The energy industry is nowadays facing the challenge to provide access of energy and fight climate change. As the oil demand will characterize 44% of the energy mix in 2044[6], reducing greenhouse gas emission arising from oil and gas activities is one of the key solutions for a more sustainable development. In the upstream Oil and Gas sector, one of the significant sources of GHG emission is represented by gas flaring, so oil companies are promoting plans to reduce this practice and achieve “zero gas flaring by 2030”[2]. Due to lack of infrastructure and the absence of established gas markets, the application of traditional flaring down techniques to developing countries appears to be however problematic as it requires significant investment. Therefore Eni is working to develop new strategies to dispose associated gas. SWAN is a Eni patented[3] flaring down methodology which exploits water hydrostatic head to re-inject gas in depleted reservoirs avoiding the use of costly compressors. Gas can be injected using jet pump or just exploiting the water hydrostatic pressure as driving mechanism (auto-injection). Starting from the results of pre-feasibility tests and previous studies, in the present work the SWAN application to a real depleted field in Nigeria is analyzed focusing on the reservoir level. It is evaluated the behavior of injected fluids, the impact on gas production and the possibility to reproduce the injected gas at high pressure using the system water in well-reservoir like a compressor. The objective is to determine which are the most impactful parameters that affect the process feasibility and propose useful guidelines to establish SWAN applicability to other candidate fields. Different scenarios have been considered and analyzed by means of the reservoir simulator software ECLIPSE®. An analytical model for the estimation of the timing of migration of injected gas and of pressure evolution has been also proposed as pre-screening tool for SWAN applicability. Sensitivity studies are also carried out to understand influence of hysteresis and of injection mode on gas recovery. The economic feasibility of the process has been evaluated considering costs of the required equipment, valorization of gas produced and saving from avoided emissions taxes. The analysis has shown that the most economical injection method is the auto-injection one.
In questi anni l’industria dell’energia si trova ad affrontare il problema di dover garantire l’approvvigionamento di energia e allo stesso tempo contrastare il cambiamento climatico. Poiché si prevede che nel 2044 le fonti fossili soddisferanno ancora il 44% della domanda di energia[6], per garantire uno sviluppo sostenibile è di vitale importanza ridurre le emissioni di gas serra del settore petrolifero. Nel settore upstream dell’industria Oil&Gas, gran parte delle emissioni di gas serra deriva dal gas bruciato in torcia. Le aziende petrolifere stanno perciò promuovendo piani per la riduzione del gas inviato a flaring in modo da raggiungere l’obiettivo di zero emissioni da gas flaring entro il 2030[2]. L’utilizzo di tecnologie tradizionali di flaring down risulta particolarmente difficoltoso nei Paesi in via di sviluppo dove i mercati gas non sono completamente sviluppati e vi è mancanza di attrezzature adeguate per la gestione del gas associato. Eni sta perciò promuovendo piani di ricerca volti a sviluppare nuove strategie per la riduzione del gas di torcia. SWAN (Simultaneous Water and Natural gas injection) è una metodologia patentata Eni[3] che sfrutta il carico idrostatico fornito dall’acqua nel pozzo per re-iniettare il gas di torcia in giacimenti depletati senza dover utilizzare costosi compressori. Il gas può essere iniettato sfruttando semplicemente la pressione idrostatica dell’acqua o utilizzando un eiettore. Mentre precedenti studi di fattibilità e test di campo hanno dimostrato la validità dell’idea proposta, in questo lavoro di ricerca è stata studiata l’implementazione di SWAN a un reale campo depletato nigeriano. Si è concentrata l’attenzione sul giacimento valutando il comportamento dei fluidi iniettati e l’effetto sulla produzione di gas e verificando la possibilità di riprodurre il gas iniettato ad alta pressione sfruttando il sistema acqua in pozzo-giacimento come un compressore. L’obiettivo è stabilire quali siano i fattori più impattanti che condizionano la fattibilità del processo e proporre linee guida da seguire per stabilire l’applicabilità di SWAN a altri campi candidati. Diversi scenari sono stati presi in considerazione e analizzati utilizzando il software di simulazione numerica ECLIPSE®. Un modello analitico per la stima del tempo di migrazione e dell’evoluzione del campo di pressione è stato inoltre proposto come strumento di pre-screening per valutare l’applicabilità di SWAN. Tramite analisi di sensitività si è inoltre studiato l’effetto del fenomeno di isteresi e della modalità di iniezione sul recupero del gas. La fattibilità economica del processo è stata valutata considerando i costi delle attrezzature richieste, la valorizzazione del gas prodotto e il risparmio derivante dal pagamento di minori tasse sulle emissioni. L’analisi ha rivelato che la modalità di iniezione più conveniente è l’auto-iniezione.
Water drive gas injection in depleted reservoirs
CERRI, MATTEO
2015/2016
Abstract
The energy industry is nowadays facing the challenge to provide access of energy and fight climate change. As the oil demand will characterize 44% of the energy mix in 2044[6], reducing greenhouse gas emission arising from oil and gas activities is one of the key solutions for a more sustainable development. In the upstream Oil and Gas sector, one of the significant sources of GHG emission is represented by gas flaring, so oil companies are promoting plans to reduce this practice and achieve “zero gas flaring by 2030”[2]. Due to lack of infrastructure and the absence of established gas markets, the application of traditional flaring down techniques to developing countries appears to be however problematic as it requires significant investment. Therefore Eni is working to develop new strategies to dispose associated gas. SWAN is a Eni patented[3] flaring down methodology which exploits water hydrostatic head to re-inject gas in depleted reservoirs avoiding the use of costly compressors. Gas can be injected using jet pump or just exploiting the water hydrostatic pressure as driving mechanism (auto-injection). Starting from the results of pre-feasibility tests and previous studies, in the present work the SWAN application to a real depleted field in Nigeria is analyzed focusing on the reservoir level. It is evaluated the behavior of injected fluids, the impact on gas production and the possibility to reproduce the injected gas at high pressure using the system water in well-reservoir like a compressor. The objective is to determine which are the most impactful parameters that affect the process feasibility and propose useful guidelines to establish SWAN applicability to other candidate fields. Different scenarios have been considered and analyzed by means of the reservoir simulator software ECLIPSE®. An analytical model for the estimation of the timing of migration of injected gas and of pressure evolution has been also proposed as pre-screening tool for SWAN applicability. Sensitivity studies are also carried out to understand influence of hysteresis and of injection mode on gas recovery. The economic feasibility of the process has been evaluated considering costs of the required equipment, valorization of gas produced and saving from avoided emissions taxes. The analysis has shown that the most economical injection method is the auto-injection one.| File | Dimensione | Formato | |
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https://hdl.handle.net/10589/133956