ABSTRACT

The Lower Permian Xiashihezi Formation of the Ordos Basin is the largest producer of tight gas sand in China. The controls on tight gas production are many and include a variety of geologic, hydrodynamic, and engineering factors from one well to another throughout the basin. In this study, we considered data from a 408km2 3D seismic volume and logs from 17 wells to investigate the geologic controls on gas production in the P1h8 member of the Xiashihezi Formation, eastern Sulige gas field, Ordos Basin. Our objective was to determine the potential of applying multiple seismic attributes to identify the higher productivity areas of a tight gas sand reservoir. To achieve this, we used amplitude, complex traces, spectral decomposition, and seismic attenuation attributes derived from the 3D seismic volume to detect gas-bearing sand areas. The results of seismic attribute analysis revealed that no single attribute is correlated to higher productivity areas. The qualitative correlations between attributes and production records reflected that higher productivity areas are associated with seismically definable higher amplitude, more stable phase, tuning frequency, and stronger attenuation features in the study area. Meanwhile, three outlier wells in the seismic attribute analysis provided a reminder of the uncertainty in geologic interpretation. The gas-sand reservoir evaluation results suggested that the Pareto principle helps to enhance the interpretation needed to determine the productivity distribution of P1h8 tight-gas reservoir in the study area.

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