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sledgehammer edit the most basic seismic source is a sledgehammer a seismic energy is generated either by striking the ground directly or more commonly striking a metal or polyethylene plate on the ground typically applied for near surface seismic refraction surveys impact of sledgehammer contact with the surface can provide sufficient seismic energy for interface depths up to 30 m or more depending on geological conditions and physical properties 4 explosives edit explosives most widely used as seismic sources are known as gelatin dynamites these dynamites are placed into three subcategories straight gelatins in which nitroglycerin also known as glyceryl trinitrate with the chemical formula c 3 h 5 ono 2 3 is the active component ammonia gelatins in which ammonia nitrite with chemical formula nh 4 no 3 as the active component and semi gelatins in which the composition consists mostly of nitroglycerin 5 upon detonation explosives release large volumes of expanding gas very quickly 6 forcing great pressure to the surroundings in the form of seismic waves citation needed using explosives as seismic sources has been in practice for decades because of the reliability and energy efficiency they provide 7 such sources are most commonly used on land and swampy environments because of high thickness in sediments citation needed typical charge sizes used in the field for reflection surveys are 0 25 kg to 100 kg for single hole sources 0 25 kg to 250 kg or more for multiple hole sources and may reach 2500 kg or more for refraction surveys 5 though dynamites and other explosives are efficient seismic sources because of their reduced costs ease of transport in difficult terrains and lack of regular maintenance compared to other sources 8 the use of explosives is becoming restricted in certain areas causing decline and increasing popularity for alternative seismic sources 7 for instance hexanitrostilbene was the main explosive fill in the thumper mortar round canisters used as part of the apollo lunar active seismic experiments 9 generally the explosive charges are placed between 6 and 76 metres 20 and 250 ft below ground in a hole that is drilled with dedicated drilling equipment for this purpose this type of seismic drilling is often referred to as shot hole drilling a common drill rig used for shot hole drilling is the ardco c 1000 drill mounted on an ardco k 4x4 buggy these drill rigs often use water or air to assist the drilling air gun edit litton lp air gun strings using in marine seismic acquisition seismologist with 18 liter air gun array secured for transport aboard the r v sikuliaq an air gun is used for marine reflection and refraction surveys it consists of one or more pneumatic chambers that are pressurized with compressed air at pressures from 14 to 21 mpa 2000 to 3000 lbf in 2 air guns are submerged below the water surface and towed behind a seismic ship when an air gun is fired a solenoid is triggered that releases high pressure air from one chamber to the back of a shuttle that is normally held in balance between the two equally pressurised chambers the instant lowering of air pressure in the first chamber allows the shuttle to move rapidly into the first chamber releasing a high pressure air reservoir that is behind the shuttle in the second chamber through ports directly into the sea producing a pulse of acoustic energy 10 air gun arrays may consist of up to 48 individual air guns with different size chambers or certain air guns volumes may be clustered together the firing of all of the array is controlled by gun controller and is usually done to within a 1 or 2 millisecond tolerance the aim being to create the optimum initial shock wave followed by the minimum reverberation of the air bubble s since the shuttle is magnetised the rapid movement into the first chamber on releasing the solenoid value provides a small current that is in effect a timing signal for the firing gun that is returned to the gun controller a near field hydrophone located at a known measured distance from the gun port can also be used to time the first break signal into the hydrophone for accurate gun timing verification air gun maintenance is important as guns can misfire the worst case scenario being an auto fire where the gun actually fires repeatedly out of synch because of a defect in the gun itself such as a damaged solenoid valve or a leaking gun o ring a single auto firing gun can result in the total array bubble signature becoming corrupted and if undetected can result in many seismic lines being re shot just for one auto firing gun when the fault is found during initial data processing during normal handling for deployment and recovery air guns must never be fully pressurised to their optimum working pressure on deck and it is normal practice to air down guns to 500 psi to prevent water ingress on deployment and recovery it is also a poor and dangerous practice to test fire guns on