COMMENTARY Quenching the wild wells of

Richard L. Garwin and Henry W. Kendall

The last of the hundreds of oil-well fires left in Kuwait by should be capped this week. Although progress has been remarkable, a mechanism is needed to cope with future large-scale disasters.

BEFORE the liberation of Kuwait by US control teams. Moreover, innovative efficiency of the capping-in effort so far. forces and their coalition partners, the techniques were thought to be required By early October, more than 550 wells government of Iraq detailed about 1,000 to deal with large numbers of mines in had been brought under control, with military explosive experts and 3G-40 en­ non-combat circumstances. There was remaining 140 expected to be capped by gineers, together with the enforced initial concern, later shown to be the end of this week. Nearly 30 crew assistance of people who worked in the groundless, that wells would be booby­ were used. oil fields, to sabotage and set fire to the trapped. Mine fields were later found to It is evident that we are not the most 1,000 or so oil wells of Kuwait. Thirty to have been laid outside, but not within, knowledgeable people about well con­ forty pounds of the military explosive C4 the oil fields. trol, but we write to provide some re­ were used with sandbag tamping. Sabot­ We, together with Howard Ris and levant information, and to indicate how age attempts were made on 732 wells the Union of Concerned Scientists, orga­ people could contribute to the solution and were successful in damaging and nised a symposium (later called Desert of such problems and similar ones that starting oil flows in 690 of them, about Quench) in Washington, DC, on 2-3 640 of which were also set on fire. Data April this year, to bring together scien­ The classical approach are scarce, but it seems that something tists and experts in wells and well control The classical and well-practiced control near 2-3 million barrels per day were - including several people from the of a wild well involves delivering cubic being lost initially, considerably less than Kuwait Petroleum Company - to metres of water per minute to the equip­ the 6 million barrels per day estimated address these problems, discuss the usual ment involved close to the fire, to keep by Kuwaiti authorities, yet still repre­ solutions, and to search for means to it at operating temperature at a distance senting a loss of as much as US$50 expedite control of the wells and deal at which it would normally melt, and to million per day. with challenges posed by the mines. cool the corrugated-iron shields behind The dollar loss was not the only con­ The problems are interesting, some and below which firefighters work to sequence of this act of sabotage: the remaining open despite the speed and remove debris by the use of caterpillar- heavy flows damaged the under­ tracked bulldozers, cranes and large ground reservoirs; plumes of smoke To water-cooled hooks. Getting the fire Christmas Tree El Cement and combustion products from the jetting straight up is almost always Ground---- flames created serious health and the first order of business. For inst­ environmental problems, not only in 3011-- ance, Red Adair in his successful quenching of the Devil's Cigarette Kuwait but at much larger dis­ Region of tances; and lakes of oil developed, Water Sand Lighter in Algeria (a blazing plume 3 more than a metre thick and many 300 It-- of 10 million m of gas per day), square kilometres in extent, creating Top of Dammam first drilled water wells to fill additional difficulties. polyethylene-lined reservoirs 10-ft Iraqi land mines and unexploded Burgan Reservoir deep and the size of three football coalition munitions in Kuwait were WeHhead Rating 2000 p.sJ. fields, about 30,000 m3 of water. expected to add to the hazard and (We hope that readers will tolerate delay, as were administrative im­ a mixture of English and metric pediments. The scale of the disaster units, English being conventional in was unique: there had never before the oil fields. Conversion is readily been more than five wells simul­ achieved as follows: 1 ( 42-gallon) 3 taneously out of control. Earlier 3100 II --- barrel = 0.159 m ; 1 inch = 2.54 em; 1 foot = 30.48 em; 1 pound per experience had shown that an ex- 9 5/8" Intermediate Casing pert well-control company could square inch (p.s.i.) = 0.0703 kg 2 2 typically kill and control a burning 3400 ft --­ cm- = 6,980m N .) Before he well in 2 weeks, although months Top of Ahmadi Shale snuffed out the fire, Adair cleared might occasionally be needed. With the site to table-top neatness and an estimated 18 teams potentially cooled the vicinity of the fire for available, it was believed that 700 days to ensure that there would be wild wells