In the world of energy, the image of flames flickering brightly day and night on oil rigs is always a familiar symbol. Many people mistakenly believe that this is a sign that oil is being burned directly. However, the truth contains many interesting details and issues that deserve more attention.
Oil is often referred to as the “blood of industry.” Gasoline, plastics, synthetic rubber, lubricants… are all products derived from oil. In our daily lives, it can be said that everything is inseparable from oil.
I believe that everyone has seen this on TV or the Internet: When extracting oil, one or more tall pipes are placed next to the oil well, and the mouths of these pipes continuously spew flames.
Many may think that the purpose of these flame-spewing pipes is to burn off excess oil or to assess whether the newly extracted oil meets purity requirements.
In our daily lives, it can be said that everything is inseparable from oil.
However, that is not the case. If we want to check the purity of the oil, we only need to take it back to a laboratory for testing; there is no need to install pipes to keep the oil burning.
Before answering this question, we need to understand how oil is extracted. In fact, during the drilling of an oil well, a casing will be installed in the area drilled by the drill bit. The purpose of this casing is to maintain the stability of the wellbore and ensure that the well does not collapse.
When the drill bit reaches the depth of the oil layer, an oil pipe will be lowered into the oil layer, and the other end of the pipe will be connected to oil-leading equipment and valves. If we want to bring oil from underground to the surface, there are currently three common methods.
When drilling an oil well, a casing will be installed in the area drilled by the drill bit.
Method One: Using the Pressure of the Oil Layer
At the depth where the original oil is found, there will be very high underground pressure, and this pressure remains balanced when no drilling is taking place. After drilling is complete, this balance is disrupted. Under pressure, oil will continuously spout from the well. This is known as an “artesian well.”
Method Two: Water Injection and Pressure Creation
After the oil has been self-pumping for a while, the pressure in the formation will decrease, and the amount of oil spouting will gradually diminish or even stop. At this point, it is necessary to open another well next to the oil well and inject water. Water is used to fill the remaining space due to oil extraction, maintain underground pressure, and allow the oil well to continue to spout.
Method Three: Using Oil Pumps
In some oil fields, the underground oil can be so thick that it cannot be pumped out even when the underground pressure is high enough. At this point, a pumping unit is needed to bring the oil to the surface. Each time the pump moves up and down, oil is lifted. Controlled by a one-way valve, the pumped oil will not flow back. Simply put, the principle of operation of the oil pump is similar to that of a water pump commonly used in rural areas at water well openings.
What is extracted from the ground is not just oil.
So why are there always “eternal” flames on oil rigs?
In reality, what is extracted from the ground is not just oil but also other substances. For example, associated natural gases, water, etc. After oil extraction, associated natural gas and water are completely separated from the oil through separation technology. Oil and water are stored in special tanks, while the associated natural gas is consumed through combustion and ignition processes.
Therefore, the pipes continuously spewing flames at oil fields do not burn oil but rather burn associated natural gas.
The pipes continuously spewing flames at oil fields do not burn oil but rather burn associated natural gas.
Contrary to popular belief, the flames on the oil rig are not caused by the burning of oil. In fact, the extracted oil is transported to storage, while the accompanying natural gas (associated gas) is the “master” of these flames.
The reason for burning associated natural gas primarily relates to safety. Associated natural gas is a colorless, flammable gas. If it enters the atmosphere and reaches a certain ratio with air, it can explode when it comes into contact with a flame or natural phenomena.
Once an explosion occurs, it poses a danger to personnel and equipment at the oil extraction facility, and if severe, it can ignite the extracted oil, causing even more serious consequences. Therefore, for safety reasons, associated natural gas is led up high through pipes and burned off through ignition devices.
Associated gas mainly consists of methane, a flammable gas that is dangerous if leaked. To ensure safety, this gas is collected and directed to a combustion system, where it is safely burned off in the atmosphere, eliminating the risk of fire and explosion while protecting the environment.
Collecting associated natural gas during the oil extraction process is an act of “wasting effort.”
Why not collect and utilize associated natural gas instead of burning it wastefully?
The main answer is that collecting associated natural gas during the oil extraction process is an act of “wasting effort.” The output of associated natural gas in oil reservoirs is very low. Each ton of extracted oil typically only comes with dozens to hundreds of cubic meters of associated natural gas.
If one wants to recover this associated natural gas, a large-scale project would need to be implemented, requiring a significant amount of machinery, equipment, personnel, and funding. From an economic perspective, recovering a small amount of associated natural gas is completely cost-ineffective.