deck in the air at pressure there must also be an isolation system in place to prevent the accidental firing of guns on deck by observers or navigators by mistake high pressure air releases on deck can amputate fingers and also result in a high pressure injection injury through the skin an almost untreatable and deadly injury in a seismic environment gunners should wear the required personal protective equipment to protect their eyes and their hearing and minimise exposure of uncovered skin air guns are made from the highest grades of corrosion resistant stainless steel large chambers i e greater than 1 l or 70 cu in tend to give low frequency signals and the small chambers less than 1 l give higher frequency signals plasma sound source edit plasma sound source fired in small swimming pool a plasma sound source pss otherwise called a spark gap sound source or simply a sparker is a means of making a very low frequency sonar pulse underwater for each firing electric charge is stored in a large high voltage bank of capacitors and then released in an arc across electrodes in the water the underwater spark discharge produces a high pressure plasma and vapor bubble which expands and collapses making a loud sound 11 most of the sound produced is between 20 and 200 hz useful for both seismic and sonar applications citation needed there are also plans to use pss as a non lethal weapon against submerged divers citation needed thumper truck edit thumper trucks noble energy northern nevada 2012 in 1953 the weight dropping thumper technique was introduced as an alternative to dynamite sources vibroseis vibroseis 2 seismic vibrator during operation a thumper truck or weight drop truck is a vehicle mounted ground impact system that can be used to provide a seismic source a heavy weight is raised by a hoist at the back of the truck and dropped generally about three meters to impact or thump the ground 12 to augment the signal the weight may be dropped more than once at the same spot the signal may also be increased by thumping at several nearby places in an array whose dimensions may be chosen to enhance the seismic signal by spatial filtering more advanced thumpers use a technology called accelerated weight drop awd where a high pressure gas min 7 mpa 1000 lbf in 2 is used to accelerate a heavy weight hammer 5 000 kg 11 000 lb to hit a base plate coupled to the ground from a distance of 2 to 3 metres 6 ft 7 in to 9 ft 10 in several thumps are stacked to enhance signal to noise ratio awd allows both more energy and more control of the source than gravitational weight drop providing better depth penetration control of signal frequency content thumping may be less damaging to the environment than firing explosives in shot holes 13 citation needed though a heavily thumped seismic line with transverse ridges every few meters might create long lasting disturbance of the soil an advantage of the thumper later shared with vibroseis especially in politically unstable areas is that no explosives are required electromagnetic pulse energy source non explosive edit emp sources based on the electrodynamic and electromagnetic principles seismic vibrator edit a seismic vibrator propagates energy signals into the earth over an extended period of time as opposed to the near instantaneous energy provided by impulsive sources the data recorded in this way must be correlated to convert the extended source signal into an impulse the source signal using this method was originally generated by a servo controlled hydraulic vibrator or shaker unit mounted on a mobile base unit but electro mechanical versions have also been developed the vibroseis exploration technique was developed by the continental oil company conoco during the 1950s and was a trademark until the company s patent lapsed boomer sources edit boomer sound sources are used for shallow water seismic surveys mostly for engineering survey applications boomers are towed in a floating sled behind a survey vessel similar to the plasma source a boomer source stores energy in capacitors but it discharges through a flat spiral coil instead of generating a spark a copper plate adjacent to the coil flexes away from the coil as the capacitors are discharged this flexing is transmitted into the water as the seismic pulse 14 originally the storage capacitors were placed in a steel container the bang box on the survey vessel the high voltages used typically 3 000 v required heavy cables and strong safety containers recently low voltage boomers have become available 15 these use capacitors on the towed sled allowing efficient energy recovery lower voltage power supplies and lighter cables the low voltage systems are generally easier to deploy and have fewer safety concerns noise sources edit correlation based processing techniques also enable seismologists to image the interior of the earth at multiple scales using natural e g the oceanic microseism or artificial e g urban background noise as a seismic source 16 for