Drilling of Wells That Provoked Natural and Man-Made Disasters

Abstract

This chapter discusses several accidents that occurred during drilling of wells, resulting in significant material damage and serious environmental consequences. The accidents were caused by the failure to take into account the geological features of the rock mass and mine operations that could be affected during drilling. Dangerous situations arise from abnormal pressure in deep horizons. Gas accumulations in the upper part of the section, watery horizons, salt deposits, and mining processes can cause disasters. The reason for these accidents is due to the fact that the features of the geological structure of the rock mass and existing mine workings that could be affected during drilling were not taken into account. These examples show the history of drilling and accidents at wells in the Caspian Region, Central Asia, Indonesia, Gulf of Mexico, and other locations.

1. Introduction

When faults break through the Earth’s crust as a result of tectonic processes, the pressure at the boundary of the mantle and the Earth’s crust decreases sharply and volcanic activity begins. This natural phenomenon has accompanied the history of the Earth since the formation of the Earth’s crust. With modern technology, humans are attempting to drill deeper into the Earth’s crust, but it is a difficult task, and accidents occur frequently. Drilling remains a complex process, and the deeper the drilling, the more complex. There is an opinion that it is easier to reach the Moon than to drill a well of 15 km in depth. The deepest vertical well—the Kola ultra-deep—reached a depth of 12,282 m and was drilled for 20 years. Many of the millions of wells drilled turned out to be emergence and ended in grand fountains of oil, gas, and water. Such wells were called “wild wells.”

“When the World Screamed” is a story written by Sir Arthur Conan Doyle that today gives the reader a little more food for thought than when it was first published in 1928. It is a science fiction story that tells of an attempt to drill through the Earth’s crust and into the mantle. The results were the “cry” (1), material damages (2), and environmental contamination (3). Here is the excerpt from the story that tells of these drilling results.

“Who is there of all the hundreds who have attempted it who has ever yet described adequately that terrible cry? It was a howl in which pain, anger, menace, and the outraged majesty of Nature all blended into one hideous shriek… No sound in history has ever equaled the cry of the injured Earth…

The first emergence from the bowels of the earth consisted of the lift cages… So the 14 lift cages appeared one after the other in the air, each soaring after the other, and describing a glorious parabola which landed one of them in the sea near Worthing pier, and a second one in a field not far from Chichester. Spectators have averred that of all the strange sights that they had ever seen nothing could exceed that of the 14 lift cages sailing serenely through the blue heavens.

Then came the geyser. It was an enormous spout of vile treacly substance of the consistence of tar, which shot up into the air to a height which has been computed at 2000 feet… This horrible stuff, which had a most penetrating and nauseous odor, may have represented the life blood of the planet, or it may be, as Professor Driesinger and the Berlin School maintain, that it is a protective secretion, analogous to that of the skunk, which Nature has provided in order to defend Mother Earth from intrusive Challengers.”

The drama described in this fictional picture of the accident periodically occurs in real-life drilling operations in different regions around the world. Currently, the main geological causes of the accidents include abnormal pressure, shallow gas, and salt deposits.

2. Abnormal pressure at the great depth

2.1 Catastrophe of the century

The drilling accident on the eastern shore of the Northern Caspian in 1985 in many ways resembled the drama described by Conan Doyle. The formation of an open fountain at a well is classic for its own reasons, due to both the complex geological and technical conditions of drilling, and the inability of specialists and personnel to meet such a formidable challenge. Well 37 was drilled at the Tengiz oilfield, where the productive reservoir with abnormal pressure was at a depth of 4400 m [1].

Drilling was carried out with a bit with a diameter of 216 mm, using a hydrocarbon-based drilling mud with a density of 2.02–2.06 g/cm³. When drilling in the range of 4465–4467 m, the mechanical speed increased by 1.5 times in the well. The well absorbed the drilling mud at a pump capacity of 10–12 l/s. In accordance with the requirements of the “Regulations...,” the tool was lifted into the shoe of a 245 mm casing string to a depth of 4382 m. The chief engineer gave a written order to lift the drill pipes to a depth of 3500 m and then seal the mouth and prepare a lightweight solution with a density of 1.97–1.96 g/cm³. When the 15th candle of the drill pipes was lifted from the well through the annular space in the gutter system, the movement of drilling mud and its “overflow” through the drill pipes began.

