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Question: Does NACE MR0175/ISO 15156 require production casing to be sour service compliant if the containment string of tubing is a sour service grade and the bottom hole temperature (below the packer) satisfies the casing material operating temperature? For example–a sour gas well with a H2S partial pressure of 0.10 psi (0.007 bar), P-110 casing, L-80 tubing, and a bottom hole temperature of 300 F (150 C). Supporting Information: Related information can be found in NACE MR0175/ISO 15156-2, Table 1, page 2. Production casing is not excluded from meeting the requirements of ISO 15156. AND ISO 15156-1/NACE MR0175, Section 6, which is reproduced in part below with the relevant parts underlined. 6. Evaluation and definition of service conditions to enable material selection 6.1 Before selecting or qualifying materials using other parts of NACE MR0175/ISO 15156, the user of the equipment shall define, evaluate and document the service conditions to which materials may be exposed for each application. The defined conditions shall include both intended exposures and unintended exposures which may result from the failure of primary containment or protection methods. Particular attention shall be paid to the quantification of those factors known to affect the susceptibility of materials to cracking caused by H2S.
1) As stated in your inquiry the secondary barrier must also be sour service and follow the requirements of NACE MR0175/ISO 15156.
2) A casing grade can be used under severity 3 of the diagram Fig. 1 of § 18.104.22.168. provided its working temperature is always above the minimum temperature given in ISO 15156-2 Table A.3. This can only be true if the material is well defined (API grade) and its temperature is always above the minimum temperature. According to Table A.3 if P110 is at a temperature ≥80°C 175°F) it can be used in Region 3 of the diagram Figure 1 of §7.2 in ISO 15156-2. It is up to the equipment user to establish that all intended and unintended exposure conditions are covered.
This question is in relation to NACE MR0175/ISO 15156-2 Clause 22.214.171.124
Reference: ISO 15156 Maintenance Panel Inquiry #2010-12