INTRODUCTION:

Oil Country Tubular Goods (OCTG) is a type of seamless pipe used as oil, natural gas, and geothermal wells according to the API (American Petroleum Institute) standard. The American Petroleum Institute (API) stipulates precisely standardized specifications that define the properties of Oil Country Tubular Goods and classify them into ten grades. These properties are achieved through the chemical composition of the steel and subsequent heat treatment.

A. OCTG Function:

1. Surface Casing : Surface casing is set to provide blowout protection, isolate water sands, and prevent lost circulation. It also often provides adequate shoe strength to drill into high-pressure transition zones. In deviated wells, the surface casing may cover the build section to prevent key-seating of the formation during deeper drilling. This string is typically cemented to the surface or to the mud-line in offshore wells. 

2. Intermediate Casing : The casing which is generally set in place before production casing and after surface casing to provide protection against the abnormally pressured or weak formations. The casing enables the use of drilling fluids with different density crucial for controlling the lower formations. It is generally set in transition zone from the normal pressure to the abnormal pressure. It is often considered as the longest section of the casing present in a well. Most of the wells are drilled with running an Intermediate Casing. The Intermediate Casing is essential on longer drilling intervals where the essential weight of the drilling mud used to prevent well blowouts that can result in hydrostatic pressure which can fracture deeper or shallower formations. This casing placement is preferred to make the hydrostatic pressure of the drilling fluids to remain at a pressure level between the fracture pressure and formation pore pressure. They are set when the borehole conditions or the geological characteristics need isolation. The conditions include, but are not limited to, formation fluid influx, hole instability and prevention of the lost control. It is possible to run multiple Intermediate Casings in a single well. 

3. Liner : A casing string that does not extend to the top of the wellbore, but instead is anchored or suspended from inside the bottom of the previous casing string. There is no difference between the casing joints themselves. The advantage to the well designer of a liner is a substantial savings in steel and therefore capital costs. To save casing, however, additional tools and risk are involved. The well designer must trade off the additional tools, complexities and risks against the potential capital savings when deciding whether to design for a liner or a casing string that goes all the way to the top of the well (a "long string"). The liner can be fitted with special components so that it can be connected to the surface at a later time if required. 

4. Production Casing : When the production zones in a gas or oil reservoirs need to be isolated, the Production Casing is used. Whenever there is an event of tubing leak, the pressure generated by hydrocarbon formations is withheld by the Production Casing. Some of the other reasons for which the Production Casing is installed are to support the casing when injection pressure is exerted from fracture jobs, for gas lift and down casing operations, to support the Injection of chemicals to increase the production rate, and to provide a conduit from the petroleum producing formation right up to the surface. 

5. Tie-back : Liner tieback string is a casing string that provides additional pressure integrity from the liner top to the wellhead. An intermediate tieback is used to isolate a casing string that cannot withstand possible pressure loads if drilling is continued (usually because of excessive wear or higher than anticipated pressures). Similarly, a production tieback isolates an intermediate string from production loads. Tiebacks can be un-cemented or partially cemented. 

6. Tubing : Tubing is the conduit through which oil and gas are brought from the producing formations to the field surface facilities for processing. Tubing must be adequately strong to resist loads and deformations associated with production and work-over. Further, tubing must be sized to support the expected rates of production of oil and gas. Clearly, tubing that is too small restricts production and subsequent economic performance of the well. Tubing that is too large, however, may have an economic impact beyond the cost of the tubing string itself, because the tubing size will influence the overall casing design of the well.

SPECIFICATION:

OCTG are used both onshore and offshore. OCTG consisting of drill pipe, casing and tubing was subject to loading conditions according to their specific application. Each wellbore proceeds in multiple phases: 

• Drill pipe is heavy seamless tube that rotates the drill bit and circulates drilling fluid. Pipe segments 30 ft (9 m) long are coupled with tool joints. Drill pipe is simultaneously subjected to high torque by drilling, axial tension by its dead weight and internal pressure by purging of drilling fluid. Additionally, alternating bending loads due to non-vertical or deflected drilling may be superimposed on these basic loading patterns; 

• Casing (lines the wellbore) is subject to axial tension by its dead weight, internal pressure by fluid purging, and external pressure by surrounding rock formations. Casing is particularly exposed to axial tension and internal pressure by the pumped oil or gas emulsion; 

• Tubing (delivery or production tubes that transport the oil and gas to the surface) is pipe through which the oil or gas is transported from the wellbore. Tubing segments are generally around 30 ft [9 m] long with a threaded connection on each end.

