Pollution: What Equipment BP Needs for Leakage Plugging?
On April 20, 2010, after the deep water blowout accident in the US Gulf of Mexico, BP took a number of rescue measures, most of which were first attempts. These rescue measures have important reference value for my country's deepwater drilling construction.
After the deep water well blowout accident happened in the Gulf of Mexico on April 20, 2010,.BP has taken several rescue measures including closing BOP with ROV separating seawater and crude oil with Macodome, separating seawater and crude oil with "top hat", drilling directional rescue wells, inserting oil conduit for oil suction, killing the well from the top "LMRP Cap" , and exporting crude oil from kill/choke pipeline, and many of them are first attempts. These emergency rescue measures are of important value as reference for the deep water drilling and construction in China.
Pollution: What Equipment BP
Needs for Leakage Plugging?
口China Classification Society/ Duan Mingxing, Li Mingliang, Chen Ruifeng, Wan Bo.
段明星 李明亮 陈瑞峰 万波／中国船级社
After the blowout in the Gulf of Mexico on April 20, BP took a series of measures to stop the blowout and reduce marine pollution. Some of these measures have a certain experience in use, and some are tried for the first time in deep water conditions; from the perspective of the use effect, some have completely failed, and some have achieved certain results; from the perspective of the implementation process, some have been completed, and some are in the process of implementation. . All these measures have important reference value for my country's deepwater drilling operations. In this paper, the above measures are divided into measures to prevent blowouts, measures to collect oil and gas from wellheads, and measures to treat oil pollution on the sea surface.
Measures to Stop the Blowout
"Underwater Robot" ---- Closing BOP with ROV
Since the evening of April 23, BP has used an underwater robot called ROV to close the underwater blowout preventer to prevent the blowout by setting the control panel on the blowout preventer body (see Picture 1). At most, 6 ROVs have been used at the same time, but this measure has been unsuccessful due to the failure of the underwater blowout preventer itself.
"Rescue Well"---Drilling a directional rescue well
The measure is to drill a directional well so that it intersects with the bottom hole of the well where the blowout occurred, use the static pressure of the liquid column formed by the heavier drilling fluid in the directional rescue well to suppress the blowout well flow, and then use cement to press the bottom of the well. Sealed to stop the blowout at all (see Picture 2). Directional rescue well technology is a mature technology with rich construction experience. With today's advanced steerable drilling technology and equipment, this measure has a high success rate. However, the construction period of the directional rescue well is relatively long, which takes 2-3 months.
On May 2, the Development Driller III, a semi-submersible drilling platform of Transocean Drilling Company, began to drill the first directional rescue well, and Development Driller II also began to drill the second rescue well on May 16. At the current rate of injection, the total amount of oil leaked is estimated to be 2 million barrels by the time the second rescue well is completed, according to Fox News estimates.
5月2日，越洋钻探公司的半潜式钻井平台Development Driller III开始钻第一口定向救授井，Development Driller II也于5月16日开始钻第二口救援井。据福克斯新闻网估计，以现在的喷油速度，到第二口救援井完工时，泄漏的原油总量估计将达到200万桶。
"Top Killing Method" --- Killing the Well at the Top
The top kill measure is to use high pressure to inject heavy drilling fluid into the wellhead from the kill/choke line located on the subsea blowout preventer, suppress the well flow, and then inject cement to seal the wellhead. On May 26, the drilling fluid did not flow down the wellbore during the implementation of the measure, but flowed into the sea through the broken riser. By May 29, BP announced that the measure had failed.
Measures to collect oil and gas from the wellhead
"Oil Barrier"---Isolate seawater and oil and gas with Macodome
The measure is to use a large cover called Macodome (see Picture 3) to cover the oil leakage at the end of the damaged riser, to isolate the oil and gas from the seawater, and then transport it through a pipeline connected to the top of the cover to The sea is transported away by oil tankers. However, when the Macodome, which went to the seabed on May 6, covered the leak, due to the high pressure and low temperature of the seabed, the gas hydrate generated by the natural gas ejected from the oil well and the seawater blocked the oil and gas outlet at the top of the cover, resulting in This measure failed.
"Small oil blocking cover"---use "top hat" to isolate seawater and oil and gas
BP learned from the Macodome's failure to create a smaller cover called a "top hat" that served the same purpose as the Macodome. The smaller volume of the "top hat" reduces the amount of seawater that mixes with the natural gas, reducing the potential for gas hydrate formation inside the cap. In addition, the top of the "top hat" has two pipes in addition to an oil guide pipe, which are used to inject heat medium and organic solvent into it to dissolve the natural gas hydrate formed. However, this measure has not been successful.
BP公司汲取了Macodome的失败教训，制造一个称为“top hat”的较小罩子，其功用与Macodome相同。“top hat”较小的容积减少了与天然气相混合的海水量，降低了罩子内部形成天然气水合物的可能。另外，“top hat”的顶部除了一支导油管还有两支管子，分别用来向其内部注入热介质和有机溶剂用来溶化化形成的天然气水合物。但是，该措施仍未能够成功。
"Siphon Method"---Insert the oil guide tube to suck oil
After two failures on May 14 and 15, BP finally inserted a 6-inch diameter oil conduit into the end of the broken 21-inch riser on the 16th. Through this pipe, more than 1,300 barrels of crude oil are collected daily. However, due to the top kill scheme implemented later, the inserted tubing was removed.
