Sedimentary microfacies distribution based on the high-frequency sequence framework of well seismic combination in less-well blocks: An example from H1-1 sublayer in Jin77 well block in Hangjinqi area, Ordos Basin

The Jin77 well block is a highly promising area in the Hangjinqi region of the Ordos Basin. However, there were few wells and little geological research in this area. In order to better understand the sequence and depositional characteristics of the Xiashihezi Formation 1 Member (also known as the He1 Member) in the Jin77 well block, as well as to describe the sedimentary microfacies distribution of the development Sublayer unit, a thorough integration and calibration of core, logging, and seismic data were conducted. By analyzing the comprehensive response characteristics of logging and seismic data, we were able to subdivide the strata of the Xiashihezi Formation and establish a high-frequency sequence framework within the study area. The He1 Member was found to consist of 4 Sublayers, each with a consistent thickness. Based on the analysis of fine cores, it was determined that the dominant sedimentary type in this area was that of a wandering, shallow braided river. This conclusion was supported by the observed lithofacies marks, vertical facies sequence, and horizontal distribution of sandstone bodies. By combining the analysis of logging and seismic data with the results of the detailed Sublayers subdivision, the relative isochronous boundaries were able to be identified. The use of geophysical slicing technology, along with well and seismic data, it was allowed to effectively characterize the microfacies boundary of the braided river within the H1-1 sublayer unit. The findings show that the H1-1 sublayer contains approximately four to five braided river channels, with widths ranging from 1.5 to 6.5 km. These results provide valuable information for reservoir prediction and the detailed description of Sublayer units.