DNV GL is leading a Joint Industry Project (JIP) aimed at solving the challenges brought about by sour service fluids from wells and the demands it places on pipeline material.

The major technical and financial challenges this issue causes for pipeline operators, with the fluids able to cause fractures and cracks affecting pipeline performance and reliability, has prompted DNV to launch the JIP in order to develop a methodology to evaluate fractures and cracks using a Single Edge Notched Tensile (SENT) test designed specifically for sour service environments.

With eight participants already on board, DNV says the JIP is still open for new participants. According to the company, a SENT test is designed to simulate loading conditions and crack depths similar to those experienced by pipelines operating under normal conditions.

According to research conducted in DNV’s laboratories, in a sour environment – where fluids such as H2S, H2O and CO2 may be present – results can be highly variable depending on numerous environmental and test parameters. Fracture toughness, for example, tends to decrease with increased H2S concentration (partial pressure of H2S) and decreased loading or strain rate.

Current guidance under DNV-OS-F101 and DNV-RP-F108 does not reflect this, says the company. According to Dr. Jens Petter Tronskar, vice president and chief technology officer of the DNV’s Deepwater Technology Centre in Singapore: “The JIP will involve detailed experiments and analysis to provide a better understanding of the key parameters known to impact fracture toughness test results. This will enable the development of a guideline, which may further develop into a Recommended Practice that will provide significant technical, logistical and financial savings to the industry.”

The JIP is a joint effort between the company’s deepwater centre in Singapore and its laboratories in Singapore and Columbus, and will be run in three phases over a two-year period.

The Columbus laboratory is also carrying out an ongoing JIP to develop best practice guidelines for performing sour service Engineering Critical Assessments (ECA), scheduled for completion in December this year. This JIP includes fatigue crack growth rate and fracture toughness tests conducted in a wide range of sour environments. The findings from the latter study will complement the new JIP to develop a sour service SENT methodology, says DNV.

Offshore