Abstract
The promotion of enhanced gas recovery (EGR) and CO2 storage is still shrouded in contention and is not well accepted, due to the excessive in situ CO2 mixing with the nascent natural gas. This adulterates the recovered CH4 and thus results in a high sweetening process cost thereby making the technique impractical. This has not only limited the field application of EGR in actual projects to a few trails but renders it uneconomical. This study aims to present, experimentally, alternating N2 injection as a potential technique for EGR and CO2 storage in sandstone rock cores. A laboratory core flooding experiment was carried out to simulate a detailed process of unsteady-state methane (CH4) displacement using Bandera grey core plug. This was carried out at 40 °C, 1500 psig, and 0.4 ml/min injection rate by alternative injection of N2 and CO2 in succession designed to suit the application based on optimum operating conditions. The results show that both CO2 storage capacity and CH4 recovery improved significantly when gas alternating gas (GAG) injection was considered. The best results were observed at lower N2 cushion volumes (1 and 2 PV). Therefore, the GAG injection method with N2 as cushion gas can potentially increase both CO2 storage and CH4 recovery of the gas reservoir. This technique if employed will assert the current position and provide vital information for further researches aimed at promoting environmental sustainability and economic viability of the EGR and CO2 sequestration processes.
Highlights
Electronic supplementary material The online version of this article contains supplementary material, which is available to authorized users.CO2 emissions are generalized as a significant factor responsible for inhibiting climate change that later results to increase in environmental temperature
The backpressure was engaged and CH4 was slowly injected into the core sample from the C H4 cylinder to saturate the core plug until the gas chromatography (GC) constantly read methane > 99%. N2 is injected as cushion gas for about 20 min (1 Produced CH4 Recovery (PV)) before the invention of C O2 at 0.4 ml/min injection rate
The Bandera grey sandstone core plug was used as the standard porous media
Summary
It was predicted that there will be a rise in world temperature and sea level from 1.9 to 3.5 °C and 18–30 cm, respectively, by the year 2100. N2 can be recovered mostly from the air separation unit (ASU) or as byproducts of oxygen plants. It requires less compression ratio, which is why a lower amount of it is needed to create high pressure in the CH4 reservoir
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