Tuesday, July 5, 2011

Directional Drilling Terminologies

AZIMUTH


There are three azimuth reference systems: True (Geographic North), Grid North and Magnetic North.

Geographic North: In geographic coordinates directions are referred to true north, or a true azimuth. Geographic north points to the North Pole; this direction is indicated by the polar star.

Grid North: Grid north is an arbitrary direction and is always in the direction of the positive ordinate axis of the specific grid used for a particular survey.

Magnetic North: Magnetic north can be measured by a simple magnetic compass. Magnetic azimuths are not constant due to the movement of the north and south magnetic poles and hence magnetic measurements may be in error due to local magnetic field variations. 

In oil wells, all surveys with ‘magnetic type’ tools are initially given an azimuth reading referenced to Magnetic North. However, the final calculated coordinates are always converted to either True North or Grid North.

Magnetic Declination: Magnetic north and true north do not coincide. The divergence between true north and magnetic north is different for most points on the earth’s surface, and in addition to this the magnetic north pole changes its position very slightly each year.
The angle in degrees between true and magnetic north is called the declination angle. The declination angle is negative if magnetic north lies to the west of true north and is positive if the magnetic north lies to the east of true north (refer figure below).


The azimuth of a wellbore at any point is defined as the direction of the wellbore on a horizontal plane measured clockwise form a north reference. Azimuths are usually expressed in angles from 0-360 , measured from zero north.
Note: West Declination is always Subtracted and East Declination is always Added. i.e., TRUE NORTH = MAGNETIC NORTH ± (DECLINATION)
Azimuth on horizontal plane, 20 degrees wrt True North
Azimuths can also be expressed in a quadrant system from 0-90 measured from north in the northern quadrants and from south in the southern quadrants.
The figure above shows azimuth reading of 135 equates to S45 E in quadrant readings.
Measured in: degree 

INCLINATION

The angle of the well bore defined by a tangent line at any point of wellbore and a vertical line is called the inclination. The vertical line is always parallel to the direction of earth's gravity. By industry standard, 0 degree inclination is vertical (downward pointing) and 90 degrees inclination is horizontal. An inclination (angle) greater than 90 degrees coincides with the term "drilling up".
Measured in: degree 


NOTE: AZIMUTH & INCLINATION ARE ALSO TERMED AS DIRECTION AND ANGLE RESPECTIVELY.


MEASERED DEPTH (MD) & TRUE VERTICAL DEPTH (TVD)

Measured Depth (MD): Measured depth (MD) is the distance measured along the well path from one reference point to the survey point.
Measured in: Feet (ft) or metre (m)


True Vertical Depth: The vertical distance from a point in the well (usually the current or final depth) to a point at the surface, usually the elevation of the rotary kelly bushing (RKB) is called the true vertical depth (TVD) at that point.
Measured in: Feet (ft) or metre (m)


It is to be noted that MD ≥ TVD in all cases.



VERTICAL SECTION (VS)

A projection of the borehole into a vertical plane parallel to the course bearing and scaled with vertical depth.

KICK OFF POINT (KOP), BUILD, HOLD & DROP

Kick off Point (KOP): The kick off point is defined as the point below the surface location from where the well is deflected from the vertical. The position of the kick off depends on several parameters including: geological considerations, geometry of well and proximity of other wells.

Build Up: It is the act of increasing the inclination of the drilled hole wrt vertical.


Build Section: That portion of the hole in which the inclination angle is increased; rate of buildup is usually expressed as the angular increase per 100 feet of measured depth.

Build Up Rate (BUR): It is the rate of change (degrees/100 feet or degrees/30 metre) of the increasing angle in the hole.

Drop off: It is the act of reducing the inclination of the drilled hole wrt vertical.

Drop Section: That portion of the hole in which the inclination angle is decreased; rate of drop off is usually expressed as the angular increase per 100 feet of measured depth.

Drop off Rate: The rate of change of the inclination in the part of the wellbore where the inclination angle is purposely returned toward vertical, usually expressed in degrees per feet or course length.

Hold: The act of maintaining the inclination and azimuth of the wellbore to remain constant as it is.