example under ideal conditions of uniform seismic illumination the correlation of the noise signals between two seismographs provides an estimate of the bidirectional seismic impulse response see also edit reflection seismology seismic refraction references edit r e sheriff 2002 p 160 and p 182 r e sheriff 2002 p312 seismic wave propagation modeling and inversion phil bording archived 2008 02 08 at the wayback machine reynolds john m 2011 an introduction to applied and environmental geophysics 2nd ed chichester west sussex wiley blackwell pp 155 156 isbn 978 0 471 48535 3 1 2 stark andreas 2010 seismic methods and applications universal publishers pp 177 178 isbn 978 1 59942 443 9 explosive chemical product encyclopedia britannica retrieved 2018 10 09 1 2 yordkayhun sawasdee ivanova alexandra giese rüdiger juhlin christopher cosma calin january 2009 comparison of surface seismic sources at the co2sink site ketzin germany geophysical prospecting 57 1 125 139 bibcode 2009geopp 57 125y doi 10 1111 j 1365 2478 2008 00737 x issn 0016 8025 s2cid 55497365 strobbia c vermeer p glushchenko a laake a 2009 06 08 advances in surface wave processing for nearsurface characterisation in land seismic netherlands eage publications bv doi 10 3997 2214 4609 201404894 isbn 978 94 6282 103 3 cite book journal ignored help nasa reference publication r e sheriff 2002 p6 8 r e sheriff 2002 p328 r e sheriff 2002 p357 chinenyeze madu types of seismic energy sources for petroleum exploration in desert dry land swamp and marine environments in nigeria and other sub saharan africa international journal of science and research 6 sheriff r e 1991 encyclopedic dictionary of exploration geophysics society of exploration geophysicists tulsa 376p jopling j m forster p d holland d c and hale r e 2004 low voltage seismic sound source us patent no 6771565 r e sheriff 2002 p295 bibliography edit crawford j m doty w e n and lee m r 1960 continuous signal seismograph geophysics society of exploration geophysicists 25 95 105 robert e sheriff encyclopedic dictionary of applied geophysics geophysical references no 13 4th edition 2002 429 pag isbn 978 1560801184 snieder roel 2004 04 29 extracting the green s function from the correlation of coda waves a derivation based on stationary phase physical review e 69 4 046610 american physical society aps bibcode 2004phrve 69d6610s doi 10 1103 physreve 69 046610 issn 1539 3755 pmid 15169121 seismic wave propagation modeling and inversion phil bording derivation of seismic wave equation can be found here external links edit photos of thumper trucks in action arctic refuge thumper trails utah thumper trails non lethal swimmer neutralization study by the university of texas may 2002 page 42 vibroseis omnilaw international a texas corporation illustration of vibroseis in 3d land seismic acquisition v t e petroleum industry petroleum primary energy benchmarks argus sour bonny light brent dubai indian basket indonesian isthmus 34 light japan cocktail opec reference basket tapis urals west texas intermediate western canadian select data natural gas consumption production reserves imports exports price petroleum consumption production reserves imports exports posted oil price price of gasoline and diesel exploration core sampling geophysics integrated asset modelling petroleum engineering reservoir simulation reservoir modeling petroleum geology petrophysics reflection seismology seismic inversion seismic source drilling blowout completion squeeze job differential sticking directional drilling geosteering drill stem test drilling engineering drilling fluid invasion lost circulation measurement shale oil extraction ljungström method tracers underbalanced drilling well logging production petroleum fiscal regime concessions production sharing agreements artificial lift gas lift pumpjack submersible pump esp downstream enhanced oil recovery eor gas reinjection steam injection midstream petroleum product pipeline refining upstream water injection well intervention xt history 1967 oil embargo 1973 oil crisis 1979 oil crisis 1980s oil glut 1990 oil price shock 2000s energy crisis 2010s oil glut 2020 russia saudi arabia oil price war nationalization gecf opec seven sisters standard oil canada france india iraq norway saudi arabia united states venezuela provinces and fields list of natural gas fields list of oil fields caspian sea daqing oil field east midlands oil province east texas gulf of mexico niger delta north sea permian basin persian gulf prudhoe bay russia venezuela shengli oil field western canada sedimentary basin other topics abbreviations classification sweet oil sour oil oil shale gas orphan wells peak oil fossil fuel phase out timing petrocurrency petrodollar recycling petrofiction shale band shale gas swing producer unconventional oil and gas reservoir heavy crude oil sands oil shale tight oil companies and organisations major petroleum companies supermajors bp chevron eni exxonmobil shell totalenergies national oil compan...