Fly ash-based geopolymer cement as alternative to ordinary Portland cement in oil well cementing operations
Author
Kyrilis, Efstathios
Term
4. term
Education
Publication year
2016
Submitted on
2016-06-09
Pages
92
Abstract
Boring af olie- og gasbrønde under højtryk og høj temperatur (HPHT) stiller store krav til den cement, der tætner brønden. Traditionel cement kan svækkes i korrosive miljøer og ved varme, hvilket kan føre til integritetsproblemer. Dette projekt undersøger alternative bindere fremstillet af aluminosilikat-rige industrielle biprodukter, især flyveaske fra danske kraftværker, for at udvikle et materiale, der kan modstå kemiske angreb og høje temperaturer og samtidig bære spændinger fra den omgivende formation. To fremstillingsmetoder blev undersøgt for at omdanne aluminosilikatkilder til en cementlignende binder: en konventionel “zeolitisk” metode, som er vanskelig at arbejde med, og en mere brugervenlig geopolymeriseringsmetode, der typisk giver lavere uniaxial trykstyrke (UCS, et mål for bæreevne). Da UCS alene ikke viser, hvornår cementen faktisk svigter i brønden, blev begge metoder – samt en hybrid tilgang – testet. Geopolymerisering kræver et ekstra tilsætningsmateriale; elektrisk lysbueslagge (EAFS) blev valgt frem for den ofte anvendte malet granuleret masovnsslagge. EAFS er ikke udbredt i Danmark, men er billig og kan importeres fra nabolande som Tyskland. Selvom den primære anvendelse er cementering af oliebrønde, vurderer studiet den bredere industrielle alsidighed, som forventes af et alternativ til almindelig Portlandcement (OPC), der bruges fra tunneler til brønde. En vigtig potentiel fordel ved geopolymer-/alkaliaktiverede bindere er deres lavere CO2-aftryk sammenlignet med OPC. Afhandlingen omfatter: et litteraturstudie af cementeringsoperationer og geopolymerisering; detaljerede eksperimentelle procedurer (materialer, blandingsdesign, forberedelse og testmetoder); resultater om binderens egenskaber, UCS, pH og flydeegenskaber, penetrometer- og holdbarhedstests, differential scanning kalorimetri og røntgendiffraktion; samt en diskussion af, hvordan parametre som hærdetemperatur påvirker ydeevnen. Arbejdet afsluttes med hovedkonklusioner og forslag til fremtidig forskning.
Drilling oil and gas wells in high-pressure, high-temperature (HPHT) conditions puts heavy demands on the cement that seals the well. Conventional cement can weaken in corrosive fluids and heat, leading to integrity problems. This project explores alternative binders made from aluminosilicate-rich industrial by-products, especially fly ash from Danish power plants, to create a material that can resist chemical attack and high temperatures while withstanding stresses from the surrounding rock. Two production routes were investigated for turning aluminosilicate sources into a cement-like binder: a conventional “zeolitic” method that is difficult to work with, and a more user-friendly geopolymerization method, which typically provides lower uniaxial compressive strength (UCS, a measure of load-bearing capacity). Because UCS alone does not indicate when cement will actually fail in the well, both methods—and a hybrid approach—were tested. Geopolymerization requires an additional additive; electric arc furnace slag (EAFS) was selected instead of the more commonly tested ground granulated blast furnace slag. EAFS is not widely available in Denmark but is inexpensive and can be imported from nearby countries such as Germany. While the primary target application is oil well cementing, the study considers the broader industrial versatility expected of an alternative to ordinary Portland cement (OPC), which is used in applications from tunnels to wells. A key potential benefit of geopolymer/alkali-activated binders is their lower CO2 footprint compared with OPC. The thesis includes: a literature review of cementing operations and geopolymerization; detailed experimental procedures (materials, mix designs, preparation, and test methods); results covering binder properties, UCS, pH and flow behavior, penetrometer and durability tests, differential scanning calorimetry, and X-ray diffractometry; and a discussion of how parameters such as curing temperature affect performance. The work concludes with main findings and suggestions for future research.
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