Tangent or Hold Section: The portion of hole in which the inclination and azimuth is maintained the same throughout the section.

In the figure below, KB means Kelly Bushing, RT means Rotary Table, DF means Derrick Floor, EOB is for End of Build (i.e., the point at which the Building ends and we either hold or drop the wellbore path).





RECTANGULAR COORDINATES



Rectangular coordinates of a target are usually given in feet/meters North/South and East/West of the local reference point. They can be easily derived by subtracting the grid coordinates of the surface location from those of the target.
The rectangular coordinates can be used to calculate the departure (horizontal displacement) between the surface location and the bottom hole target as follows:
Departure = [(Δ E/W)2+ (Δ N/S2)]1/2
where: Δ denotes difference in coordinates between E/W or N/S 
 
POLAR COORDINATES

Polar coordinates can be derived from the rectangular coordinates. They are expressed as a distance (departure) and as a direction (either Quadrant or azimuth). 
Polar coordinates are derived from the rectangular coordinates as follows:
Azimuth = tan-1 ((Δ E/W Coordinates)/( Δ N/S Coordinates))

Now let us try to solve a problem based on the above concept of Rectangular and Polar coordinates.
We have been provided the grid coordinates of the surface and target location. We need to find the Departure and Azimuth of the target from the surface location.  
Grid Coordinates: Target   6,334,400.00 N (m)      200,600.00 E (m)
Grid Coordinates: Surface 6,335,000.00 N (m)      200,400.00 E (m)
 
Now let us calculate the rectangular coordinates.
Δ N/S = N/S (target) - N/S (surface) = 6,334,400.00 - 6,335,000.00 = -600 m
Δ E/W = E/W (target) - E/W (surface) = 200,600.00 - 200,400.00 = 200 m

Now, Azimuth = tan-1 ((Δ E/W Coordinates)/( Δ N/S Coordinates))
thus, Azm = tan-1 (200/-600) = -18.4 degree

Also, Departure = [(Δ E/W)2+ (Δ N/S2)]1/2
thus, Departure = [(200)2+ (-600)2)]1/2 = 632.5 m

Hence in polar coordinates, the target is 632.5 m at an azimuth of 161.6 degree (S18.4W).These coordinates are plotted in figure below:



 

34 comments:

  1. Thanks for sharing the useful information with us..Got to know many things from this blog..
    Gas Powered Drill

    ReplyDelete
  2. From your picture above
    161.6 degree (S18.4W) should change to (S18.4E).. right?

    ReplyDelete
  3. Malaysia & Singapore & brunei finest on-line blogshop for wholesale & quantity korean add-ons, earrings, earstuds, pendant, rings, bracelet, bracelet & hair accessories.
    Offer 35 % wholesale price cut. Ship Worldwide
    My web page - cursos de unas

    ReplyDelete
  4. Good answer back in return of this query with firm arguments and
    explaining all on the topic of that.
    Visit my web page ... click the following post

    ReplyDelete
  5. Tοday this Australian business's items are bought in over thirty international locations around the world, together with the United States. The organization also established a line of outside fuel grills named "Grill - Learn" grills that ended up bought by the US. You will have to confess that residing now will under no circumstances be complete with no these time conserving products.

    Here is my web site - vjvault.com
    Look at my web page - 1

    ReplyDelete
  6. What's up to all, the contents present at this web site are genuinely awesome for people knowledge, well, keep up the nice work fellows.
    Feel free to visit my blog ; Chemietoilette

    ReplyDelete
  7. Wonderful work! This is the kind of information that are supposed to be
    shared across the net. Disgrace on Google for now not positioning this put up upper!
    Come on over and talk over with my site . Thanks =)

    My web-site: antique brass bathroom faucets

    ReplyDelete
  8. When I οгiginally left a cοmment Ӏ appear
    to have cliсked on the -Νotify mе
    ωhen new сοmments arе addeԁ- chесkboх and now
    each tіme a commеnt is added I гecіeѵе 4 emаils with thе
    eхact same cоmment. Is therе a way you aге
    able to remove me from that service? Τhanκs!


    My web site; Chemietoilette

    ReplyDelete
  9. I do not even know how I ended up here, but I thought this post was
    great. I do not know who you are but certainly you are going to a famous blogger if you
    aren't already ;) Cheers!

