed for fast connection, which shortens erection time from 4 – 6 months to 6 – 8 weeks.

The cost saving on site erection is significant. However, for a project to be successful, daily operation and the oil production must be maintained at maximum. One of the problems facing SAGD operators is maintenance and cleaning of the evaporator tubes, which results in expensive downtime.

Removable tube bundle

Evaporator availability is critical in SAGD operation. When the water train is down no steam is generated and oil production is stopped. The cleaning of evaporator tubes is done once or twice a year; it may take a whole week to complete, which is a significant downtime. The cleaning, which is done on site, is labour-intensive and involves the use of hazardous chemicals.

As part of the modular evaporator development, IDE offers removable tube bundle capabilities. During system turnaround, a fouled tube bundle can be removed from the evaporator shell and replaced with a spare clean bundle. The fouled tube is sent for offsite cleaning so no hazardous chemicals are handled on site, resulting in shorter and safer turnarounds on-site.

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