淡水泥浆侵入条件下储层电阻率的变化研究

理论分析和实验结果证实，钻井过程中，当淡水泥浆滤液电阻率相对于原始地层水电阻率大到一定程度时，油层的电阻率侵入剖面中才可能出现低阻环带；并且侵入结果使一些油层同水层具有相同的侵入特征，即高侵电阻率剖面，表现在浅感应(侧向)电阻率大于深感应(侧向)电阻率，同时均小于微球电阻率。通过实例分析可知，在使用淡水泥浆条件下，双感应测井比双侧向测井更有利于识别储层的流体性质。在实际配制泥浆时应考虑其矿化度与原始地层水矿化度的可比性，以避免由于矿化度差异造成对油层的错误评价。

On Variations of Formation Resistivity in Fresh Drilling Mud Invasion

Theoretical analysis and experimental results have proved that annulus zone with low resistivity exists if the resistivity of fresh mud filtrate, compared with that of initial formation water, is higher than a certain value. Invasion results cause the same properties of some oil-bearing zones as water-bearing zones, showing invasion profile of increasing resistivity. Analysis of some practical examples show that it is more useful to identify the fluid properties of reservoir by dual induction log than by dual lateral log under the condition of fresh mud. The salinity ratio of drilling mud to formation water should be taken into account when preparing drilling mud, so as to avoid wrong interpretation for oil-bearing zone by the same or different resistivity between flushed and un-invaded zones.