渤南洼陷深层碎屑岩储集层中的黏土矿物特征及油气意义

应用岩心观察、X-衍射分析、薄片鉴定、扫描电镜、全岩矿物鉴定、岩心物性和含油级别分析测试等手段,揭示了渤南洼陷古近系碎屑岩储层中的黏土矿物特征及其与油气的密切关系。研究区黏土矿物主要为伊利石、伊-蒙混层、高岭石和绿泥石,垂向序列由下到上可分为伊利石-绿泥石发育带、高岭石异常高值带和伊利石-伊-蒙混层发育带3个变化带。不同阶段的黏土矿物主控因素差异导致黏土矿物的演化过程极其复杂,主要分为4个阶段:沉积期主要受沉积环境的影响,黏土矿物以伊利石和伊-蒙混层为主;有机质成熟期主要受成岩作用影响,在酸性成岩环境下高岭石大量产生;构造活动期受烃类侵位和深部流体的影响,在油气聚集区,高岭石得到保存,在岩浆活动区,绿泥石大量生成;油气成藏期受多种因素的影响,油层内的高岭石得到保存,油层外的高岭石转化为其他黏土矿物,出现了与油层对应的高岭石含量相对高值带。高岭石的相对高含量带是工业油层出现的重要标志。

Characteristics of clay mineral and its hydrocarbon significance in Paleogene clastic reservoir of Bonan Sag

The characteristics of clay mineral in the Paleogene clastic reservoir of Bonan Sag were revealed by core observation, thin-section analysis, scan electricity microscope observation, X-ray analysis, physical property and oil-bearing level analysis.According to different types of clay minerals from bottom to top, the vertical sequence of clay mineral could be divided into 3 layers. Illite and chlorite are abundant at bottom layer, kaolinite is abundant in middle layer, and illite and illite-smectite mixed layer are abundant in the upper layer. The diagenetic evolution of clay mineral could be divided into 4 stages. In the sedimentary stage, sedimentary environments controlled the evolution of clay mineral,illite-smectite mixed layers and illite dominated the clay fraction composition. In the organic matter maturity stage, the evolution of clay mineral was influenced by diagenesis. In the tectonic activity stage, the evolution of clay mineral was influenced by hydrocarbon emplacement and deep fluid. In the oil-gas accumulation stage, the evolution of clay mineral was influenced by diagenesis, hydrocarbon emplacement, abnormally high pressure and deep fluid. Kaolinite in oil layer was protected, but kaolinite was changed into other clay mineral out of oil layer. High-content kaolinite zones correspond to oil layer. The total amount of clay mineral controls the type of reservoir spacing. The abnormally high-content kaolinite zone is an obvious index of oil-gas layer.