轮南低幅度披覆构造低电阻率油层成因

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

近年来轮南油田通过测井和试油相继在古近系、白垩系和侏罗系发现了低电阻率油层。对塔里木盆地22个油气田57个油气层的统计表明,低电阻率油层对储集层的物性条件及原油密度有一定的选择性,物性较差的储集层易表现为低油层电阻率,流体密度中等的凝析气藏或轻质油油藏易于形成低电阻率油层。高不动水饱和度是形成低电阻率油层的主要原因。通过对轮南油田低电阻率油层成因的分析,指出:具有主力油藏(或古油藏)背景的低幅度披覆构造具备形成低电阻率油层的有利条件;储集空间与油气类型的配伍关系可能是导致部分油层呈现低电阻率特征的关键。

Recently, low resistivity oil 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 of 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 oil layers. High immovable water saturation is the main reason for the formation of the low resistivity oil layers. The origin analysis of the low resistivity oil reservoirs shows that low angle drape structures with the background of being major reservoirs or paleo-reservoirs have the favorable conditions of forming low resistivity oil layers. The matching of reservoir space and hydrocarbon types is the key reason for part of the oil reservoirs having low resistivity.