At The Treating Facility
When the oil is brought to the treating facility or "battery" the semi truck driver weighs his load before unloading and again when he is done unloading so the amount of the fluid taken from each individual well can be recorded. The trailer is unloaded by opening a valve at the bottom of the trailer and the oil is dumped into an underground tank called " the truck pit." A sample of oil is taken when being unloaded so the amount of oil, sand and water in each load can be verified because each individual well can vary greatly between amount of water and sand contained in the oil.
From the "truck pits" the oil is pumped into a tank called a surge tank. A demulsifier chemical is added to the oil emulsion mixture between the truck pits and surge tank, this chemical assists in separating the oil and water. The water which is at the bottom level of the surge tank is pumped off and is put into the produced water tank. The oil which now contains approximately 10% water is pumped from the surge tank into a heated vessel called a free water knockout. More demulsifier chemical is added to the oil between the surge tank and the free water knockout to assist in removing the water from the oil as it goes through the "treating vessels."
The free water knockout is a vessel that is 3m in diameter and 12m long. The function of the free water knockout is to take the majority of the water and sand out of the oil before is goes into a "treating vessel." The free water knockout has a burner in it similar to that in a production tank except larger. The oil emulsion goes into the top, at the burner end of the vessel and travels along the length of the vessel towards the opposite end. The burner heats up the oil to approximately 90oC temperature. The sand goes to the bottom of the vessel and is removed through the desand system. The water is drawn off the vessel at approximately 1/3 of the way up from the bottom (at the opposite end of where it entered the vessel) and is pumped into the produced water tank. The oil that is drawn off the vessel at approximately 3/4 of the way from the bottom now contains approximately 2% water and goes into a treater vessel.
The treating vessel or the "treater" is a cylindrical vessel that is very similar to the freewater knockout but is approximately 9m longer. The function of the treater is to take the water content of the oil to below 0.5% water so the oil can then be sold as "sales oil". The oil in the treater is heated to approximately 130o C and flows through the vessel in the same manner as it does in the knockout. It enters the vessel at the top at the burner end and travels along the vessel to the opposite end where the water is drawn off and pumped into the produced water tank. The oil then goes into a series of tanks called the "sales oil" tanks. From the sales oil tank the oil is pumped through underground pipelines to an upgrader or refining facility where further processing takes place to change the oil into a more marketable oil product.
The treating vessel is checked frequently to make sure a proper water/oil level is in the vessel and that an oil that is below 0.5% water content has been achieved before the oil is put into the sales oil tanks. Operators can change the volume of the flow through the vessel, the amount of demulsifier being added, the temperature of the vessel or the water/oil level in order to achieve the 0.5% or less water content needed.
The produced water from the production well
tanks, the surge tank and the treating vessels all goes into
the produced water tank at the battery facility. From there the water is pumped
back down underground into the dyna formation. This formation is approximately
650m deep and has very "loose"
sand in it making it easier to pump water into which is why it is used as the
disposal formation.
The produced sand that is cleaned out of the production tanks in the field is taken from the treating facilities' tanks and vessels. This sand is disposed of at the ExxonMobil Celtic facility by a sand disposal unit. This disposal unit is a high pressure pump driven by a 1400 horsepower diesel engine that is used to pump a mixture of produced water, produced sand and waste oil down into the same formation as the produced water is disposed of into (the dyna formation). Another way of disposing of produced sand is to take it to a location where there is an empty salt cavern and pump it down into the cavern. Produced sand has also been put on gravel roads to create a dust free surface.
As you can tell there are many different applications to bring the oil to a marketable state. First of all you have to find the oil and drill a producing well. This well must be complete with a well head, appropriate downhole pump, production tubing and surface facilities. These surface facilities include a flowline, pumping unit and production tank. This work must all be completed before the oil is even brought out of the ground. Once out of the ground this oil must be hauled to a treating facility where it undergoes several different treating processes before it is classified as sales oil and then shipped down a pipeline to be further processed. This whole oil production process involves many different people (doing many different jobs) all working together in order for this oil to be useable for individuals like you and me..