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Stratigraphic and Sedimentary Characteristics of the Fourth Member of the Shahejie Formation in the Western Sag of the Liaohe Depression

Yang Li¹², Peng Lai¹, Xiaolong Zhou¹, Youlin Huang³

Environment and Resource / 2026,8(2): -- / 2026-06-24 16 12

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• Information:

  1. Liaohe Oilfield, CNPC, Panjin, Liaoning;
  2. College of Petroleum Engineering, Liaoning Petrochemical University, Fushun, Liaoning;
  3. Research Institute of Exploration and Development, Qinghai Oilfield, CNPC, Dunhuang, Gansu

• Keywords:
  Liaohe depression; Western sag; Fourth Member of Shahejie Formation; Cyclostratigraphy; eccentricity; Sedimentary facies evolution; Well correlation
• Abstract: The Fourth Member of the Shahejie Formation in the Leijia area, Western Sag, Liaohe Depression, was deposited against a background of intense tectonic activity during the early rifting stage. The sedimentary system was controlled by a combination of differential subsidence of boundary faults, sediment supply, and lakelevel– climate fluctuations, making stratigraphic surface identification and facies belt tracking challenging. This study integrates core and sidewall core, mud logging, and conventional wireline logging data to: (1) clarify the identification characteristics of the top and bottom boundaries of the Fourth Member and establish three sets of regional correlation marker beds; (2) conduct eccentricity-scale cyclostratigraphic analysis based on logging curves from 37 wells, identify stable 405 kyr long eccentricity signals and distinct short-period responses, and construct a fine correlation framework of fourth-order sequences (sq1–sq6) and sublayers (c1–c13); and (3) within this framework, discriminate sedimentary facies and microfacies by integrating core sedimentary structures, lithological associations, and logging responses, and determine the spatiotemporal migration patterns of the sedimentary system through representative well facies sequence analysis and multi-well cross-section correlation. Results show that: the bottom boundary of the Fourth Member exhibits a clear electrical contrast with the underlying Fangshenpao Formation, whereas the top boundary in the sag center requires constraint by marker beds and well-to-well tracking; lacustrine facies dominate, followed by fan-delta facies, with delta facies locally developed in the western gentle slope belt and sublacustrine turbidite fan deposits identifiable within the lake basin; within the sequence framework, facies belt migration shows staged evolution—early stages were strongly controlled by paleogeomorphology and differential subsidence, deep-lake fine-grained deposits dominated at the basin scale during the maximum lake flooding period, followed by a relative regression stage with enhanced progradation and lateral compensation with deep-water fine-grained deposits, and late-stage re-deepening led to re-expansion of deep-lake deposits. Integrating the tectonic framework and sedimentary responses, we establish an asymmetric sedimentary facies model for the Fourth Member characterized by “proximal fan-delta clastic input along the eastern steep slope / delta and shallow-lacustrine deposits along the western gentle slope / semideep to deep-lacustrine fine-grained deposits in the basin center.”
• DOI: 10.35534/er.08020xx (registering DOI)
• Cite: Li, Y., Lai, P., Zhou, X. L., Huang, Y. L. (2026). Stratigraphic and Sedimentary Characteristics of the Fourth Member of the Shahejie Formation in the Western Sag of the Liaohe Depression. Environment and Resource, 8(2),