China Petroleum Exploration ›› 2025, Vol. 30 ›› Issue (5): 1-15.DOI: 10.3969/j.issn.1672-7703.2025.05.001

   

Geological characteristics, depositional environment, and differential hydrocarbon storage properties of laminated shale in the Huanghua Depression

Chen Changwei1,Guan Quansheng1,Du Zhiyuan2,Cui Yu1,Lu Yongchao2,Wang Hua2   

  1. 1 PetroChina Dagang Oilfield Branch; 2 Key Laboratory of Tectonics and Petroleum Resources, Ministry of Education, China University of Geosciences (Wuhan)
  • Published:2025-09-14

Abstract: The development of laminae is one of the typical characteristics of continental shale in faulted lake basins in eastern China. There are three sets of shale layers in the Paleogene Kong 2 Member, Sha 3 Member and Sha 1 Member in the Huanghua Depression,which are formed in different sedimentary environments, thus forming different laminae units. However, the oil-bearing property, reservoir property and compressibility of different types of laminae are different, which affects the exploration and development effect of shale oil. Based on the core samples, wireline logging and mud logging data of three shale successions in the second member of Kongdian Formation, the third member of Shahejie Formation and the first member of Shahejie Formation in the Huanghua Depression of Bohai Bay Basin, on the basis of basic geochemical and rock mineral analysis, combined with AMICSCAN mineral scanning, high resolution scanning electron microscopy, energy spectrum elements, micro-CT scanning and true triaxial hydraulic fracturing simulation and other techniques to carefully characterize the types of laminae in shale, and to clarify the formation environment, reservoir capacity, seepage capacity and fracturing characteristics of different laminated shales. The shale of the second member of the Kongdian Formation in the Huanghua Depression are mainly felsic shale and mixed shale and a small amount of dolomitic shale. The shale of the third member of the Shahejie Formation are mainly mixed shale and felsic shale, while the shale of the first member of the Shahejie Formation are mainly mixed shale and a small amount of dolomitic shale and felsic shale. The second member of the Kongdian Formation shale mainly develops felsic laminae and a small amount of dolomitic laminae and clay laminae. The third member of the Shahejie Formation shale mainly develops dolomitic laminae and clay laminae and a small amount of felsic laminae. The first member of the Shahejie Formation shale mainly develops dolomitic laminae and a small amount of felsic laminae and clay laminae. Clay laminae generally have high organic matter content, acting as a hydrocarbon generation part in the microscopic source-reservoir system, which is beneficial to shale oil enrichment. Felsic laminae and dolomitic laminae usually have high reservoir quality, acting as a reservoir part in the microscopic sourcereservoir system, providing reservoir and storage space for shale oil. Compared with layered and massive shale, shale reservoirs with highfrequency lamination have larger specific surface area, larger filling area of oil and gas, better pore connectivity, and continuous hydrocarbon generation. It has been in an overpressure state. At the same time, the organic acid dissolution feldspar and dolomitic minerals produced in the process of hydrocarbon generation form micron-scale dissolution pores and melodic pores, which can improve the storage and flow capacity of shale reservoirs. The results of physical simulation fracturing experiments show that the laminated felsic shale has the best fracturing effect, followed by the laminated mixed shale, and the massive dolomitic shale has the least fracturing effect.

Key words: the Second Member of Kongdian Formation; the Third Member of Shahejie Formation; the First Member of Shahejie Formation; Laminaed shale; oil-bearing probability; Reservoir Quality; Fracturing effects; Huanghua Depression

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