Developing Made-In-Canada Solutions To Fight Mild Sour Environments

Sour service environments are usually associated with high H2S content, harsh conditions, high pressures and deep and deviated wells. As reservoirs grow older, however, formations tend to become sour, even in environments not initially considered corrosive, increasing the risk of tubular failures due to Sulfide Stress Cracking (SSC).

In response to these challenges, Tenaris has developed Mild Sour Service grades to allow for safe tubular operational conditions in this type of well, which may not qualify under severe sour service environments but still presents SSC risks.

“In Tenaris, we rely on our extensive local field experience, engineering and R&D expertise to develop the most cost-effective grades to address the needs of the Canadian well conditions,” says Ricardo Prosperi, Tenaris President for Canada. With this in mind, Tenaris is currently investing in its Sault Ste. Marie seamless pipe facility to provide these steel grades locally.

As reservoirs age, the level of sourness starts to increase as in the case of the East Duvernay, Montney shales, and wells in Northeast British Columbia, due to many factors such as bacterial activity and the maturation of the field. “Operators start to see that the fields have become more sour, which means that unconventional wells that have always used conventional API grades need to step into Mild Sour Service grades,” adds Emad Hanna, Tenaris Technical Sales Director for Canada.

Technology you can trust

As a cost-effective solution, Tenaris’s Mild Sour Service grades reduce corrosion rates and mitigate the risk of SSC. Suitable for regions 1 and 2, as defined by the National Association of Corrosion Engineers (NACE), these grades are available in minimum yield strengths ranging from 80 ksi to 110 ksi (TN 80S to TN 110S).

Tenaris performs a stringent testing program on every grade. For instance, the qualification program for TN 110S material was defined and conducted following Annex B ANSI/NACE MR0175-2/ISO 15156-2, for region 2. All the tests completed 720 hours of exposure, as per NACE method A testing, showing no failures. Further QA/QC testing was conducted beyond that region for extra assurance.

“It’s our responsibility to ensure every E&P operator is aware of these testing qualifications. This gives our customers peace of mind, knowing that our Mild Sour Service Steel grades meet all the specifications requested by local regulations,” says Hanna.

Side by side with the customers

The Tenaris technical sales team works alongside their customers on material selection in order to find the best product combination and improve the corrosion resistance for each specific well. They are trained and certified to support customers during string design, combining the experience of a global team and sophisticated industry-recognized software.

“Our technical sales team, backed by our R&D network, help oil and gas customers get the most from their operations. One of the biggest aspects of our job is to collect data from the well conditions, gas chemistry and water chemistry and then run material selection analysis in order to recommend the most cost-effective material to meet their needs,” says Hanna.

Investing for growth

Tenaris provides a complete range of proprietary steel grades for all kinds of oil and gas operations. The company produces steel grades with performance properties that surpass those indicated by the API as well as API grades for general applications, including all the additional Supplementary Requirements (SR) and/or Product Specification Levels (PSLs).

The company is currently expanding its product capabilities and improving its operational performance to support domestic manufacturing for the oil and gas sector in Canada. Its AlgomaTubes facility — the only seamless pipe manufacturing facility in Canada — located in Sault Ste. Marie, Ontario, is being upgraded in order to incorporate a state-of-the-art premium connections line and expand capacity for sour service grades and a wider range of tubular diameters.

“Following AlgomaTubes’ revamping, we will be able to offer Sour Service and Mild Sour Service proprietary grades and the most advanced premium connections for shale gas and thermal applications from Canadian sources,” says Prosperi.

Figure 2: SSC Regions according to NACE and suggested Steel Grades for each region

The above graph is for general reference only. For specific cases further analysis is required in order to consider additional variables and ensure correct product selection.

The physical phenomenon associated with Sour Service environments is usually known as Sulfide Stress Cracking (SSC) or H2S embrittlement.

In combination with water and low pH, H2S releases free hydrogen, which is absorbed through the steel surface. Hydrogen atoms diffuse into the steel matrix and then interact with the steel itself, thus making it brittle.

Factors leading to SSC include elevated H2S content, low pH, low temperatures and tensile stress. When these are combined, a crack may initiate in the material and propagate, increasing the risk of catastrophic failures, even when stresses are substantially lower than the yield limit of the material.