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A Kind of Seismic Hydrocarbon Detection in Deepwater Turbidite Reservoirs: A Case Study Using Frequency-Dependent AVO Inversion

Texto do resumo

The exploration of turbidites in deepwater stratigraphic traps is garnering increasing global interest. In potential exploration blocks, particularly in new areas with few or no wells, identifying favorable targets often relies solely on seismic data, making it crucial for hydrocarbon detection in deepwater oil and gas exploration. However, due to the complexity of deepwater sedimentation mechanisms, many geophysical reservoir characterization techniques fail to yield satisfactory results in well-sparse or well-free regions. Consequently, a hydrocarbon detection technology suitable for deepwater sedimentary sandstones in these regions is necessary. This study focuses on a type of Direct Hydrocarbon Indicator (DHI) for deepwater turbidites in potential exploration areas. Utilizing the dispersion medium model proposed by Chapman (2003), we extract the dispersion attributes of deepwater turbidites using Frequency-dependent Amplitude Variation with Offset (FAVO) inversion based on pre-stack seismic data, predicting their hydrocarbon-bearing attributes. The workflow comprises three main steps: processing the CRP pre-stack gathers using the generalized S transform, based on prior analysis of pre-stack data in the study area, using gathers with incident angles of 5°-35° as input data, and selecting an inversion frequency range of 20-70Hz with a main frequency of 35Hz according to the spectral characteristics of the data volume; selecting an appropriate area near the target layer as the reference layer, dividing the data volume, and performing spectral equalization to eliminate wavelet effects; and extracting the dispersion attributes of the target area along the target layer to highlight the sensitive portions within the turbidites. This method has been successfully applied to the exploration of deepwater turbidites in the Bay of Bengal, Myanmar, yielding favorable practical results. Calculated using pre-stack common receiver gather seismic data, this method retains and emphasizes angle information sensitive to hydrocarbon responses in turbidite reservoirs, unlike post-stack seismic data with full-angle stacking. This approach reduces interference from irrelevant factors, highlights seismic responses of hydrocarbon reservoirs, and offers high computational efficiency and practicality. Furthermore, it is well-suited for early exploration stages without drilling and relies on high-quality pre-stack seismic data. This method holds significant reference value for the exploration of the deepwater turbidites in Pelotas Basin or Guyana offshore.

Palavras Chave

Deepwater turbidites; Pre-stack seismic; FAVO inversion; Dispersion attributes