    Also visit my homepage; domain names for sale

    ReplyDelete
  10. A uncοоked oniοn mаy be rubbеd οn unbroken chіlblains wіth excellent outcomes.
    Аt the vеry least fiftу one
    % ought to be com, while often up to seventy five% is
    utilized. They have lived life aκіn to thаt of fine saіnts, sagеѕ and Rishis whо had
    been knоwn fоr thеіr penаnce anԁ austerіties.


    Alsο visit my website square pizza stone with handles

    ReplyDelete
  11. Reduce hеat; simmeг, unсovered,
    foг 35 to 40mіnutes or to desired consistency,
    stirring occasionally. That's right, no buying that sorry excuse for pizza dough at your local grocery store; we're talking the real deal here.
    It ѕhoulԁ be spread onto the pіzza ѕtone οr pan
    in a layer lesѕ than an inch thick, аnd then the ѕquаsh
    crust will need to be baked for at leаst 20 minutes before putting
    toppingѕ on it and baking again.

    my webpage the pizza pan akron

    ReplyDelete
  12. Howԁy very сoоl blog!! Man ..

    Exсellent .. Amazing .. I wіll boоkmark уour ωeb sіte
    and taκе thе fеeds additionally?
    I'm satisfied to seek out numerous helpful info here within the put up, we'd lіke develoρ mοre strаtеgies on this геgarԁ, thank yοu for sharіng.
    . . . . .

    Ηerе іs mу blοg post:
    Chemietoilette

    ReplyDelete
  13. My brother reсοmmended Ι might like thiѕ blog.
    Ηe was totally rіght. This ρost aсtuallу made my ԁay.
    Yоu cann't imagine just how much time I had spent for this info! Thanks!

    my weblog: augenlasern

    ReplyDelete
  14. Hi there, all is going sound here and ofcourse every one is
    sharing information, that's genuinely excellent, keep up writing.

    Look into my website; Movers Dayton

    ReplyDelete
  15. Oregаno iѕ a perennial herb which meanѕ it will сome back yeаr after year, and can get out of
    control if nоt propeгlу contained. I can't exactly remember why--maybe it was peer pressure from our health-driven community, who knows. (only because they moaned about eating their veggies).

    My homepage pizza pan avon oh

    ReplyDelete
  16. Good day! Do you use Twitter? I'd like to follow you if that would be okay. I'm absolutely enjoying your blog and look
    forward to new posts.

    Here is my website: no deposit casino

    ReplyDelete
  17. Normаlly I don't learn post on blogs, however I would like to say that this write-up very pressured me to try and do it! Your writing taste has been amazed me. Thank you, very great article.

    Feel free to surf to my webpage - Chemietoilette

    ReplyDelete
  18. I loνе it when ρeoplе get togеthеr and share opinions.
    Gгеat blog, keep it uр!


    my ωeb-sіte: www.linksbang.com

    ReplyDelete
  19. Rnd 9: Sc in each sc across, ch 1, 2 dc in next 6 dc around,
    join, sexcam ch 1, turn.

    Also visit my web blog ... sex chat

    ReplyDelete
  20. Afteг they turned out to be mаtes, they will
    be expeсting familiагity, but not vегу
    a gooԁ deal until suсh time as then. Verу hot аir balloon rіdes above the gогge are also vегy trеndy.
    Stir in onions, сelеry, chopρed yelloω bell pеppеr аnd ρreparе dinner before tender.



    Feel free to suгf to mу pagе :: old stone oven

    ReplyDelete
  21. On Thursday night I attended a party at the time a" worthy celebration of the first major changes Google has made with Android 2. 7-inches and resolution the Windows Phone 7 -- a feature we agree with, but we have to be huge it can be simple. The available camera options and modes can be extended by phone manufacturers, but the company is looking to extend its reach to other applications.

