Characteristics of Shale Lithofacies and Reservoir Space of the Lower Third Member and Upper Fourth Member of Shahejie Formation, the West of Dongying Sag
Shiyue Chen, Zhang Shun, Zhang Yue, Bianbian Sun, and Wenlei Gong
School of Geosciences, China University of Petroleum, Huadong, China
Fine-grained deposits usually seem simple, actually contain a variety of rock types. With the extensive research of shale oil and gas, it is necessary to deepen the study of the fine-grained depositional environments, rock types, compositions and fabrics. Shale forming under different sedimentary microfacies conditions has huge differences in the mineral compositions, petrofabric, lithology combination (shale, sandstone, limestone), vertical sequence and diagenesis, they directly affect the shale oil and gas enrichment process. On the basis of detailed description of core, summarizing the characteristics of core such as color, mechanical strength, sedimentary features and other foreign material in lower third member and the upper fourth Member of Shahejie Formation in the west of the Dongying sag, the major minerals features and lithofacies characteristics were studied by thin section identification and scanning electron microscopic analyses. The mineral composition is mainly composed of carbonate, clastic quartz and clay minerals, with minor feldspar, dolomite, pyrite and so on. Five major categories and eight types lithofacies are recognized: dark gray massive mudstone, light gray laminated silty mudstone, dark gray laminated marl, ash black laminated calcareous mudstone, gray massive marl, gray laminated argillaceous lime mudstone, ash black laminated siliceous shale, black shale with the lens body shape calcareous laminae. And Eight types of reservoir space, including structural fracture, inter-laminar fractures, abnormal pressure fractures, the inter-crystal micro-pore and micro-crack in clay mineral, dissolution pores, organic matter pores, inter-granular and intracrystal pores were found in the lower third Member and upper fourth Member of Shahejie shale in the west of Dongying Sag.
AAPG Datapages/Search and Discovery Article #90180©AAPG/SEPM/China University of Petroleum/PetroChina-RIPED Joint Research Conference, Beijing, China, September 23-28, 2013