Choosing Produced Water Treatment Technologies Based on Environmental Impact Reduction

Abstract

Reduced environmental impact should be the goal when choosing produced water treatment technologies. On the Norwegian sector the method used for quantifying this impact is the Environmental Impact Factor, EIF. This method is computerized in a tool that calculates the environmental impact from each of a number of chemical component groups that are present in produced water. Reinjection of produced water is obviously an option that should be considered if the reservoir needs pressure support. This paper, however, describes four new treatment technologies aimed at produced water being released to sea. The technologies are suitable for different produced water compositions. The four technologies described are the PECT-F (Performance enhancing coalescence technology) for enhanced removal of dispersed oil, the MPPE (Macro Porous Polymer Extraction) technology for removal of volatile aromatics, the CTour technology for the removal of heavy aromatics and alkylated phenols, and the Framopure C100 injection system for H2S scavenger. The potential of these technologies has been illustrated by choosing typical produced water compositions where one of these technologies has a significant potential to reduce the environmental impact. Given an estimated efficiency of these technologies, the EIF is calculated before and after applying the technology to show the reduced environmental impact obtained. The main conclusion is that knowledge is needed about which compounds contribute to the environmental impact of produced water before deciding which technology to use. Results are also presented that correlate the content of dispersed oil and PAH (poly aromatic hydrocarbons). Introduction The main focus in reducing the possible pollution from produced water to the sea has traditionally been on reducing the content of dispersed oil. Even though some countries have placed their attention on other compounds, international regulations like the new OSPAR regulations [1] still focus mainly on dispersed oil content in produced water. On the Norwegian sector of the North Sea, all operators must, in addition to fulfilling and reporting according to the dispersed oil regulations, report the total environmental impact of the produced water release to the sea to the Norwegian pollution authorities (SFT) [2]. This reporting is done on an annual basis and is based on thorough (GC-MS) analysis of the produced water to quantify the content of all compounds of interest. The method for quantifying the environmental impact is the Environmental Impact Factor, EIF [3], which relies on DREAM (Dose Related Risk and Effect Assessment Model) [4]. In this model a comparison is made between the concentrations of possible environmentally harmful compounds and the predicted no effect concentration, based on an environmental risk assessment approach. The compounds of interest are: PAH, NPD (naphthalenes, phenanthrenes and dibenzo-thiophenes), BTEX (Benzene, Toluene, Ethylbenzene and Xylene), phenol, alkylated phenols, metals, and added chemicals. The later being substances such as: production chemicals, corrosion-, scale-, and hydrate-inhibitors, separation chemicals, and H2S scavenger. The EIF is not only a valuable tool for quantifying the total environmental impact from one platform or a group of them, but also for evaluating the contribution from the different constituents in the produced water. The compositions of produced water from different fields vary significantly. Hence, each field should be evaluated with respect to which compounds contribute to the environmental risk. When selecting produced water treatment technologies, one should focus on the major contributors to reduce the total environmental impact. Experience has shown that the major contributors to the EIF are dispersed oil, volatile aromatics, heavy aromatics, alkylated phenols, and added chemicals.

Constructed Treatment Wetlands: Innovative Technology for Petroleum Industry

“…After a couple of years, wells start to produce increasing quantities of water from the reservoir 7 . Experience has shown that the major contributors to the environmental impact factor (EIF) are dispersed oil, volatile aromatics, heavy aromatics, alkylated phenols, and added chemicals 11 . Over the economic life of a producing field, the volume of produced water can exceed by ten times the volume of hydrocarbon produced 9 .…”

Advances in Produced Water Treatment Technologies: An In-Depth Exploration with an Emphasis on Membrane-Based Systems and Future Perspectives

“…The process involves injecting condensate into the produced water stream and allowing inline mixing to take place. By means of this mixing, the hydrocarbon impurities present in the produced water are extracted and combined with the injected condensate [76]. During the extraction process, the impurities and condensate coalesce, forming lighter and larger oil droplets.…”

“…The C-Tour process provides an efficient and effective solution for treating produced water while simultaneously recovering valuable hydrocarbons [76,77]. By employing solvent extraction principles and optimizing the mixing and separation steps, the C-Tour process facilitates the efficient extraction of hydrocarbon contaminants.…”

Experimental Study of Condensate Vaporization into Bubbles under Different Operating Parameters

“…Sabey et al [13] named the process CTour, which investigated the effects of dissolved gas in water, free gas in water, solid particles, and oil-water interfacial tension on the performance of the CTour system and concluded that these parameters do not affect the performance, but the structural design of the injection and mixing system and the operating conditions can have a significant effect on the oil removal efficiency. Statoil conducted an offshore test in the statfjord field, where the use of the CTour process resulted in a 70% improvement in oil droplet removal efficiency, as well as effective removal of corrosion inhibitor and hydrocarbon components from the produced water [14] . Thus, in this paper, the CTour air flotation method was also adopted to study the pattern of bubble generation from condensate solution at different temperatures after decompression and release.…”