Review of BP's Global Gas Injection Projects
- James Brodie (BP) | Bharat Jhaveri (BP) | Victoria Daae (BP) | Pinggang Zhang (BP)
- Document ID
- World Petroleum Congress
- 21st World Petroleum Congress, 15-19 June, Moscow, Russia
- Publication Date
- Document Type
- Conference Paper
- 2014. World Petroleum Council
- Miscible gas flooding, WAG, enhanced oil recovery
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- 53 since 2007
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BP has developed a range of innovative techniques to maximize economic oil recovery from its global miscible gas floods. The results have been reported in a series of publications over the past three decades. While some of these gas floods have been applied early in field life in secondary mode, in other cases gas flooding has been successfully initiated in mature, waterflooded fields. The purpose of this paper is to provide an overview of BP’s experience of establishing, managing and optimizing miscible gas floods.
Prudhoe Bay (Alaska) is the world’s largest miscible rich hydrocarbon gas project. Conventional and unconventional methods have been applied in a variety of different settings. An extensive surveillance program has facilitated a good understanding of the processes operating at field scale and surveillance data are used to optimize the flood. In 2000, a large-scale gas cap water injection project was implemented to slow the decline in field pressure. This project has made the vaporization process more efficient at higher pressure, resulting in additional recovery. Miscible gas injection has been extended to numerous other fields on the North Slope of Alaska.
BP has two active miscible gas projects in the North Sea: Magnus and Ula. Tertiary miscible water-alternating-gas (WAG) flooding in Magnus field started in 2002 and its impact on reservoir performance is significant and well understood. Tertiary miscible WAG injection in Ula field started in 1998 and has played a key role in arresting production decline. The WAG scheme in Ula is currently being expanded. In addition to these projects, BP operated a CO2 injection and storage project at In Salah, Algeria, where more than 3.2 million tonnes of CO2 have been stored since 2004. BP also operates a large crestal gas injection project in the Caspian.
Miscible gas injection has generated considerable benefits for BP over the past three decades and will continue to do so. The potential availability of large sources of CO2 in the future, supplied by carbon capture, could help maintain a leading role for miscible gas injection for years to come.
Miscible gas flooding is an established technique for enhancing oil recovery compared to primary depletion and secondary water flooding. The principle is to reduce the interfacial tension between the displacing solvent (gas) and displaced oil, which reduces the residual oil saturation compared to water flooding. Under ideal conditions, miscible flooding can recover almost 100% of the oil originally in place. Under field conditions, this limit is seldom achieved owing to imperfect volumetric sweep, incomplete displacement of oil in rock that is swept, failure to achieve miscibility due to dispersive mixing and inadequate capture of displaced oil (Stalkup, 1983). In addition, commercial and other factors may limit the amount of miscible gas that is available. Despite these limitations, there are many successful miscible gas projects around the world, and the prospects for miscible flooding in the future look bright if new sources of gas (including CO2) become available for enhanced oil recovery. Gas can be injected either in tertiary mode (i.e. after extensive water flooding) or secondary mode. Miscibility is not necessarily required for a commercially successful project: there are numerous sub-miscible gas projects that rely on oil swelling and viscosity reduction to enhance recovery.
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