【作者】 武文慧；

【导师】 黄思静；

【作者基本信息】 成都理工大学 ， 矿物学、岩石学、矿床学， 2011， 博士

【摘要】 以普通薄片与铸体薄片、阴极发光、扫描电镜、全岩和粘土矿物X射线衍射、同位素、包裹体测温等为研究方法和手段,运用沉积学和地球化学等理论,对鄂尔多斯盆地上古生界储层砂岩的岩石学特征、自生矿物的构成与形成机制、孔隙类型与孔隙演化、成岩作用与成岩演化进行了系统研究和合理解释。鄂尔多斯盆地上古生界储层砂岩岩芯得出的孔隙度平均值为6.33%,渗透率平均值为1.559×10^-3μm²,属于低孔低渗—致密性的砂岩储层。地层尺度上,从上部的从石千峰组到太原组及下部的本溪组,储层砂岩的岩石成分成熟度（Q1/（F1+R1）指数）逐渐升高、而长石含量逐渐降低,两者之间显示出良好的互补性,这主要因为成岩过程中由煤系地层产生的酸性流体对长石等易溶组分的溶解造成的,显微镜鉴定和X衍射分析证明被溶解的长石主要是钾长石。上古生界储层砂岩的孔隙主要是由岩屑溶孔、长石溶孔、铸模孔和晶间孔等构成的。从石千峰组到上石盒子组受煤系地层的影响比较小,压实作用造成总面孔率的减少,孔隙构成主要是原生孔。下石盒子组到太原组面孔率是逐渐增加的,次生孔隙对面孔率的贡献值远大于原生孔隙,尤其是太原组,其孔隙空间几乎全由次生孔隙构成的,而太原组的平均渗透率是上古界地层组最低的,仅为0.35×10^-3μm²,但0¹%的孔隙占了总孔隙度的21.35%,这就使得太原组砂岩孔隙的连通性变差,储层质量下降。不同地层组储层砂岩压实作用和胶结作用对储层的影响结果不同,石千峰组和上石盒子组地层中压实作用对的砂岩孔隙度影响较大,虽然埋藏深度相对较浅,但压实强度却比下伏地层高;下石盒子组、山西组和太原组等地层中胶结作用对砂岩孔隙的影响较大,虽然埋藏深但压实作用强度却比上覆地层低,较早时期发生的胶结作用使这些地层的粒间孔隙体积高于上覆地层。鄂尔多斯盆地上古生界自生矿物平均含量为10.8%,总体上具有较高的硅质胶结物和高岭石胶结物和较低的方解石胶结物。自生矿物的构成具有明显的地层专属性,石千峰组、上石盒子组等上部地层的绿泥石含量较高,下石盒子组、山西组和本溪组等地层的自生高岭石和硅质胶结物含量较高,山西组下部地层段与太原组具较高白云石含量,太原组同时也具有较高的自生伊利石含量。从石千峰组到山西组,高岭石含量呈现出逐渐增加的变化趋势,并与碎屑长石含量之间表现出良好的消长关系。自生高岭石在纵向上的变化趋势表现出两个旋回,即本溪组—太原组旋回和山西组—石千峰组旋回,两个旋回代表了两种成岩流体介质的变化过程。硅质胶结物常与高岭石相伴,都是长石溶解的产物,但有部分硅质胶结物的沉淀与同期火山物质的蚀变有关,硅质胶结物的包裹体均一化温度主要集中在90℃¹00℃之间,显示较低的沉淀温度和较早的沉淀时间。石千峰组和上石盒子组地层现今仍有含量较高的凝灰质,这些火山物质也是形成硅质胶结物的重要来源之一。方解石胶结物平均含量为2%,且具有很负δ（13）^C值和很高的包裹体均一化温度（150℃左右）,其形成与有机酸的有关和较晚的沉淀时间,方解石常会占据长石溶解空间。白云石胶结物的δ（13）^C值显著高于方解石,并靠近海水值,δ（18）^O值显著高于方解石,沉淀温度低于方解石,沉淀时间早于大多数方解石和自生石英,白云石胶结物较少占据长石溶解空间。高岭石对储层的影响是正面的,而硅质胶结物和白云石对储层演化的影响是中性的或保持性的,方解石胶结物对储层的影响是负面的。溶解作用是鄂尔多斯盆地上古生界非常重要的成岩作用,溶解介质主要来自煤系地层产生的酸性流体,溶解时间从同生阶段—埋藏成岩作用初期一直到深埋藏的晚成岩阶段,由此造就了其独具特色的成岩条件。在对各层位砂岩储层特征、自生矿物的形成机理、成岩作用对储层的影响的研究基础上,对不同地层组的成岩历史、成岩序列和孔隙演化模式进行了归纳总结,为鄂尔多斯盆地上古生界砂岩的储层质量预测提供理论指导。更多还原

