Optimal Options for Treatment of Produced Water in Offshore Petroleum Platforms
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During Petroleum exploration, water, which is trapped in underground formations, is brought to the surface along with oil or gas. This water, offshore processing options for oil platforms to as Produced water, has constituents that make it unsafe to be discharged into the environment without adequate treatment.
In offshore locations, the situation is even more difficult since there is always limited space for produced water treatment. The treatment of Produced water will not only provide water for use but will protect our environment against pollution. This paper has reviewed exhaustively the various ways of handling produced water on the basis of its constituents, expected use of the effluent fluid, adherence to the local regulations on environmental protection, available expertise, and cost of its treatment.
Furthermore, the paper has selected some key produced water treatment techniques, discussed their advantages as well as limitations to enable oil and offshore processing options for oil platforms operators to make informed decision depending offshore processing options for oil platforms the circumstances surrounding their operations. Home Publications Conferences Register Contact. Case Report Open Access.
J Pollut Eff Cont 1: This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Select your language of interest to view the total content in your interested language. Can't read the image? Related article at Pubmed Scholar Google. Oil is a major global energy source and its exploration and production is extremely important. While oil production is desirable, it results in some unfavorable effects to the environment.
In underground structure, rocks that occur normally are accompanied with fluids water, hydrocarbon, or a combination of the two. The less dense hydrocarbons drift to trap sites, shifting offshore processing options for oil platforms of the formation water in hydrocarbon reservoirs. This informs why hydrocarbon reservoirs contain water as well. This water might have arrived from the flow from within the hydrocarbon zone, flow from below or above the hydrocarbon zone, or flow from injected solutions and chemicals for the purpose of managing the reservoir by the producers [ 1 ].
The oil reservoir is the main source of this produced water, which may as well include sea water that has been injected to sustain the reservoir pressure. The large quantities of formation and injected water, which is eventually produced along with the oil and gas, is one of the most crucial sources of unfavorable effects to the environment. Handling of produced water is therefore critical in Petroleum exploration and production operations because of its significant contribution to capital cost of operating oil or gas reservoir.
Considerable amounts of liquid waste streams are regular outcomes within onshore and offshore oil production much higher in offshore locations. After some treatments on the platform, these wastes are discharged usually into the aquatic environment. During the early years of production, the amount of liquid wastes produced beside the oil is generally low; however, as the reservoir becomes older, the amount increases perhaps several times more than the produced oil [ 2 ].
For instance, the quantity of produced water dumped into the North Sea by the UK increased radically by 43 million tons in 4 years by the same reservoirs from offshore processing options for oil platforms [ 3 ]. In general, the produced water is offshore processing options for oil platforms to eight times greater by volume than oil produced at any particular oilfield offshore processing options for oil platforms 4 ].
Separation of oil, gas, and water from produced hydrocarbon stream on an offshore platform is by addition of certain chemicals; these chemicals that include corrosion inhibitors, deemulsifiers, defoamers and biocides [ 5 ] are toxic to the marine environment.
This depends on several factors such as allowed fraction of each chemical in the mixer with the produced water and the quantity of discharged produced water in each batch [ offshore processing options for oil platforms ]. Produced water contains a wide variety of constituents such as organic and inorganic pollutantssuspended solids, and iron. The following are predominant contaminants [ 78 ] Table 1. The weight fractions of these contaminants vary from one oil production offshore processing options for oil platforms to another depending on the nature of the well, its age and production conditions.
One can observe that radioactive particles can be present in the produced water, which can potentially have a severe impact on the environment. There are various chemical constituents that could be present in the Produced water. These chemicals, individually or collectively, could have significant impact on the environment. Some of the impacts include disruption of physiological and behavioral offshore processing options for oil platforms of the aquatic life, bioaccumulation, and deterioration of physical environment amenity beach.
The impact of produced water on marine life depends on the constituents and concentration of the chemicals present in the produced water. For offshore operations, the impact is also dependent on the discharge point, physical properties as well as hydrology of receiving environment [ 10 ].
Globally, the oil and gas industry generates more than seventy 70 billion barrels of produced water per annum [ 11 ].
This represents huge volumes and requires economical and environmentally friendly methods of treatment. The management of produced water represents the single largest waste stream challenge facing the industry worldwide. A variety of management options for produced water exists, however the selection of any option is largely dependent on certain factors such as regulatory acceptance, site location, technical feasibility, cost as well as availability of infrastructure and equipment.
Industry Operators evaluate the various management options in a bid to find the most cost effective approach to handling their produced water. For instance, Shell established a offshore processing options for oil platforms program with which, it attempts to minimize water production, reduce costs of produced water treatment and considers opportunities for existing facilities to handle larger volumes of produced water [ 12 ]. The Management options can be described in terms of a three tiered system, which is implemented consecutively.
They include as follows:. The aim of this tier is to reduce the volume of water produced from the oil production well. This is achieved by modifying the existing processes, adapting technologies old and new or substituting products to ensure that less water is generated from the onset. Tier 1 option presents great opportunity to better protect the environment as well as to save some costs.
Following the implementation of the Tier 1 option, Tier 2 option is employed depending on the end use of the produced water. The type of reuse option that would be considered is usually dependent on the cost of produced water treatment.
