TREATMENT OF PRODUCED WATER TO MEET IRRIGATION STANDARD
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
|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.