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Increased Oil Recovery from a Mature Oil Field by Gas Injection
- Publisher: European Association of Geoscientists & Engineers
- Source: Conference Proceedings, IOR 2015 - 18th European Symposium on Improved Oil Recovery, Apr 2015, cp-445-00007
- ISBN: 978-94-6282-141-5
Abstract
Increased oil recovery from a mature oil field by gas injection. The Varg field is located offshore Norway. The field is produced through a fixed well head platform and a leased FPSO. Late life reservoir management has proven challenging due to complex geological setting, marginal resource and production rates. The Varg field has first oil in 1998 and was sanction with a 33 mmstb reserves in the PDO. Currently 100 mstb is produced. The increases in reserves are mainly due to infill drilling and putting new segments of the field on production, but also trough IOR and reservoir management. Field life could be extended further trough successful infill drilling, 3rd party tie in, effective reservoir management or cost reductions. Gas based IOR has been successfully applied in several wells on Varg. In the East segment WAG in the well pair A07C-A10A has resulted in more than 2 mmstb incremental oil. The paper will show comprehensive analysis of the production results, a discussion of recovery mechanism and modelling results. In other parts of the field huff’n puff gas injection has been used. This has been an opportunistic and cost effective way to get gas injection benefits without having gas injectors. Gas has been injected into the reservoir using the gas lift system. The objectives have been reduction of water production, deeper lift and displacing attic oil. Analysis has been carried out to optimize oil production from From February 2014 Gas Export started from the Varg field. The gas injection; the value of sales gas has to be evaluated against value of incremental oil from gas injection. These economic evaluations are based on a simple cash flow analysis which in some cases favours gas export and in other gas injection.