Well Blowout: Well Control Equipment Fails Accidentally
Well Blowout: Well Control Equipment Fails Accidentally?
口本刊记者/王云建 Reporter/ Wang Yunjian
中国船级社/段明星 李朋亮 陈瑞峰 万波China Classification Society/Duan Mingxing Li Pengliang Chen Ruifeng Wan Bo
As of the publication of this issue, more than 100 days have passed since the U.S.-Mexico oil spill. The incident is still under investigation, and no matter what the final official explanation is, it is certain that this disaster was a rather serious "blowout" accident in the history of human offshore oil and gas development.
Who opened the blowout "magic bottle"?
What is a "blowout"? In the process of drilling and workover, when the liquid column pressure in the well is lower than the formation pressure, the formation fluid will enter the wellbore and flow to the wellhead. If there is natural gas in the formation fluid, the natural gas will slip under pressure and rise rapidly, and the volume will expand rapidly. If no effective measures are taken to control it, the formation fluid will flush out of the wellhead and cause a blowout. When there is an ignition source near the wellhead, it is very likely that a fire will cause a tragedy, destroying the oil reservoir, wasting resources and polluting the environment. Around 22:00 on April 20. This is what happened on the Gulf of Mexico platform.
In the story of "One Thousand and One Nights", the fisherman accidentally caught a magic bottle and accidentally released the devil. For oilfield operators, a "blowout" is like opening a "magic bottle" unintentionally. Although the probability is small, once opened, the consequences are serious. However, how was the "magic bottle" of the oil well in the Gulf of Mexico opened?
Since the explosion of the platform in the Gulf of Mexico, the incident has attracted great attention from relevant units in China, including oil companies, oilfield technology service companies, universities and scientific research institutes. Some technical experts, scholars and technicians have collected a large amount of foreign information, conducted many technical discussions, and have been paying attention to the latest progress of the event. At present, the accident analysis mainly focuses on the process operation on the day of the blowout. According to the normal operation process, cement plugging is a process in the well abandonment operation. But before, the pressure dropped after the seawater replaced the mud, and a terrible disaster occurred in this link.
"The technology of offshore oil exploitation is complex, and any small mistake may have catastrophic consequences," China National Petroleum Offshore Engineering Company said after analysis. "As long as the drilling rig in the Gulf of Mexico where the explosion occurred, the accident can be completely avoided. , Zhou Shouwei, deputy general manager of China National Offshore Oil Corporation and academician of the Chinese Academy of Engineering, believes that "if the technology and design operations are strictly followed, the probability of such a major accident would have been very small."
"The Gulf of Mexico accident was an explosion caused by a well control problem," a technical expert pointed out. In addition to the major suspicion of process operation, as one of the effective measures for 'three-level well control' to prevent oil leakage, the blowout preventer system Well control equipment such as , diverter system is the second important line of defense to prevent blowouts. But in this accident, the blowout preventer failed.
Based on this, it is speculated that on April 20, the deepwater drilling platform in the Gulf of Mexico lost its defense because of the first two lines of defense, and the "magic bottle" was opened in an instant....
The "crime and punishment" of deep water well control equipment?
After the oil spill, according to foreign media reports, some experts and people raised serious doubts about the defective design of the cement "shell", the use of high-risk casing, the failure of the blowout preventer and the failure of the automatic backup system. On May 11, BP, Transocean Drilling, and Halliburton attended the U.S. Congressional hearing for the first time. When being questioned, BP accused Transocean Drilling of its blowout preventer in court, and the other two companies also pointed the finger at it. Point directly.
The truth will always come to light. Experts pointed out that deepwater oil and gas development has huge risks and many challenges. Even as a reflection on normal events, the industry should check and self-examine themselves. For the oil equipment manufacturing industry, it should also appreciate the pain of "scraping bones" of others.
As a "safety equipment", the deep water blowout preventer system is the core well control equipment. Its function and reliability are related to the safety of personnel and property in deep water oil drilling, as well as the protection of the marine environment. According to industry insiders, in addition to the blowout preventer system, the deep water well control equipment also includes a diversion system, a well killing/throttling system and a well flow treatment system. As well as high pressure mud systems and cementing systems associated with well control operations. If you operate the raccoon, blowout accidents can be completely prevented and dealt with.
