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Pore Structure Characteristics of Shale Gas Reservoir of Yingcheng Formation in Lishu Depression, Songliao Basin
Author(s) -
ZHOU Sandong,
LIU Dameng,
CAI Yidong,
TANG Jigaung
Publication year - 2015
Publication title -
acta geologica sinica ‐ english edition
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.444
H-Index - 61
eISSN - 1755-6724
pISSN - 1000-9515
DOI - 10.1111/1755-6724.12302_60
Subject(s) - beijing , china , geology , structural basin , mining engineering , chinese academy of sciences , archaeology , geomorphology , geography
organic-rich shale from Lishu Depression (LSD) of the southern Songliao Basin located in northeast China has significant shale gas potential by geochemistry and petrology. The organic-rich shale contains kerogen type II and III, and has a total organic carbon (TOC) content of 1.5 wt. %. The random vitrinite reflectance (Ro, m >2.0%) is in the high thermal evolution stage, which is prone to shale gas generation, but few have researched the shale reservoir characterization in LSD. Multiple methods, including optical microscope, scanning electron microscope and energy dispersive spectrum analysis (SEM-EDS), nitrogen adsorption/desorption analysis and X-ray diffraction (XRD) were conducted to determine the shale reservoirs characteristics of pore size/ volume distribution and their affecting factors. The LSD shale reservoirs develop a variety of etiogenic pore types, including mineral matrix pores (intergranular pore and intragranular pore), matrix pores and fracture-pores. The charred sporangium pores, air holes, charcoal pore group, higher plant debris pores, celestitemicrolite pores are well developed. The LSD shale occurs a large number of nanoscale pores, which mostly found in the dispersed particles of organic matter, but also found a few nanoscale pores between the parallel bedding in organic-rich shale. Nanometer pore shapes present the oval, a swirl shape edge, multifaceted angle pores or grape-like micellar structure. N2 adsorption/desorption analysis shows that the pore structures are mainly the ink bottle pore, wedge shaped pore and tablet slit pore. The absorbed pore (<100 nm) accounted for 85% of BJH pore volume and 87% of BET specific surface area ,which are the main contributor for the Yingchang Formation shale. The mineral analysis results show a significant percentage of brittle minerals (32%~63%) and clay minerals dominated by illite and montmorillonite. Morphology of minerals is crystal gypsum, granular barite and quartz vein. The shale TOC content, minerals constitute and content influence the development of shale pores. Overall, shale BJH pore volume increases with increasing TOC content, clay mineral, especially the montmorillonite and illite contents has significant effects on shale gas content and organic matter maturity is negatively related to the LSD shale porosity. ZHOU Sandong, LIU Dameng, CAI Yidong and TANG Jigaung, 2015. Pore Structure Characteristics of Shale Gas Reservoir of Yingcheng Formation in Lishu Depression, Songliao Basin. Acta Geologica Sinica (English Edition), 89(supp.): 142.