The Produced Water Management programme focuses on reducing the environmental footprint associated with hydrocarbon extraction in the North Sea. The program is all about improving how we treat and dispose of the water that is being produced together with the hydrocarbons. When the flow of oil, gas, and water comes out of the wells, the fluids go through a separation and conditioning process. After having been separated out, the water is cleaned to meet requirements in the environmental legislation and the discharge permit that is a part of the production license.
The current technology for cleaning the water is so good that the purity of the water being let out to sea is far better than the requirements given in the legislation and the discharge permit. Statistics for the last few years show that the discharged water contains around 8 ppm hydrocarbons whereas the legislation permits up to 30 ppm. The vision for this new research program is to completely eliminate harmful discharges associated with handling and disposing of the produced water.
The OSPAR convention (Convention for the Protection of the Marine Environment of the North-East Atlantic) regulates discharge of harmful substances in the North Sea area. This convention regulates how much dispersed oil in water (oil droplets) and chemicals that are allowed in the water being discharged. The Danish oil and gas operations remain well within these requirements. The current methods being used to measure toxicity of the water (EIF - Environmental Impact Factor) is not able to explain all of the components that contribute to the harmfulness of produced water. We will therefore attempt to improve the current testing methodology to document EIF.
We will also test how quickly the toxic components in the produced water breaks down in the marine environment. These tests will be conducted on seawater sampled around several Danish offshore installations. This will inform us of the persistence of toxic components in the marine environment.
Finally we aim to develop new technology for measuring toxic components in the produced water. This will allow direct measurement of toxic molecules to support and improve the models used to calculate contents of production chemicals in the produced water.
This knowledge will be linked to developing new water treatment technology to specifically address dissolved hydrocarbons, as well as potentially remove harmful chemicals. For the DUC Operator, the workflows developed will become an improved tool for measuring effects of operational adjustments and new technology, and for reporting environmental performance to stakeholders.
Produced Water Treatment
We aim to develop new technology for treating produced water, and to improve existing treatment systems. We will be looking to improve and stabilize the water treatment process with new instrumentation technology and advanced process control technology. Biological treatment methods and advanced oxidation will be tested and, if found to be potentially feasible, further developed to demonstrate the technology in offshore applications. We will do work with more traditional treatment methods like gas flotation and smarter use of membranes. Furthermore, we will lift the understanding of how chemicals affect emulsions and thereby also separation technologies, and we will develop new analysis methods to support development of new technology.
Produced Water Reinjection
If we inject the produced water in existing water injection wells, or in dedicated disposal reservoirs, then we eliminate discharge of potentially harmful components to the marine environment. However, drilling new wells and using energy on injecting water also comes at an environmental cost. So we will primarily focus on replacing some of the seawater that is injected to increase production, with produced water, to achieve a net reduction of the environmental impact.
Injecting produced water in existing water injection wells comes with significant challenges related to reservoir damage, reservoir souring and fouling of pipelines, wells and reservoir contacts. In this research theme we aim to resolve some of these challenges to enable increased reinjection of produced water in the DUC fields.
In 2021, we started four new projects related to produced water reinjection. We will conduct experiments and modelling work to better understand the mechanisms behind skin formation at the reservoir contact and develop a method to hopefully prevent this skin formation. We will also conduct a concept verification study of a metal oxide framework (MOF) to replace oxygen scavenger chemicals from the water treatment process and improve de-oxygenation of water before injection.
By green chemicals, we mean biologically based chemicals that are based on sugars, plant extracts, etc. In theory, such chemicals should be biodegradable and hence less harmful for the marine environment. This hypothesis can be verified with our improved methods for documenting environmental impact and biodegradability.
The first project in this theme started in December 2020 at University of Copenhagen. The project will develop a multifunctional, self-enhancing H2S scavenger based on myo-inositol. Myo-inositol is a sugar that is abundant in nature. It is produced in the brains of mammals and stimulates neural activity in the brain. However, it can also be produced from wastes from food crops and other readily available organic source products. It is therefore a cheap and environmentally friendly raw material.