Title: Improved Oil Recovery by Pattern Gas Injection Using Horizontal Wells in a Tight Carbonate Reservoir
Abstract: Abstract This paper presents an evaluation on the combined use of horizontal wells and gas injection in a tight reservoir. The application of geo-statistics and compositional reservoir simulation are demonstrated in the evaluation to model heterogeneity and understand fluid behaviour. Normally, gas injection performance in a low-relief reservoir is poor due to adverse gravity segregation. Furthermore, gas injection performance tends to worsen if permeability improves toward the top of the reservoir. The combined use of horizontal wells and gas injection under various configurations was evaluated to optimise oil recovery in the tight part of a major reservoir in a giant oil field offshore Abu Dhabi. This part of the reservoir is characterised by very low permeability (<5 millidarcy average) with the best permeability in the upper portion. The evaluation concludes that the use of horizontal wells in a line drive pattern together with gas injection should greatly improve oil recovery in this tight reservoir. The improvement is attributed to the combined effect of linear flow and a large pressure gradient between the injector and producer due to the low permeability, drastically reducing the effect of gas over-ride due to gravity. Hence, as permeability increases, gas injection is predicted to be less effective. The results from the evaluation were used to optimise a pilot gas injection project. The effect of permeability heterogeneity at the scale modelled is not likely to be detrimental to gas injection. This is because the reservoir is predominantly of low permeability, even though, statistically, high permeability does exist. The geo-statistical modelling suggests that the likelihood of high permeability continuity is low and therefore is not likely to channel gas to producers. More important in the predicted performance of the geostatistical models is the method of up-scaling and permeability averaging. Misleading conclusions may result if the averaging process does not correctly account for the predominant flow regime.
Publication Year: 1996
Publication Date: 1996-10-13
Language: en
Type: article
Indexed In: ['crossref']
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Cited By Count: 1
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