would take several years no re-ignition when the fire was put to control. Numerous ideas were out. The flame is snuffed out in the proposed by specialists to deal with classical method by exploding hun­ the problems of bringing the oil dreds of kilograms of high explosive fields under rapid control. But oil carefully shaped inside a thermally wells are far more complex than insulated oilfield drum supported by many realized and the vast majority a crane at the base of the flame, and of the ideas were poorly suited to Fourlh detonated from the safety of a the challenge. For example, the big trench or burrow at a distance of problem is not in extinguishing the hundreds of metres. fires, but in stopping the flow of oil FIG. 1 A typical oil well in the greater Burgan field, south Adair's biography, An American and gas with low risk to the well- of Kuwait city, not to scale. Hero, by P. Singerman (Little, NATURE · VOL 354 · 7 NOVEMBER 1991 11 © 1991 Nature Publishing Group COMMENTARY

Brown, 1990) is a highly readable corresponding to about 4 p.s.i. stress per removed by explosives above ground account of the technology and of the foot of depth. The Christmas tree starts level, whereas others had the casing and remarkable people who have developed above the floor of a smaii concrete tubing severed in the well cellar. With and practiced the demanding profession cellar, typically 2 m in diameter, extend­ pipehangers gone the production casing of control of wild weils, often with an ing 2-3 m below ground, which reduced and the production tubing will drop into unbeatable safety record. Not one of the required derrick height during the the weii, damaging it, but not stopping Adair's team has died in fighting wild driiiing and casing of the well. Some the flow. Many wells are gushing free weiis. But the traditional approach typi­ Kuwait wells are 'sour', yielding substan­ from unimpeded bores at typical rates of caiiy takes much time in preparation, tial H 2S, a gas lethal at concentrations of one or two thousand cubic metres per and much water; it had been practised at 200 parts per million, and one that leads day. Others, whose jets impinge on most against five simultaneously burning wreckage or which are venting laterally, weiis, compared with the hundreds in are flooding oil at similar rates, which Kuwait. then burns (incompletely) near the ground in great pool fires. The thermal The sabotaged wells power from a weii flowing at this rate is The nature of the problems of gaining about 300 megawatts. Conical mounds of control of a sabotaged weii can be hardened coke wiii have accreted around understood by reference to Fig. 1. The many of the wellheads. The well-known weii has a production casing of 7-inch problem of clearing hundreds of tons of diameter extending nearly to the total driiiing rig from the weii is absent on depth of the weii, containing a 3.5-inch occasions like these, of course. production tubing; each tube is of wail thickness adequate for the expected cap­ Flow control ped pressure. Oil may be produced from the annulus between these two pipes in With destruction only of the gathering pipeline or of a valve on the Christmas additiona to the production tubing. Cellar Top tree above the lowest control valves, the Figure 1 shows the casing set for a well might be brought under control typical weii in the Burgan field of Kuwait, indicating the depth of the pro­ simply by closing one of these lower valves. But if there are no valves left on duction zone and other characteristics. a production casing, and no flange, a The weilhead pressure rating is 2,000 massive fitting must be assembled to be p.s.i., with a test pressure of 4,000 p.s.i .. Some weiis have weilhead pressures of fitted over the casing after preparation, First cooling, and usuaiiy after snuffing the more than 6,000 p.s.i. The conductor WellHead- flame. This phase of the operation is casing of steel tubing 20-30 inches in diameter is drilled or driven about 30 fraught with danger, for example, from feet into the ground before weii drilling ignition by equipment spark, by lighting begins to stabilize the driii rig. Cellar Base from dust or rain storms, or from static The weii itself consists of four to seven electricity. Casing/ With eroded pipe, a pit is usuaiiy dug concentric tubes, including the two de­ scribed above, that terminate at different to give access to the casing set at a depth FIG. 2 Wellhead valving and piping, known at which sound casing can be found. depths and may have different pressure as the Christmas tree, typical of many in Even if there is no erosion, the casing or ratings. Tubes other than the production Kuwait. The cellar top is at ground level, the casings may need to be exposed and then tubing are called