After attempts to seal the well were not successful, the well, having thrown out the drilling fluid, began to gush oil and gas through the annulus and drill pipes. During the preparatory work for closing the cutting preventer and cutting the drill pipe, spontaneous combustion of the gushing gas-oil jet occurred. After 12 minutes, the rig fell, and when it fell, both branches of the anti-discharge equipment were bridged. In addition to the gushing vertical jet, additional powerful pockets of flame appeared. All equipment and metal structures were engulfed in flames, and due to incomplete combustion of oil, a powerful smoke screen was formed, hiding the wellhead site from view (Figure 1).

Figure 1.

Disaster at Tengiz oilfield, well 37.

The situation became seriously complicated, requiring a radical revision and the development of new strategic and tactical solutions to eliminate the uncontrolled burning of open oil and gas fountain. The work to eliminate the fountain required the mobilization of almost all the safety services of the USSR Ministry of Oil and Gas Industry and lasted 13 months. In addition, the collapsed drilling rig (more than 300 tons of metal), its concrete foundation, and the soil melted from the high temperature created a powerful blockage at the site of the well, which interfered with work and had to be cleared. This was hindered by the high temperature. At a distance of 100 m from the fountain, the air temperature reached 150°C, and the ground temperature reached 200°C. People working in the area of the emergency well wore cotton underwear, cotton suits, suits made of woolen overcoat cloth, felt boots, headsets, and oxygen breathing apparatus, on top of which special fire-resistant suits were worn. People were continuously watered with water from fire barrels, but despite this, it was impossible to work for more than three to 5 minutes.

Fire-resistant suits flared up, cloth suits smoldered, the water on the ground boiled. During the liquidation of the accident, more than 2000 fire-fighting suits were burned. In total, up to 4000 tons of water, which was pumped from the Caspian Sea through a specially laid water pipe, were consumed per day to reduce the temperature of the torch. At particularly crucial moments, up to 1000 tons of water per hour were pumped into the fire. When it became clear that it would not be possible to clean the well of debris with purely human hands, it was decided to use military equipment. A T-54 tank that was brought to the site first bombarded the blockage with steel blanks, and then with shells. After that, almost 4 km of drilling pipes (more than 150 tons) were squeezed out of the well into the sky by pressure. It looked like a pipe was coming out of the well high into the sky, which broke off from above as it was squeezed out of the ground. It was like a long bundle of sausages. Remember the story written by Conan Doyle!

The shot fragments of equipment were pulled out with the help of powerful equipment, hooked with a 10-meter anchor. When the remnants of the equipment were removed, the liquidators moved on to demolition work—blowing up the drilling rig’s reinforced concrete foundation and cleaning its wellhead. When laying explosives, a huge amount of water had to be poured to cool the soil at the wellhead. The idea was to drag a massive steel plate with a hydraulic booster mounted on it to the wellhead, which would “put” a preventer on the emergency well. The device was supposed to be dragged to the wellhead along the mounted rails with the help of tractors. That is why it was necessary to clear the well of debris.

In total, in November–December, three attempts were made to “throw” a locking device on the well. The first two were unsuccessful. And only on New Year’s Eve—December 31, 1985, it was possible to “tighten” the “stranglehold” on the well. But the final elimination of the accident was still far away. The well was plugged only on July 27, 1986. Several hundred tons of lime-bitumen solution were pumped into the well and it was finally contained. Since it was not possible to cement it to the full depth, the well is considered “sick” to this day and it is constantly monitored.

2.2 Drilling operation with a nuclear explosion

Another “famous” accident occurred in December 1963 at the Urtabulak field in Uzbekistan. At a depth of more than 2400 meters, a gas-bearing reservoir opened in a well. This reservoir was characterized by a high content of hydrogen sulfide and an abnormally high reservoir pressure, more than 300 bars. The drill string was squeezed out of the well, and a powerful fountain of gas ignited. Under the pressure of the gas, the drilling rig collapsed and partially melted. Within a short time, the protective fittings at the wellhead collapsed and the flare increased. This torch has been burning for more than 2 years and 9 months. Its height reached 120 meters, the volume of burned gas was at least 12 million m³ per day (Figure 2).

Figure 2.

Open fountain at the Urtabulak gasfield.

