One of the major challenges facing the global oil and gas industry in the coming years is the decommissioning of offshore platforms. Offshore platforms have a life cycle ranging from 20 to 40 years and, at the end of their exploitation, must be decommissioned. The complete removal of these structures, however, presents high costs and significant ecological impacts. The platforms, during their productive life, support abundant and diverse marine communities; they can provide shelter for overexploited or threatened species and increase environmental complexity by providing an additional hard substrate. In addition, commercial fishing is prohibited near the platform, which makes the structure a de facto marine protected area. It is therefore unlikely that the complete removal of the extraction platforms would be the best solution from an environmental point of view. Leaving obsolete structures in situ and converting them into artificial reefs could combine economic and ecological objectives and represent a viable alternative. The main challenge is to increase the durability and stability of structures by protecting them from corrosion. The solution can be found in mineral accretion technology by low-voltage electrolysis of seawater that leads to the precipitation of a thick layer of calcium carbonate above metal structures. This technology is used for the restoration of corals and applies the same principle of impressed current cathodic protection, used in corrosion protection. When applied to disused offshore platforms it could provide more stability and protect them from corrosion. In addition, calcium carbonate deposits could provide a suitable substrate for colonization of marine organisms. Prokaryotes are the first settlers of any submerged surface through biofilm formation. The properties of biofilm can affect trophic relationships, colonization, and the recruitment of macrofouling organisms. This study aims to explore and compare the microbial diversity (prokaryotic and fungal) associated with prototypes of oil and offshore gas platforms using both traditional (epifluorescence microscopy) and metabarcoding analysis (considering the 16S and Internal Transcribed Spacer 2 genes of ribosomal RNA). The prototypes consisted of two modules composed by 8 cathodes in the shape of cylindrical bars; one of the two modules was subjected to mineral accretion technology while the other was used as a control. The study lasted ten months. The results showed that the biofilm developed on not electrified prototypes featured groups such as Zetaproteobacteria, Desulfobacterota, Clostridia, Sulfurimonadaceae, and Arcobacteraceae normally responsible for corrosion of metal structures. These were almost completely absent in the electrified prototypes. This could demonstrate the effectiveness of mineral accretion technology in providing corrosion protection. The fungal community has developed on both the types of substrate but some taxa generally parasitic (Chytridiomycota and Rozellomycota) were more present in non-electrified prototypes suggesting that electrification may provide protection from pathogenic fungi to marine organisms. This study represents a first step towards a better understanding of microbial colonization on electrified prototypes that should be considered in future monitoring programs as an early indicator to successfully apply electrification to the offshore oil and gas platforms making them real artificial reefs.
Una delle principali sfide che l'industria globale del petrolio e del gas si troverà ad affrontare nei prossimi anni riguarda la disattivazione delle piattaforme offshore. Le piattaforme offshore hanno un ciclo di vita che va dai 20 ai 40 anni e, al termine del loro sfruttamento, devono essere dismesse. La rimozione completa di queste strutture presenta, tuttavia, costi elevati e notevoli impatti ecologici. Le piattaforme, durante la loro vita produttiva, supportano comunità marine abbondanti e diversificate; possono fornire rifugio per specie sovra sfruttate o minacciate e aumentare la complessità ambientale fornendo un substrato duro aggiuntivo. Inoltre, nei pressi della piattaforma è vietata la pesca commerciale, cosa che fa sì che la struttura funzioni di fatto come un’area marina protetta. È pertanto improbabile che la completa rimozione delle piattaforme estrattive rappresenti la migliore soluzione da un punto di vista ambientale. Lasciare in situ le strutture obsolete e convertirle in reef artificiali potrebbe combinare obiettivi economici ed ecologici e rappresentare una valida alternativa. La principale sfida è quella di aumentare la durabilità e la stabilità delle strutture proteggendole dalla corrosione. La soluzione può essere trovata nella tecnologia di accrescimento minerale mediante elettrolisi a bassa tensione di acqua marina che porta alla precipitazione di uno spesso strato di carbonato di calcio al di sopra di strutture metalliche. Questa tecnologia è utilizzata per la restoration dei coralli e applica lo stesso principio della protezione catodica a corrente impressa, impiegata nella protezione dalla corrosione. Se applicata alle piattaforme offshore dismesse potrebbe fornire maggiore stabilità e proteggerle dalla corrosione. Inoltre, i depositi di carbonato di calcio potrebbero fornire un substrato adatto per la colonizzazione da parte degli organismi marini. I procarioti sono i primi colonizzatori di qualsiasi superficie sommersa attraverso la formazione del biofilm. Le proprietà del biofilm possono influenzare le relazioni trofiche, la