In 2020, the planet's oil wells will produce nearly 12.7 billion gallons a day of, surprisingly, water. The water is reused to meet technical requirements at installations, sidestepping the need both to tap the natural water supply and discharge the water produced into the environment. Known as reinjection, this is already common practice. Its future growth, especially in offshore fields, is part of the environmental engagement of oil companies, which are also experiencing mounting regulatory pressures. Most important, it's a daunting technical challenge, forcing operators to grapple with production requirements that differ in each case.
No oil without water
You can't produce oil without water, because water is present naturally in both onshore and offshore oil reservoirs. This naturally occurring water is called formation water. Minimal when a field first comes on stream, it can make up more than 90 percent of the fluids extracted after wells have been in service for 20 or so years.
Used as a drilling or production fluid, water is also vital to managing an oil field sustainably. It is injected into fields via special wells, called injection wells. The injected water offsets declining pressure in the reservoir as oil is produced over time. Lastly, water enhances oil recovery by "flushing" the reservoir. For a long time, injection water was drawn from the natural environment, including oceans, rivers, lakes and estuaries. But it's the water produced along with the oil or gas that is increasingly used today. Water from the biggest Floating Production Storage and Offloading units — FPSOs — can, for example, reach 400,000 barrels — nearly 17 million gallons — a day, an amount that would fill 21 Olympic-size swimming pools.
Consequently, an average of three to five barrels of water1 is produced with one barrel of oil2. That means water is the number one fluid produced by the oil industry. According to a study by IFP Énergies nouvelles (IFPEN), an estimated 250 million barrels of water a day were produced in 2008, a figure expected to jump to 300 million3 in 2020, an increase of 20 percent. That's because a large percentage of today's global production is from fields brought on stream 20 years ago.
So increased energy demand means a growing need for water. However, although alternatives to oil and gas exist, there's nothing that can replace water. Yet oil development and production can't be allowed to stress the water supply, especially when it's assumed that climate disruption will amplify the problem. For the oil industry, water management is a core challenge.
10,000 cubic meters of water (2.6 million U.S. gallons) an hour — here on Moho Nord in the Republic of the Congo, no water is discharged into the sea. Total treats all produced water before reinjecting it into the reservoir.
At the source is possible, but far from simple
Produced water was long considered a byproduct that, depending on its quality, required specific treatment before discharge, but wasn't reused. In onshore production, the water was either discharged into the natural environment or handled by wastewater collection systems. On offshore platforms, it was mainly discharged into the ocean, taking advantage of a strong dilutive effect while complying with applicable international or local standards4 (generally, less than 30 milligrams of hydrocarbon per liter of water discharged).
But practices are changing. For the last decade, produced water has been looked at as more of a resource. There are several reasons for this shift in attitude:
- Oil companies' commitment to do more to manage the environmental impact of their activities, especially with respect to water management.
- International or local environmental standards and the demands of civil society, which are rightfully more stringent.
- The fact that oil installations are producing more and more water, given the age of wells.
As Pierre Pedenaud, a water treatment specialist at Total, says: "Both onshore and offshore, the first option people study now is avoiding any discharge into the natural environment and instead injecting produced water back into the reservoir it came from." This "recycling" requires installing equipment that has to be tailored to the site. "Produced water is always different. Some contains sulfates, some barium or strontium, and all of it comes with varying quantities of solid particles. Chemical reactions can occur, especially on contact with seawater that may mix with the produced water. This can plug or corrode pipelines or injection wellheads and tubing."
So reinjection installations are always tailored to specific needs. "We start with a standard architecture that we adapt to the specific physicochemical properties of the water to be reinjected." The main risk is the formation of solid sulfate deposits that are very difficult to remove and can compromise the reinjection equipment. A range of parameters measuring quality, such as bacterial growth, are monitored. "The higher the water quality desired, the more expensive the installation will be. We have to constantly make trade-offs to strike the right quality, cost and environmental balance," says Pierre Pedenaud.
- For more on the subject: A Bird's-Eye View of Oil Exploration
The circularity challenge
Yet one solution Total is looking at for its exploration and production activities is expanding reinjection at onshore and offshore sites. "Water has a wide range of uses, including agriculture, food and hygiene," stresses Total's expert. "We aim to minimize the water we draw from the environment, by deploying a type of circular process to avoid competing with those other uses. It's also a question of respect."
So limiting water use and discharges into ecosystems is a company choice, a first option for responding to environmental concerns and balancing the demands of industrial efficiency and regulations. Produced water reinjection must adapt to each production site's always different environmental, technical and regulatory requirements. "We consider it a pioneering initiative that lets us implement and develop know-how," says Pierre Pedenaud. "For example, in Uganda, at a future onshore site that will produce saline water, reinjection is mandatory because discharging it into freshwater meant for communities is out of the question."
As they say, what goes around comes around. So circularity is likely to be a characteristic of future oil production.
1 Source: IFP Énergies Nouvelles: "Water in Fuel Production."
2 One barrel is approximately 159 liters, or 42 U.S. gallons.
3 Or 47,700,000 cubic meters.
4 There is no international standard. Every country or group of countries has its own standards. For example, in the OSPAR region — the one covered by the Convention for the Protection of the Marine Environment of the North-East Atlantic, called the OSPAR Convention — the goal is to achieve Zero Harm Discharge (ZHD) by 2020. In Brazil, Resolution 393 of the Conselho Nacional do Meio Ambiente (2007) limits the discharge of oil from offshore platforms to a daily maximum concentration of 42 mg/l.