INJECTION OF LEAN GAS INTO AN ULTRALIGHT OIL BEARING RESERVOIR: INTERFACIAL ASPECTS
Application of lean gases, particularly a methane rich gas, nitrogen, carbon dioxide, air and their mixtures in an ultra light oil bearing reservoir located in Southern Hungary, is in an advanced stage. The relevant studies and mathematical simulations have definitely indicated a substantial surplus oil production and it was also revealed that gravity segregation and vaporization of light hydrocarbons were the main elements of the displacement mechanism. However, well founded arguments have arisen about anomalous interfacial phenomena and precipitation of some oil constituents during the recovery process since the oil was strongly paraffinic and the predicted vaporization was high.
Therefore, a detailed laboratory study was commenced to determine the effect of nitrogen, carbon dioxide and lean methane on surface and interfacial properties. On the basis of the experimental results, it was concluded that the well known surface and interfacial effects, like enrichment of asphaltenes, resins and heavy hydrocarbons at interfaces, can be neglected when lean and non-reactive gases are injected into an ultra light bearing reservoirs. On the other hand, the precipitation of paraffins and other waxes at oil/water interface may take place even at very low vaporization in both the reservoir space and the surface facilities. Since that interfacial, probably catalyzed phenomena is newly recognized, further laboratory and field studies are needed to elucidate its detrimental effects on recovery efficiency, well performance and surface technology.