万物皆流

发表在我在Nature Blogs上的博客（英文）

Rheology is indeed involved in oil drilling engi­neer­ing, includ­ing enhanced recov­ery method and spill con­trol. Therefore I thought I could tell quite a lot about the dis­ater in the Gulf of Mexico, until I found that the prob­lem is mainly mechan­ics — the spill occurs because of the unex­pected fail­ure of blow out pre­ven­ter (BOP). From ask­ing “what is a BOP” I have to extend my knowl­edge to the whole mechanic aspect of oil drilling engi­neer­ing. The fol­low­ing texts are the result of my books and web­pages ad hoc read­ing and are not meant to be expert opinions.

Semi-submersed plat­form

Ocean has the amount of energy and resources that prob­a­bly define how long in the future can human race last on this planet, energy and resources on the land approach­ing to the end. However the courage to built posi­tioned bases in the ocean — a huge brave trial — is finally granted by high prof­its behind the abun­dance of oil under the seabed (among many other e.g. wind, tidal, etc.).

US was the first of the world to design and prac­tice off­shore drilling rigs. As the drilling depth increases, dif­fer­ent designs appeared in the his­tory. Deepwater Horizon is a semi-submersed rig, a design known to sup­port the deep­est oil well off­shore ever known. Allegedly DH has the abil­ity to drill the worlds’s deep­est oil well, with­out using a newer design. No design, how­ever, can be a final one and sup­port an infi­nite drilling depth. DH may be a sign that the old design, not only the rig but the whole drilling design, after more than a decade of appli­ca­tion if not mis­in­for­ma­tion, has now reached its limit. Or put it in another word, it was the unex­plored depth that causes the fail­ure. To answer against my ill-disposed, arbi­trary con­clu­sion one should know clearly what cause this event actu­ally and is it unpre­ventable under the same rig design? or is it unre­lated to the rig design?

Dynamic posi­tion­ing

We all know that first the rig caught fire and then sank. Although up till now I don’t know how the fire started but it could hardly be related to the design of the rig of any­thing to do with the hard­ware. because the same design is used else­where. However the fire was really a big one. It causes the rig to sink and, cat­a­stroph­i­cally, off­set from its orig­i­nal posi­tion. As you can see from the struc­ture of a off­shore drilling sys­tem, con­sid­er­ing the length of the oil pipe sub­mersed in the sea water, the rig must be pre­cisely posi­tioned above the oil well hold­ing the pipe per­pen­dic­u­lar to the sea hori­zon, oth­er­wise the oil pipe must be bro­ken. Before the acci­dent DH was drilling a new main well. That means once bro­ken the oil well has well extra pres­sure to push the oil out by itself, caus­ing an oil spill acci­dent. Historically off­shore rigs were posi­tioned by anchors. With the devel­op­ment of pow­er­ful pro­pellers, GPS, and sig­nal pro­cess­ing tech­nol­ogy, dynamic posi­tion­ing — posi­tion­ing with­out anchors — played its role in newer drilling rigs includ­ing the DH. Under dynamic posi­tion­ing the real time posi­tion of the rig is con­tin­u­ously analysed and fed back to the pro­peller sys­tem with proper com­mands of new strengths and direc­tions. Because this feed­back cycle is del­i­cately main­tained by AI rather than phys­i­cally by anchors, once the signal/control sys­tem fail (e.g. in a fire) the rig will be sud­denly turned back to a sim­ple unchained flow­ing boat on the sea. The design of dynamic posi­tion­ing, although hi-tech, adds risks of oil spilling acci­dent to the system.

The blow out pre­ven­ter (BOP)

The Wall Street Journal did an excel­lent expla­na­tion about the BOP. The blow out pre­ven­ter is located at the oil well on the sea bed. As the oil pipe broke at some­where, it leaves to the blow out pre­ven­ter to stop the oil from the exit of the well (trig­ger­ing it per­haps by a drop­ping sig­nal of flow pres­sure). According exclu­sively to BP, how­ever, the BOP ceased to work as expected by unknown rea­son. News reporters also found from the safety eval­u­a­tion of DH 10 years ago evi­dence that BP planned not to imple­ment emer­gent man­ual “stop” but­ton for the BOP, i.e. a remote acoustic trig­ger. It seems that the pro­ducer of the BOP was very con­fi­dent with their prod­uct at that time, and suc­cess­fully con­vinced its cus­tomer BP not to imple­ment addi­tional remote trig­ger for DH due to eco­nomic rea­sons. All these infor­ma­tion rep­re­sent an atmos­phere of over-confidence around the con­struc­tion of this plat­form which is to drill the deep­est seabed ever.

