Introduction of Directional Drilling in Oil & Gas Indutry - Wikipedia

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Directional drilling - Wikipedia, the free encyclopedia Page 1 of 5 Directional drilling From Wikipedia, the free encyclopedia Directional drilling (or slant drilling) is the practice of drilling non-vertical wells. It can be broken down into three main groups: Oilfield Directional Drilling, Utility Installation Directional Drilling ( or H.D.D., Horizontal Directional Drilling, Directional boring) and in-seam directional drilling (Coal-Bed methane). Contents ■ 1 History ■ 2 Benefits ■ 3 Disa
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  Directional drilling From Wikipedia, the free encyclopedia Directional drilling (or slant drilling ) is the practice of drilling non-vertical wells. It can be brokendown into three main groups: Oilfield Directional Drilling, Utility Installation Directional Drilling ( orH.D.D., Horizontal Directional Drilling, Directional boring) and in-seam directional drilling (Coal-Bedmethane). Contents 1 History ■ 2 Benefits ■ 3 Disadvantages ■ 3.1 Stealing oil ■ 3.2 New Technologies ■ 4 In popular culture ■ 5 See also ■ 6 Sources and notes ■ History Many prerequisites enabled this suite of technologies to become productive. Probably the firstrequirement was the realization that oil wells (or water wells, but since they are shallower, mostdevelopment was in the oil industry) are not necessarily vertical. This realization was quite slow, and didnot really grasp the attention of the oil industry until the late 1920s when there were several lawsuitsalleging that wells drilled from a rig on one property had crossed the boundary and were penetrating areservoir on an adjacent property. Initially, proxy evidence such as production changes in pre-existingwells was accepted, but such cases fueled the development of small diameter tools capable of surveyingwells during drilling.Measuring the inclination of a wellbore (its deviation from the vertical) is comparatively simple,requiring only a pendulum. Measuring the azimuth (direction with respect to the geographic grid inwhich the wellbore is running from the vertical), however, was more difficult. In certain circumstances,magnetic fields could be used, but could be influenced by metalwork used inside wellbores, as well asthe metalwork used in drilling equipment. The next advance was in the modification of small gyroscopiccompasses by the Sperry Corporation, who were making similar compasses for aeronautical navigation.Sperry did this under contract to Sun Oil (who were involved in a lawsuit as described above), and aspin-off company Sperry Sun was formed, which brand continues to this day, absorbed intoHalliburton. Three components are measured at any given point in a wellbore in order to determine itsposition: the depth of the point (measured depth), the inclination at the point, and the magnetic azimuthat the point. These 3 components combined are referred to as a survey . A series of consecutive surveysare needed to track the progress and location of a wellbore. Many of the earliest innovations such asphotographic single shot technology and crow's feet baffle plates for landing survey tools werePage 1 of 5Directional drilling - Wikipedia, the free encyclopedia8/3/2009http://en.wikipedia.org/w/index.php?title=Directional_drilling&printable=yes  developed by Robert Richardson, an independent directional driller who first drilled in the 1940s andwas still working in 2008.(JPT, vol 17, issue 4, pg.32)Prior experience with rotary drilling had established several principles for the configuration of drillingequipment down hole ( Bottom Hole Assembly or BHA ) that would be prone to drilling crookedhole (initial accidental deviations from the vertical would be increased). Counter-experience had alsogiven early directional drillers ( DD's ) principles of BHA design and drilling practice which wouldhelp bring a crooked hole nearer the vertical.Combined, these survey tools and BHA designs made directional drilling possible, but it was perceivedas arcane. The next major advance was in the 1970s, when downhole drilling motors (aka mud motors,driven by the hydraulic power of drilling mud circulated down the drill string) became common. Theseallowed the bit to be rotated on the bottom of the hole, while most of the drill pipe was held stationary.Including a piece of bent pipe (a bent sub ) between the stationary drill pipe and the top of the motorallowed the direction of the wellbore to be changed without needing to pull all the drill pipe out andplace another whipstock. Coupled with the development of Measurement While Drilling MWD tools(using mud pulse telemetry or EM telemetry, which allows tools down hole to send directional data back to the surface without disturbing drilling operations), directional drilling became easier. Certain profilescould not be drilled without the drill string rotating at all times.The most recent major advance in directional drilling has been the development of a range of RotarySteerable tools which allow three dimensional control of the bit without stopping the drill string rotation.These tools [ Revolution ] from Weatherford Drilling Services,Well-Guide from Gyrodata, PowerDrivefrom Schlumberger, AutoTrak from Baker Hughes, PathMaker from PathFinder Energy Services (AnOperating Division of Smith International, Inc), GeoPilot & EZ-Pilot from Sperry DrillingServices/Halliburton) have almost  automated the process of drilling highly deviated holes in the ground.They are costly, so more traditional directional drilling will continue for the foreseeable future.Until recently the drive toward reducing the high cost of these devices has been led from outside the Big Three oilfield service companies such as the mid sized company from West Texas - Black Viper,a company specializing in custom directional equipment and drill bits that is also designing their ownlow cost, low maintenance rotary steerable system, and by entrepreneurs and inventors workingessentially alone. Benefits Directional wells are drilled for several purposes:Increasing the exposed section length through the reservoir by drilling through the reservoir at anangle ■ Drilling into the reservoir where vertical access is difficult or not possible. For instance an oilfieldunder a town, under a lake, or underneath a difficult to drill formation ■ Allowing more wellheads to be grouped together on one surface location can allow fewer rigmoves, less surface area disturbance, and make it easier and cheaper to complete and produce thewells. For