This is evident at the later stages of the life cycle of the producing reservoir or well. However, at the early stages of oil production, produced water poses a great disposal challenge, especially in the offshore environment since no injection water is required.
In this, the produced water is treated prior to discharge or disposal. The treatment process or technology to be used depends on nature of water body receiving the treated produced water or the quality of water needed. At present, over seventy international conventions and agreements are directly relates with protecting the marine environment [ 13 ]. However, not one of these conventions and agreements is exclusively devoted to regulating offshore oil production [ 14 ].
The proposal of Greenpeace International to International Maritime Organization IMO to amend the International Convention on the prevention of marine pollution by dumping of wastes and other matter London Convention including all waste products generated by offshore production was rejected in due to absence of an international legal framework; however, IMO advised concerned countries to initiate national and regional legislations for offshore development.
It seems that management of offshore platform effluents is driven by legislations, best available technology application and environmental effects considerations. In view of the foregoing, discharges to the ocean from offshore platforms have been regulated by limitations and requirements set by National and Regional Regulatory Agencies through the issuance of discharge permits. Offshore processing options for oil platforms permits offshore processing options for oil platforms intended to protect receiving water body, environment and its uses from harm attributable to the permitted discharge.
It is important to highlight that regulation of offshore oil production in most countries require that technology based limits are consistent with cost effective best available treatment technology. It is expected that new conventions, agreements, and other international mechanism may be foreseen in a future not too far, but there still remains a need now to address environmental issues with the best approach and with a more detailed and strict environmental legislation regarding offshore platform discharges.
Produced water from offshore platforms has been conventionally treated over the years through gravitational separation and skimming, dissolved air floatation, de-emulsification, coagulationand flocculation. This relatively low-cost equipment is not effective in removing small droplets of oil, thus used in most cases as primary step in the treatment of produced water. It is also possible to remove dispersed oil in the influent water to this system by use of chemicals deemulsifiersthermal energy, or both.
The chemicals are used to aid coagulation of the particle size, hence increase the droplet size to make separation easier.
Heating of offshore processing options for oil platforms produced water will normally reduce offshore processing options for oil platforms viscosityweaken the interfacial film stabilizing the oil phase, and bring about obvious density difference between oil and water. This thermal process is usually followed by acidification and addition of alum to neutralize the negative charges on the oil droplets.
The pH is then raised to induce the flocculation of inorganic salt while the resulting precipitates are separated from the oil. The processes of electro-coagulation and electro-floatation that utilize both physical and chemical mechanisms in the presence of an electric field could be employed in breaking of oil emulsion Figure 1.
Gravity separation is most commonly used primary separation technique in treatment of produced water in offshore production platforms.
However, in most cases, the effluents do not meet the regulatory discharge limits; hence the use of secondary treatment steps that lower the level of dissolved, emulsified, and dispersed oil. Chemical treatments followed by sedimentation or DAF mechanism are commonly deployed as secondary treatment steps for gravitation separation technique.
Chemical emulsion breaking technique is an effective technique if properly applied. However, the technique has many limitations which include:. It is highly customized since the type and quantity of chemicals required is site specific.
It requires close control and skilled operators to achieve optimal operation. There could be corrosion problems due to the acidification of the influents. Mechanical problems may arise due to clogging of chemical feeding lines. Dissolved solids content in the effluent increases as operation progresses; and. It is more suitable for large volumes e.
Heating of the fluid, as in evaporation and incineration, is very suitable for many types of oily emulsions but also has its associated limitations. The high energy cost associated with this process as well as oil loss in vapors from the evaporators that necessitates the treatment of the condensates makes the technique less fancied.
Membrane technology has become a highly ranked separation technology in the last few years. Membrane filters are basically developed into four configurations for industrial applications namely tubular, hollow fibers, plate and frame, and spiral membranes; each having its own distinct advantages and disadvantages in operation.
Polysulfone, polyamide, cellulose acetate, nylon, polytetrafluoroethylene, and polypropylene are some of the materials which are currently being used for making membranes [ 16 ]. The major classification of membrane processes corresponds to the size of particles they are able to reject in operation: Microfiltration rejects offshore processing options for oil platforms in the range: In the oil and gas industry, these processes are currently being deployed in different degrees for the treatment of produced water with a view to ensuring that stringent regulatory conditions are met.
In the application of this technique, it may sometimes be necessary to pass the influent through pre—treatment in order to remove large particles and free phase oil especially if a thin channel membrane is used. The membrane process is usually operated in a semi—batch cycle: Apart from the treatment offshore processing options for oil platforms discussed so far, produced water could also be treated with other technologies.
The technology applied for a particular kind of treatment is determined by offshore processing options for oil platforms factors which include desired final quality of the effluent water, available technical support, capital provisions for the project and the would be operating expenses and composition of the produced water etc.
The process of evaporation involves the vaporization of water molecules into the gaseous phase. Produced offshore processing options for oil platforms can be treated using this principle by providing latent heat to the produced water feed to generate vapor that would offshore processing options for oil platforms condensed into pure water form.
The liquid after evaporation contains high concentration of salts brine. In practice, produced water is initially de—oiled before it is subjected to the heat treatment. The energy cost for the technique could be very high for production process where much produced water is generated.