Blowout (well drilling)

A blowout is the uncontrolled release of crude oil and/or natural gas from an oil well or gas well after pressure control systems have failed.

Prior to the advent of pressure control equipment in the 1920s, the uncontrolled release of oil and gas from a well while drilling was common and was known as an oil gusher, gusher or wild well.

History

File:Lucas gusher.jpg

The Lucas Gusher at Spindletop, Texas (1901)

Gushers were an icon of oil exploration during the late 19th and early 20th centuries. During that era, the simple drilling techniques such as cable-tool drilling and the lack of blowout preventers meant that drillers could not control high-pressure reservoirs. When these high pressure zones were breached the hydrocarbon fluids would travel up the well at a high rate, forcing out the drill string and creating a gusher. A well which began as a gusher was said to have "blown in": for instance, the Lakeview Gusher blew in in 1910. These uncapped wells could produce large amounts of oil, often shooting 200 feet (60 m) or higher into the air. A blowout primarily composed of natural gas was known as a gas gusher.

Despite being symbols of new-found wealth, gushers were dangerous and wasteful. They killed workmen involved in drilling, destroyed equipment, and coated the landscape with thousands of barrels of oil; additionally, the explosive concussion released by the well when it pierces an oil/gas reservoir has been responsible for a number of oilmen losing their hearing entirely; standing too near to the drill at the moment it contacts the oil reservoir is extremely hazardous. The impact on wildlife is very hard to quantify, but can only be estimated to be mild in the most optimistic models — realistically, the ecological impact is estimated by scientists across the ideological spectrum to be severe, profound, and lasting.

To complicate matters further, the free flowing oil was — and is — in danger of igniting. One dramatic account of a blowout and fire reads,

"With a roar like a hundred express trains racing across the countryside, the well blew out, spewing oil in all directions. The derrick simply evaporated. Casings wilted like lettuce out of water, as heavy machinery writhed and twisted into grotesque shapes in the blazing inferno."

The development of rotary drilling techniques where the density of the drilling fluid is sufficient to overcome the downhole pressure of a newly penetrated zone meant that gushers became avoidable. If however the fluid density was not adequate or fluids were lost to the formation, then there was still a significant risk of a well blowout.

In 1924 the first successful blowout preventer was brought to market. The BOP valve affixed to the wellhead could be closed in the event of drilling into a high pressure zone, and the well fluids contained. Well control techniques could be used to regain control of the well. As the technology developed, blowout preventers became standard equipment, and gushers became a thing of the past.

In the modern petroleum industry, uncontrollable wells became known as blowouts and are comparatively rare. There has been a significant improvement in technology, well control techniques and personnel training that has helped to prevent them occurring. From 1976 to 1981, 21 blowout reports are available.

Notable gushers

1. The Shaw Gusher in Oil Springs, Ontario, was Canada's (and possibly the world's) first oil gusher. On January 16, 1862, it shot oil from over 60 metres (200 ft) below ground to above the treetops at a rate of 3000 barrels per day, triggering the oil boom in Lambton County.
2. Lucas Gusher at Spindletop in Beaumont, Texas in 1901 flowed at 100,000 barrels (16,000 m³) per day at its peak, but soon slowed and was capped within nine days. The well tripled U.S. oil production overnight and marked the start of the Texas oil industry.
3. Masjed Soleiman, Iran in 1908 marked the first major oil strike recorded in the Middle East.
4. Lakeview Gusher on the Midway-Sunset Oil Field in Kern County, California of 1910 is believed to be the largest-ever U.S. gusher. At its peak, more than 100,000 barrels (16,000 m³) of oil per day flowed out, reaching as high as 200 feet (60 m) in the air. It remained uncapped for 18 months, spilling over nine million barrels (380 million gallons / 1.4 million m³) of oil, less than half of which was recovered.
5. A short-lived gusher at Alamitos #1 in Signal Hill, California in 1921 marked the discovery of the Long Beach Oil Field, one of the most productive oil fields in the world.
6. The Barroso 2 well in Cabimas, Venezuela in December 1922 flowed at around 100,000 barrels (16,000 m³) per day for nine days, plus a large amount of natural gas.
7. Baba Gurgur near Kirkuk, Iraq, an oilfield known since antiquity, erupted at a rate of 95,000 barrels (15,000 m³) a day in 1927.
8. The Wild Mary Sudik gusher in Oklahoma City, Oklahoma in 1930 flowed at a rate of 72,000 barrels (11,500 m³) per day.
9. The Daisy Bradford gusher in 1930 marked the discovery of the East Texas Oil Field, the largest oilfield in the contiguous United States.
10. The largest known 'wildcat' oil gusher blew near Qom, Iran on August 26, 1956. The uncontrolled oil gushed to a height of 52 m (170 ft), at a rate of 120,000 barrels per day. The gusher was closed after 90 days' work by Bagher Mostofi and Myron Kinley (USA).
11. The largest underwater blowout in U.S. history occurred on April 20, 2010, in the Gulf of Mexico at the Macondo Prospect oil field. The blowout caused the explosion of the Deepwater Horizon, a mobile offshore drilling platform owned by Transocean and under lease to BP at the time of the blowout. While the exact volume of oil spilled is unknown, as of June 3, 2010 (2010-06-03), the United States Geological Survey (USGS) Flow Rate Technical Group has placed the estimate at between 35,000 to 60,000 barrels (1.5–2.5 million US gallons; 5,600–9,500 m³) of crude oil per day. The extent of the flow is attributable to the depth of the well; at over 4,000 feet (1,200 m) underwater the technical ability to regain control is made far more difficult than in shallow water or on land.^{[citation needed]}