casings and may be up base about 5 ft in the ground. The produc­ to 20 inches in diameter. The lower end tion tubing is 31f2 inches in diameter and cut cleanly. The fitting (weighing at least 3 of each casing is cemented to the forma­ successive casings are 9%, 13 /4 and 20 a ton) must be puiied over the geyser in tion for a hundred feet or more to inches in diameter, respectively. a controiied manner and puiied down over the casing, or clamped around the prevent flow between otherwise herme­ to hydrogen embrittlement of high­ pipe. Grooved, tapered ramps, caiied tic geological strata. The annulus just strength steels. The petroleum from va­ slips, can be inserted between fitting and inside the largest casing may also be rious wells in Kuwait has a great range casing to prevent the large forcs that wiii cemented. Annuli may also be closed of viscosity, and a gas content reportedly be present after flow is stopped from permanently or temporarily by the use of in the range 35-70 m3 of gas at STP per pushing the fitting off the casing. For a packers near their lower ends, instaiied m3 of oil. This high gas content requires typical casing of 7-inch diameter and a along with the next smaiier casing, lining a gas-liquid separator under normal pro­ wellhead pressure of 5,000 p.s.i., this or tubing. duction conditions. Sand entrained in amounts to about 100 tons of force. An The weils in Kuwait are topped by the flow at the weii foot becomes more appropriate packing or seal is used to 'Christmas trees' of plumbing for de­ abrasive at the higher linear flow speed retain the fluid after the valve is even­ livering the oil into the gathering pipe­ existing in the two-phase flow near the tually closed. The high-flow Kuwaiti line and for access for well maintenance wellhead; under normal conditions sand­ wells pose particular problems to the and control (Fig. 2). The Christmas tree induced erosion of production tubing is traditional approach, as the typical well includes many features for control and monitored and the production tubing wiii spill 1,000 tons of oil a day on the safety. protectors, essential to replaced when necessary. activities at the weiihead between the safe driiiing, are removed from com­ After the Iraqi sabotage, it was re­ time the flame is snuffed and the flow is pleted weiis, as are the derricks used for ported that two-thirds of the weilheads stopped, and may flood the area with driiiing and casing. The production tub­ had been blown off and the rest badly poisonous and explosive gas. ing and the casings normaiiy hang from damaged. Some of the uncontroiled and flanges in the Christmas tree and, while burning weiis needed only to have their cemented in at their lower ends, can be valves closed, but in most cases substan­ Snuffing the flame under great tension at the surface, the tial work had to be done first. In some Classicaiiy, flames are snuffed by the use weight of steel - 60 tons or more - the valves and wellhead facilities were of high explosive. More recently, as 12 NATURE ·VOL 354 · 7 NOVEMBER 1991 © 1991 Nature Publishing Group COMMENTARY described at the symposium and used used in the casing. desert soil with great speed down to a simultaneously by a well-control com­ depth of from 1--4 ft, as desired. pany in Kuwait, liquid nitrogen has been Other proposals Mounted at the end of a movable boom used to quench the flame in a controll­ Several proposals were introduced and 30--50 ft long on a tracked vehicle with a able fashion, with clear advantage over discussed at Desert Quench for speeding protected cab, it might move at 100 ft any technique that uses explosives that up both access to mined and booby­ per min. It would either detonate mines would imperil people and equipment trapped wells and bringing the uncon­ or transport them out of the way along near the wellhead. Nevertheless, liquid strained flows of gas and oil under con­ with other debris. Used in conjunction nitrogen has been used only on wells of trol. A few were unrealistic or unwork­ with sled mine sweeping, and with multi­ relatively small flow. able; we discuss some of these briefly ple passes over the ground, areas could Many have proposed the use of fuel­ here to report the unexpected obstacles be cleared to a reasonable level of confi­ air explosives instead of high explosives, that surfaced. dence. It could be used to construct or the use of Halon gas or even fer­ Mine clearing by robust harrows. Con­ access roads, staging and work areas, rocenc to terminate the flame­ ventional mine-clearing techniques are and ditches and ponds for either water propagating chemical chain-reactions. unsatisfactory for the circumstances in or oil. The device might dig a pit around Although some of these techniques may