A variety of tests were conducted on graptolite shale samples from Middle Ordovician Pingliang Formation in three typical areas in Ordos Basin to find out the relationship between micro-nano pore structure, graptolite content, rock composition, TOC, maturity, main and trace elements and gas content. The graptolite of Pingliang Formation concentrates in the black shale at the lower section of this layer. Pores in the shale are diverse in types, including extracellular polymeric substance (EPS) pore, pore in bio-graptolite body, clay mineral inter-granular pore, intra-granular pore, interstitial pores between mineral crystals, micro-fractures, and intra-granular dissolution pores etc. Test analysis shows graptolite has some effect on sedimentary environment and shale gas accumulation; graptolites content is positively correlated with TOC, in a certain range, specific surface area is positively correlated with TOC and maturity; the main reason is related to lithology, inorganic minerals and organic matter. The rare earth elements (REE) patterns of the three areas are similar, indicating the same provenance. Rare earth amount, Fe, Al and Ti content are negatively correlated with TOC, indicating the high REE content is not caused by organic matter enrichment, but related to minerals REE adsorbed to. Gas content is positively correlated with specific surface area, TOC and maturity. The above factors have significant effects on micro-nano pores in shale, so TOC and maturity should be taken into consideration in pore structure study.
DENG Kun
,
ZHOU Wen
,
ZHOU Lifa
,
WAN Yanzhou
,
DENG Hucheng
,
XIE Runcheng
,
CHEN Wenling
. Influencing factors of micropores in the graptolite shale of Ordovician Pingliang Formation in Ordos Basin, China[J]. Petroleum Exploration and Development, 2016
, 43(3)
: 378
-385
.
DOI: 10.11698/PED.2016.03.07
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