colonizzazione e il reclutamento di organismi del macrofouling. Il presente studio si propone di esplorare e confrontare la diversità microbica (procariotica e fungina) associata a prototipi di piattaforme petrolifere e di gas offshore utilizzando sia analisi tradizionali (microscopia a epifluorescenza) che analisi di metabarcoding (considerando i geni 16S e Internal Transcribed Spacer 2 dell'RNA ribosomiale). I prototipi consistevano in due moduli composti da 8 catodi a forma di barre cilindriche in acciaio; uno dei due moduli è stato sottoposto a tecnologia di accrescimento minerale mentre l’altro è stato usato come controllo. Lo studio ha avuto una durata di dieci mesi. I risultati hanno mostrato che il biofilm sviluppatosi sui prototipi non elettrificati presentava gruppi come Zetaproteobacteria, Desulfobacterota, Clostridia, Sulfurimonadaceae e Arcobacteraceae normalmente responsabili di corrosione di strutture metalliche. Questi erano quasi del tutto assenti nei prototipi elettrificati. Ciò potrebbe dimostrare l'efficacia della tecnologia di accrescimento minerale nel fornire protezione contro la corrosione. La comunità fungina si è sviluppata su entrambi i tipi di substrato ma alcuni taxa generalmente parassiti (Chytridiomycota e Rozellomycota) erano maggiormente presenti nei prototipi non elettrificati suggerendo che l'elettrificazione possa fornire protezione da funghi patogeni agli organismi marini. Questo studio rappresenta un primo passo verso una migliore comprensione della colonizzazione microbica su prototipi elettrificati che dovrebbe essere presa in considerazione nei prossimi programmi di monitoraggio come indicatore precoce per applicare con successo l’elettrificazione alle piattaforme offshore di petrolio e gas rendendole dei veri e propri reef artificiali.
SUCCESSIONI MICROBICHE MARINE SU PROTOTIPI DI PIATTAFORME PETROLIFERE OFFSHORE SOTTOPOSTI A TECNOLOGIA DI ACCRESCIMENTO MINERALE
SALVATORI, ANNA
2020/2021
Abstract
One of the major challenges facing the global oil and gas industry in the coming years is the decommissioning of offshore platforms. Offshore platforms have a life cycle ranging from 20 to 40 years and, at the end of their exploitation, must be decommissioned. The complete removal of these structures, however, presents high costs and significant ecological impacts. The platforms, during their productive life, support abundant and diverse marine communities; they can provide shelter for overexploited or threatened species and increase environmental complexity by providing an additional hard substrate. In addition, commercial fishing is prohibited near the platform, which makes the structure a de facto marine protected area. It is therefore unlikely that the complete removal of the extraction platforms would be the best solution from an environmental point of view. Leaving obsolete structures in situ and converting them into artificial reefs could combine economic and ecological objectives and represent a viable alternative. The main challenge is to increase the durability and stability of structures by protecting them from corrosion. The solution can be found in mineral accretion technology by low-voltage electrolysis of seawater that leads to the precipitation of a thick layer of calcium carbonate above metal structures. This technology is used for the restoration of corals and applies the same principle of impressed current cathodic protection, used in corrosion protection. When applied to disused offshore platforms it could provide more stability and protect them from corrosion. In addition, calcium carbonate deposits could provide a suitable substrate for colonization of marine organisms. Prokaryotes are the first settlers of any submerged surface through biofilm formation. The properties of biofilm can affect trophic relationships, colonization, and the recruitment of macrofouling organisms. This study aims to explore and compare the microbial diversity (prokaryotic and fungal) associated with prototypes of oil and offshore gas platforms using both traditional (epifluorescence microscopy) and metabarcoding analysis (considering the 16S and Internal Transcribed Spacer 2 genes of ribosomal RNA). The prototypes consisted of two modules composed by 8 cathodes in the shape of cylindrical bars; one of the two modules was subjected to mineral accretion technology while the other was used as a control. The study lasted ten months. The results showed that the biofilm developed on not electrified prototypes featured groups such as Zetaproteobacteria, Desulfobacterota, Clostridia, Sulfurimonadaceae, and Arcobacteraceae normally responsible for corrosion of metal structures. These were almost completely absent in the electrified prototypes. This could demonstrate the effectiveness of mineral accretion technology in providing corrosion protection. The fungal community has developed on both the types of substrate but some taxa generally parasitic (Chytridiomycota and Rozellomycota) were more present in non-electrified prototypes suggesting that electrification may provide protection from pathogenic fungi to marine organisms. This study represents a first step towards a better understanding of microbial colonization on electrified prototypes that should be considered in future monitoring programs as an early indicator to successfully apply electrification to the offshore oil and gas platforms making them real artificial reefs.File | Dimensione | Formato | |
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https://hdl.handle.net/20.500.12075/8248