Definition
NACE MR0175 — NACE MR0175 (ISO 15156) is the standard governing materials selection and metallurgical requirements for equipment used in hydrogen sulfide–bearing (sour) oil and gas environments to prevent sulfide stress cracking and other forms of environmental cracking.
Also known as: NACE MR0175, MR0175, ISO 15156, sour service standard
What NACE MR0175 is
NACE MR0175 / ISO 15156 specifies the requirements and recommendations for the selection and qualification of metallic materials for use in oil and gas production environments containing hydrogen sulfide (H2S). Its purpose is to avoid sulfide stress cracking (SSC) and related environmental cracking mechanisms that can cause sudden, brittle failure of high-strength steels exposed to sour fluids.
The standard sets limits on parameters such as hardness, yield strength, heat treatment and chemistry for qualified materials, and it defines environmental severity in terms of H2S partial pressure, pH and chloride content. Components are then chosen and controlled so they remain resistant to cracking within the specified service envelope.
Why sour service is controlled
- Hardness limits — typically restricting steels to a maximum hardness (often around 22 HRC) to resist SSC.
- Environmental limits — H2S partial pressure, in-situ pH and temperature define acceptable regions.
- Qualification — materials must meet MR0175 criteria for the intended sour environment.
Meeting MR0175 is often a contractual and regulatory requirement for any tubular or tool run in a sour well.
Why it matters for rentals
For sour wells, rented workstring, tubulars and downhole tools must be documented as MR0175 compliant to the required severity. See our workstring tubing and quality program, or contact us with your H2S data.