Kuwait, particularly because of the high­ a wellhead 60 ft in diameter and 20 ft be feasible and valuable, it remains true er safety standards traditionally deman­ deep in less than an hour. Not only that existing techniques of snuffing ded for operations in peace time. The could such an approach clear mines and flames are cheaper. mines are virtually non-magnetic and booby traps in an area inaccessible be­ Snuffing the fire has traditionally been could be equipped with anti-tamper fus­ cause of radiant heat from the fire, it a prerequisite to stopping the flow, and ing. Many land antitank mines consist of would also remove ground in the well­ difficult operations frequently have to 10 kg of high explosive packaged in a head area heated by months of exposure precede snuffing. It would be highly disk-shaped plastic container, and are to the flame. advantageous to be able to stop the flow capable of driving a hole through the Sand added to the air stream would without (or before) snuffing the flame to bottom of a heavy armoured tank, and provide an effective abrasic cut-off tool avoid dealing with the flood of oil and of killing passengers in military or civil which would rapidly deal with oil well gas that would both hinder work and vehicles. Such mines can be swept by pipes and valving, reinforced concrete pose a hazard of explosion. Three ploughing, requiring exceptionally well­ and other materials, facilitating debris approaches are immediately apparent protected sweep vehicles to prevent in­ removal and nondestructive preparation and were discussed by participants of jury to their operators. The plough of the well head. Air-blast excavation Desert Quench. structures rapidly degrade from the de­ and high flow air-abrasive cutting would (1) Approaching the wellhead with a tonations. An alternative is to search for benefit from increased theoretical and gathering culvert system, into which the the mines on foot by probing with sharp practical study, including the scaling geyser is suddenly diverted without snuf­ rods. Complex fusing options, which laws applicable to currently available fing the flame. This is being developed may involve more than one signature, information. by several groups. such as pressure or magnetic influence, Explosive pipe closure. Ring or cylindric­ (2) Tunnelling below the surface to or which count or use inert periods, al shell explosives can be used to pinch reach the casing set, drilling the produc­ make confident clearing uncertain. shut a pipe or multiple annular pipes. tion casing (and producing tubing, if There have been no satisfactory clearing The explosive charge or charges must be necessary) by machines similar to those techniques for mines submerged under a selected, placed and detonated with used at relatively low pressure in domes­ layer of oil. more care than, for example, in pipe tic distribution systems for hot-tapping One potentially valuable approach to cut-off. The technique appears unsuit­ an existing gas main, and inserting a mine clearing, proposed by W.H. Wat­ able for oil-well control because of the stopper(s) adequate to stem or divert the tenburg and tested at Yuma proving difficulty of ensuring no further damage. flow. This is not viewed with favour by grounds by Lawrence Livermore Labor­ The production tubing and production the drilling industry. atories, uses a sled of chains that in­ casing may have suffered wall thinning (3) Inserting and fixing a hollow probe corporates harrow-like blades than can from stream erosion that is difficult to or stinger in the bore, which is then reach to a depth of a foot or so, clearing assess; some of the wells are decades old valved off. Such a technique has been in a 20-ft path. The device digs up mines and the metal of the pipes may have use for some time in undamaged wells which either detonate, degrading the become embrittled from exposure to and was used successfully, early on, in sled only slowly, or are entangled in the H 2S. Hence the task of selecting a small, damaged wells in Kuwait. It be­ chains for later destruction. It is drawn charge that will confidently close the came the technique of choice for the by a helicopter at a safe distance. For pipes without severing them becomes bulk of the well-capping and, with area-clearing in Kuwait, the sled could difficult, especially as the pipes are sus­ numerous small improvements, has been be dragged back and forth among sever­ pended under tension. Squeezing pipes responsible for the great success of the al winches, to reduce the cost below the shut inside a cemented casing set poses effort. $3,000 per hour typical of helicopter additional difficulty. In some cases, the In this method, a stinger equipped operations. task may be complicated by the transient