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

Abstract

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.

Keywords

• sand body stack mode
• seismic forward modeling
• facies analysis
• thin layer reflection
• reservoir prediction
• tight clastic reservoir
• upper paleozoic
• southern part of ordos basin