Origin of low resistivity reservoirs in low angle drape structure in Lunnan, Tarim Basin

Abstract

Recently, low resistivity reservoirs of Jurassic, Cretaceous, and Early Tertiary in Lunnan Oilfield have been discovered successively. The statistics for 57 oil and gas layers of 22 oilfields in the Tarim Basin shows that reservoirs with poor physical properties are prone to have low resistivity and those condensate gas reservoirs of moderate fluid density or light oil reservoirs are prone to form low resistivity reservoirs. High immovable water saturation is the main reason for the formation of the low resistivity reservoirs. The origin analysis of the low resistivity reservoirs shows that low angle drape structures with the background of being major reservoirs or paleo-reservoirs have favorable conditions for forming low resistivity reservoirs. The matching of reservoir space and hydrocarbon types is the key reason for part of the reservoirs having low resistivity. Key words: low resistivity reservoirs, low amplitude, paleo-reservoir, well log interpretation, high immovable water saturation, matching of reservoir fluids