Artillery shelling and cooling of the wellhead with a water curtain were used to destroy the failed ground equipment. In January 1964, it seemed possible to clear the well’s mouth and install a valve diverting part of the outgoing gas, with the help of which it was planned to lower drill pipes into the well. However, the matter was complicated by the penetration of high-pressure gas from the emergency well into permeable rocks, which led to the appearance of gas griffins that threatened poisoning of a significant area. Later in the process, water injection into the gas-bearing reservoir and drilling of bypass wells were undertaken to combat gas emissions, but this did not lead to success.

Due to the high temperature, it was impossible to get closer to the torch than 250–300 meters. The area around was covered with soot, the behavior of animals changed in the vicinity of the well. In the end, specialists proposed a nuclear explosion to destroy the fountain. The decision on the date of the explosion was approved at a meeting, which was personally headed by Leonid Brezhnev. To lay the charge, an inclined tunnel was drilled, in which the charge was placed at a depth of 1500 meters below the surface of the earth. At this point, the temperature was very high, so the charge lowered to the detonation point had to be additionally cooled. The detonation of a nuclear charge was carried out on the morning of September 30, 1966. The result was fully achieved: the gas well was squeezed by the shifted layers of rock, the flame fountain went out 22–23 seconds after the explosion.

2.3 The Kumzhi disaster with another nuclear explosion

One of the largest drilling accidents occurred at the K-9 well of the Kumzhinsky gas condensate field [2]. The exploration well was located on the bank of the Pechora River at a distance of 3 km from Korovinskaya Bay. The disaster occurred On November 27, 1980 during a well productivity test, when high pressure was detected in the inter-column space of the casing. In addition, further studies of the well showed the leakiness of the production column in the interval of 39 m. It was decided to relieve pressure in the inter-column space, as a result of which griffin formation began in the mouth of the well, accompanied by a fountain of a mixture of gas condensate, calcium chloride solution, mud, and cement. The multiple griffins that emerged merged into one large one. The work on the elimination of the accident, which was carried out in January–April 1981, did not result in success.

It was decided to liquidate the fountain at the K-9 exploration well with the help of a “Pyrite” nuclear charge. For this purpose, the K-25 well was drilled with a depth of 1530 m at a distance of 600 m northwest of the mouth of the emergency well K-9 above the assumed position of the K-9 borehole. The detonation of the “Pyrite” nuclear charge in the K-25 well was carried out vertically on May 25, 1981 at a depth of 1470 m. The explosion power was 37.6 kt in TNT equivalent. As a result of this underground nuclear explosion, an underground cavity with a radius of 35 m was formed, as well as zones of crushing and cracking with a radius of 261 m. Following the nuclear charge detonation, the release of a gas condensate mixture at the K-9 well stopped, but the next day the gas began to come to the surface again, forming griffins. At the same time, the water surface and the coast were polluted with liquid hydrocarbons.

In order to limit the ingress of hydrocarbons into subsidence zones in June 1981, the construction of the dam around the perimeter of the emergency site was started. In 1982–1983, along the Pechora River and in the Korovinskaya Bay at distances up to 3 km from the K-9 well, gas sips were observed, indicating the formation of man-made deposits. Attempts to eliminate the disaster continued, but did not lead to success. In particular, wells K-26 and K-27 were drilled, the construction of which was accompanied by emissions from man-made deposits formed as a result of a nuclear explosion. The liquidation work resulted in the subsidence and river flooding of the earth’s surface with an area of about 50 thousand m² and the formation of three large craters with griffins of gas and condensate.

2.4 Drilling on mud volcanoes

On March 8, 2006, drilling of the Banjar Panji-1 deep gas exploration well began in the eastern part of Java Island, Indonesia, located almost directly on the Watukosek fault. When drilling at a depth of about 2834 m, 170 m to the west of the well, a small release of water, steam, and gas occurred (Figure 3). The next two brief eruptions occurred on June 2 and 3, about 800–1000 m to the northwest of the well. During these eruptions, hydrogen sulfide and mud came to the surface at a temperature of 60°C [3, 4].

Figure 3.

The eruption of the LUSI mud volcano. Photo: Adriano Mazzini/Lusi Lab project.

On the day of the eruption, drillers claimed that they had problems stabilizing the pressure in the well when they tried to extract the drill bit. This, as well as the absence of a preventer, led to the release of dirt under high pressure. When trying to block the release, cracks began to form around the well. The emissions quickly reached a daily volume of tens of thousands of cubic meters of mud, which buried an area of 25 square kilometers, including four neighboring villages and a section of a nearby highway. Their residents were temporarily relocated to the building of the local market, turned into a refugee camp.

