HIPPS-Based No-Burst Design of Flowlines and Risers
A methodology is proposed for design of subsea flowlines and risers coupled with a subsea high-integrity pressure protection system (HIPPS) for fields with high shut-in tubing pressure (SITP). The proposed approach uses a design pressure that is lower than the SITP while maintaining a high reliability against burst failure. This approach enables an inherently safer design and ensures that the system integrity is not compromised in the unlikely event that HIPPS valves fail to close upon demand. The proposed design methodology is supported by a combination of analytical and experimental results. Further, an example is provided for demonstration purposes.
Background. As the oil and gas industry moves to high pressure reservoirs in deepwater with SITP in excess of 15 ksi, the design of fully rated flowlines and risers becomes extremely challenged because of increased wall thickness, difficulty of welding and inspection, and weight of the line pipe. For such fields, the use of HIPPS becomes an enabler (i.e., by allowing a reduced design pressure for the components downstream of HIPPS and hence reducing the wall thickness of flowlines and risers).
By definition, HIPPS is a high-integrity system with a low probability of failure on demand. The proposed design philosophy focuses on the unlikely event of the HIPPS valves failing to close upon demand and sets the following design objectives:
- In case of HIPPS failure and exposure of the system to SITP, flowlines and risers should have an adequate margin of safety against failure. This objective is set by introducing reliability-based acceptance criteria for flowlines and risers.
- Risers should be stronger than flowlines, thus keeping any potential failure away from the facility and avoiding harm to people.
- In case of HIPPS failure, there should be little or no damage to the flowlines and risers in order to minimize any follow-up replacement and repair.
In addition, in case of HIPPS valves successfully closing upon demand, a section of the flowline immediately downstream of the HIPPS may be subjected to pressures exceeding the design pressure and thus requiring to be fortified [as required by HIPPS design guidelines (Collberg 2010)]. It is proposed that this fortified section be designed with the same reliability objective as that adopted for risers.
Keystone XL Pipeline Temporarily Blocked
A decision by the US District Court in Montana deals a blow to the TransCanada project, which is designed to transport heavy crude from Alberta to Nebraska.
Natural Gas Pipeline Capacity to South Central US To Reach 19 Bcf/D by Year's End
With new projects scheduled to come on line later this year, the region, which mostly comprises states along the US Gulf Coast, will shift from being a source of natural gas supply to a source of growing demand.
McDermott Nets Subsea Tieback Contract for Pemex's Ayatsil Field
The deal covers the installation of a pair of rigid flowlines for the shallow heavy oil field, Pemex’s largest discovery to date. Work is expected to be completed early next year.
Don't miss out on the latest technology delivered to your email every two weeks. Sign up for the OGF newsletter. If you are not logged in, you will receive a confirmation email that you will need to click on to confirm you want to receive the newsletter.
29 November 2018
10 December 2018
27 November 2018
19 November 2018
05 December 2018