"Cap method"---LMRP Cap
On June 3, BP installed a cover called LMRP CAP on the top of the LMRP to collect part of the oil and gas ejected from the wellhead. It collected 15,000 barrels of crude oil and 830,000 cubic meters of natural gas per day. The oil and gas were collected on the Discoverer Enterprise and Massachusse barges. . However, because the device was made in a hurry, the cover was made of steel plates by tailor welding, and the pressure bearing capacity was limited. Moreover, there are multiple pressure relief channels, which cannot fundamentally prevent the well flow from blowing out (see Picture 4).
6月3日BP公司将一个称为LMRP CAP的罩子安装于LMRP的顶部，收集井口喷出的部分油气，日收集原油15000桶，天然气83万立方米，油气被收集到Discoverer Enterprise和Massachusse驳船上。但是由于该装置为仓促赶制，罩子由钢板拼焊而成，承压能力有限。且设有多个泄压通道，不能从根本上遏止井流喷出（见图4）。
Export oil and gas from kill/choke lines
The measure, which was implemented on June 16, is to use the manifolds and pipelines of the previous top kill to guide the oil and gas ejected from the underwater wellhead to the Q4000 work over platform on the water surface and burn it directly. The daily collection of crude oil is up to 10,000 barrels, and the collected oil and gas are directly burned.
Use a second set of blowout preventers to seal wells and export oil and gas
On July 10, BP removed the LMRP Cap and replaced it with a wellhead shut-off device consisting of a transition short and a second set of blowout preventers (see Picture 5). The device can close the wellhead and deliver the oil and gas ejected to multiple vessels on the surface through a self-floating riser. The installation of the device was completed on July 16. Before the author's publication, the three sets of rams of the device have been closed and the sealing test is underway. So far, no oil and gas have been sprayed into the sea.
Long-term plan to collect oil and gas
On July 10, BP unveiled a long-term plan to collect oil and gas spewing from wellheads on the ocean floor. (See Picture 6) Oil and gas from the second set of blowout preventers are guided to two drillships through self-floating risers for collection. A portion of the oil and gas collected in the kill/choke line is collected by the self-floating riser on board the Toisa Pisces for processing, and the other portion enters the CDP manifold. The oil and gas output from the CDP manifold is led to the Helix Producer ship through a self-floating riser, and the other pipeline leads to a subsea unit that stores carburetors. The device can handle the oil and gas spewing from the wellhead when hurricane weather arrives and surface ships are evacuated. When the entire unit is in normal operation, its crude oil processing capacity will reach 60,000 to 80,000 barrels.
7月10日，BP公司公布了一项收集海底井口喷出的油气的长期计划。（见图6）第二套防喷器装置中导出的油气通过自浮式立管导引至两艘钻井船上收集起来。压井/节流管线的收集的油气一部分通过自浮式立管收集Toisa Pisces 号船上进行处理，另一部分进入CDP管汇。CDP管汇输出的油气一路经自浮式立管引至Helix Producer号船上处理，另一管路通往一个储有化油剂的水下装置。该装置可以在飓风天气到来，水面船只撤离时处理井口喷出油气。整套装置正常运行时，其原油处理能力将达到6~8万桶。
Oil slick treatment
For the treatment of oil pollution on the sea surface, the work mainly focuses on the protection of the coast and the treatment of oily sewage on the sea surface. The measures used to treat oil pollution on the sea surface are to spray carburetor on the sea surface to decompose the crude oil, or use an oil boom to gather the oil layer in one place, and then collect it for treatment and recycling, or directly burn it on the sea surface (see Picture 7).
Analysis of various measures
The story of the blowout happened suddenly, and the relevant parties were not sufficiently prepared. Although various rescue measures were used, they failed to stop the oil and gas from being sprayed into the sea in a short time. The problems exposed and accumulated experience during this period are worthy of summarization and research by the industry.
Among the measures to stop the blowout, the costly top kill measure ultimately failed due to an underestimation of well flow pressure. The directional rescue wells that have been drilled successively are the fundamental measures to solve the blowout, but the implementation period of this measure is long, and if there is no effective measures to control and bury the spewed oil and gas during its implementation, it will still cause serious losses.
Among the various measures for exporting oil and gas from subsea wellheads, except for the successful implementation of the second set of blowout preventers to seal wells and export oil and gas, the other measures were hastily formulated and implemented immediately, and they were not completely Stop oil pollution of the oceans. BP's long-term plan for oil and gas collection takes into account the impact of hurricane weather and enhances its ability to handle oil and gas. If the plan can be implemented normally, it will produce good results.
The treatment of sea slop oil is mostly conventional methods. But this is a long-term job that requires mobilizing a large number of ships and aircraft, mobilizing a large number of people, and consuming huge amounts of money.
The so-called "stones from other mountains can attack jade", our country should also learn from the experience and lessons accumulated in the handling of this accident, systematically study and formulate emergency plans for dealing with deep water blowout accidents, and establish a corresponding coordination mechanism to ensure that my country's oil industry develops into deep water. The sea has entered the sea smoothly.
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Rescue measures, oil and gas collection measures, sea surface oil pollution treatment measures, ROV shut-down blowout preventer, drilling directional rescue wells, top killing wells, cement plugging wellheads, isolation of seawater and oil and gas, natural gas hydrate, oil blocking cover, siphon method, guide Tubing suction, capping method, kill/choke lines, second set of blowout preventers, long-term planning, handling of oil slicks on the sea surface, analysis of various measures.
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