Many attempts to stop the emissions including the dumping of giant concrete balls into the mud spuiring mouth have not been successful. And now, according to some reports, LUSI has begun to collapse under its own weight, threatening to form a giant caldera. According to experts of the Bandung Institute of Technology, “in a number of places in the center of the flooded area there are already sinkholes up to three meters deep, which may indicate the beginning of the formation of a caldera—a large volcanic depression.”

At its peak, LUSI spewed 180,000 cubic meters of mud per day. On September 27, 2006, the Indonesian Government declared the eruption area a disaster zone, which was aggravated on November 22 by the rupture and explosion of the East Java gas pipeline, which resulted in 13 people being killed. The explosion of the pipeline occurred in the fault zone near the wellhead due to its damage during subsidence of the earth’s surface and possible horizontal displacements, which repeatedly damaged the railway track. The explosion of the pipeline, in turn, partially destroyed the constructed dam. The diameter of the resulting explosion funnel was about 50 m.

3. Offshore accidents

Accidents at offshore wells are especially dangerous. The danger of offshore accidents is associated with the high cost of platforms and damage to the environment. Most offshore accidents are associated with storms and hurricanes, but in some cases, the cause of accidents is due to the complex geological conditions of the section. Several such accidents with the destruction of drilling platforms have occurred during the offshore operations. The last major accidents have occurred in the Brazilian offshore, the Gulf of Mexico, and Australian offshore.

3.1 Deepwater horizon

Tragedy in April 2010 cost the lives of 11 people, and 5 billion barrels of oil flowed into the waters off the Gulf of Mexico coast [5]. The Deepwater Horizon rig, owned and operated by offshore-oil-drilling company Transocean and leased by BP was situated in the Gulf of Mexico located about 65 km off the Louisiana coast. The oil well was located on the seabed 1520 m below the surface. On 20 April 2010, during the final phases of drilling at the depth of 5486 m, a geyser of seawater erupted from the marine riser onto the rig, shooting 70 m into the air. This was soon followed by the eruption of a combination of drilling mud, methane gas, and water. The gas component of the slushy material quickly transitioned into a fully gaseous state and then ignited into a series of explosions and then a firestorm. An attempt was made to activate the blowout preventer, but it failed. The final defense to prevent an oil spill, a blind shear ram, was activated but failed to plug the well [5].

The burning natural gas traveled up to the platform, where it killed 11 workers and injured 17. The rig capsized and sank on April 22, rupturing the riser, through which drilling mud had been injected in order to counteract the upward pressure of oil and natural gas. Without any opposing force, oil began to discharge into the gulf. The volume of oil escaping the damaged well was to have peaked at more than 60,000 barrels per day. The resulting oil spill continued until 15 July when it was closed by a cap. Relief wells were used to permanently seal the well, which was declared “effectively dead” on 19 September 2010 (Figure 4).

Figure 4.

Deepwater horizon on fire.

The main reason for the disaster was that the decision was taken to replace the mud before plugging the well, even though this would increase the chances of an explosion—and even though the operation failed a critical pressure test the same day. When the cement failed, gas began to force its way up the riser. At this point, concrete well plugs in the pipe should have blocked the gas. But contrary to normal practice, the final plug had not been installed, and the salt water was not heavy enough to stop the high-pressure gas from rising.

The Deepwater Horizon oil spill is still considered the worst oil spill in the history of the United States. In the years since the blowout, scientists have studied many aspects of the spill. They have tried to measure its ongoing environmental and public health impacts. The Gulf was exposed to 3 million tons of oil that affected not only wildlife, but also employment. Tourism decreased, seafood was considered contaminated, and some respected businesses shut down. The recovery was estimated to cost tens of billions of dollars. President Obama created a “National Oil Spill Commission” to seek the principal causes of the Deepwater Horizon disaster.

3.2 Montara accident

Many of the aspects relating to the Deepwater Horizon casualty are relevant to the Montara incident. The mobile offshore drilling unit was 254 km off the northwestern Australian coast in 77 meters of water. The disaster occurred after a blowout and fire on the Montara wellhead platform. The blowout occurred on August 21, 2009. Shortly after the initial release, the unit was evacuated. On 14 September, work began on drilling a relief well and, on 1 November, fire broke out on the wellhead platform after a relief well intercepted the leaking well.