According to reports, the platform explosion accident occurred before the last cement plug was injected during the well abandonment operation. The deepwater BOP group used at that time had a combination of subsea wellhead devices: wellhead connector + test ram + lower variable diameter ram + upper Variable Diameter Ram BOP + Casing Shear BOP + Shear Shear Ram BOP + Lower Annular BOP + Riser Connector + Upper Annular BOP + Flexible Joint + Riser adapter (Figure 1). The rated pressure of the ram BOP is 103.4.2MPa, the rated pressure of the upper annular BOP is 68.9SMPa, and the rated pressure of the lower annular BOP is 34.47MPa. The BOP control system is produced by CAMERON, except that it has no voice-activated backup system, it has emergency release function, automatic shear function, automatic shutdown function (Dead man System) and remote control vehicle (ROV) operation function (Picture 2).
据介绍，平台爆炸事故发生在弃井作业注最后一个水泥塞之前，当时所用的深水防喷器组其海底井口装置组合为：井口头连接器＋测试闸板＋下可变径闸板＋上可变径闸板防喷器＋套管剪切防喷器＋全封剪切闸板防喷器＋下环形防喷器＋隔水管连接器＋上环形防喷器＋挠性接头＋隔水管适配器（图1）。闸板防喷器的额定压力是103.4.2MPa，上环形防喷器的额定压力是68.9SMPa，下环形防喷器的额定压力是34.47MPa。该防喷器控制系统由CAMERON公司生产，除了没有声控备份系统，它具有应急解脱功能、自动剪切功能、自动关闭功能（Dead man System）和遥控潜水器(ROV)操作功能（图2）。
Technically, this deep water BOP system is powerful. The emergency release system can quickly separate the drilling platform from the wellhead in an emergency. After the automatic shearing system is set to the active state, it can automatically close the wellhead when the lower riser assembly (LMRP) and the blowout preventer group are abnormally disengaged. The automatic shutdown system can automatically start the blowout preventer to close the wellhead when the underwater blowout preventer loses control signal transmission and hydraulic supply. The ROV operating system can operate the BOP through the control panel located on the underwater BOP body.
But the actual situation is just the opposite. When the blowout occurred, the failed blowout preventer failed to close the wellhead; because the upper and lower parts lost contact, the emergency relief system failed to start; after the platform sank, the ROV operating system also went out of control. In an emergency, a group of 450-ton high-tech blowout preventers were instantly "frozen".
Is it too late to "repair the dead sheep"?
After the accident, all parties conducted investigation and research on the failure of the blowout preventer, and found that there were many problems with the blowout preventer used in the accident well. For example, in this accident, the emergency release system failed to start, indicating that the control line between the platform and the underwater blowout preventer was damaged, and the operation command could not be transmitted to the actuator. In terms of functional settings, the blowout preventer does not have a voice-activated backup system (using sound wave transmission to control the blowout preventer device), and unlike the regulations in some countries such as Norway, the United States did not mandate this system before the accident.
In addition, according to the periodic investigation reports of the parties involved in the accident, there are many problems with the blowout preventer itself. First, after the hydraulic system of the blowout preventer is modified, the hydraulic pipeline that should be connected to the variable diameter ram is connected to the test ram. , and the content of this modification is not documented in writing. Second, there were multiple leaks in the hydraulic system of the blowout preventer, and one of the two subsea control boxes lost part of its function. Finally, the rubber parts of the blowout preventer were severely damaged during drilling operations. Large pieces of rubber were found in the mud that returned.
In response to the failure of the blowout preventer exposed by the accident, the U.S. Department of the Interior Mineral Management has made a number of strict regulations on the deep water blowout preventer. The main contents include: requiring operators engaged in offshore drilling to review past operations to ensure that their well control equipment complies with federal regulations; The function conforms to the original design; an independent third party is required to prove that the BOP system is compatible with other equipment on the platform and compatible with the construction well; the deep water BOP is required to be equipped with ROV operating system, automatic shearing system, and automatic shutdown system and voice-activated backup system, and test the ROV operating system; and require an independent third party to prove that the fully enclosed shear ram can cut all sizes of pipe strings in the wellbore.
