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Geoscience ›› 2023, Vol. 37 ›› Issue (05): 1306-1320.DOI: 10.19657/j.geoscience.1000-8527.2023.014

• Petroleum Geology • Previous Articles     Next Articles

Development Characteristics of Fracture-Cave and Their Formation Mechanism in Carbonate Rocks of Ordovician Majiagou Formation in Northwestern Henan Province

SHAO Weimeng1(), NIU Yongbin1(), CHENG Mengyuan1, HAN Kelong2, SUN Fengyu1, CHENG Yigao1, JING Chuhan1   

  1. 1. College of Resource & Environment, Henan Polytechnic University, Jiaozuo, Henan 454003, China
    2. Petroleum Exploration & Production Research Institute, SINOPEC, Beijing 100083, China
  • Received:2022-10-09 Revised:2023-02-08 Online:2023-10-10 Published:2023-11-14

Abstract:

The reservoir space of fracture-caves is well developed in the Ordovician Majiagou Formation carbo-nate rocks in northwestern Henan Province.Based on observations of local field outcrops, we studied the development characteristics of fracture-caves using geostatistics, and analyzed their formation mechanism in detail in relation to the regional tectonic evolution.The results show that: (1) the local caves can be divided into three types,i.e.small caves (height <1 m), medium caves (height 1-5 m) and large caves (height >5 m), among which medium and small caves predominate; (2) Based on the development characteristics and distribution rules of fracture-caves, fracture-caves can be divided into three development modes,i.e.fault-controlled, strata-controlled and superficial karst-controlled, among which the development scale of the fault-controlled fracture-caves is the largest; (3) The local reservoir space was mainly formed in the Paleozoic and Cenozoic. Tectonics, lithology and hydrological conditions are the most important factors controlling the development of fracture-cave reservoir space, among which tectonics has a greater influence on the spatial development and distribution pattern of fracture-caves, controlling the development intensity, and the location and direction of fracture-caves; lithology and hydrological conditions have also substantial influence on the development degree of fracture-cave reservoir space.The high calcite content in the rocks and the rich surface runoff, the reservoir space of fracture-caves were better developed.This study provides a good outcrop analogy, which is important for the understanding of the genetic mechanism of fracture-cave carbonate reservoirs and prevention and control of coal-bottom water in the North China basin.

Key words: fracture-cave, Ordovician, Majiagou Formation, carbonate rock, Henan Province

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