Cause of blowouts

Reservoir pressure

See also: Petroleum formation

File:OilReservoir.png

A petroleum trap. An irregularity (the trap) in a layer of impermeable rocks (the seal) retains upward-flowing petroleum, forming a reservoir.

Petroleum or crude oil is a naturally occurring, flammable liquid consisting of a complex mixture of hydrocarbons of various molecular weights, and other organic compounds, that are found in geologic formations beneath the Earth's surface. Because most hydrocarbons are lighter than rock or water, they often migrate upward through adjacent rock layers until either reaching the surface or becoming trapped within porous rocks (known as reservoirs) by impermeable rocks above. However, the process is influenced by underground water flows, causing oil to migrate hundreds of kilometres horizontally or even short distances downward before becoming trapped in a reservoir. When hydrocarbons are concentrated in a trap, an oil field forms, from which the liquid can be extracted by drilling and pumping. The down hole pressures experienced at the rock structures change depending upon the depth and the characteristic of the source rock.^{[citation needed]}

Formation kick

The downhole fluid pressures are controlled in modern wells through the balancing of the hydrostatic pressure provided by the mud used. Should the balance of the drilling mud pressure be incorrect then formation fluids (oil, natural gas and/or water) begin to flow into the wellbore and up the annulus (the space between the outside of the drill string and the walls of the open hole or the inside of the last casing string set), and/or inside the drill pipe. This is commonly called a kick. If the well is not shut in (common term for the closing of the blow-out preventer valves), a kick can quickly escalate into a blowout when the formation fluids reach the surface, especially when the influx contains gas that expands rapidly as it flows up the wellbore, further decreasing the effective weight of the fluid.

Additional mechanical barriers such as blowout preventers (BOPs) can be closed to isolate the well while the hydrostatic balance is regained through circulation of fluids in the well.

A kick can be the result of improper mud density control, an unexpected overpressured gas pocket, or may be a result of the loss of drilling fluids to a formation called a thief zone. If the well is a development well, these thief zones should already be known to the driller and the proper loss control materials would have been used. However, unexpected fluid losses can occur if a formation is fractured somewhere in the open-hole section, causing rapid loss of hydrostatic pressure and possibly allowing flow of formation fluids into the wellbore. Shallow overpressured gas pockets are generally unpredictable and usually cause the more violent kicks because of rapid gas expansion almost immediately.^{[citation needed]}

Early warning signs of a well kick are:

• Sudden change in drilling rate;
• Change in surface fluid rate;
• Change in pump pressure;
• Reduction in drillpipe weight;
• Surface mud cut by gas, oil or water.

