双侧向测井曲线形状与地层侵入关系研究

Investigation on the relation between form of laterologs and invasion state of reservoir

通过对具有不同侵入特征地层的双侧向理论曲线的计算,研究双侧向测井曲线的形状与泥浆侵入地层状态的关系.发现双侧向视电阻率曲线在高侵剖面的地层界面处出现‘反冲’,曲线‘峰’和‘谷’均较尖锐,而在低侵剖面,深侧向和浅侧向视电阻率曲线在地层界面处出现‘过渡’趋势,且曲线形状较圆滑.研究表明:产生上述现象的原因是由于原状地层对电流的吸引和排斥,使主电极和屏蔽电极供出的电流增大或减小,因而屏流比变化,进而导致视电阻率的变化.

In order to investigate the relation between form of laterologs and invasion state of reservoir, resistivity logs of Dual-Laterolog are calculated for different invasion profiles. The results show ＇over-shoot＇ for resistive invasion and the logs vary relatively acutely at the formation boundaries, whereas a trend of ‘ transition＇ is to see on the logs for conductive invasion. Through analysis the reason of the effects are revealed. The uninvaded formation could attract or repel electric current that depends on its resistivity relative to the invasion zone and the adjacent layer. This makes the currents from guard and main electrodes decrease or increase, and thus the ratio of guard-to-main current, that leads to the variation of the logs.