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					Well Design – Spring 2011




                              Well Design
                                 PE 413


                  Introduction and API Standards of Casing




  Prepared by: Tan Nguyen
Well Design – Spring 2011



                                       Casing Design
                                           Introduction

         Choosing the correct size, type, and amount of casing that is used in well
         construction is of utmost importance to the success of the well. The casing must
         be of sufficient size and strength to allow the target formations to be reached and
         produced.

         Casing has become one of the most expensive parts of a drilling program; the
         average cost of tubulars is about 18% of the average cost of a completed well.
         Thus, an important responsibility of the drilling engineer is to design the least
         expensive casing program that will allow the well to be drilled and operated safely
         throughout its life




  Prepared by: Tan Nguyen
Well Design – Spring 2011



                                       Casing Design
                                           Introduction


       The main functions of the casing in any well are:

       1.Maintain hole integrity

       2.Isolate abnormally pressured zones

       3.Protect shallow weak formations from heavier mud weights required in the
       deeper portions of the hole

       4.Prevent contamination of freshwater-bearing strata

       5.Support unconsolidated sediments




  Prepared by: Tan Nguyen
Well Design – Spring 2011



                                Casing Components
                            Component Parts of A Casing String




  Prepared by: Tan Nguyen
Well Design – Spring 2011



                                   Casing Components
                                        Conductor Casing

      • Sea off unconsolidated formations at shallow depths

      • Stop washouts under the drilling rig.

      •   Protect fresh water sands.

      • To give a base and support for the next string of
      casing

      The conductor pipe is the first casing to be put in place,
      and is generally installed before the rig arrives on
      location. Such casing can be driven to 250 feet.
      Conductor casing measuring between 16 to 24" outside
      diameter is used onshore, and between 24 to 48" for
      offshore.

  Prepared by: Tan Nguyen
Well Design – Spring 2011



                                  Casing Components
                                            Surface Casing

        • Protect, water sands

        • Support the wellhead and BOP equipments

        • Case unconsolidated formations

        • Support other casings

        • Case off lost circulation zones

        Surface casing is the first string of casing used after the
        conductor pipe. It is required in some instances by law
        (to protect ground water) and is normally cemented full
        length. Surface casing supports the BOP stack and
        subsequent casing and tubing strings, and is normally
        the only string designed to carry compression loads.


  Prepared by: Tan Nguyen
Well Design – Spring 2011



                                   Casing Components
                                      Intermediate Casing


        Intermediate casing is any string between the
        surface and production string. Intermediate casing
        may or may not be cemented full length.

        Intermediate casing may be used to:

        1. Seal off weaker zones

        2. Protect previous casing strings from higher Pburst

        3. Provide support for liner casing.




  Prepared by: Tan Nguyen
Well Design – Spring 2011



                                  Casing Components
                                       Production Casing


        The fourth but not necessarily the final string of pipe
        run in the hole is the production casing. The production
        casing is used to control the hydrocarbon bearing
        zones that will be produced. This string of pipe adds
        structural integrity to the wellbore in the producing
        zones.

        Production casing should be set before completing the
        well for production. It should be cemented in a manner
        necessary to cover or isolate all zones which contain
        hydrocarbons.




  Prepared by: Tan Nguyen
Well Design – Spring 2011



                            Casing Components
                               Running Casing




  Prepared by: Tan Nguyen
Well Design – Spring 2011



                                  Casing Components
                                         Running Casing


         Mississippi: Not encounter abnormal formation pressure, lost circulation zones, salt
         sections. Required only conductor casing, surface casing and production casing


         Offshore Louisiana and Texas Delaware Basin: Encounter abnormal pore
         pressure, lost circulation zones, salt sections, unstable shale sections. Required
         intermediate casing to protect formation below the surface casing from the
         pressures created by the required high drilling fluid density. Liner is used to lower
         the cost of drilling. It serves similarly to intermediate casing in that it isolates
         troublesome zones that tend to cause well problems during drilling operations.




  Prepared by: Tan Nguyen
Well Design – Spring 2011



                            Casing Design
                            Bit – Hole - Casing




  Prepared by: Tan Nguyen
Well Design – Spring 2011



                                         API Standard
                                           API Standard


         The size of the casing refers to the outside diameter (O.D.) of the main body of the
         tubular (not the connector). Casing sizes vary from 4.5" to 36" diameter. Tubulars
         with an O.D. of less than 4.5” are called Tubing.