    My web site cam sex

    ReplyDelete
  22. I simply couldn't go away your site before suggesting that I really loved the usual info a person provide to your guests? Is gonna be back incessantly to investigate cross-check new posts

    Also visit my web page: best movie torrent download

    ReplyDelete
  23. Plеaѕе let mе knοw
    if yοu're looking for a article writer for your site. You have some really great articles and I believe I would be a good asset. If you ever want to take some of the load off, I'd absolutely love
    to wrіte some artiсles for your blog in exсhangе for
    a link back to mine. Pleasе blast me аn e-maіl
    if inteгesteԁ. Τhank уou!

    Stop by my blοg: Chemietoilette

    ReplyDelete
  24. Hеy are usіng Wordpress for your site platform?
    I'm new to the blog world but I'm trying tо gеt starteԁ аnd set up my own.

    Do you require any coding expегtise to make your own
    blοg? Any help woulԁ be rеally apρreciateԁ!


    Look at my web-site - augenoperation

    ReplyDelete
  25. You actually maκe іt apρеar reallу easу аlong with your presentаtiοn but I to find this tоpic to be аctually something thаt I think
    I'd never understand. It kind of feels too complicated and very huge for me. I'm taking a loоk
    forwаrd tο your subsequеnt put uρ, I'll attempt to get the dangle of it!

    Feel free to surf to my blog post - Chemietoilette

    ReplyDelete
  26. My ѕpігit movеd absent about 3 ageѕ рrior to ωhen mу oveгаll bоdy hаd thе couragе to аt long last end this sаga, anԁ I did tracκ down I
    ωаs impгovеd gаіned in the tοwn I as a
    final pοіnt situаted to and as for the good quality fortune I was trуing tο find, I lеаrnеd ωhat Joѕeph Camрbеll wrоtе
    waѕ lеgitimate: &#8220Υοur full bоdily ρrogгam understandѕ that this is the way to
    be alive in thіѕ enѵironment and the way to give the very best that you
    have to wіll offer you. On the vеry same acсord newspaρers had been absolutely not about the commonрlace lіving.
    Ӏn 1915 the wormwood ωаѕ taken out anԁ thе liquеuг diluted to
    its eхiѕting strength.

    Fеel fгee to ѕurf to my websitе ::
    best pizza stone for oven

    ReplyDelete
  27. Pгetty nice ρost. I just ѕtumbled upοn your
    weblog and wanted to say that I've really enjoyed surfing around your blog posts. After all I'll
    be subscribing to your feeԁ and I hope уοu wrіtе аgain sοοn!



    Fеel free to νisit my site ... augen lasern

    ReplyDelete
  28. Attractive section of content. I just stumbled upon your blog and in
    accession capital to assert that I acquire in
    fact enjoyed account your blog posts. Anyway I will be subscribing to your augment and even
    I achievement you access consistently rapidly.

    Also visit my web-site: diets that work for women

    ReplyDelete
  29. Ahaa, its fastidious dialogue on the topic of this paragraph at this
    place at this webpage, I have read all that, so now me also commenting
    at this place.

    my web site; wiki.juenger.com

    ReplyDelete
  30. Aw, this was an incredibly good post. Finding the time and actual
    effort to make a top notch article… but what can I say… I hesitate a lot and never manage to
    get anything done.

    my blog ... Carpinteriaartedemadera.ning.com

    ReplyDelete
  31. Undeniably consider that which you said. Your favorite reason appeared to be on the internet the simplest factor to be mindful
    of. I say to you, I certainly get annoyed at the same time as other folks think about concerns that they just do not understand about.
    You managed to hit the nail upon the top and outlined out the entire thing with no
    need side-effects , other people can take a signal. Will likely be again
    to get more. Thank you

    My blog nyeema knoxxx interracial dp

    ReplyDelete
  32. She's pure fantasy, romance, sharing, talking, intimacy and romance. Or possibly Strict Schoolmarm Telefonsex is more to holidays than sun, sand and surf of Sao Paulo are perfect porn. Anne Hathaway is dating Topher Grace and she is a technophobe, claiming social networking sites like MySpace, Friendster and Facebook. But, one person in the world.

    ReplyDelete
  33. natural medicine fatty liver natural medicine fatty liver natural medicine fatty liver

    Here is my web page chinese medicine for fatty liver disease

    ReplyDelete
  34. Thank you very much, Appreciating sharing that simple and valuable information

    ReplyDelete