Oil has a very high demand all over the world since it is a major source of energy. Therefore, constant exploration and extraction to meet this demand is undertaken. Unfortunately, this exploration and extraction comes at a cost, with danger of causing loss of life, property and pollution of the environment.
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Prevention of oil pollution and disasters entails costly daily operations that integrate preventive measures into operations through planned industrial processes. Cleaning spillages after a disaster takes a lot of time and money not to mention that the damage that they cause is not completely reversible.
The best that we can do is to reduce its effects. However, disasters are preventable through careful design and extensive consultation before exploration of oil commences. That not withstanding constant maintenance and troubleshooting of oilrigs to avert the risk of a disaster is done.
Oil pollution has a devastating effect on the environment particularly on aquatic life not to mention the high cost of mitigating an oil spill disaster. Oil tankers, drilling rigs, petroleum products as well as offshore platforms may cause pollution when they release crude oil. In some instances, natural oil may pollute the marine environment if it seeps through fissures.
Therefore, to prevent incurring high costs and destruction of aquatic life it is important to prevent potential oil disasters by implementing sound mechanical engineering measures with a view of averting such risks. The various stages of well drilling, work over and repair operations present challenges since oil spills are likely to occur during these operations.
Purpose of the report
This report explores possible causes of disasters in oil drilling and the preventive measures that can be undertaken to mitigate these disasters. The report also evaluates actual disasters and attempts to outline their causes.
Preview of issues
The Macondo Deep Sea Horizon oil spill in the Gulf of Mexico in 2010 served as a wake up call for oil drilling companies. The disaster elicited an outcry from environmentalists and transferred a heavy financial burden on BP. This is just an example of the consequences of neglecting safety procedures in oil drilling. Prevention of engineering disasters is cheaper than dealing with the consequences of the disasters (Don 7).
There are two types of oilrigs; where in one drilling of oil is done offshore while in the other drilling is done on the land. The offshore drilling rig otherwise called an oil platform and is most prone to cause extensive pollution of the marine environment. The oil platform extracts and temporarily stores the crude oil before transportation to the shore for further refining.
These platforms also house the oil extraction workforce. The platforms may be floating, fixed or consist of an artificial island. According to how stuff works (2), the oil rig system has various components which include; power systems, mechanical systems for hoisting heavy loads and the drilling apparatus and the circulation system which pumps the drilling mud and expels rock cuttings.
Causes of oil disasters and prevention
Natural gas and crude oil under high pressure may cause blowouts during drilling causing loss of life, property and environmental pollution. A drilling fluid is pumped into the well bore to prevent natural oil from surging up the well the by creating hydrostatic pressure in the wellbore.
After completion of the drilling, a completion fluid with sufficient density to prevent escape of oil from the rock formation is filled into the well bore. However, the design of completion and drilling fluids must be ensure that they do not create excessive hydrostatic pressure that may cause wastage.
High hydrocarbon pressures are taken care of additives in the drilling fluid preventing aqueous fluid loss from the wellbore. An example of additive used is barium sulphate. If a well is rendered uneconomical after drilling and analysis of the amount of oil it can yield, leakage cementing the wellbore is done.
If the well is economical, for instance in the Macondo Deep Sea horizon, well a casing wider than the drill pipe is lowered into the well and cement slurry is pumped through the casing. This cement slurry also contains additives with retarders, which delay the rate of cement hardening until the desired location in the wellbore receives the cement slurry.
Tests are performed to determine whether hydrocarbons are entering the well bore once the cement is hardened. The test is then repeated a few hours. Squeeze cementing is done incase of leakages which involves sealing the leaking cracks in the well bore by injecting small amounts of cement slurry at high pressure.
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Memagazine website postulates that a blowout is a can be prevented by the use of a blowout preventer (3). Blocking the oil from escaping through the well bore is done by blowout preventer that closes the valves and seal the drill pipe and well casing by use of shear rams. Incase a blowout occurs a seal is formed by the shear rams that cut through and crush the pipe.
The shear rams have two blades each one at the top and the other at the bottom. The crushing of the drill pipe is occasioned by powerful springs that push the blades through it. A barrier is formed when the ram blades seal against each other thus preventing fluid flow. In deep waters, the blowout shear rams are designed to have sufficient power to cut through thick drill pipe which is usually thicker than the drill standpipe.
Transfer operations pose a great risk for disaster especially where a ship is used for transportation. Fuelling and defueling must be undertaken cautiously by examining and checking all piping systems for tightness and correcting all leaking glands, gaskets and seals. Spilling oil on the bilge while changing oil should be avoided as it may also result to oil pollution.
Centrifugal purifiers should be constantly checked while in operation to prevent loosing the water seal causing them to discharge the oil on to the bilge. Oil pollution may also occur during de-ballasting operations hence care must be taken to ensure that oil is not pumped overboard along with the water emanating from the ballast tanks. A sludge barge should be used to contain all oily waste. Prevention of oil pollution from ships is a complex task given the various sources of shipboard oily waste.
Therefore, control systems that prevent such pollution should be installed on ships consequently reducing pollution by reducing oil waste generation rates, storage and monitoring of oily waste, transferring oily waste to offshore facilities and processing the waste. Furthermore, all engineering personnel are trained thoroughly on the maintenance and troubleshooting procedures for oil pollution control systems.
On 20 April 2010, a disaster occurred on a drilling rig in Deepwater Horizon on the Gulf of Mexico. The semi-submersible drilling rig was as result of poor well design that resulted into a blow out and consequently an oil spill. This disaster was as result of inadequate cement between the production and protection casings. This disaster culminated into a severe environmental impact and efforts to stem the spill were by the use of an insertion tube. Furthermore, drilling of two adjacent relief bores that intersected the MC 252 well bore was effective.
Another disaster occurred in 1993 when an oil pipeline in Virginia ruptured spewing oil into the air to a height of up to 30m. Over 400,000 gallons of oil released polluted the environment severely (Cesar 2-5) due to pipeline material failure. The design of a pipeline must consider the conditions under which the pipeline is to be operating hence ensuring a viable choice of material properties for the pipeline.
Oil is a precious resource and the whole world for depends on it for the generation of energy. Its extraction and transportation is particularly risky because of the remoteness of oil reserves. Moreover, it is highly flammable calling for extra caution when handling this resourceful product.
From the time of exploration, extraction to transportation, due procedure must be followed while adhering to strict safety guidelines to avoid disasters. The personnel working at oilrigs must be thorough on safety procedures and response in event of a disaster. The material used for design of the oilrig must be tested and constantly checked for signs of failure and appropriate corrections undertaken.
Cesar, Azevedo. “Failure analysis of a crude oil pipeline”. ND, 2011. 22 November 2011, <https://www.sciencedirect.com/>
Don, Lawson. “Engineering disasters”. Lessons to be leaned. ND. ASME Press, 2004.
How stuff works. “Oil drilling”, 2010. Web. <https://www.howstuffworks.com/>
Memagazine.“Avoiding blowout”, 2010. Web. <https://www.asme.org/topics-resources/society-news/asme-news>