Subsequent investigations, including an Australian commission, concluded that the blowout may have started with the cementing of the casing shoe at the bottom of the inner casing. It is likely that the integrity of the cement was never proven and the outcome was a “wet shoe,” with the cement contaminated by drilling or reservoir fluids. Secondary barriers ought to have been in place was extinguished and the oil leak contained, but not before 400 to1,500 bbls of oil per day had spilled into the Timor Sea. The well’s blowout preventer had not yet been installed.

Chris Spencer in your article “Lessons from the Deepwater Horizon and Montara disasters” [6] wrote that there are many conclusions that can there be drawn from these accidents. The principal aspects that will be kept under consideration are as follows: the effectiveness of safety management systems, inspection systems, process control systems, employee competence, management of communications.

4. Shallow gas accumulations

Shallow gas is currently being produced from Pleistocene and from Miocene-Pliocene sands in many places on the continental shelf. The presence of gaseous hydrocarbons in near-surface sediment may represent a hazard for drilling operations and offshore construction. Shallow hydrocarbon accumulations often appear as “bright spots” on seismic data and these investigations may assist in mitigating the risks associated with drilling operations. Sonar and high-resolution seismic surveys were carried out to obtain information about the effects of gas and gas-filled sediments and are marked by bright and cloudy spots, sometimes pockmarks and acoustic voids (Figure 5).

Figure 5.

Images of “bright spots” on seismic data [7].

According to recommendations [8], once a shallow gas zone is encountered (e.g. with early gas kick signs), the drilling operation should be stopped immediately, and a well killing fluid with an estimated density should be injected into the wellbore using a higher circulation rate. After the well is killed and gas in well bore is discharged, cementing can be used to seal the shallow gas formation. And then drilling operation can be restored to drill through the shallow gas formation using heavier drilling fluid. Underestimation of this danger has led to many accidents during drilling on the continental shelf.

4.1 Caspian shelf

During the development of the Caspian shelf, the main danger during the construction of platforms is associated with gas emissions from the upper part of the section and their consequences. They are confined to certain lithological and stratigraphic levels, localized in the most porous traps. When drilling these deposits, the formation of griffins occurs from the violation of the bases of the platforms and the release of gas and its ignition. The most typical scenario of a disaster in the Northern Caspian is described in the book by M.A. Mirzoev [9]. A floating drilling rig “60 years of Azerbaijan” was grounded on the Rakushechnoe-Sea floor near the Kazakh shores. The sea depth was 43 meters, the project depth was 4500 m. At first everything was fine. An 812-millimeter water-separating casing was driven to a depth of 87 m, after which the drillers began to deepen the well. At the bottom of 445 m, the washing liquid circulating in the well was interrupted by gas. Having weighed down the washing liquid, they reached a depth of 511 m.

The next operation was the descent of the conductor—casing with a diameter of 508 millimeters to the drilled depth. After the descent of this column, it was cemented and put on cement hardening. Already 6 hours after the end of filling the column, the movement of clay solution from the inter-column space began, which turned into open gushing with gas. A powerful water-gas mixture with mud hit the sky. Later, the flow of gushing liquid reached a 10-meter height from the rotor, and an hour later the fountain grew to 45–50 meters. Another stream hit under the rotor. At the same time, another griffin appeared along the entire perimeter of the floating drilling rig—mud seeping into the sea—from the side of the second support column. The situation has become catastrophic.

And only then it was decided to remove the rig “60 years of Azerbaijan” from the drilling point. But the ever-growing fountain simply did not allow this to be done. The situation was further complicated by the fact that it became impossible to move the portal with the drilling rig to carry out further operations and to leave the scene of the accident. The supporting columns of the platform began to sink into the ground leading to the erosion of the supporting columns by the affected griffin. The rig gave a strong roll toward the second support column. From that moment, the evacuation of the crew began. Due to the roll of the platform, normal evacuation was impossible. The boats were rocking. In addition, a strong wind has risen. Someone from the boat began to jump right into the sea. Others were simply pushed out by the waves. A group of specialists, who did not have time to evacuate in boats, huddled on the edge of the rig pontoon, which overhung the sea. The floating drilling rig capsized abruptly and sank.

