Tubing grade guidelines

When聽selecting聽steel聽type聽for聽pipes聽and聽connections聽it聽is聽important聽to聽consider聽the聽corrosive environment that聽the聽steel聽will聽be聽subjected聽to.聽There聽are聽several聽parameters聽in聽the聽well聽that聽affect the corrosion, like temperature, chloride ion concentration, partial pressure of CO2 and H2S, pH and presence or absence of Sulphur [Craig et al. 2011].

When聽selecting聽a聽material聽there聽are聽certain聽aspects聽that聽have聽to聽be聽taken聽into聽consideration聽[NORSOK聽M-001聽2004]:

  • Corrosivity;
  • Design聽life;
  • Availability;
  • Failure聽possibility聽and聽the聽consequences聽related聽to聽failure;
  • Resistance聽to聽brittle聽fracture;

API tubing steel grades are identified by letters and numbers which dictate various characteristics of the steel. For each grade, the number designates the minimum yield strength. Thus L-80 grade steel has a minimum yield strength of 80,000 psi. In other words, it can support a stress of 80,000 psi with an elongation of less than 0.5%. The letter in conjunction with the number designates parameters such as the maximum yield strength and the minimum ultimate strength which for L-80 pipe are 95,000 psi.

The following table shows the yield values for various API tubing grades:

In addition to API grades, there are many proprietary steel grades which may conform to API specifications, but which are used extensively for various applications requiring properties such as:

Many tubing strings are run which contain these non-API Tubulars. This pipe is made to many but not all API specifications, with variations in steel grade, wall thickness, outside diameter, thread connections, and related upset. Due to these variations, the ratings of burst, collapse, and tensile specifications are non-API.

Guidelines applied to the selection/use of tubing grades:

The following table gives guidelines applied to the selection and use of tubing grades:

Tubing Grade Guidelines applied to the selection/use of tubing grades
H40 路聽聽聽聽聽聽聽聽 An API grade,路聽聽聽聽聽聽聽聽 The Yield strength is relatively low and the cost saving over J55 is minimal. This is why H40 is generally not used in tubing sizes,

路聽聽聽聽聽聽聽聽 聽Used only for non-critical, shallow wells,

路聽聽聽聽聽聽聽聽 Do not use for sour service applications,

路聽聽聽聽聽聽聽聽 H40 couplings don鈥檛 have an API toughness requirement. K55 couplings are used instead.

J55 路聽聽聽聽聽聽聽聽 A commonly used grade when it meets the design criteria and has been the 鈥渟tandard鈥 grade for shallow tubing strings (< 9,000 ft) and low-pressure (< 4,000 psi) wells on land,路聽聽聽聽聽聽聽聽 Fit for H2S service at all temperatures.
K55 路聽聽聽聽聽聽聽聽 Fairly common for large diameter surface casing couplings, although line pipe grades X52 and X56 are becoming a popular replacement,路聽聽聽聽聽聽聽聽 Fit for H2S service al all temperatures,
C75 路聽聽聽聽聽聽聽聽 No longer an official API grade,路聽聽聽聽聽聽聽聽 It was developed as a higher-strength material for sour service but was replaced by L80 tubing.
N80 路聽聽聽聽聽聽聽聽 Acceptable for sweet oil and gas wells when it meets design conditions.路聽聽聽聽聽聽聽聽 Fit for H2S service at temperature greater than 150掳F if quenched & tempered (Q&T),

路聽聽聽聽聽聽聽聽 Fit for H2S service at temperature greater than 175掳F if Normalized (N) & tempered (N&T),

路聽聽聽聽聽聽聽聽 Normally less expensive than L80 grades.

L80 路聽聽聽聽聽聽聽聽 Very common tubular grade, and often used for sour service production casing, production liners, and tubing.路聽聽聽聽聽聽聽聽 Has a maximum hardness requirement.

路聽聽聽聽聽聽聽聽 Satisfactory for SSC (sulfide stress cracking) resistance in all conditions but may incur weight-loss corrosion.

路聽聽聽聽聽聽聽聽 Insist on hot rotary straightening when ordering this product.

路聽聽聽聽聽聽聽聽 Available in three different chemical requirements: Type 1, 9 Cr and 13 Cr,

路聽聽聽聽聽聽聽聽 Type 1 L80 is less expensive than 9 Cr and 13 Cr but more subject to weight-loss corrosion,

路聽聽聽聽聽聽聽聽 Type 9 Cr largely has been replaced by Type 13 Cr. L80 13 Cr tubing has gained popularity because it has good CO2聽-induced weight-loss corrosion resistance properties; however, it is more costly,

路聽聽聽聽聽聽聽聽 Type 13 Cr may not be suitable in all hydrogen sulphide (sour) service environments. Typically, the H2S partial pressure should be less than 1.5 psi for safe use of L80 Type 13 Cr. For more details, refer to 鈥 NACE MR 0175/ISO 15156: Materials for use in H2S-containing environments in oil and gas production 鈥 issued by the National Association of Corrosion Engineers.

C90 路聽聽聽聽聽聽聽聽 API grade,路聽聽聽聽聽聽聽聽 Has a maximum hardness requirement.

路聽聽聽聽聽聽聽聽 Available in two different chemical requirements: Type 1 and Type 2.

路聽聽聽聽聽聽聽聽 Only Type 1 is recommended for use in sour service.

路聽聽聽聽聽聽聽聽 The use of this grade has been generally replaced by T95.

C95 路聽聽聽聽聽聽聽聽 Not a sour service grade.路聽聽聽聽聽聽聽聽 Fit for H2S service at temperature greater than 150掳F.

路聽聽聽聽聽聽聽聽 Usually used for intermediate casing strings that may be exposed to H2Sduring a gas kick.

T95 路聽聽聽聽聽聽聽聽 A high-strength tubular grade,路聽聽聽聽聽聽聽聽 Has a maximum hardness requirement.

路聽聽聽聽聽聽聽聽 Often used for HPHT sour gas production casing strings when L80 and C90 don not have enough strength for the desired well thickness.

路聽聽聽聽聽聽聽聽 Available in two different chemical requirements: Type 1 and Type 2.

路聽聽聽聽聽聽聽聽 Only Type 1 is recommended for sour service.

路聽聽聽聽聽聽聽聽 Sulphide Stress Cracking (SSC) resistant but not weight-loss resistant.

路聽聽聽聽聽聽聽聽 Very expensive.

P110 路聽聽聽聽聽聽聽聽 The old P105 tubing grade,路聽聽聽聽聽聽聽聽 API has absolutely minimal chemistry requirements for this grade.

路聽聽聽聽聽聽聽聽 Insist on hot rotary straightening when ordering this product.

路聽聽聽聽聽聽聽聽 High-strength tubing typically is used in deep sweet oil and gas wells with high pressures.

路聽聽聽聽聽聽聽聽 Sensitive to Sulphide Stress Cracking (SSC) failures unless the temperatures are relatively high (> 175掳F).

Q125 路聽聽聽聽聽聽聽聽 API tubing grade, often used for critical service wells.路聽聽聽聽聽聽聽聽 Fit for H2S service at temperature greater than 225掳F.

路聽聽聽聽聽聽聽聽 Type 1 chemistry is preferred.

Reference:

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