Historically when the off­shore drilling task did not involved very deep sea, peo­ple use BOPs with the same design as those used on dry land oil wells. As we drill from deeper and deeper the seabed this sim­ple copy­ing started to cause prob­lems. Under increased hydro­dy­namic pres­sure the hydraulic trans­mis­sion sys­tem used for the BOP become more inef­fi­cient, lim­ited by the diam­e­ter of hydraulic tubes. Thus the deeper the BOP goes down the sea, the slower for the hydraulic trans­mis­sion sys­tem to response, and in the worst con­di­tion, the sys­tem just fails. Although this has been his­tory and now these prob­lems must have been over­come, the expe­ri­ence tells us that drilling from new depth poses new unex­pected fac­tors and chal­lenges. Confidence on the BOP com­po­nent base on pre­vi­ous suc­cess in shal­lower con­struc­tions is faint.

The res­cue

Underestimation extended to the res­cue phase of this event. As I wrote this post news that the con­tain­ment domes plan has failed come to my eyes. The idea of using domes is not the first idea, but after the ear­lier fail­ure of remotely oper­ated under­wa­ter vehi­cles (ROVs). However, the speed of spilling was already warned of by many source of infor­ma­tion before these fail­ures, while BP kept assur­ing us of the effec­tive­ness of the ROVs, then the con­tain­ment domes by pre­vi­ous suc­cess of these meth­ods, despite pub­lic ques­tions whether these would also work under the depth we never have explore.

The ocean is no more acces­si­ble than the moon

Offshore projects, although started more than 50 years ago in USA and later in other coun­tries (includ­ing China), are still kind of adven­tures. The most impor­tant obsta­cles — ocean cur­rents, winds and envi­ron­men­tal impacts, are cur­rently still out of mankind’s pre­dic­tion and con­trol. We are proud to say that a small step deeper of the drilling rig is a large step of the mankind, just like what we call about the moon land­ing project. However, as BP described ear­lier, although it took full response of the acci­dent but it is not BP’s own fault (from Chinese news sources). In other words, any small fault in this adven­ture may also be a big one of the mankind, just like what we have in the space shut­tle Columbia disaster.

Does the US gov­ern­ment treat their off­shore explo­ration projects equally well as their moon or Mars explo­ration projects?

拿到5月份《新知客》后，看到一个之前没见过的栏目——“观察”。题目恰为：《奥巴马为何要吃窝边油》。

《新知客》5月“观察”

5月份的杂志，应该是4月中旬就组版了。因此此文应该是四月初写就的。美国墨西哥湾油灾事件是四月底开始引起广泛关注的。成为新闻热点应该是刚刚5月前后。因此我实在惊异于行内人的预言能力。我这个行外人在博客里写的东西，仅能作为自己学习了解此事的个人笔记罢了。所幸我发现我了解了一番之后，所形成的基本见解跟行内人的看法类似；更庆幸的是我在此次事件关注系列的第一篇文章开头就清醒地认识到：

人人IQ都高，你的价值不在于你比别人聪明多少，而在于你的职业，你的生存环境和阅历的个人性、独家性。想要“独家”，就“独家”在此。如果人人都最大程度地利用自己的IQ，就能在最少的时间里把事情推进到最前沿的程度，任何发展都会因此加速；放在有IQ不用，做那种看译文的懒事，很可耻，跟听信谣言的不明真相群众无异。……

我打的文字，主要是补充这些资料所没有的内容，同时把这些零碎的资料连接成一起。哪怕是这项工作，我价值也是为零的……

所以，可以认为，以下引用于原文的话，其实是行内人早就知道的事情了。站在这些话的高度之上去看待此次油泄露事件（这是起码的），就能感觉到它不仅仅是不堪设想的生态灾难，而且还是不堪设想的政治灾难。好像有个什么名言说人类的政治全都是非理性的胡言乱语，因此人类的愚蠢是注定的。