The primary means of detecting a kick is a relative change in the circulation rate back up to the surface into the mud pits. The drilling crew or mud engineer keeps track of the level in the mud pits and/or closely monitors the rate of mud returns versus the rate that is being pumped down the drill pipe. Upon encountering a zone of higher pressure than is being exerted by the hydrostatic head of the drilling mud at the bit, an increase in mud returns would be noticed as the formation fluid influx pushes the drilling mud toward the surface at a higher rate. Conversely, if the rate of returns is slower than expected, it means that a certain amount of the mud is being lost to a thief zone somewhere below the last casing shoe. This does not necessarily result in a kick (and may never become one); however, a drop in the mud level might allow influx of formation fluids from other zones if the hydrostatic head at depth is reduced to less than that of a full column of mud.

Well control

The first response to detecting a kick would be to isolate the wellbore from the surface by activating the blow-out preventers and closing in the well. Then the drilling crew would attempt to circulate in a heavier kill fluid to increase the hydrostatic pressure (sometimes with the assistance of a well control company). In the process, the influx fluids will be slowly circulated out in a controlled manner, taking care not to allow any gas to accelerate up the wellbore too quickly by controlling casing pressure with chokes on a predetermined schedule.

In a simple kill, once the kill-weight mud has reached the bit the casing pressure is manipulated to keep drill pipe pressure constant (assuming a constant pumping rate); this will ensure holding a constant adequate bottomhole pressure. The casing pressure will gradually increase as the contaminant slug approaches the surface if the influx is gas, which will be expanding as it moves up the annulus and overall pressure at its depth is gradually decreasing.^{[citation needed]}

This effect will be minor if the influx fluid is mainly salt water. And with an oil-based drilling fluid it can be masked in the early stages of controlling a kick because gas influx may dissolve into the oil under pressure at depth, only to come out of solution and expand rather rapidly as the influx nears the surface. Once all the contaminant has been circulated out, the casing pressure should have reached zero.

Sometimes, however, companies drill underbalanced for better, faster penetration rates and thus they "drill for kicks" as it is more economically sound to take the time to kill a kick than to drill overbalanced (which causes slower penetration rates). In this case, calling a well-control specialist is usually unnecessary as qualified personnel are already on site.^{[citation needed]}

Capping stacks are used for controlling blowouts. The cap is an open valve that is closed after bolted on.http://www.jwco.com/technical-litterature/p10.htm

Types of blowouts

File:IXTOC I oil well blowout.jpg

Ixtoc I oil well blowout

Well blowouts can occur during the drilling phase, during well testing, during well completion, during production, or during workover activities.

Surface blowouts

Blowouts can eject the drill string out of the well, and the force of the escaping fluid can be strong enough to damage the drilling rig. In addition to oil, the output of a well blowout might include sand, mud, rocks, drilling fluid, natural gas, water, and other substances.

Blowouts will often be ignited by an ignition source, from sparks from rocks being ejected, or simply from heat generated by friction. A well control company will then need to extinguish the well fire or cap the well, and replace the casing head and hangars. The flowing gas may contain poisonous hydrogen sulfide and the oil operator might decide to ignite the stream to convert this to less hazardous substances.

Sometimes, blowouts can be so forceful that they cannot be directly brought under control from the surface, particularly if there is so much energy in the flowing zone that it does not deplete significantly over the course of a blowout. In such cases, other wells (called relief wells) may be drilled to intersect the well or pocket, in order to allow kill-weight fluids to be introduced at depth. Contrary to what might be inferred from the term, such wells generally are not used to help relieve pressure using multiple outlets from the blowout zone.

Subsea blowouts

Deepwater Horizon drilling rig blowout, 21 April 2010

Subsea wells have the wellhead and pressure control equipment located on the seabed. They vary from depths of 10 feet (3.0 m) to 8,000 feet (2,400 m). It is very difficult to deal with a blowout in very deep water because of the remoteness and limited experience with this type of situation.

The Deepwater Horizon well blowout in the Gulf of Mexico in April 2010, in 5,000 feet (1,500 m) water depth, is the deepest subsea well blowout to date.

Underground blowouts

An underground blowout is a special situation where fluids from high pressure zones flow uncontrolled to lower pressure zones within the wellbore. Usually this is from deeper higher pressure zones to shallower lower pressure formations. There may be no escaping fluid flow at the wellhead. Underground blowouts can be very difficult to bring under control, and if left unchecked the fluids may find their way to the surface or ocean floor nearby.^{[citation needed]}

Blowout control expertise

Myron M. Kinley was a pioneer in fighting oil well fires and blowouts. He developed many patents and designs for the tools and techniques of oil firefighting. His father, Karl T. Kinley, attempted to extinguish an oil well fire with the help of a massive explosion — a method that remains a common technique for fighting oil fires. The first oil well put out with explosives by Myron Kinley and his father, was in 1913. Kinley would later form the M.M. Kinley Company in 1923.