The next morning, a griffin with a diameter of 30–35 m was seething in the area of the death of the drilling rig. After firing a rocket launcher, the sailors set fire to the gas. The height of the fountain reached 20–25 m. Later, the fountain intensified and reached a height of 30–35 m. Over time, the griffin began to weaken. In a month, the height of the fountain was only one and a half meters with a diameter of 80 m, and soon the griffin disappeared altogether. And over the sea for eight long years, only a part of the support column of the platform stood out. The diving survey led to the conclusion that the rise of the rig is unprofitable. Sometimes, a fountain appeared again at the site of the death of the rig. But after a while the fountain stopped.

“The Gates of hell.” The next man-made object formed during the drilling of a well is located in the Karakum desert 270 km from Ashgabat, the capital of Turkmenistan. This unique sinkhole appeared after drilling of a well that was started near the village of Darvaz in 1971. Geologists unexpectedly uncovered a large underground cavity with shallow gas, which absorbed all their equipment, including a drilling rig and transport. As a result, a huge hole was formed in the earth’s crust, into which fell all the equipment used for drilling operations: a drilling rig, equipment, transport (human casualties, fortunately, were avoided). After this accident, gas began to escape through the newly formed crack (Figure 6). In order to prevent a full-scale ecological catastrophe due to poisoning of people, flora and fauna, the pit was set on fire. According to the calculations of geologists, the discovered reserves of methane were supposed to run out in just a few days. The deposit in this area turned out to be so large that since 1971, the fire is still burning.

Figure 6.

Fire in the crater Darvaza, Turkmenistan.

It is believed that during this time several billion cubic meters of natural gas have already burned here. Environmentalists continue to talk about the negative impact of the Darvaza crater on the environment and the health of the local population. Heeding their arguments, the former President of Turkmenistan Gurbanguly Berdimuhamedov ordered “to find a solution to extinguish the fire.” In addition to environmental harm, he drew attention to the economic component. “We are wasting valuable natural resources, from which we could make a profit, and it would go to improving the welfare of our people,” Berdimuhamedov said. But nobody knows how to solve this problem.

5. Drilling in salt deposits

5.1 The catastrophe in the Sahara

On October 26, 1986, a major geological disaster occurred in Algeria—the formation of a sinkhole at the Houd Berkaoui oil field, southwest of the city of Ouargla. A crater was formed with a depth of 80 m and a diameter of almost 200 m. As a result, the OKN-32 oil well was flooded. A few months later, in the spring of 1987, the crater expanded to the nearby OKN-32 bis oil well. The collapse increased to 320 m in diameter. Since then, the crater has continued to expand, which has serious environmental consequences for the Ouargla region [10, 11].

The collapse occurred after many disruptions in the operation of the well in the period from 1978 to 1982. The destruction of the casing was discovered, which isolated the Continental Intercalary aquifer of the Alban-Barremian age, which is the main source of water supply in the Northern Sahara. Rising to the surface with a significant flow rate of several thousand m³/hour, the water passes through the saline deposits of the Upper Cretaceous. It was the dissolution of the salt that caused the formation of the failure (Figure 7). The situation is aggravated by the fact that water saturated with salt rises to the surface and pollutes surface aquifers, which are vital for the needs of the local population.

Figure 7.

Formation of a failure at the OKN-32 well [11].

Thus, the Albian water rises to the surface with a great debit and a temperature of more than 50°C at a speed of 1 to 1.5 m/s through a layer of salt of 200 m in thick. Salt dissolves in this water, resulting in a huge cave with a depth of 450 to 650 m, which expands. In May 1991, it was noted that a network of concentric faults formed 600 m from the center of the crater; their width near the crater is about a meter (Figure 8). In 1990, the flow rate of rising water was estimated at 2500–2800 m3 per hour. This is the amount that could provide drinking water to a city with a population of about 300,000 people! Seismic studies were carried out to estimate the size of the cave formed as a result of the dissolution of salt deposits as a result of the eruption of water.

Figure 8.

Satellite image of 14.01.2015 showing the crater at the haud Berkaoui field, diameter is about 350 m.

According to a study conducted by the engineering company Enageo in 1991, the maximum length of the underground cavity was about 740 m in the North-West/South-East direction. In the south-west/north-east direction, the length was estimated at 570 m. With regard to surface water pollution, the authors mention that an initial study conducted in 1987 “revealed the spread of salt water pollution in four directions, starting with OKN 32, whose boundaries lie within: — to the east, about 3 km; — to the south, about 2.5 km; — to the north, about 1.5 km away; — to the west about 1 km away.” Subsequent studies of the same type revealed the progression of salinization in all directions.

