Sunday, June 6, 2010

Blow Outs: A Short History

A blowout is the uncontrolled release of crude oil and/or natural gas from an oil well after pressure control systems have failed.[1]

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

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.[2] 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. In addition, the free flowing oil was in danger of igniting.[3] 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."[4]
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.[5] 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.[1] From 1976 to 1981, 21 blowout reports are available.[1]

[edit] Notable gushers
The 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.[6] Masjed Soleiman, Iran in 1908 marked the first major oil strike recorded in the Middle East.[7] The 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 (378 million gallons/1.4 million m³) of oil, less than half of which was recovered.[2] 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.[8] 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.[9]

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.[10] The Wild Mary Sudik gusher in Oklahoma City, Oklahoma in 1930 flowed at a rate of 72,000 barrels (11 500 m³) per day.[11] The Daisy Bradford gusher in 1930 marked the discovery of the East Texas Oil Field, the largest oilfield in the contiguous United States.[12] 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).[13].

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 British Petroleum at the time of the blowout. While the exact volume of oil spilled is unknown, as of June 3, 2010, the United States Geological Survey (USGS) Flow Rate Technical Group has placed the estimate at between 12,000 to 19,000 barrels per day.[14]

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.

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 mechnical barriers such as blowout preventer (BOP) can be closed to isolate the well whilst 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.

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 an increase in this level would indicate that a higher pressure zone has been encountered at the bit. Conversely, a drop in this level would indicate lost circulation to a formation (which might allow influx of formation fluids from other zones if the hydrostatic head at depth is reduced from less than a full column of mud). The rate of mud returns also can be closely monitored to match the rate that is being pumped down the drill pipe. 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, but this is not necessarily yet a kick (and may never become one). In the case of a higher pressure zone, an increase in mud returns would be noticed as the formation influx pushes the drilling mud toward the surface at a higher rate.

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.

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.

Types of blowouts

Ixtoc I oil well blowoutWell blowouts can occur during the drilling phase, during well testing, during well completion, during production, or during workover activities.[1]

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.[15]

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.

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.[16] Kinley would later form the M.M. Kinley Company in 1923.[16]

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 has helped in controlling many offshore blowouts, including;

CATCO fire in the Gulf of Mexico in the 1959
"The Devil's Cigarette Lighter" in 1962 in 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.[17]
In 1994, Adair retired and sold his company to Global Industries. Management of Adair's company left and created International Well Control. 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.

Notable offshore well blowouts
Data from industry information.[1][18]

Year Rig Name Rig Owner Type Damage / details

1955 S-44 Chevron 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)
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 whilst drlling relief well.
1977 Maersk Explorer Maersk Drilling Jackup Blowout and fire in North Sea
1977 Ekofisk Bravo Phillips Petroleum Platform Blowout during well workover.[19]
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.[19]
1980 Sedco 135G Sedco Drilling Semi-submersible Blowout and fire of Nigeria.
1980 Discoverer 534 Offshore Co. Drillship Gas escape caught fire.
1980 Ron Tappmeyer Reading & Bates Jackup Blowout in Persian Gulf, 5 killed.
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.[20]
2001 Ensco 51 Ensco Jackup Gas blowout and fire, Gulf of Mexico, no casualties[21]
2004 Adriatic IV Global Sante Fe Jackup Blowout and fire at Temsah platform, Mediterranean Sea[22]
2007 Usumacinta PEMEX Jackup Storm force rig to move, causing well blowout on Kab 101 platform, 22 killed.[23]
2010 Deepwater Horizon Transocean Semi-submersible Blowout and fire on the rig, subsea well blowout, killed 11 in explosion.

[edit] See also


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