Analysis on Mineral Components and Frangibility of Shales in Dongying Depression
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摘要: 对东营凹陷泥页岩矿物组成、脆度进行了系统研究,并与北美页岩进行了对比。研究表明:东营凹陷沙三下和沙四上亚段泥页岩主要由黏土矿物、陆源碎屑矿物(主要指石英和长石)和自生非黏土矿物(主要指碳酸盐和黄铁矿)三部分组成;泥页岩黏土矿物含量平均只有25%左右,远低于海相泥岩和传统观点;石英含量平均为29%,远低于海相页岩;长石含量平均约5%,高于海相泥岩;自生的碳酸盐矿物含量较高,平均约37%;分析认为,陆相盆地面积较小、距物源区近以及相变快是导致研究区泥页岩矿物组成特征的主要原因。鉴于此,提出了新的脆度计算方法并计算了东营凹陷泥页岩的石英脆度、碳酸盐脆度和总脆度。对比发现,碳酸矿物盐含量与泥页岩脆度相关性较好,是影响泥页岩脆度的主要因素。最后指出:研究区泥页岩脆性较好,易于形成天然裂缝或被压裂,是页岩气潜在的有利储层。Abstract: The mineral components and frangibilities of the shales of Es4sand Es3xof Shahejie Formation in Dongying depression were researched, and were compared with those of North America shales. The results show that those main mineral components include detrital minerals (feldspar and quartz) from land, clay minerals and non-clay minerals (carbonate rocks and pyrite) self-engendered. The average content of clay minerals is only 25%, much lower than marine shale and conventional viewpoint (over 50%). The average content of feldspar is average about 5%, higher than general marine shale. Self-engendered carbonate rocks content is rich, with average value about 37%, and changing dramatically. Short distance from origin deposition and frequently changing sedimentary facies is genesis of above shale mineral component characters. In addition, the enumerated quartz frangibility, Carbonate frangibility and total frangibility was formulated for continental basin shale, and the enumerated quartz frangibilities, carbonate frangibilities and total frangibilities of shales of the Dongying depression were calculated, it was founded that the content of carbonate is mainly affection factor for frangibility of the shales. The results indicate that the shale of the Dongying depression are easily to form natural fractures or easily to be crushed, and are potential reservoirs for shale gas.
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Key words:
- shale /
- mineral component /
- shale gas /
- reservoir /
- frangibility /
- Dongying depression
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