with appropriate valving is inserted Mine clearing with compressed air. Com­ pressures expected from the hydraulic into the flow and restrained by heavy pressed air with sufficient pressure and ram effect induced by the near­ downward force. Powerful pumps are flow could be used to clear away earth instantaneous halt of the mixed oil-gas then used to inject drilling mud into and mines rapidly with a relatively high fluid in a couple of kilometres of well the well at a high flow rate until the degree of safety. To illustrate his con­ tubing and, even more important, shock­ weight of the mud column halts the flow cept at Desert Quench, S.A. Colgate induced overpressure of the fluid in the from the well. Stingers can also be used described a unit with a compressor in the pipe or annuli near the explosion that in wells with flow both through the 10,000-hp range; air from a 4-inch nozzle can induce rupture. With the very gassy production tubing as well as through the at a pressure in the range 200--400 psi oil in Kuwait these transient overpress­ production casing: the production tubing will have a flow of about 5,000 ft"' per ures would be mitigated. hanger is cut off and the tubing drops a min and will develop a reaction force of Penetrating bomb. Use of an air­ few feet down, allowing a stinger to be more than a ton, sufficient to remove delivered, earth-penetrating bomb to NATURE · VOL 354 · 7 NOVEMBER 1991 13 © 1991 Nature Publishing Group COMMENTARY seal off an injured well 50--100 ft below explosion could not develop in the tube reduced sooner by well control than by the surface suffers all the problems and and that erosion of the diverter was modification of the burn. more of explosive pipe closure, owing to controlled. The oil could be delivered to Gaining control. Shields against the the lack of precision with which the plastic-lined holding ponds, dirt tanks, radiant heat of the flame have for de­ bombs can be delivered at depth, and to constructed in the desert and using heat­ cades been made like medieval shields, the inherent one-sided nature of the sealed plastic sheets to prevent evapora­ from corrugated steel, with handles. explosion. Severing a well below the tion and seepage into the sand. Spray from water monitors has been surface converts a difficult situation into The flow emerging from an uncontrol­ used to cool the shields and the fire­ a disastrous one, in which the excess led well is highly abrasive, in view of the fighters, as well as the hot ground. It pressure in the sub-surface soil exceeds entrained sand and the high velocity to would be useful to have a light, thin, by far the available lithostatic pressure, which the gas content carries the fluid on robust, multi-layer shield that would not and leads to the formation of a crater. expansion to near-atmospheric pressure. be damaged by contact with water or oil. Shallow relief well. In cases where the Means are required to retain the integri­ Reflective shields do not long remain stinger approach is for some reason un­ ty of the elbow exposed to this environ­ reflective in the rain of combustion de­ workable, consideration might be given ment; measures such as diamond-coating bris around a burning well. It would also to using a very shallow intercept by a or massive self-feeding rubber blocks be desirable to have a shield mat that large-diameter, low-pressure, steeply might be useful. could be placed on the ground to keep angled well. Connection could be made Stove pipes and liquid nitrogen. Cylin­ shoes from melting or burning. in conventional manner by explosives at drical tubes (3-8 m long) have been used For wild wells that feed a pool fire the foot of the relief well, blocking the to elevate the flame from a burning well instead of a plume fire, control might original well so long as no impediment much in the manner of a Bunsen burner. most readily be achieved in two steps was posed to the flow of oil out the relief They do not require the cooling screen (without first snuffing the flame). First, a well and into the gathering system. Re­ needed with the burner to prevent flash­ surface culvert could be built to placeable lining, resistant to abrasion, back; the relative absence of oxygen in approach near the wellhead, with oil would probably be necessary for the the fuel and its high velocity result in the diverted into it from the pool by means relief well. In due time, re-entry could flame base remaining at the top of the of a centrifugal pump placed remotely in be made through the original well head tube. A tube hinged along one side, the well cellar or in an expedient sump. with several options, including pulling parallel with the tube axis, could prevent A large lid could then be placed remote­ the production tubing