Tenaris and Eni have published the findings of joint field scale tests that evaluated the combined resistance of two casing strings in salt and other creeping formations. The technical paper was scheduled to be presented by Tenaris and Eni specialists at the Offshore Technology Conference in Houston last May. However, the event was cancelled due to the ongoing COVID-19 pandemic, with the study and the accompanying recorded presentation available on OTC’s website.
Casing collapse resistance is a key variable in structural integrity, especially in critical environments where salt or other creeping formations complicate casing string analysis and design. The limited knowledge of the impact of salt-induced loads often leads to over-conservative design, which can significantly increase well costs for operators. This is largely due to the lack of scientific studies based on full-scale tests, which would help to determine the actual collapse rating of the solutions implemented during well construction.
To address this shortfall and to gain new insights into these phenomena, Tenaris and Eni have recently engaged in a series of experiments, resulting in a new well design formula.
“We carried out two different laboratory test set-ups applied to two casing strings in three different cementing configurations,” explains Raffaello Zambetti, Well Design Solutions Manager at Tenaris. “First, we conducted a collapse test in a high-pressure vessel under hydrostatic conditions, aiming to reproduce salt uniform loading. The second set of tests – among the first of its kind in the world – was conducted with a mechanical press equipped with an ad-hoc designed indenting tool, aiming to reproduce punctual non-uniform and shear loading.”
Simone Malesani, Technical Sales Senior Engineer at Tenaris, who co-authored the paper with Zambetti, adds, “The experiments have improved our understanding of collapse resistance and will inform the design of “pipe-in-pipe” cemented casing strings going forward, with positive impact on both well costs and integrity.”
To learn more about Tenaris products for high-pressure, high-temperature and deep well applications, visit https://www.tenaris.com/en/products-and-services/octg/hp-ht-deep-wells/.
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