TREATMENT OF PRODUCED WATER TO MEET IRRIGATION STANDARD
INTRODUCTION
1.1 BACKGROUND
Produced water was defined by Veil et al. (2004) as saline water with hydro-carbons extracted from the rocks to the surface. The oil and gas industry is a combination of industries: oil, coal-bed methane and conventional non-associated gas producers. The aqueous effluent from such process operations is the largest volume stream in the oil and gas operation and exploration processes. Different types of fluids such as saline-water, oil and gas are held down by rocks in the sub-surfaces. The hydrocarbon compounds are saturated with saline water and then captured in the rocks. Due to the density difference, the hydrocarbons with lower density travelled to capture locations in rocks. This led the displacement of saline water. At certain thermodynamic conditions, saline water and hydrocarbons are absorbed by the rocks. Saline water comes from lower side, above and the flow within hydrocarbon zone. There is another type of water that comes with saline water referred to as “connate water” or “formation water”. Formation water is the water which is produced during the production activities by the injection of fluids and additives.
Table 1.1:Some of the possible options available for the management of produced water are
Options
Description
Avoid production of water onto the surface
Using polymer gels that block water contributing fissures or fractures or Downhole Water Separators which separate water from oil or gas streams downhole and reinject it into suitable formations.
Inject produced water
Inject the produced water into the same formation or another suitable formation; involves transportation of produced water from the producing to the injection site.
Discharge produced water
Treat the produced water to meet onshore or offshore discharge regulations.
Reuse in oil and gas operations
Treat the produced water to meet the quality required to use it for drilling, stimulation, and workover operations.
Consume in beneficial use
In some cases, significant treatment of produced water is required to meet the quality required for beneficial uses such as irrigation, rangeland restoration, animal consumption, and drinking water for private use.
Options
Description
Avoid production of water onto the surface
Using polymer gels that block water contributing fissures or fractures or Downhole Water Separators which separate water from oil or gas streams downhole and reinject it into suitable formations.
Inject produced water
Inject the produced water into the same formation or another suitable formation; involves transportation of produced water from the producing to the injection site.
Discharge produced water
Treat the produced water to meet onshore or offshore discharge regulations.
Reuse in oil and gas operations
Treat the produced water to meet the quality required to use it for drilling, stimulation, and workover operations.
Consume in beneficial use
In some cases, significant treatment of produced water is required to meet the quality required for beneficial uses such as irrigation, rangeland restoration, animal consumption, and drinking water for private use.
Increased agricultural production to feed the increasing world population and the everexpandingneed of industry, have made great demands on the limited water supply. The total global water (surface and ground water) is estimated to be 1,52 million km cubic from which, salty water (sea and oceans) 95-97%, polar water 4.2%. Hence, only 1% can be used and is available as surface and ground water.A reliable and suitable irrigation water supply can result in vast improvement in agricultural production and the economic vitality of the region.Irrigated agriculture is dependent on an adequate water supply of suitable quality. Water quality concerns have often been neglected because water supplies have been plentiful and readily available in the past, this situation is now changing in many countries.There is a steady increase of the amount of water used and wastewater produced by urban communities and industry. This poses potential health and environmental hazards. An effective way of treatment and reuse or disposal is necessary. At some time increased attention is being focused on agricultural plantations to make use of this water.
1.2 STATEMENT OF PROBLEM
Water produced during oil and gas extraction operations constitutes the industry’s most important waste stream on the basis of volume. The volume of water produced globally by oil and gas operations is staggering. The last major global study of produced water, dating from the late 1990s, estimated that the industry was bringing up 210m barrels of produced water each day. The produced water contains both dissolved and dispersed oil and these pose health hazards to human health and contamination of the environment.
Oil and gas production companies have always faced the problem of how to treat or dispose produced water. Stricter environmental controls have added pressure to the issue. High level of impurities make this water an unusable by-product. This project will address the issue of pollution caused by produced water discharge by treating the produced water to meet irrigation purpose.
1.3 AIMS AND OBJECTIVES
The aim of this project is to treat produced water to meet irrigation standard. The objective is to treat, analyse and compare produced water physico chemical parameters with Central Coast Regional Water Quality Control Board (CCRWQCB) criteria for irrigation and DPR standard for disposable water.
1.4 SIGNIFICANCE OF STUDY
Treated produced water has the potential to be a valuable product rather than a waste.Treating oil well produced water helps facilitate water management options for operators, such as beneficial uses that provide certain community and economic advantages. This project intends to tackle the problem of pollution pose by produced water by treating the water to meet irrigation standard.
1.5 SCOPE AND LIMITATION
This work will focus on using distillation and banana peel as a biosorbent to treat produced water from Umutu flowstation, Oredo flowstation and Oredo field. Only produced water from Umutu flowstation will be analyse. DPR standard and the Central Coast Regional Water Quality Control Board (CCRWQCB) water quality requirement for irrigation is the standard used, other standards were neglected.
CONCLUSSION AND RECOMMENDATION
5.1 CONCLUSION
Produced water is inevitable for oil and gas production, this offers both opportunities and challenges for sustainable recovery of hydrocarbon resources and water resources. Produced water has the potential to be recycled or re-used for many purposes. With proper treatment of produced water it has the potential to play a key role in relieving demand on natural freshwater systems and reducing pollution.The purpose of this research paper is to determine whether the produced water from Umutu flow station, Oredo flowstation and Oredo field that are being discharged can be treated to meet irrigation standard using banana peel. The bisorption studies with the peel showed that it can be used in the removal of oil (both dissolved and dispersed) from produced water providing above 96% removal at an equivalent dosage representing 300mg banana peel in produced water (from Umutu flowstation) after 30minutes exposure and initial oil concentration of 40.48mg/l. It is worthy to note that the use of banana peel alone cannot treat produced water to meet irrigation standard. To meet irrigation standard, the banana peel treated produced water has to be distilled.The concentration of contaminants in the treated water is within allowable limits as recommended by CCRWQCB criteria for irrigation and DPR standard for disposable water.
5.2 RECOMMENDATIONS
a. Produced water from Oredo flowstation and Oredo field were only treated but not analysed due to financial constrain, I hereby recommend that further work can be done in carrying out analysis for the produced water from those locations.
b. In order to use the treated produced water from Umutu flowstation for crop irrigation, since the treated water is slightly acidic the treated water can be mixed with an alkaline substance or be used on an alkaline soil to compensate for its slight acidity.
c. Water systems monitoring and its quality for a wide variety of contaminants should be carried out at schedules to verify that the water provided for crop irrigation meet standard. In addition, testing for contaminants should take place on varying schedules and at different locations throughout the water system.
d. There is usually a significant variation in seasonal water demand for agriculture but the treated produced water from oilfield operation is, however, generated continuously throughout the year. Surface or underground storage facilities should be put in place to store water generated during non-peak demand periods.
e. Farmers may be afraid to use this treated water for irrigation therefore significant effort has to be make in convincing the farmers to accept the recycled water source for irrigation.
f. Lastly the cost of treating and delivering the water must be compared with the benefit of increased oil production prior to implementation of this project.
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