选取鄂尔多斯盆地中奥陶统平凉组笔石页岩3个典型地区样品,通过多项测试分析,探讨了微—纳米孔隙特征与笔石含量、岩矿组分、有机碳、成熟度、主微量/稀土元素及含气性的关系。平凉组笔石主要聚集式保存在下段黑色页岩中,页岩孔隙类型复杂,镜下观察到的孔隙类型有胞外聚合物孔隙、生物笔石体腔孔隙、黏土矿物粒间孔隙、粒内孔隙、矿物晶体间孔隙、溶蚀孔、微裂缝等。多项测试分析表明：笔石对页岩气聚集具有一定意义,对沉积环境也具有一定指示意义,笔石含量与有机碳含量呈正相关性,在一定范围内,比表面积与有机碳、成熟度具有相关性,其原因主要与岩性、无机矿物和有机质相关。样品稀土配分模式具相似性,推测物源相同,稀土总量、Fe、Al及Ti含量与有机碳含量负相关,说明稀土总量较高不是有机质富集所致,而与稀土元素赋存矿物有关。吸附气量与比表面、有机碳含量和成熟度正相关。上述诸因素对页岩微—纳米孔隙具有显著影响,孔隙结构研究需考虑有机碳和成熟度等。图6表3参13
邓昆
,
周文
,
周立发
,
万延周
,
邓虎成
,
谢润成
,
陈文玲
. 鄂尔多斯盆地奥陶系平凉组笔石页岩微孔隙特征及其影响因素[J]. 石油勘探与开发, 2016
, 43(3)
: 378
-385
.
DOI: 10.11698/PED.2016.03.07
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.
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