砂岩储层中长石的异常分布及成因——以鄂尔多斯盆地二叠系石盒子组8段为例

发布时间：2018-09-01 10:00

【摘要】：为了揭示鄂尔多斯盆地石盒子组8段砂岩储层中长石异常分布及成因,在盆地尺度范围内,利用大量岩石薄片、阴极发光、扫描电镜分析手段,研究了储层岩石学特征及长石分布特征;并在此基础上,结合真实岩心酸溶蚀模拟实验、埋藏史、热史及成岩特征,探讨了长石异常分布的成因,认为长石的减少与成岩过程中溶蚀作用密切相关.研究结果表明:鄂尔多斯盆地腹部盒8段致密砂岩在成岩前存在大量长石(百分比平均为7.5%),而现今砂岩中低或无长石使得储层演化为具有"高成分成熟度"的石英砂岩和岩屑石英砂岩,这一现象与盆地周缘相对高长石含量形成明显的差异.现今长石的产状主要表现为完全溶蚀型,碳酸盐岩充填型及高岭石化型;地质历史时期长石的溶蚀需在高温条件下进行,而盒8段储层在溶蚀作用期叠加的一次热异常事件促使了上古生界煤系烃源岩的生烃作用,为长石的大量溶蚀提供了持续高温和酸性介质条件,使得在相对高热演化的腹部地区溶蚀作用强烈,储层中长石百分比小于1%,局部地区(苏里格地区)甚至为零,长石的大量溶蚀很好地改善了致密砂岩储集空间;而在热演化程度较低的边缘地区溶蚀作用较弱,长石保存相对较好,溶孔发育较少.对鄂尔多斯盆地砂岩储层中长石的异常分布研究有助于今后致密气甜点区的预测.
[Abstract]:In order to reveal the anomalous distribution and genesis of feldspar in 8 member sandstone reservoirs of Shihezi formation in Ordos Basin, a large number of thin pieces of rock, cathodic luminescence and scanning electron microscopy were used in the basin scale. The petrological characteristics and feldspar distribution characteristics of reservoir are studied, and on the basis of this, the origin of the abnormal distribution of feldspar is discussed in combination with the simulation experiment of acid dissolution in real rock core, burial history, thermal history and diagenetic characteristics. It is considered that the reduction of feldspar is closely related to dissolution during diagenesis. The results show that there are a large number of feldspar (average 7.5%) before diagenesis in tight sandstone of Bo8 member in the abdomen of Ordos Basin, while the present sandstone with low or no feldspar makes the reservoir evolve into a stone with "high compositional maturity". British sandstone and lithic quartz sandstone, This phenomenon is obviously different from the relatively high feldspar content around the basin. The occurrence of feldspar is mainly composed of complete dissolution type, carbonate filling type and kaolinite type, and the dissolution of feldspar in geological history period needs to be carried out under high temperature. However, a superimposed thermal anomaly event in the reservoir of member 8 during dissolution promotes the hydrocarbon generation of the Upper Paleozoic coal measure source rock, and provides a continuous high temperature and acidic medium for the mass dissolution of feldspar. The dissolution of feldspar in the relatively high heat evolution area is strong, the percentage of feldspar in reservoir is less than 1, the local area (Sulige area) is even zero, and the large amount of dissolution of feldspar can improve the reservoir space of tight sandstone. On the other hand, the dissolution of feldspar is weaker, the feldspar is better preserved and the dissolution pore is less developed in the edge area with lower thermal evolution. The study of the anomalous distribution of feldspar in sandstone reservoirs in Ordos Basin is helpful to predict the dense gas desserts in the future.
【作者单位】：中国石油勘探开发研究院廊坊分院;中国石油大学(北京)油气资源与探测国家重点实验室;长庆油田分公司勘探开发研究院;
【基金】：国家科技重大专项(2016ZX05007-003) 中国石油天然气股份有限公司重大科技专项(2011E-1301)
【分类号】：P618.13

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