  Prepared by: Tan Nguyen
Well Design – Spring 2011



                                       API Standard
                                         Casing Length


         The API standards recognize three length ranges for casing:

         Range 1 (R-1): 16 – 25 ft

         Range 2 (R-2): 25 – 34 ft

         Range 3 (R-3): > 34 ft

         Casing is run most often in R-3 lengths to reduce the number of connections in the
         string. Since casing is made up in single joints, R-3 lengths can be handled easily
         by most rigs.




  Prepared by: Tan Nguyen
Well Design – Spring 2011



                                         API Standard
                                          Casing Weight

         For each casing size there are a range of casing weights available. The weight of
         the casing is in fact the weight per foot of the casing and is a representation of the
         wall thickness of the pipe. There are for instance four different weights of 9 5/8"
         casing. (Drift diameter refers to the guaranteed minimum ID of the casing.)




  Prepared by: Tan Nguyen
Well Design – Spring 2011



                                      API Standard
                                        Casing Grade


          In addition to the API grades,
          certain manufacturers produce
          their own grades of material.
          Both    seamless   and   welded
          tubulars are used as casing
          although seamless casing is the
          most common type of casing
          and only H and J grades are
          welded.




  Prepared by: Tan Nguyen
Well Design – Spring 2011



                                               API Standard
                                        Definition of Yield Strength


    Proportionality limit:
    Up to this amount of stress, stress is proportional to strain
    (Hooke’s law), so the stress-strain graph is a straight line,
    and the gradient will be equal to the elastic modulus of the
    material.


    Elastic limit (yield strength):
    Beyond the elastic limit, permanent deformation will occur.
    The lowest stress at which permanent deformation can be
    measured is defined as yield strength.                          Typical yield behavior for non-ferrous alloys.
                                                                    1: True elastic limit
                                                                    2: Proportionality limit
                                                                    3: Elastic limit
                                                                    4: Offset yield strength



  Prepared by: Tan Nguyen
Well Design – Spring 2011



                                         API Standard
                                           Casing Grade

         The chemical composition of casing varies widely, and a variety of compositions
         and treatment processes are used during the manufacturing process This means
         that the physical properties of the steel varies widely. The materials which result
         from the manufacturing process have been classified by the API into a series of
         “grades”. Each grade is designated by a letter, and a number. The letter refers to
         the chemical composition of the material and the number refers to the minimum
         yield strength of the material e.g. N-80 casing has a minimum yield strength of
         80000 psi and K-55 has a minimum yield strength of 55000 psi. Hence the grade of
         the casing provides an indication of the strength of the casing. The higher the
         grade, the higher the strength of the casing.




  Prepared by: Tan Nguyen
Well Design – Spring 2011



                                       API Standard
                                           Connections

         Individual joints of casing are connected together by a threaded connection. These
         connections are variously classified as: API; premium; gastight; and metal-tometal
         seal. In the case of API connections, the casing joints are threaded externally at
         either end and each joint is connected to the next joint by a coupling which is
         threaded internally.

         The standard types of API threaded and coupled connection are:

         • Short thread connection (STC)

         • Long thread connection (LTC)

         • Buttress thread connection (BTC)




  Prepared by: Tan Nguyen
Well Design – Spring 2011



                            API Standard
                             Connections




  Prepared by: Tan Nguyen
Well Design – Spring 2011



                                            API Standard
                            API Specifications, Standard and Bulletins

       API SPEC 5CT, “Specification for casing a tubing”: Covers seamless and welded casing and tubing,
       couplings, pup joints and connectors in all grades. Processes of manufacture, chemical and
       mechanical property requirements, methods of test and dimensions are included.

       API STD 5B, “Specification for threading, gauging, and thread inspection for casing, tubing, and line
       pipe threads”: Covers dimensional requirements on threads and thread gauges, stipulations on
       gauging practice, gauge specifications and certifications, as well as instruments and methods for the
       inspection of threads of round-thread casing and tubing, buttress thread casing, and extreme-line
       casing and drill pipe.

       API RP 5A5, “Recommended practice for filed inspection of new casing, tubing and plain-end drill
       pipe”: Provides a uniform method of inspecting tubular goods.




