Two cases study as method
A case study methodology is adopted for two oil fields. The study is in two oil companies, Mellitah Oil and Gas (MOG) Company and Royal Dutch Shell. The study focuses on how produced water is treated and disposed of in each of the companies.
Mellitah Oil and Gas Company ; Bu Attifel Oil Field
The Bu Attifel Oil Field is one of the largest reservoirs under exploitation by the MOG which has advanced in the separation of water which would otherwise be the main contaminant to the oil produced. The company has 39 wellheads and associated flow lines which are connected through a gathering system to a center where oil & and gas and water separation and stabilization is done. The system is designed to such that it achieves the required crude oil characteristics and specifications necessary for separating the gas and water contained in the well fluids. The process of separation consists of three stages where at the end, each of the three constituents from the well is channeled to different storage units (BU Attifel Field 2010).
During the first stage, the gas and liquid content from the wellheads are whereby the gas is routed to two directions after measurements of the pressure level; one goes to the Meter Bank while the other is conveyed to the high-performance flares. The liquid is discharged into the second stage for under the right pressure and temperature. During the second stage, gas, oil, and water are separated in and horizontal vessel. The gas is fed to medium gas comprehension or in some instance to the flare while the two liquids which form an interface by the virtue of the different densities are discharged separately through control valves. The water is sent to a flash tank for degassing and then to a skimmer before discharging it into a dessert pit. The liquid oil continues to the final stage of the process.
The third stage which is also the final stage is designed for advanced gas, oil and water separation. The gas received flows to the medium comprehension stage while the oil and water are separated just like in the previous stage. Oil is then sent to the storage tank while the water is measured, taken to the degassing chambers before finally disposing it into the desert pit. During the three stages, pressure and temperature are regulated precisely since they determine a lot the refined level of the three constituents from the wellheads. The amount received at each stage is measured to keep a consistency of the percentage achieved for each of the stages (BU Attifel Field 2010).
The highest percentage of water is received from the 2nd and 3rd separation stages with the little amount being received from the discontinuous streams in the storage tanks, a flash tank, and L. P. G. C plant separators. It is worth noting that the water received is oily which should first be treated before being discarded in the desert pits. The maximum water expectation based on the design capacity is 65, 000 BPD which constitutes around 33% of the cut from the Bu Attifel Oil Field. A number of hydrocarbons in the water sample at the end of the process varies greatly with samples taken from the company data sheet showing as low as 56 mg/l and as high as 108 mg/l.
Water separated from Bu Attifel Oil Field is considered a useless waste which is discarded off in desert pits. M.O.G has no measures or alternatives that can the water become a useful by-product from the wellheads. It is also worth noting that the heating system that is required to maintain the content at the right pressure and temperature incorporated water which is sourced a fresh. The technology used determines a lot about the water quality that M.O.G produces and it is debatable whether the quality of water received at the end of the process is the best that possible. There were wide discrepancies between the volumes in a given month, which apart from being attributed to the source, can also be as a result of the approach used (BU Attifel Field 2010).
Royal Dutch Shell
The Royal Dutch Shell commonly referred to as Shell is an Anglo-Dutch oil and gas multinational companies with headquarters in both London and Hague. It was as a result of the merger between Shell- Max and BP in 1976 when the companies, having been operated separately joined forces amid tuff economic conditions. In the United Kingdom, the company still uses the original flag bearer and is among the leading oil and gas production companies. The main wellheads are situated in the North Sea where drilling and extraction are done and transported to on-shore for separation and further refinery (The Shell United Kingdom, 2016). In Shell fields, oil-water separation is achieved through Corrugated Plate Interceptor which among other advantages has the highest efficiency and very cost-effective.
CPI was developed by using Shell’s technology which was originally developed by Hazen and Camp based on specific gravity to separate the oily wastewater in treatment plants. Currently, a few changes have been developed whereby the plastic packing are placed in parallel to enhance the gravity separation. It consists of corrugated plates that are angled at 45 degrees to the horizontal to allow for the separation to occur which are placed in a basin like a vessel. The basin is then equipped with adjustable effluents and oil weirs. The CPIs chambers are built underground with series of units that the produced water moves before it being cleaned as wastewater for discharging (Chiyoda Corporation 2016).
