Emerging Technologies Safety Topics
When BSEE determines a piece of equipment or system doesn’t perform safely offshore, technical staff from the Systems Reliability Section (SRS) collaborate with operators, industry professionals, and subject-matter experts to conduct and/or oversee challenging technical equipment evaluations. The section assesses fitness for service, or/and the root causes of incidents and near-miss events. Upon completion of the root cause analysis of a technological failure or near miss, they provide recommendations for further action or alert BSEE officials of critical safety issues that may require immediate action such as a safety alert. The topics listed below are considered to be emerging technical safety issues.
High Pressure/High Temperature Research
As offshore oil and gas exploration and development advances in relation to both deeper water depth and deeper wells, the operating environment becomes more extreme especially in terms of temperatures and pressures encountered. For use in the Federal Code of Regulations, high pressure has been defined as greater than 15,000 psi and high temperature has been defined as greater than 350o. BSEE has received the draft Argonne National Laboratory report, “Evaluation of Pressure Rating Methods Recommended by API RP 17TR8,” and pending a peer review of the report is making available an advance draft report. The peer review of this report will be conducted according to BSEE’s scientific integrity procedures.
Recently, industry has begun to design equipment for high pressure and or high temperature service using the methodologies described in API’s Technical Report 17TR8, “HPHT Design Guidelines”. Two of these methodologies are new to the oil and gas community and the modeling method(s) above a certain threshold are of greater concern. Therefore, two special test bodies were designed and manufactured then hydro-tested to failure; and, they were examined under both elastic-plastic and linear-elastic FEA using ASME procedures. Pressure ratings were based on methods allowed by 17TR8. The margins of safety from all the rating methods were calculated and compared.
The study raises questions concerning the validity of the criteria and assumptions that are currently being used in the design of HPHT subsea equipment. The report concludes that the Division 3 elastic-plastic method is not recommended for HPHT subsea equipment as published with a 1.8 design-load factor. However, additional tests and/or validation data could still be used to provide justification for the 1.8 factor provided the data supports it. The Division 2 elastic-plastic method with a design-load factor of 2.1 is more in line with historically successful equipment for calculating load ratings for HPHT subsea equipment. For a Division 2 linear-elastic analysis, it is recommended that stress intensities and not von Mises stresses be compared with allowable stresses. Additional recommendations for future research are also suggested.
Connector and Bolt Failures: Numerous connector/bolt related failures have occurred on the Outer Continental Shelf that have resulted in bolt recalls, several safety alerts from BSEE and the original equipment manufacturers, and increased concern of a more systemic, global problem with bolting on critical safety equipment. This has resulted in a broad collaborative approach initiated by BSEE.
Seal Assembly & Cement Failures
Liner Seals and Liner Cementing: During drilling operations in the Gulf of Mexico region, a gas kick occurred in which the casing, cement and liner top seal assembly failed resulting in a loss of well control. The elastomeric-based liner top seal assembly may not have been qualified for exposure to high operating temperatures and gas exposure. The SRS (formerly call the QC-FIT) evaluated the QA/QC “fit for service” concerns for liner seal assembly and cementing failures. Current industry practices and BSEE regulations for pressure testing may not be sufficient to evaluate the integrity of the seal assembly and/or the cement column. Currently both barriers are not independently pressure tested, therefore the dual barrier system is tested as a whole. The performance rating of down-hole equipment may not be clearly communicated or understood between operators and manufacturers globally.