The Sequence Stratigraphic Division and Geological Significance of Lower-Middle Ordovician Carbonate Rocks in Fuman Area, Tarim Basin, China

Oil and gas exploration conducted in the main fault zone of the Fuman Oilfield has yielded large-scale and high-production results. Against this background, the non-fault zone has emerged as a new domain for oil exploration endeavors. Nevertheless, the establishment of a unified sequence division scheme for the study area remains unachieved, primarily constrained by two key factors: first, the high costs associated with ultra-deep high-density coring operations; and second, the inconspicuous response characteristics exhibited by logging curves. This absence of a standardized scheme has further impeded the progress of oil and gas exploration in the non-main fault inter-region within the study area. Consequently, the present study is based on multi-source data, including seismic data, logging data, and field outcrop data. The magnetic susceptibility of the cement plant section and the natural gamma data sequence of the Yangjikan section were measured for cyclostratigraphy analysis. The sedimentary noise model was introduced to reconstruct the sea level, and the sequence division scheme of the Fuman area was discussed. The results show that the Middle-Lower Ordovician Yijianfang Formation-Penglaiba Formation preserves relatively intact astronomical signals. The DYNOT model reconstructs a good correspondence between sea level rise and fall and field characteristics, which can be used as a new method for sequence division in this area. Finally, the third-order and fourth-order sequence division schemes in Fuman area are proposed. The Yijianfang Formation-Penglaiba Formation is divided into 4 third-order sequences and 11 fourth-order sequences, which provides a basis for the characterization of dominant facies belts in Fuman area and regional exploration between non-faults.