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储层监测的主要任务之一是确定注入液的位置及其流动方向。井间电磁波成像(EM)是一种用于储层管理的新技术,尤其是用于提高石油采收率(EOR)期间对流体在井间范围内的流动进行成像和监测。井间电磁波成像与传统的测井的区别在于它可以对井间空间成像而不只是对井孔周围较小的体积范围成像。由井间电磁波技术而获得的电导率(电阻率的倒数)图像与储层特征参数(如含水饱和度、矿化度及孔隙度)直接相关。井间电导率成像能够揭示监测井之间从前无法接近区域的地层详细信息。电导率图像对于岩石孔隙流体(水或油)的变化尤其敏感,因此与地震速度和衰减测量这类对岩石骨架的物理性质的变化更加敏感的技术不同,电磁波和地震成像方法可互为补充用于增强储层监测。井间电磁波的理论和所使用仪器都已获得了显著进展,对于流体监测,在EOR过程中于不同的时间使用电导率成像可提供关于油、水和水蒸汽运动的信息;不久前在Lawrence Lvermore国家实验室的合作下,在Chevron的水蒸汽注入场地进行了现场实验。时间推移测量清楚地表明了由于注入(蒸汽)而导致的异常电导体的运移。本文主要论述这一方法的应用、物理理解和资料处理。人们发现分辨率依赖于数据采样、空间覆盖和操作频率。另外,基于测井和其它地质资料的约束条件,只要在反演中能够获得,就应该用于优化成像质量。从理论上和现场实验中,井间电磁波成像被证明是储层监测中具潜在价值的一项技术。
One of the primary tasks of reservoir monitoring is to determine the location of the injection and its direction of flow. Crosswell electromagnetic imaging (EM) is a new technique for reservoir management that is used to image and monitor the flow of fluid between wells in the well, especially for enhanced oil recovery (EOR). The difference between interwell electromagnetic imaging and conventional logging is that it can image the crosswell space and not just the smaller volume range around the wellbore. Conductivity (reciprocal of resistivity) images obtained by interwell crossover electromagnetic techniques are directly related to reservoir characterization parameters such as water saturation, salinity and porosity. Cross-well conductivity imaging reveals detailed formation information of previously inaccessible areas between monitoring wells. Conductivity images are particularly sensitive to changes in rock pore fluids (water or oil) and, as seismic velocity and attenuation measurements are more sensitive to changes in the physical properties of the rock framework, electromagnetic wave and seismic imaging methods complement each other To enhance reservoir monitoring. Significant advances have been made in the theory and instrumentation of interwell crossovers, and for fluid monitoring, the use of conductivity imaging at different times during EOR can provide information about the movement of oil, water and steam; not long ago at Lawrence Lvermore In cooperation with National Laboratories, field experiments were conducted at Chevron’s steam injection site. Time-lapse measurements clearly show the migration of anomalous electrical conductors due to injection (steam). This article mainly discusses the application of this method, physical understanding and data processing. People find that the resolution depends on data sampling, spatial coverage and operating frequency. In addition, constraints based on well logs and other geologic data should be used to optimize image quality, provided they are available during inversion. In both theoretical and field experiments, cross-well electromagnetic imaging has proven to be a potentially valuable technique in reservoir monitoring.