  Prepared by: Tan Nguyen
Well Design – Spring 2011



                                               API Standard
                            API Specifications, Standard and Bulletins

       API RP 5B1, “Recommended practice for thread inspection on casing, tubing and line pipe”: The
       purpose of this recommended practice is to provide guidance and instructions on the correct use of
       thread inspection techniques and equipment.

       API RP 5C1, “Recommended practice for care and use of casing and tubing”: covers use,
       transportation, storage, handling, and reconditioning of casing and tubing.

       API RP5C5, “Recommended practice for evaluation procedures for casing and tubing connections”:
       Describes tests to be performed to determine the galling tendency, sealing performance and
       structural integrity of tubular connections.

       API BULL 5A2, “Bulletin on thread compounds”: Provides material requirements and performance
       tests for two grades of thread compound for use on oil-field tubular goods.




  Prepared by: Tan Nguyen
Well Design – Spring 2011



                                            API Standard
                            API Specifications, Standard and Bulletins

       API BULL 5C2, “Bulletin on performance properties of casing and tubing”: Covers collapsing
       pressures, internal yield pressures and joint strengths of casing and tubing and minimum yield load
       for drill pipe.

       API BULL 5C3, “Bulletin on formulas and calculations for casing, tubing, drillpipe and line pipe
       properties”: Provides formulas used in the calculations of various pipe properties, also background
       information regarding their development and use.

       API BULL 5C4, “Bulletin on round thread casing joint strength with combined internal pressure and
       bending.”: Provides joint strength of round thread casing when subject to combined bending and
       internal pressure.




  Prepared by: Tan Nguyen
Well Design – Spring 2011



                                    Rig-Site Operation
                                 Casing Running Procedures

       Casing leaks are often caused by damaging the threads while handling and running
       the casing on the rig. It has also been known for a joint of the wrong weight or grade
       of casing to be run in the wrong place, thus creating a weak spot in the string. Such
       mistakes are usually very expensive to repair, both in terms of rig time and
       materials. It is important, therefore, to use the correct procedures when running the
       casing.




  Prepared by: Tan Nguyen
Well Design – Spring 2011



                             Rig-Site Operation
                            Casing Running Procedures




  Prepared by: Tan Nguyen
Well Design – Spring 2011



                                    Rig-Site Operation
                                  Casing Running Procedures

       As more joints are added to the string the increased weight may require the use of
       heavy duty slips (spider) and elevators

       If the casing is run too quickly into the hole, surge pressures may be generated
       below the casing in the open hole, increasing the risk of formation fracture. A
       running speed of 1000 ft per hour is often used in open hole sections. If the casing
       is run with a float shoe the casing should be filled up regularly as it is run, or the
       casing will become buoyant and may even collapse, under the pressure from the
       mud in the hole.

       The casing shoe is usually set 10-30 ft off bottom.




  Prepared by: Tan Nguyen
Well Design – Spring 2011



                                       Rig-Site Operation
                                      Casing Running Procedures




                       Regular Slip
                                                          Heavy duty slip




  Prepared by: Tan Nguyen
Well Design – Spring 2011



                                     Rig-Site Operation
                                    Liner Running Procedures


       Liners are run on drillpipe with special tools which allow the liner to be run, set and
       cemented all in one trip. The liner hanger is installed at the top of the liner. The
       hanger has wedge slips which can be set against the inside of the previous string.
       The slips can be set mechanically (rotating the drillpipe) or hydraulically (differential
       pressure). A liner packer may be used at the top of the liner to seal off the annulus
       after the liner has been cemented.




  Prepared by: Tan Nguyen
Well Design – Spring 2011



                                       Rig-Site Operation
                                      Liner Running Procedures


       The basic liner running procedure is as follows:

       (a) Run the liner on drillpipe to the required depth;

       (b) Set the liner hanger;

       (c) Circulate drilling fluid to clean out the liner;

       (d) Back off (disconnect) the liner hanger setting tool;

       (e) Pump down and displace the cement;

       (f) Set the liner packer;

       (g) Pick up the setting tool, reverse circulate to clean out cement and pull out of hole.



  Prepared by: Tan Nguyen
Well Design – Spring 2011



                            Rig-Site Operation
                            Liner Running Procedures




  Prepared by: Tan Nguyen

				
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