A. OCTG Classification: 

    1.  Classification material based on grouping at API 5CT. 

    2.  API 5CT material leveling based on application: 

         a.  PSL 1 : Low and Medium Pressure Oil Well, Low Depth, Vertical Section 

         b.  PSL 2 : High Pressure Oil Well, Low and Medium Gas Well, Medium Depth,

              Deviated/Horizontal Section, Special Application: Rotating while cementing or

              Rotating Casing 

         c.  PSL 3 : High Pressure Gas Well, High Depth, Deviated/horizontal Section,

             Special application such as Drilling with Casing,Liner or Tubing 

    3. Grade/ Material selection based on well condition

        a. Material Selection Guide Low CO₂ Content 

        b. Material Selection Guide High CO₂ Content 

        c. Thread Connection           

        d. Short thread connection (STC) and Long thread connection (LTC) 

             -  STC is a good choice for a shorter length Casing application that does not need a high

                 axial load and bending. 

             -  LTC is well suit for situation where some axial load is encountered but overall well

                 conditions do not include extreme of temperatures and pressure.

        e.  Buttress thread connection (BTC)

             BTC is an excellent connection for use in a well

             situation involving higher axial load and moderate internal pressure and temperature. 

        f.   Non-Upset tubing (NU)

             NUE use 8rd or 10rd Thread Design, well suited to light duty, and general

             propose Application. 

        g.  External Upset tubing (EU)

             EUE use 8rd or 10rd Thread Design and a non run out thread of round thread design.

             EUE can be deployed for general proposed Drilling and production application where 

             internal pressure is moderate. 

        h.  Premium Connection

             Proprietary designs for casing and tubing that uses vaious connections designs 

             approaches to achieve high level of seals integrity and structural strength.

RANGE/SIZE:

We had vast experience in supplying OCTG to oil and gas company in Indonesia since 2004. Our capability can be described as follows:

A. Size Range :

     2.3/8’’ – 20’’

B. Grades :

     1. API 5CT : Carbon Steel grade J/K 55 to Q125;

     2. Proprietary grades : L80-3%Cr;

     3. CRA Materials : Super 13C, Duplex 22Cr, Super Duplex 25Cr, Austenitic Alloy, and Nikel Base

        Alloy.  

C. Product Level  :

     1. PSL 1;

     2. PSL 2;

     3. PSL 3;

D. Threads :

     1. API Connections (BTC, LTC, STC, EUE, NUE, and IJ);

     2. Premium Connections (NSCT, VAM, TENARIS, etc.).

SUCCESS STORY:

A. CNOOC SES/ PT. Pertamina Hulu Energi OSES

    We had successfully delivered 3% Cr high grade proprietary material to PHE OSES in August

    2018. The supplied items are:

       1. Casing 5-1/2" 15.50 ppf L80-3%Cr LTC;

       2. Tubing 4-1/2" 12.75 ppf L80-3%Cr EUE;

       3. Tubing 3-1/2" 9.30 ppf L80-3%Cr EUE;

       4. Tubing 2-7/8" 6.50 ppf L80-3%Cr EUE;

    The heat treatment and threading process was carried out in Batam and then delivered PHE

    OSES yard in Kalijapat, Jakarta with a controlled delivery system. The delivery is completed

    successfully without problems. 

B. Pertamina EP

    Since 2008, we supplied various sizes of OCTG from 2-3/8” up to 13-3/8” with API grade

    J55/K55 until P110, and Proprietary grade using API or Premium connection. We supplied

    Super Duplex 25% Cr material, which is a material categorized as Corrosion Resistant Alloy

    (CRA) with Premium Connection VAM 21 for the casing and VAM 21 x TENARIS BLUE  for 

    the Crossover in 2018.

    Super Duplex 25% Cr is a special material with special handling and shipping because even

    though the material is resistant to H2S  but is vulnerable with contact to other metals. 

    VAM 21 and TENARIS BLUE is a premium  connection that has a metal-to-metal seal to 

    withstand high pressure at high temperatures. The supplied items were:

    1. Casing Seamless 9-5/8” 47 ppf SM25CR-110 VAM 21;

    2. Crossover 9-5/8” 47 ppf L-80 VAM 21 PIN X 9-5/8” 47 ppf L-80 TENARIS BLUE BOX.

    Shipping packaging utilized econowrap and was covered with tarpaulin to protect against

    contamination of rainwater, sea water, heat, and other contamination that can damage the  

    material. The project was successfully delivered without any material damage. 

C. PetroChina International Jabung Ltd.

     We  supplied casing size of 7” until 9-5/8” and Tubing 2-7/8” grade K55, L80, and L80-13%Cr,

     with API connection and Premium Connection, to Petrochina. In Dec 2018, we succeeded

     supplied Tubing 2-7/8” 6.5 ppf L80 EUE, 30 deg beveled  coupling to Betara Staging Area,

     Jambi. 

D. Nana Yamano Technik (NYT)

    We supplied various sizes of casing and tubing from 2-7/8” until 20” for IPM drilling program at

    Pertamina EP Field Tanjung and PT. Adaro. This IPM Drilling project is conducted by PT. Nana 

    Yamano Technik (NYT). We delivered the items to Field Tanjung, South Kalimantan. The material

    was send from Batam to Tanjung through Banjarmasin without any problems.