Pore Characteristics and Controlling Factors of Chang 7 Shale in Southeastern Ordos Basin

doi:10.7657/XJPG20220102

Abstract

Abstract:

In order to identify the pore characteristics of the continental shale in the seventh member of Yanchang formation (Chang 7 member) in southeastern Ordos basin, the shale cores taken from pure shale and silty laminae of Chang 7 member were analyzed for pore characteristics with the aid of experimental methods such as SEM, cast slice, gas adsorption method, and mercury intrusion, and the factors that may affect pore development were discussed. The results show that pure shale mainly contains clay mineral intergranular pores and organic pores, and silty laminae holds intergranular pores and intragranular dissolved pores. Compared with pure shale, silty laminae has mesopores-macropores with larger porosity, pore diameter and pore volume. In pure shale, the development of pores is mainly controlled by the contents of rigid particle and organic matter. In silty laminate, the controlling factors for shale pore development are mainly the preservation conditions. For instance, the enrichment of rigid particles such as quartz and feldspar is conducive to pore preservation, acidic fluid can corrode feldspar to create more pores, and liquid hydrocarbons can wrap minerals to inhibit cementation. The shale in silty laminae is superior to pure shale with respect to pore structure and physical properties. Thus, the silty laminae zones should be paid more attention in shale oil/gas exploration.

Key words: Ordos basin, Yanchang formation, Chang 7 member, shale, silty laminae, pore characteristic, controlling factor

CLC Number:

TE122.23

CAO Shang, LI Shutong, DANG Hailong, XING Haixue, ZHANG Lixia, ZHANG Tianlong, BAI Pu. Pore Characteristics and Controlling Factors of Chang 7 Shale in Southeastern Ordos Basin[J]. Xinjiang Petroleum Geology, 2022, 43(1): 11-17.

Figures/Tables 6

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Table 1

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