instance, on an oil platform or jacket offshore, up to about 40 wells can be groupedtogether. The wells will fan out from the platform into the reservoir below. This concept is beingapplied to land wells, allowing multiple subsurface locations to be reached from one pad, reducingenvironmental impact. ■ Drilling relief wells to relieve the pressure of a well producing without restraint (a blow out ).In this scenario, another well could be drilled starting at a safe distance away from the blow out, ■ Page 2 of 5Directional drilling - Wikipedia, the free encyclopedia8/3/2009http://en.wikipedia.org/w/index.php?title=Directional_drilling&printable=yes  but intersecting the troubled wellbore. Then, heavy fluid (kill fluid) is pumped into the relief wellbore to suppress the high pressure in the srcinal wellbore causing the blowout.Most directional drillers are given a well path to follow that is predetermined by engineers andgeologists before the drilling commences. When the directional driller starts the drilling process,periodic surveys are taken with a downhole camera instrument ( single shot camera ) to provide surveydata (inclination and azimuth) of the well bore.These pictures are typically taken at intervals between 30-500 feet, with 90 feet common during activechanges of angle or direction, and distances of 200-300 feet being typical while drilling ahead (notmaking active changes to angle and direction)During critical angle and direction changes, especially while using a downhole motor, an MWD(Measurement While Drilling) tool will be added to the drill string to provide continuously updatedmeasurements that may be used for (near) real-time adjustments.These data indicate if the well is following the planned path and whether the orientation of the drillingassembly is causing the well to deviate as planned. Corrections are regularly made by techniques assimple as adjusting rotation speed or the drill string weight (weight on bottom) and stiffness, as well asmore complicated and time consuming methods, such as introducing a downhole motor.Such pictures, or surveys, are plotted and maintained as an engineering and legal record describing thepath of the well bore. The survey pictures taken while drilling are typically confirmed by a later surveyin full of the borehole, typically using a multi-shot camera device.The multi-shot camera advances the film at time intervals so that by sealing the camera instrument into atubular housing and dropping the assembly into the drilling string (down to just above the drilling bit),and then withdrawing the drill string at time intervals, the well may be fully surveyed at regular intervals(approximately every 90 feet being common, the typical length of 2 or 3 joints of drill pipe, known as astand, since most drilling rigs stand back the pipe withdrawn from the hole at such increments, knownas stands .)With modern technology great feats can be achieved. Whereas 20 years ago wells drilled at 60 degreesthrough the reservoir were achieved, horizontal drilling is now normal.Drilling far from the surface location still requires careful planning and design. The current recordholders manage wells over 10 km (6 miles) away from the surface location at a depth of only 1600– 2600 m (5,200 –8,500 ft). These are wells drilled from a land location to underneath the sea (WytchFarm (BP), south coast of England, ARA (Total), south coast of Argentina (TFE) Dieksand (RWE),north coast of Germany, Chayvo (ExxonMobil), east coast of Sakhalin Island, Russia, and most recentlyAl Shaheen (Maersk Oil Qatar AS), Offshore Qatar. [1] Disadvantages Until the arrival of modern downhole motors and better tools to measure inclination and azimuth of thehole, directional drilling and horizontal drilling was much slower than vertical drilling due to the need tostop regularly and take time consuming surveys, and due to slower progress in drilling itself (lower rateof penetration). These disadvantages have shrunk over time as downhole motors became more efficientand semi-continuous surveying became possible.Page 3 of 5Directional drilling - Wikipedia, the free encyclopedia8/3/2009http://en.wikipedia.org/w/index.php?title=Directional_drilling&printable=yes  What remains is a difference in operating costs: for wells with an inclination of less than 40 degrees,tools to carry out adjustments or repair work can be lowered by gravity on cable into the hole. For higherinclinations, more expensive equipment has to be mobilized to push tools down the hole.Another disadvantage of wells with a high inclination was that prevention of sand influx into the wellwas less reliable and needed higher effort. Again, this disadvantage has diminished such that, providedsand control is adequately planned, it is possible to carry it out reliably. Stealing oil In 1990 Iraq accused Kuwait of stealing Iraq's oil through slant drilling. Such claims are doubted to havebeen serious enough to justify war or the occupation of Kuwait, since the limits of directional drilling (atthe time) made it unlikely that any such well could have been drilled much more than a mile from thesurface location. Even doing so would have involved drilling sites close to the border and the use of sophisticated and easily identifiable equipment and personnel for extreme distances. The United Nationsredrew the border after the 1991 Gulf war that liberated Kuwait from a seven-month Iraqi occupationunder former leader Saddam Hussein. It placed 11 oil wells, some farms and an old naval base that usedto be in Iraq on the Kuwaiti side. [2] In the mid-twentieth century, a slant-drilling scandal occurred in the huge East Texas Oil Field. [3] New Technologies Between 1985 and 1993, NCEL (now the NFESC) of Pt Hueneme, California developed horizontaldrilling technologies. [4] These technologies are capable of reaching 10,000 to 15,000 feet and may reach25,000 feet (approximately the distance from Kuwait to Iran, across the coast area of Iraq) when usedunder favorable conditions. [5] In popular culture In an episode of The Simpsons ([2F16] Who Shot Mr. Burns? Part One), Mr. Burns appropriates oilfrom underneath an existing structure via pipelines running diagonally from his 'Slant Drilling Co.' [6] See also Geosteering ■ Mud logging ■ MWD (Measurement While Drilling) ■ LWD (Logging While Drilling) ■ Horizontal directional drilling ■ Rotary Steerable System ■ Devico AS ■  Page 4 of 5Directional drilling - Wikipedia, the free encyclopedia8/3/2009http://en.wikipedia.org/w/index.php?title=Directional_drilling&printable=yes
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