鄂尔多斯盆地南部上古生界致密碎屑岩储层预测——以镇泾地区为例

Prediction of tight clastic reservoirs of Upper Paleozoic in southern Ordos Basin:a case study of Zhenjing district

岩石物理特征难以有效区分储层与非储层,黄土塬叠后地震资料品质较差,储层预测成为鄂尔多斯盆地南部上古生界久攻不克的技术瓶颈,也成为制约该区勘探推进的原因之一。区带评价认为镇泾区块东北部是有利勘探区带,二叠系山西组二段、下石盒子组一段是主要勘探目的层。镇泾3D波形聚类地震相分析结果与镇泾地区物源、砂体展布特征一致,表明地震资料可以用来开展储层预测研究。结合沉积相展布特征的一系列地震正演模拟发现,山二段内与盒一段大套砂体有一定距离、具有一定厚度的砂体能够形成可识别的地震反射,这种地层岩性纵向上的空间组合与区域叠加型及厚层单一型砂体沉积模式吻合,正是周边已发现气藏的典型储盖组合类型。根据正演模拟结果优选的波峰数地震属性储层预测证实,山二段叠加型砂体及厚层单一型砂体呈SW-NE向宽幅条带状展布,进而开展的地震剖面特征同相轴的拾取解释与构造成图,直接圈定了山二段叠加型与厚层单一型砂体岩性圈闭的分布范围与埋深,为该区勘探部署提供了钻探目标。

It is difficult to distinguish reservoirs and non-reservoirs based on the rock’s physical properties.The quality of post-stack seismic data in the loess plateau is poor,which makes it a technical bottleneck for the prediction of reservoir of the Upper Paleozoic,and the exploration in the southern Ordos Basin was then constrained.Block evaluations have indicated that the northeastern part of Zhenjing district has a good potential for exploration,with the second member of Permian Shanxi Formation and the first member of Xiashihezi Formation as the main target beds.The results of 3D seismic facies analysis in Zhenjing area are consistent with the regional sedimentary facies studies on provenance and the distribution of sand bodies,indicating that seismic data can be used for the prediction of reservoir.The distribution of sedimentary facies of a series of seismic forward modeling showed that the sand bodies distributed with a certain distance and thickness in the second member of Shanxi Formation and the first member of Xiashihezi Formation formed recognizable seismic reflections.This vertical spatial combination of stratigraphic lithology is consistent with the depositional model of regional superimposed and thick single-type sand bodies,which is the typical form of reservoir-caprock combination that has been discovered in the surrounding gas reservoirs.The reservoir prediction based on the optimal number of wave crests from the forward simulation results confirmed that the superimposed and the thick single-type sand bodies of the second member of Shanxi Member were distributed in SW-NE directions.Furthermore,the picking and interpretation of co-phase axis and the structural mapping of seismic profile were carried out,which directly delineated the distribution range and burial depth of lithologic traps in the sand bodies of the second member of Shanxi Formation,and provided drilling targets for exploration and deployment in this area.