目前，美国一半以上的石油依赖进口，……（陆地）油田不再像以前那样大量产出……

随着美国人的石油胃口越来越大，以及石油峰值的来临（我注：什么是Peak Oil），事情越来越不如人意。……

……在声称石油储量大约在700亿桶、能满足美国数年（注意，仅仅是数年！）（我注：现在该处某油井正以每天25000桶的速度消散）石油消耗量的墨西哥湾，其中400亿桶储存在没有发现的超深水域，相当于美国石油储备的最后疆界……

……超深水域的绘图和钻探难度无异于石油科技上的珠穆朗玛峰，每一个探索都须付出巨大代价。状如阿尔卑斯山的盐层让地质学家至今还示能准确描绘这里的地质构型，墨西哥湾的暖流和9000多米深的沉积层让精密的钻机随时可能折断，还不必说因为超深水域带来的高温高压危险，以及飓风的袭击，种种因素让墨西哥湾石油的开采成本极高，平均一艘钻船每日营运成本高达50万美元，而一个小小的意外，都可能带来上亿美元的损失。

（要看全文请购买5月份的《新知客》。）

关于从此次事件引申出的消费高度发达的资本主义社会弊端的思考，我在高度在国外一个很活跃的石油话题论坛网站The Oil Drum看到这样的回复：

一人说：Why are BP drilling in GOM (我注：即Gulf of Mexico) any­way? Because Americans like to live 50 miles from work and like to live a con­sumerist lifestyle too. All of which needs oil, and a bloody shed load too.

So per­haps Obama and all you other Americans should take the plank out of your own eyes before try­ing to crit­i­cize and damn BP. Y’all want the frig­gin oil… live with it.

另一人回复上文：Because they failed to cre­ate low cost, high effi­ciency pho­to­voltaic pan­els when gov­ern­ments paid oil com­pa­nies to cre­ate them.

Because indus­try refuses to pro­vide options for con­sumers and prefers to use meth­ods like General Motors used to destroy the EV-1.

British Petroleum is run by oil men who know no other prod­uct. Since they have no inter­est in adapt­ing to some­thing else, they seek to extract oil where ever they can still find it, even though it lies in ever more dif­fi­cult loca­tions. At the fuel pump American con­sumers do not give a hoot whether their fuel came from BP or Saudi Aramco.

Where’s the elec­tric car that would put oil men out of business?

我又联想到我们国家。《新知客》“观察”文章说美国多少多少比例的石油主要靠进口，说陆上的石油要采光了，看着就好像是在描述中国的国情。大庆等老牌大陆油天正在拼命地研究三次采油复合驱，关心石油的国人一直都在把眼睛瞄准我国的南海，难道那里不正就是我国“石油储备的最后疆界”么？我国其实面临着跟美国同样的问题。

今年2月份，由中国海油投资、我国自行建造的深水半潜式钻井平台“海洋石油981”在上海外高桥造船有限公司顺利出坞，这个东西就是跟现在墨西哥湾出事的Deepwater Horizon同一级别的东西（严格来说更高级，Deepwater Horizon是第5代，海洋石油981据称是第6代，具体什么差别恕我外行）。而此前中海油荣获2008年度国家科技进步二等奖的“中国南海西部海域复杂构造安全快速钻井技术”介绍中也明确提到：

针对中国南海西部海域所存在的高温超压并存、井壁失稳严重等世界级重大钻井技术难题，通过技术引进……使钻井井眼复杂事故率从40%～72%降至5%以下……

而（不知道是不是我犯概念混淆）据媒体报道此次出事的Deepwater Horizon平台，当初正是因为BP评估事故风险为5%，觉得够低了，所以在方方面面免去了价格昂贵但能大大降低此次灾难等级的应急保险措施（包括但不仅限于现在曝露出来的远程触发开关缺如、深海求急技术方案可行性演练等）。5%是一个什么概念？就是每二十次会发生一次！这如此高的风险竟被业界公认为“很低”，背后到底是何等巨大利益驱使如此胆大的冒险成为业界公认？让人更关心的简单问题是：如何避免海洋石油981成为人类下一个Deepwater Horizon？近海工程可借鉴经验极少，这就是此次Deepwater Horizon之灾的唯一宝贵之处。