利用双感应曲线正负幅度差识别水淹层

Using Positive and Negative Range Differential of Dual Induction Curves to Distinguish Oil Zone from Water-flooded Zone

在泥浆浸泡井眼期间,由于泥浆柱与地层间存在正向压差,使泥浆滤液向地层渗流侵入,这不仅改变了受侵入地层孔隙中流体的分布,而且也改变了地层中未被排挤走的导电流体的矿化度,因而改变了受侵地层电阻率。对于油(气)层和弱水淹层,侵入的泥浆滤液所排挤走的孔隙中流体主要为油(气),对于水层和强水淹层,侵入的泥浆滤液所排挤走的孔隙中流体主要为水,根据双感应测井原理,侵入带地层对中、深感应测量值的贡献存在着明显的差异,当泥浆滤液电阻率满足一定条件时,利用双感应曲线正、负幅度差能够较准确识别水淹层。该方法在WL油田的实际应用,大大提高了水淹层的解释符合率,

As positive pressure differential exists between mud column and formation, mud filtrate pervading into formation not only changes fluid distribution of formation pores, but also changes salinity of formation conductive fluid which is not squeezed out by invaded mud filtrate, and hense changing the invaded formation resistivity. The fluid which is squeezed out in the invaded formation is mostly oil (gas) in oil zone and slightly water-flooded zone, and the fluid which is squeezed out in the invaded formation is mostly water in water zone and strong water-flooded zone. According to the principle of dual induction log, deep induction log value to which the invaded formation contributes differs absolutely from mediun induction log value. Positive and negative range differential of dual induction curves can accurately distinguish oil zone (slightly water-flooded zone) from severe water-flooded zone (water zone) when mud filtrate resistivity agrees with some conditions. The log application result of WL oilfield shows that the interpretation agreement rate of water-flooded zone is greatly increased.