摘要
已发表文献资料指出鄂尔多斯盆地长7段存在欠压实现象，并用平衡深度法预测了长7段剩余压力。而本文基于地质、地球化学等资料分析，认为延长组长7段富有机质页岩不存在欠压实现象，声波时差偏离正常压实趋势并不代表泥页岩异常高的孔隙度和异常高流体压力，而是高丰度有机质的测井响应。长7段页岩单层厚度较薄，最大累计厚度为35m左右；有机质纹层发育，黄铁矿富集且压实程度较高；实测孔隙度值较低．可见孔不发育，均未表现出欠压实的特征。异常高的有机质丰度会造成声波时差偏大．从而使得平衡深度法不适用于恢复富有机质页岩的剩余压力，欠压实属于假象．
The published data indicate that there is an undercompaction in the Chang7 Member of the Ordos Basin, and the residual pressure in the Chang7 Member is predicted by the equilibrium depth method. In this paper, based on geology, geochemistry and other data analysis, it is considerod that the Yanchang Formation Chang7 Member with organic-rich shale does not have an undereompaction phenomenon. The delta t （interval transit time, or slowness） deviation from the normal compaction trend does not mean that the shale is of exceptionally high porosity and unusually high fluid pressure, but is a well logging response to high abundance of organic matter. The thickness of the single layer of Chang7 is thin, with the maximum cumulative thickness of about 35m. The organic matter lamina is developed. The pyrite is enriched and the compaction degree is high. The measured porosity is low, and visible pores are not developed. All these do not show up undercompaeted features. Abnormally high abundance of organic matter will increase the delta t （ interval transit time）, so that the balanced depth method does not apply to restore the residual pressure of organic- rich shale. The undercompaction is an illusion.
