Prediction method of thin sand reservoir with coal bearing: An example from PB area of Xihu Sag at East China Sea

Abstract

In the sedimentary environment shaped by river-tidal bidirectional flow, thin coal seams are typically located within the oil- and gas-bearing strata of the Pinghu Formation in the PB area of the Xihu Sag. These coal seams significantly influence the seismic amplitude, phase, and frequency of the reservoirs. Objective To betterclarify the specific impact of coal seam development in the PB area on reservoir identification and effective identification techniques, Methods this paper focuses on analyzing seismic and logging data to evaluate the prestack and poststack seismic response characteristics of the reservoirs. We then investigate the seismic response characteristics of the reflection coefficient after the coal seam is removed and perform poststack seismic forward modeling based on the wave equation. This analysis elucidates the influence of coal seams on seismic responses. Finally, rock physics multiparameter intersection analysis is employed to identify the sensitive parameters and establish the thresh values for reservoir lithology identification within the study area. Results When the reservoir thickness is less than the tuning thickness, the seismic data can be rotated by 90°, which reduces the impact of the coal seam on the reservoir diminishes. Conclusion For thin reservoirs with associated thin coal seams in the study area, we adopt a three-step high-quality reservoir prediction process that involves broadband spectrum inversion, specifically prestack Vp/Vs and prestack AVOG. This approach allows amore effective description of the distribution range of aerated sand bodies in the study area.

Keywords

• pb area
• thin sand reservoir with coal
• seismic response characteristics
• reservoir prediction
• distribution of the thin sand reservoir
• xihu sag at east china sea