The mode of operation is quite simple since unlike conventional methods, there is no need to break the oil droplet unnecessarily; the oil is fed to the system by gravity. In cases where there might be solid waste. The influent flows into a quiescent zone located in the ahead of the CPI packing. For effective separation, the liquid should be slowed down to have a laminar flow by the time it reaches the CPI. The liquid with the lighter specific gravity (density) rises to peaks of the corrugation and continues to rise till it reaches the troughs located at the inlets. At this instance, it flows unimpeded by the primary flow into the bucket. The heavier liquid will then flow out through the lower sections of the pack into the effluent trough (Zuniga 2014).
Further treatments are given to the effluent to remove dissolved gasses from a floatation chamber at atmospheric pressure. The wastewater is placed in above 6’ containers for a retention period of between 10 and 40 minutes to tap out any gas dissolved due to the induced pressure.
Oil exploration and production are controlled by one of the most elaborate structures in the country. The Oil & Gas, UK, is chartered with the responsibility of drafting the rules and regulation which must be followed by the respective companies. The body also acts as a watchdog to ensure that the rules are followed to the letter and even provides relevant information concerning the geological and seismic surveys, productions, offshore & onshore water storage and transfer and any other relevant information (Oil & Gas, UK).
From the above cases, it was observed that a lot of wastewater after the oil-water separation is discarded. In the scenario for Bu Attifel, the by-product is channeled into desert pits which can be considered to be some form of waste. There are international guidelines on conservation as stated by the United Nations and Environmental Program which is complimented by additional national policies on water management (UNEP, 1997). If these regulations are met during the treatment process, this water can find use in various ways either in the oil company or related plants. This research has outlined some ways in which this by-product can be used in a more economical way rather than having to discard it out in the desert. These solutions are discarded below.
Solution 1: To sell the produced water as a by-product of the oil field
During oil extraction, water can constitute to more than 33% of the product that is brought to the surface (Bu Attifel Field 2010). In some instances especially in offshore drilling, this amount can be even above 50% which should be separated from the oil before any further refinery process can take place. Water tables are known to lie at shallow depths compared to the oil rigs hence in many cases, the drill bits must pass through this zone before they can reach it. On financial grounds, it presents an additional cost to the exploration and production process since it has no economic value to the company. Water has been identified as a major factor that is considered in exploration as it is a key determinant of the whole process.
It is also interesting to note that oil well centers consume a large amount of water. Water is integral to all industrial process and a fundamental necessity for the survival of the labor force in the work environment. To maintain the extracted oil at the right temperature in the piping system, hot water I pumped through concentric pipes. It also injected into the wells to heat the oil to the less viscous status which will then be pumped to the surface. The overall plant maintenance also requires water for cleaning operations. In many wells, they drill separate wells specifically for water that will be used for these and other purposes including human consumption (Arthur, Langhus and Patel 2005).
From an analytical point of view, it can be seen that this is an extra overhead cost which has absolutely no returns. Apart from the initial drilling process of a water supply well, there are additional costs associated such as maintenance of the submersible pumps. The study proposed that the wastewater which is dumped in desert pits can be used for the above purposes rather than having to incur an extra cost in finding a water source. It has the advantage of being readily available and the fact that it is a by-product of the extraction process would be considerably low. There are specifications which have been set forth by governing bodies such as ISO rules and regulations which set forth the standards to be adhered to in a safe working environment. It is the strong belief of this study that the cost of purifying the waste water to attain such recommendation is far less compared to the having to drill a water well.
In other cases, it is even possible to sell this wastewater to nearby oil fields for use in their operations. If such cases, the by-product would become a source of revenue to the plant. Irrespective of the use, it can be seen that the wastewater has a potential of reducing the operational cost of the plant if it covers the water aspect of the whole process or can even be a source of income to the plant. Being able to sell oil, gas, and water can be a great investment to the plant.
Solution 2: Utilizing the water after treatment in the re-injection in reservoir
Extraction of oil from long depths is not an easy task. On normal scenarios, only about a third of the total reservoir can be brought up to the surface hence the need to come up with the option to be able to exploit the maximum possible. The extraction process creates a void which should be filled so that the recovery process can be continued. Since the drill hole is central, there are sections within the reservoir which are far from reach presenting a problem of how to reach it. In normal cases, water is pumped to fill the void, create the necessary pressure and push the oil toward the wellhead to boost further recovery from that particular reservoir. The water is sought from outside sources, taken through the necessary treatment before it can be pumped as required (Zuniga 2014).