Paul N. "Red" Adair joined the M.M. Kinley Company in 1946, and worked 14 years with Myron Kinley before starting his own company, Red Adair Co., Inc., in 1959. Asger "Boots" Hansen and Edward Owen "Coots" Matthews also begin their careers under Kinley.

Red Adair co. has helped in controlling many offshore blowouts, including;

• CATCO fire in the Gulf of Mexico in 1959
• "The Devil's Cigarette Lighter" in 1962 in Gassi Touil, Algeria, in the Sahara Desert
• The Ixtoc I oil spill in Mexico's Bay of Campeche in 1979
• The Piper Alpha disaster in the North Sea in 1988
• The Kuwaiti oil fires following the Gulf War in 1991.

In 1994, Adair retired and sold his company to Global Industries. Management of Adair's company left and created International Well Control (IWC). In 1997, they would buy the company Boots & Coots International Well Control, Inc., which was founded by two former lieutenants of Red Adair in 1978.

Methods of quenching blowouts

Although several experimental methods exist which attempt to capture as much oil as possible from a blown out well, they are very far from perfect, capturing between 20% - 50% of the leaking oil, by optimistic estimates. Ideally, the well could be made to stop gushing oil entirely - thus putting a stop to the cumulating pollution.

Use of nuclear explosions

On Sep. 30, 1966 the Soviet Union in Urt-Bulak, an area about 80 kilometers from Bukhara, Uzbekistan, experienced blowouts on five natural gas wells. It was claimed in Komsomoloskaya Pravda that after years of burning uncontrollably they were able to stop them entirely. The Soviets lowered a specially made 30 kiloton nuclear bomb into a 6 kilometres (20,000 ft) borehole drilled 25 to 50 metres (82 to 160 ft) away from the original (rapidly leaking) well. A nuclear explosive was deemed necessary because conventional explosive both lacked the necessary power and would also require a great deal more space underground. When the bomb was set off, it proceeded to crush the original pipe that was carrying the gas from the deep reservoir to the surface, as well as to glassify all the surrounding rock. This caused the leak and fire at the surface to cease within approximately one minute of the explosion, and proved over the years to have been a permanent solution. A second attempt on a similar well was not as successful and other tests were for such experiments as oil extraction enhancement (Stavropol, 1969) and the creation of gas storage reservoirs (Orenburg, 1970). As nuclear historian Robert S. Norris notes in the Times, all these Soviet nuclear blasts were on land and did not involve oil. That being the case, the general principles involved are the same.

Notable offshore well blowouts

Data from industry information.

