Geopolymers as alternative to Portland Cement in P&A

Cardoso Machado Macedo, Ricardo Nuno

4. term

Oil and Gas Technology, Master

2016

2016-06-08

120

Mange olie- og gasbrønde i Nordsøen nærmer sig slutningen af deres levetid og skal derfor permanent forsegles og opgives (Plug and Abandonment, P&A). P&A er den sidste fase i en brønds livscyklus: Der etableres langtidsholdbare barrierer, hvorefter brønden forlades. Operatøren har fortsat ansvar for den opgivne brønds integritet, og derfor er en effektiv, pålidelig forsegling afgørende. En permanent barriere skal dække hele brøndens tværsnit, inklusive alle ringrum, så der ikke kan ske lækage. Portlandcement er standardmaterialet til sådanne barrierer, men kan få svagheder under brøndforhold med høje temperaturer og korrosive miljøer. Denne afhandling undersøger flyveaske-baserede geopolymerer som et alternativt forseglingsmateriale. Geopolymerer er uorganiske bindemidler, der fremstilles ved alkalisk aktivering af flyveaske (en fin mineralrest fra forbrændingsprocesser). Der blev udviklet flere forskellige blandinger med varierende molariteter og aktivatorer. For at vurdere materialernes ydeevne blev der udført enaksiale trykstyrketests for at sammenligne de forskellige opskrifter. Resultaterne viste, at højere koncentrationer af alkaliske opløsninger gav højere trykstyrke. Derudover blev holdbarhed undersøgt ved at udsætte prøver for et korrosivt miljø: en opløsning med 15 % saltsyre (HCl). Her viste geopolymererne god modstandsdygtighed ved kontakt med syren. De lovende resultater peger på et stort potentiale for geopolymerer som tværsnitsbarrierer i P&A. Hvis det yderligere kan bekræftes, at de har et lavere miljøaftryk, kan de blive et attraktivt alternativ for industrien.

Many oil and gas wells in the North Sea are reaching the end of their service life and must be permanently sealed and abandoned (Plug and Abandonment, P&A). P&A is the final stage in a well’s life cycle: long-lasting barriers are installed and the well is left. Operators remain responsible for the well’s integrity long after abandonment, so efficient and reliable sealing is essential. A permanent barrier must span the entire cross-section of the wellbore, including all annuli, to prevent any fluid leakage. Portland cement is the standard sealing material, but it can develop weaknesses under well conditions with high temperatures and corrosive environments. This thesis evaluates fly-ash-based geopolymers as an alternative sealant. Geopolymers are inorganic binders produced by alkali activation of fly ash (a fine mineral residue from combustion processes). Several formulations were prepared using different molarities and activators. To assess performance, uniaxial compressive strength tests were conducted to compare the recipes. Results showed that higher concentrations of alkaline solutions led to higher compressive strength. Durability was also evaluated by exposing samples to a corrosive environment: a 15% hydrochloric acid (HCl) solution. In these tests, the geopolymers exhibited good resistance when in contact with the acid. These promising findings indicate significant potential for geopolymers as cross-sectional barriers in P&A. If future assessments confirm a lower environmental impact, they could be a strong alternative for the industry.

[This abstract was generated with the help of AI]

P&A ; Geopolymer ; Plugging

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