This presents another cost to the plant as the water, river water or in other cases, separate water well is drilled to cater for the demand. Wastewater can function quite well for this purpose since in the first place it requires minimum treatment so that it can meet the standards required. If see water is used as an alternative, it undergoes a purifying process to remove any compound that can be corrosive or course scaling on the pipe used. The process of creating dessert pit is just an unnecessary cost on discarding the water there can affect the seasonal water points. To counteract this pollution, the company must alternative between the seasons to ensure that there is the minimum interaction of the waste water and the rain water. Even with such careful disposal, it is a must to treat the wastewater to meet certain regulations set by the environment.
The surest and safest of discarding the by-product is through re-injection. In any surface discarding, the wastewater can sip into the ground and with time mix with other water bodies posing a threat to living things. It will also help maintain the serenity of the area as no unnecessary pits will be dug to create a reservation. After the possible oil has been recovered, the water will have been returned from the very source where it was obtained in the first place.
Solution 3: Use the latest technology to obtain less contaminated water for safe disposal to the environment.
Governmental and nongovernmental organizations, as well as the corporate world, are becoming increasing conscious about the environment with the case from all corners about the need to conserve the environment. One of the ISO charters, ISO 14000, is purely about environmental management (ISO, 2016). Countries like the United Kingdom have set forth the national standards which oil exploring companies to adhere to before, during and after the recovery of oil in the environment. Companies which fail to observe such rules and regulations face strict penalties and in some cases, their activities banned in the country. Petroleum and petroleum by-products pose one of the greatest threats in the event of water and land pollution. The reclamation process is quite difficult and such pollution can declare a given species extinct within a short duration even before the process has kicked off.
Ensuring that the water from the oil heads can be safely released to the environment has been the greatest challenge to oil exploring companies. This is the main reason why Bu Attifel Oil Field under M.O.G sought the later option of having to dig the pits in the desert to dispose of it. However, water is becoming a rare commodity around the globe and Libya having a large percentage of the land mass being a desert, it can be treated to a level that makes it salable or usable for irrigation purposes. The process has been difficult in the past but with the current technology, it is possible to have it purified to level whereby it can be used for general household chores and farming.
In the modern world, every resource should be used for the maximum benefit that it can offer to the human population and discard wastewater should be a thing of the past. Meeting the standards can be quite achievable compared to the recent as technology has explored more avenues for reaching the said standards.
Solution 4: Other Alternatives
It is possible to avoid the production of the wastewater to the surface. Polymer gels can be used to block the water contributing fissures during the drills process hence reducing the amount of water that mixes with the oil in the first place. Downhole Water Separators can also be used to separate the water from oil/gas streams and re-inject it into the suitable formation (Zuniga 2014). This option, however, elegant it might sound is not quite possible and might come along with certain challenges depending on specific factors of the wellhead.
Each of the above solution given as an alternative to having to discard the by-product in dessert pits comes along with its own challenges, with some suiting a given environment compared to the rest. In actual execution, it is recommendable that a weighted approach is used to compare and contrast them before landing to the specific alternative. In the 21st century, it is very unfortunate to find such old methods of dealing with wastes. They add no value and when the world is facing limited resources, appropriate use of water should advocate. There are means and ways that can be used to make wastewater beneficial in different aspect depending on economies and the immediate need. It is, therefore, necessary to harness such water since it is readily available and use it for the best available option. The list might not be exploitive and there could be more options that can be used to achieve the same results. Irrespective of the method, the benefits are numerous which range from economical to technical and even environmental.
Arthur D, Langhus BC, and Patel C, (2005). Technical Summary of Oil and Gas Produced Water Treatment Technologies, ALL Consulting, LLC.
Bu Attifel Field (2010). Operating Processes, Melitah Oil and Gas B.V, Libya Branch
Bu Attifel Field (2010). Produced Water Systems, Melitah Oil and Gas B.V, Libya Branch
Bu Attifel Field (2010). Water Samples from API separator – S560, Melitah Oil and Gas B.V, Libya Branch
Chiyoda Corporation (2016). CPI Oil Separator. Retrieved from https://www.chiyoda-corp.com/technology/en/environment/cpioilseparator.html on August 15, 2016
Shell United Kingdom (2016). ENERGY FROM DEEP WATER. Retrieved from http://www.shell.co.uk/energy-and-innovation/energy-from-deep-water.html#iframe-L3dlYmFwcHMvZGVlcF93YXRlci92Mi9pbmRleC5odG1s on August 15, 2016
UNEP, (1997). Environmental management in Oil and Gas production, UNEP Technical Publications.
Zuniga, (2014). Separation Technologies in Oil and Gas Production, Norges teknisk-naturvitenskapelige universitet.