Year	Rig Name	Rig Owner	Type	Damage / details
1955	S-44	Chevron Corporation	Sub Recessed pontoons	Blowout and fire. Returned to service.
1959	C. T. Thornton	Reading & Bates	Jackup	Blowout and fire damage.
1964	C. P. Baker	Reading & Bates	Drill barge	Blowout in Gulf of Mexico, vessel capsized, 22 killed.
1965	Trion	Royal Dutch Shell	Jackup	Destroyed by blowout.
1965	Paguro	SNAM	Jackup	Destroyed by blowout and fire.
1968	Little Bob	Coral	Jackup	Blowout and fire, killed 7.
1969	Wodeco III	Floor drilling	Drilling barge	Blowout
1969	Sedco 135G	Sedco Inc	Semi-submersible	Blowout damage
1969	Rimrick Tidelands	ODECO	Submersible	Blowout in Gulf of Mexico
1970	Stormdrill III	Storm Drilling	Jackup	Blowout and fire damage.
1970	Discoverer III	Offshore Co.	Drillship	Blowout (S. China Seas)
1970	Discoverer II	Offshore Co.	Drillship	Blowout (Malaysia)[citation needed]
1971	Big John	Atwood Oceanics	Drill barge	Blowout and fire.
1971	Unknown	Floor Drilling	Drill barge	Blowout and fire off Peru, 7 killed.
1972	J. Storm II	Marine Drilling Co.	Jackup	Blowout in Gulf of Mexico
1972	M. G. Hulme	Reading & Bates	Jackup	Blowout and capsize in Java Sea.
1972	Rig 20	Transworld Drilling	Jackup	Blowout in Gulf of Martaban.
1973	Mariner I	Sante Fe Drilling	Semi-sub	Blowout off Trinidad, 3 killed.
1974	Meteorite	Offshore Co.	Jackup	Blowout of Nigeria[citation needed]
1975	Topper III	Zapata Offshore	Jackup	Blowout and sinking.[citation needed]
1975	Mariner II	Sante Fe Drilling	Semi-submersible	Lost BOP during blowout.
1975	J. Storm II	Marine Drilling Co.	Jackup	Blowout in Gulf of Mexico.[citation needed]
1976	Petrobras III	Petrobras	Jackup	No info.
1976	W. D. Kent	Reading & Bates	Jackup	Damage while drilling relief well.[citation needed]
1977	Maersk Explorer	Maersk Drilling	Jackup	Blowout and fire in North Sea[citation needed]
1977	Ekofisk Bravo	Phillips Petroleum	Platform	Blowout during well workover.
1978	Scan Bay	Scan Drilling	Jackup	Blowout and fire in the Persion Gulf.
1979	Salenergy II	Salen Offshore	Jackup	Blowout in Gulf of Mexico
1979	Sedco 135F	Sedco Drilling	Semi-submersible	Blowout and fire in Bay of Campeche Ixtoc I well.
1980	Sedco 135G	Sedco Drilling	Semi-submersible	Blowout and fire of Nigeria.
1980	Discoverer 534	Offshore Co.	Drillship	Gas escape caught fire.[citation needed]
1980	Ron Tappmeyer	Reading & Bates	Jackup	Blowout in Persian Gulf, 5 killed.[citation needed]
1980	Nanhai II	Peoples Republic of China	Jackup	Blowout of Hainan Island.[citation needed]
1980	Maersk Endurer	Maersk Drilling	Jackup	Blowout in Red Sea, 2 killed.[citation needed]
1980	Ocean King	ODECO	Jackup	Blowout and fire in Gulf of Mexico, 5 killed.
1980	Marlin 14	Marlin Drilling	Jackup	Blowout in Gulf of Mexico[citation needed]
1981	Penrod 50	Penrod Drilling	Submersible	Blowout and fire in Gulf of Mexico.[citation needed]
1985	West Vanguard	Smedvig	Semi-submersible	Shallow gas blowout and fire in Norwegian sea, 1 fatality.
1981	Petromar V	Petromar	Drillship	Gas blowout and capsize in S. China seas.[citation needed]
1988	Ocean Odyssey	Diamond Offshore Drilling	Semi-submersible	Gas blowout at BOP and fire in the UK North Sea, 1 killed.
1989	Al Baz	Sante Fe	Jackup	Shallow gas blowout and fire in Nigeria, 5 killed.
1993	Actinia	Transocean	Semi-submersible	Sub-sea blowout in Vietnam. .
2001	Ensco 51	Ensco	Jackup	Gas blowout and fire, Gulf of Mexico, no casualties
2002	Arabdrill 19	Arabian Drilling Co.	Jackup	Structural collapse, blowout, fire and sinking.
2004	Adriatic IV	Global Sante Fe	Jackup	Blowout and fire at Temsah platform, Mediterranean Sea
2007	Usumacinta	PEMEX	Jackup	Storm force rig to move, causing well blowout on Kab 101 platform, 22 killed.
2009	West Atlas / Montara	Seadrill	Jackup / Platform	Blowout and fire on rig and platform in Australia.
2010	Deepwater Horizon	Transocean	Semi-submersible	Blowout and fire on the rig, subsea well blowout, killed 11 in explosion.
2010	Vermilion Block 380	Mariner Energy	Platform	Blowout and fire, 13 survivors, 1 injured.

See also

• Petroleum geology
• Oil well fire
• Drilling mud
• Drilling rig
• Oil platform
• Oil well
• List of oil spills
• Underbalanced drilling
• Oil well control

External links

• San Joaquin Geological Society article on famous Californian gushers
• "Blowout Control, Part 10 - Surface Intervention Methods". http://www.jwco.com/technical-litterature/p10.htm. Retrieved 2010-06-19.de:Blowout (Tiefbohrtechnik)