from depth and its interrupting the fuel stream during ly over the wellhead area, excluding air restoring the well. insertion but for the lengths so far used and serving as a crude gas-liquid separ­ Tunnelling to the well. Efficient tunnell­ this has not been necessary. Liquid nit­ ator, with the gas taken through a large ing techniques could provide a very shal­ rogen was used in the first of the dam­ elevated culvert to be flared (burned) at low intercept by a cased, large-diameter aged Kuwaiti wells, a small one, to have a reasonable distance. tunnel from a point 30-40 m or so from a its fire put out. A tube stove pipe was damaged well to the cemented casing set used and the fire extinguished and re­ Conclusions of the well 30--50 ft below the surface of ignited several times to fine tune the We have attempted to provide an analy­ the ground. The tunnel shaft would be process. Liquid nitrogen can be advan­ sis of the problems and constraints relat­ cased and a room mined, shored and tageous where water is in short supply. ing to controlling the types of wild wells cased to provide working space around Pollution from burning oil. Wells should encountered in Kuwait. We hope that the casing. To avoid potential explosion burn more cleanly if there is better new ways of dealing with such catas­ hazards from encountering gas or pet­ mixing with air (see R. Seitz, Nature trophes will emerge from our discussion. roleum fumes, or from minor leaks in 350, 183; 1991), and drilling But it is difficult to prepare for a disaster the apparatus, the tunnel might be kept operations have long practised the addi­ that is likely to happen to somebody else, in a community in which interests inerted with C02 , exhaust gas or nit­ tion of sea water to the oil after the start rogen, with air supplied to masks or of free flow of oil to the production are divided and even opposed. In the hoods for any workers. For the many platform and into the atmosphere, where case of Kuwait, there have certainly low-pressure wells, one might bare the the oil is burned to avoid pollution of the been missed opportunities. For instance, outermost casing and attach a saddle to sea. The water clearly reduces the if a share in the future production of allow drilling under pressure, removal of atmospheric pollution from the burning several wells had been given to one successive cores, insertion of stoppers oil, and similar approaches could help in company (and that replicated tenfold), and the like ~ all within the environ­ Kuwait. with the proviso that the methods used ment of a massive set of pressurized Ducts or driven air can swirl a rising, to control their wells would be available valves and tubes. This technique is flaring column of burning fuel. In small to be practised by others, progress might essentially foreign to the well-control flames this produces a narrowing of the have been made more rapidly and with teams, who emphasize open and quick column, will raise the level at which higher confidence. As $50 million a day escape routes, but it might be practised burning of the fuel first starts, and was being lost in Kuwait, considerable by those experienced in tunnelling, with appears to promote improved air-fuel money could have been saved by a fast much help from those experienced in mixing and therefore combustion effi­ response to the problem. Not only have well control. ciency. If successfully applied to a well important resources been destroyed by Flow diverters. It is possible in principle fire, such flame control could decrease the action of Iraq, they have been un­ to place a flow diverter over a well the radiant heat at the wellhead without necessarily squandered by an inability to (extinguished or not) and conduct the the need to extinguish the fire. This permit technical measures to be im­ oil-gas mixture into a long culvert-like would decrease or eliminate the produc­ plemented to control the wild wells of pipe fitted with one or more sumps that tion of pollutants. Kuwait. D would provide for separation of the gas Further research into the potential of Richard L. Garwin is at the IBM Thomas J. from the oil, with the gas flared under vortex alteration of large flames would Watson Research Center, PO Box 218, York­ control. This scheme temporarily halts be valuable. On the other hand, if less town Heights, New York 10598, USA; Henry the production of soot and other pollu­ effort is involved in stopping the flow W. Kendall is in the Department of Physics, tants, and recovering the oil. Care would from a typical well than in providing air MIT, Cambridge, Massachusetts 02139, have to be taken to ensure that an or water entrainment, pollution could be USA. 14 NATURE · VOL 354 · 7 NOVEMBER 1991 © 1991 Nature Publishing Group