Material Data Sheet

• Proprietary SM-TXS  series.TGP-3162 (latest revision)
• API 5CT / ISO 11960
• NACE MR0175 / ISO 15156-2
• API 5C3 / ISO 10400
• API 5C1 / ISO 10405
• VAM Book

External Pressure driven applications in severe Sour Service environments corresponding to region 3, as defined by NACE MR0175/ISO15156-2 (Fig 1) :

Fig. 1 : Sour Service regions in the pH vs H₂S diagram
* Note : Even though this low pH corner is considered non-sour as far as H₂S is concerned, caution needs to be exercised, as High Strength materials may become susceptible to Environmental Cracking (EC) even with no or very limited H₂S.

Sulfide Stress Cracking phenomenon is less critical when temperature increases (i.e. increasing depth), whereas problems associated with extreme external pressure conditions usually increases with depth. As a consequence, the necessity of SM-95TXS usage results from the specific combination of unusually high pressure gradient and / or low temperature gradient. Typical applications are :

• Pre-salt formations, salt dome, clastic formation
• Wildcat drilling 

In addition, enhanced collapse resistance can offer well design flexibility where controls of string weight and wall thickness are critically important:

• Tight clearance applications such as contingency drilling liners
• Oversized Drift for intermediate and production Casing
• Deep Offshore applications where slim and light design is critical

For each manufactured SM-95TXS heat, SSC resistance is verified through testing in accordance with NACE TM0177 method A, in solution A, using an applied stress of 90% SMYS while API T95 is delivered based on 80% SMYS on a standard basis. Additionally, as part of Nippon Steel QA/QC system, using the same frequency as for the tensile test, a physical Collapse test is performed at the mill on each production run to ensure that the minimum declared material collapse properties are exceeded.

For a more detailed assessment please contact Nippon Steel engineers.

While the increase of temperature minimizes SSC susceptibility as outlined in Figure 2, SM-95TXS remains SSC resistant at all temperatures.

Fig. 2 : Dependency of SSC susceptibility on test temperature.
Nippon Steel modified 4130 material,σappl=100%AYS, pH₂S=100kPa at 25 deg.C, NACE Method A, solution A.
[Ref : R.D.Kane et,.al.J.Petroleum Technology, 1483(1977)]

In addition, Figures 2 features the major sensitivity of SSC resistance to the material strength : SSC susceptibility increases along with material Yield strength. On that regards, SM-95TXS preserves its SSC resistance across the full range of its specified Yield strength range, as shown in Figure 3.

Fig. 3 : H₂S partial pressure versus materials SSC behavior.
Nippon Steel modified 4130 material, σappl=100%AYS, 4PB, solution A, 25 deg.C.

While NACE TM0177 has standardized its testing environments to 100kPa H₂S, Nippon Steel has explored SSC susceptibility at higher H₂S partial pressure, as illustrated in Figure 3, in order to assess the robustness of its material designs and processes. SM-95TXS was successfully tested up to 1000 kPa or 10 bar H₂S, and is to be considered full fledge Sour Service.

Pipe dimensions such as Diameter (D) or wall thickness (t) and mechanical characteristics such as the material Yield Strength are the first parameters dictating tubular Collapse resistance. Figure 4 specifically illustrates the commensurate influence of the D/t ratio (Diameter over wall thickness).

Nippon Steel, on SM-TXS High Collapse & Sour Service series, applies tighter tolerances to influential parameters, such as ovality, eccentricity, OD and wall thickness. In addition, a specific chemistry and strict heat treatment control are used to ensure steel structural homogeneity and low residual stresses.

Figure 4 demonstrates SM-95TXS enhanced performances compared to API T95 collapse resistance (derived from API 5C3 / ISO 10400 formula), through its physical test results, guaranteeing the published minimum Collapse ratings.

Fig. 4 : Collapse pressure on SM-95TXS versus API T95

Table 5 features SM-95TXS High Collapse values for a large selection of pipe sizes. They exceed API T95 collapse ratings by a factor ranging from +10% to +40%.

Table 5 : SM-95TXS High Collapse values

Table 5 covers most common sizes and wall thicknesses; upon request Nippon Steel can provide larger sizes up to 16", specific or tailor-made sizes, weights or special drifts.

For additional information about material performances please contact Nippon Steel engineers.

Health, Safety and Environment

While state-of-the-art HSE rules are applied throughout Nippon Steel manufacturing process, proprietary and specific HSE regulations shall be applied along the life cycle of the pipe until it reaches its final position in the well, according to each operator’s rules. This particularly applies to all phases of handling and transportation, assembly on the rig floor, and rig return if applicable. OCTG are heavy and by nature unstable. Special care shall be paid to potential risks of injury whenever handling OCTGs. Walking on pipes shall be avoided at all times. Usage of Personal Protection Equipments (PPE) is mandatory. Equipment and procedures will be established to capture the possible wastes generated during maintenance (cleaning, coating, doping) and disposed according to local regulations. This applies in particular to storage dope, running dope, or cleaning water wastes.

Best practices for transportation, handling and storage of OCTG in general are covered by ISO 10405 / API RP5C1. VAM Book is also a good source of handling practices for VAM connections. In addition to these general rules, specific care is recommended pertaining to SM95TXS, because improper handling could affect the material performances and by extension the corrosion resistance :

• Prevention of Spot Hardening

For more specific information please contact Nippon Steel engineers.