The main suppliers of underwater blowout preventers are Cameron, Hydril and Shaffer. At present, the new generation of deep water blowout preventers has made new breakthroughs in the pressure compensation of underwater accumulators, the enhancement of ram closing force and the monitoring of control circuit faults. The accident will be able to re-examine the reliability of the relevant performance, and will provide an important reference for future technological development.
水下防喷器的主要供应商有Cameron 、 Hydril和Shaffer。目前新一代的深水防喷器产品，在水下蓄能器压力补偿、闸板闭合力增强和控制线路故障监控等方面又有新的突破。此次事故将得以从新审视相关性能的可靠性，对今后技术发展将提供重要借鉴。
Deep water oil drilling in my country is in its infancy, and domestic research on deep water BOPs has just been carried out. This accident has important implications for the use and research of deep water BOPs in my country: in the functional design and selection of BOP systems, The requirements of the deep water marine environment for well control operations should be fully considered, an emergency control system that meets construction safety requirements should be set up, and the reliability of the BOP system should be enhanced; BOP test technology; learn from the experience and lessons of this accident, and improve the regulations, technical specifications and supervision mechanisms related to deep water well control.
The lessons from the oil spill in the Gulf of Mexico may rewrite and improve the market access standards for well control equipment. "It's not too late to make amends." For manufacturing companies, it may usher in the next development opportunity.
Gulf of Mexico Incident Platform and Well Archives
["Deep water Horizon"]
Deep water Horizon is a fifth-generation semi-submersible drilling platform designed by R&B Falcon with a working water depth of 2,438 meters and a drilling depth of 9,144 meters. The daily rent is $533,000. On September 2, 2009, the world's deepest oil well was drilled at 10,683 meters.
Deep water Horizon号为第五代半潜式钻井平台，由R&B Falcon设计，工作水深2438米，钻探深度9144米。日租金53.3万美元。2009年9月2日，钻探了当时世界上最深的油井10683米。
The platform started construction in December 1998 and was delivered by South Korea's Hyundai Heavy Industries in February 2001. The cost is 3.65 US dollars, and the current market price is about 560 million US dollars. It has a displacement of 52,587 tons, a length of 121 meters, a width of 78 meters, a height of 97.4 meters, a draft of 23 meters, a total installed power of 42 megawatts, and a capacity of 130 people. The outer diameter of the riser is 21 inches, the platform weight is 32,588 tons, and the displacement is 52,587 tons. It is dynamic positioning for the DP-3.
[Accident oil well]
Well 252#-01 in the Mississippi Canyon block is located in the Maconda exploration area in the Louisiana state of the United States. The Macondo structure is an exploration vertical well; the drilling depth is 5596 meters, and the urban water depth of the operation area is 1544 meters. On April 22, 2010, the Deep water Horizon sank 400 meters northeast of the wellhead.
密西西比峡谷区块252#-01井，位于美国路易斯安那州海洋Maconda探区，Macondo构造，属于勘探直井；钻探深度5596米，作业区城水深1544米。2010年4月22日，Deep water Horizon号沉没于井口东北方400米。
[Operators and Contractors]
BP has a 65% interest, the US Anadarko Petroleum Company and Japan's Mitsui & Co. have 25% and 10% respectively. Operating water depth: 1524 meters; Offshore distance: 77 kilometers; Oil company: BP; Drilling contractor: Transocean; Cementing service company: Hardan Bojie; Subsea BOP supplier: Cameron company.
At the time of the accident, there were 126 people on the platform, including 79 employees of Transocean Drilling Company, 6 employees of BP and 41 employees of contractors.
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blowout, well control equipment, liquid column pressure, formation fluid, cement plug, oil extraction process, blowout preventer system, deep water well control equipment, high risk casing, upper variable diameter ram blowout preventer, riser connector, Riser adapter, emergency release function, automatic shear function, automatic shutdown function, ROV operation function, underwater accumulator, pressure compensation, maintenance, supervision mechanism.
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