Xinjiang Petroleum Geology ›› 2023, Vol. 44 ›› Issue (3): 299-306.doi: 10.7657/XJPG20230305

• OIL AND GAS EXPLORATION • Previous Articles     Next Articles

Microscopic Characteristics of Fine-Grained Reservoirs in Lucaogou Formation, Santanghu Basin

QIN Enpeng1(), ZHANG Junying2, ZHANG Shengbing1, LIU Juntian1, ZHANG Xiaoqin1(), CHEN Yonghui1   

  1. 1. Research Institute of Exploration and Development, Tuha Oilfield Company, PetroChina, Hami, Xinjiang 839009, China
    2. Research Institute of Exploration and Development, Changqing Oilfield Company, PetroChina, Xi’an, Shaanxi 710000, China
  • Received:2022-09-13 Revised:2022-10-27 Online:2023-06-01 Published:2023-05-19

Abstract:

The fine-grained rocks in volcanic-active strata are characterized by complex composition, tight cementation, and strong heterogeneity. The concept and classification methods of fine-grained rocks were systematically reviewed. Combined with rock thin section identification, whole-rock X-ray diffraction (XRD) experiment, and scanning electron microscope-energy dispersive spectroscopy (SEM-EDS) experiment, a method for studying the microscopic characteristics of fine-grained reservoirs was established. By using this method, the petrological characteristics, and types and genesis of reservoir spaces of the fine-grained rocks in the Lucaogou formation of the Santanghu basin were analyzed. The results show that the fine-grained reservoirs in the Lucaogou formation are mainly composed of fine-grained carbonate rocks and fine-grained volcanoclastic rocks. The reservoir space is mainly contributed by fractures and pores, and the fractures are dominantly structural fractures and interbed. Fine-grained volcanoclastic rocks generally have volcanic dust solution pores, rock debris solution pores, crystal debris solution pores, and calcite vein solution pores. Micro-nanopores are relatively developed in fine-grained carbonate rocks, including dolomite intercrystalline pores, calcite intercrystalline pores, and clay mineral intercrystalline pores. The enrichment of volcanic material provides material basis for high-quality fine-grained reservoirs in volcanic-active strata, and the alternation of various laminae in fine-grained reservoirs is conducive to the formation of micropores and microfractures.

Key words: Santanghu basin, Lucaogou formation, fine-grained rock, reservoir, microscopic characteristic, reservoir space

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