激发极化法探测油气田——效果及异常模式探讨

本文是在20多个油气藏上作激发极化法找油气的试验结果。在华北的第三系油田,四川的中生界油气田,新疆的中生、古生界大逆掩断层带油田,以及华东的第三系油田上试验,普遍得到好的效果。各地区的充电率、电阻率及金属因数等参数的反应特点有差异,异常明显程度受盖层影响很大。该方法可以探测到埋深不小于3000m的油气藏,并在许多油气藏发现了具有共同特征的典型异常模式:它在浅部中心部位表现为高阻,高极化;两侧为低阻,低极化;深部表现为低阻,高极化;深浅两带之间为过渡带,异常无固定的特征。此模式可用以分辨油气藏异常,选择合适工作极距,以及研究引起异常的机制等。

PROSPECTING FOR OIL AND GAS WITH INDUCED POLARIZATION METHOD——A DISCUSSION ON THE EFFECT AND ANOMALY MODEL

This paper gives the experimental results by use of induced polarization method to detect, directly, oil and gas reservoirs over more than 20 reservoirs. All of the experiments carried out on Tertiary oil fields in North and East China, Mesozoic oil fields in Xichuan and the great zone of reversed faults of Mesqzoic and Palaeozoic Era in Xinjiang, gave good results. But the characteristics of different parameters, changeability, apparent resistivity and metal factor, are not the same in different areas, and the degree of clearness is greatly influenced by overburdens. The depth at which we can detect an oil and gas reservoir with IP method is not less than 3000 m. We find a typical anomaly model over many reservoirs. It is characterized, at small electrode spacings, by the high apparent resitivity and the medium high chargeability anomalies superposed upon each other at the centeral part of the anomaly, while there are apparent resistivity and a chargeability lows on both sides of it; at large electrode spacings, an apparent resistivity low and a chargeability high are over the reservoir; between these two zones of this anomaly is the transition zone of anomaly and in this zone the curves of each parameter have no fixed pattern. Using this typical anomaly model, we can identify the oil type anomalies, select appropriate electrode spacings and investigate the mechanism causing the anomalies. So, it has a great practical value. We have conducted some IP surveys to directly detect oil and gas reservoirs in Xinjiang and North China, and obtained good results.