Advances in Earth Science ›› 2024, Vol. 39 ›› Issue (8): 847-861. doi: 10.11867/j.issn.1001-8166.2024.056

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Effect of Multi-stage Dissolution and Cementation on Physical Properties of Cretaceous Bioclastic Limestone in the A Oilfield, Iraq

Guanghui DUAN 1( ), Meiyan FU 1( ), Ya DENG 2, Jiacheng XU 2, Zhiqi ZHONG 1, Dong WU 1, Zhaoheng LIU 1, Siyi WANG 1   

  1. 1.College of Energy, Chengdu University of Technology, Chengdu 610059, China
    2.Research Institute of Petroleum Exploration & Development, Beijing 100083, China
  • Received:2023-12-26 Revised:2024-06-17 Online:2024-08-10 Published:2024-08-26
  • Contact: Meiyan FU E-mail:duangh578@163.com;fumeiyan08@cdut.cn
  • About author:DUAN Guanghui, Master student, research area includes reservoir characteristics. E-mail: duangh578@163.com
  • Supported by:
    the National College Students’ Innovation and Entrepreneurship Training Program of Chengdu University of Technology(s202310616040)

Guanghui DUAN, Meiyan FU, Ya DENG, Jiacheng XU, Zhiqi ZHONG, Dong WU, Zhaoheng LIU, Siyi WANG. Effect of Multi-stage Dissolution and Cementation on Physical Properties of Cretaceous Bioclastic Limestone in the A Oilfield, Iraq[J]. Advances in Earth Science, 2024, 39(8): 847-861.

The bioclastic limestone of the Mi4 section of the Mishrif Formation has undergone multiple phases of dissolution and cementation in oilfield A in Iraq. To investigate the impact of multiphase dissolution and cementation on the physical properties of bioclastic limestone and analyze the primary controlling factors during the dissolution and cementation of the early stages of the process. Based on qualitative and semi-quantitative analysis methods, including core observation, thin-section identification, image analysis, petrographic characteristics, carbon and oxygen isotopes, cathodoluminescence, and fluid inclusion homogenization temperature data, the dissolution and cementation periods of Mi4 bioclastic limestone were divided. These results indicate that the bioclastic limestone in the Mi4 section underwent diagenetic transformation during the eogenetic-early and mesodiagenetic stages, resulting in five phases of dissolution cementation. Eogenetic fabric selective dissolution, eogenetic-early diagenetic karstification, mesogenetic dissolution, eogenetic-early diagenetic cementation, and eogenetic-early diagenesis superimposed with mesodiagenetic cementation. The physical properties significantly evolve during eogenetic-early diagenetic due to solution-cementation processes with permeability ranging from 6.96~27.73×10-3 μm2. Dissolution was found to be controlled by bioclastic types during both the eogenetic-early stages, with algae-rich pelitic limestone exhibiting the highest degree, followed by the Mi4-3 and Mi4-4 layers with low algae-debris content. Furthermore, it was observed that the paleo-geomorphology and distance between reservoirs influenced the cementation process during the eogenetic-early stage, with the Mi4-1 layer showing the highest degree under the quaternary sequence interface.

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