The formation mechanism and characterization method of the fractured reef: A case study of the Ordovician formation in the Tarim Basin

The fractured reef, a novel reservoir type, is found in the Ordovician strata of the Fuman Oilfield in the Tarim Basin and holds significant potential for oil and gas production (Ma et al. 2020). The fractured reef is a reservoir characterized by dual control: both sedimentary facies and faulting High-yield wells in this region underscore the importance of studying this reservoir type. However, the Ordovician formations in the Tarim Basin are deeply buried, with depths reaching approximately 6 km, which results in seismic data with low signal-to-noise ratios and limited resolution. This presents a significant challenge for identifying fractured reefs. This paper introduces a seismic identification methodology for fractured reefs, leveraging physical simulation, seismic data, and well log information. The proposed approach first utilizes waveform inversion to delineate the boundaries of the reef structures, followed by the application of neural networks to model the main faults and their associated secondary fault networks. These identification results are subsequently integrated to produce a detailed characterization of both the boundaries and internal structure of the fractured reef. The findings suggest that the formation of fractured reefs is primarily influenced by the modification of reef facies along the platform margin and within the platform itself, driven by the activity of major faults and secondary fault networks, indicating that the reservoir is under the combined control of sedimentary facies and faulting.