5.2 A sinkhole in a salt mine

Peigneur – a lake in Louisiana near the city of New Iberia was freshwater, shallow, and popular, until its ecosystem was completely changed due to a man-made disaster [12]. On November 21, 1980, an Oil Company conducted exploration drilling in the lake. At some point, the drill got stuck, and the rig began to list on its side. The workers hurried to the shore, and literally in a matter of minutes, a huge platform went to the bottom of the lake with a depth of just over three meters. Directly under the lake there was a salt mine, the vault of which was pierced as a result of reconnaissance work. The mine was a network of tunnels 30 meters wide and 24 meters high. The ceiling of the shaft was supported by the salt pillars left for this purpose (Figure 9).

Figure 9.

Lake Peigneur and salt mine cross-section.

The water very quickly eroded the 35-centimeter hole and gushed down. As a result, a giant whirlpool was formed, which reached 55 meters in diameter. The whirlpool sucked in a tugboat, a drilling rig, 11 barges, a dock, houses, cars, and a small island with a botanical garden. In just three hours, the lake lost 13 million cubic meters of water (Figure 10). A few days later, when the water level in the lake stabilized, nine of the eleven barges surfaced.

Figure 10.

A lake flew down into the pit, and it is occurred in one hour.

Further, the shallow lake, connected by the Delcambre with the Gulf of Mexico, began to fill with salt water. At the same time, the water level in the canal dropped by a meter. In place of the mine shaft, a “geyser” of water and rocks about 120 meters high soon shot up—water entered the tunnels faster than air could escape. The maximum depth of Lake Peigneur has increased 100 times, reaching 396 meters. Wilson Brothers and Texaco paid 32 million to Diamond Crystal Salt for the mine and almost thirteen million to local authorities for the ruined lake.

6. Conclusion

The reason for these accidents is due to the fact that the features of the geological structure of the rock mass and existing mine workings that could be affected during drilling were not taken into account. Shallow gas accumulations, aggressive groundwater, salt deposits, mine workings create dangerous situations and have caused catastrophes, which are considered in this paper. Another aspect of the problem is the misunderstanding of the hydrodynamic system “well-reservoir” in a particular case that is the most common cause of the incident.

6.1 Penetration to highly productive reservoir with abnormal pressure

This is the most common cause of uncontrolled fountains. The drilling liquid creates excessive pressure on the highly permeable reservoir and absorption begins with a drop in the liquid level in the pipes. The situation becomes more complicated if the productive zone is penetrated to a considerable depth. Different pressure profiles in the borehole (heavy drilling fluid) and in the reservoir (oil and gas) lead to the effect when the lower part of the borehole works for injection to reservoir, and the upper part of the reservoir erupts fluid to borehole. The introduction of oil and gas into the wellbore facilitates drilling fluid and provokes the release of a gaseous mixture. The reliability of the preventers is very important here in order to prepare for plugging the well.

A similar hydrodynamic effect probably manifested itself when the drilling mud entered the mouth of the LUSI mud volcano. The rise of mud led to a decrease in pressure, the release of gas followed by an eruption.

6.2 Shallow gas accumulations

Gas accumulations at shallow depths create similar problems already at the beginning of drilling. The process features are related to the fact that gas emission takes place in unconsolidated rocks, which is accompanied by geysers and landslides where all equipment is submerged. Shallow hydrocarbon accumulations often appear as “bright spots” on seismic data and these investigations may assist in mitigating the risks associated with drilling operations. To minimize the risk of an accident when opening the upper gas, it is necessary to follow the recommendations given in the article [8].

6.3 Drilling in salt deposits

Drilling through salt sections requires that the particular properties of high solubility be recognized and incorporated in the drilling program. Problem is encountered in drilling through salt include hole closure by unstable salts leading to stuck tools, differential dissolution of beds of. carnallite, bischofite and other halides, encountering insoluble rocks in salt strata always a challenging phase of the drilling. There are many facts when these qualities of salt formations led to a disorder of the drilling process. This chapter discusses cases where salt is an integral part of a rock mass. Disasters occurred due to violations of continuity in adjacent rocks. The outstanding disaster at Lake Peigneur occurred because the managers were negligent and did not study the situation in the drilling area.