【Abstract】 Using theories of sedimentology and geochemistry, the petrologic characteristics, composition and formation mechanism of authigenic minerals, type and evolution of pore, digenesis and digenetic evolution of the upper Paleozoic sandstones reservoir of Ordos Basin were systematically studied through impregnated thin sections, cathodoluminescence, scanning electron microscopy, whole rock and clay mineral X-ray diffraction, isotope, and inclusion temperature.The upper Paleozoic sandstone reservoirs in Ordos basin presents low porosity of average porosity of 6.33% and permeability of average permeability 1.559×10^-3μm² derived from sandstone cores. The compositional maturity （Q1 / （F1 + R1） index） and feldspar content of sandstone reservoirs increase and reduce respectively which shows good complementarity from upper Shiqianfeng Formation to lower Taiyuan and Benxi Formations, primarily because of the diagenetic process of acid fluid dissolution of feldspars and other soluble components and the dissolved feldspar is mainly K-feldspar under microscopic and X diffraction analysis. The porosity of upper Paleozoic sandstone reservoirs are mainly dissolution porosity of feldspar, mold porosity and intragranular dissolved porosity. The porosity of thin sections shows a decreasing trend from the upper Shiqianfeng Formation to the lower Shangshihezi Formation, and the porosity constitute mainly primary porosity and pore reduction is mainly caused by the compaction and relatively small by the formation of coal. The porosity of thin sections increases from Xiashihezi Formation to Taiyuan Formation and secondary porosity is much larger than the original porosity in total porosity, especially in Taiyuan Formation, their porosity is almost entirely composed of secondary porosity, but the porosity of 0 to 1% account for 21.35% of the total porosity, while the average permeability is the Taiyuan Formation is the lowest of the Upper Paleozoike, only 0.35×10^-3μm², which makes the connectivity and reservoir quality of the Taiyuan formation poorer.The different Formation of the upper Paleozoic sandstone reservoirs has undergone the different compaction and cementation. The compaction of the Shihezi Formations and Shiqianfeng Formations is stronger although at relatively shallow burial depth, while the cementation of the low Shihezi, Shanxi and Taiyuan Formations are weaker, because the earlier cementation occurred to makes intergranular pore volume of sandstones higher than the overlying strata.The average content of authigenic minerals in of the upper Paleozoic of Ordos Basin is 10.8%. The authigenic minerals of sandstones are made of high silica cement and kaolinite cements and low calcite cement. The composition of authigenic minerals have obvious specificity that the Shiqianfeng Formation and Shihezi Formation show higher levels of chlorite while the Xiashihezi, Shanxi and Benxi Formations of higher authigenic kaolinite and silica cement. The lower Shanxi and Taiyuan Formation have high dolomite content and the former is also of a high authigenic illite content.The kaolinite content of Shiqianfeng to Shanxi Formation shows a growing trend, and the feldspar content is on the contrary. The trends of authigenic kaolinite display the Benxi– Taiyuan Formation cycles and the Shanxi - Shiqianfeng Formation cycles, which represents two types of changing diagenetic fluids. Silica cement is often accompanied with kaolinite, which is the product of feldspar dissolution, sometimes, the part of the precipitation of silica cement are related to alteration of volcanic materials on the same period. The siliceous cement homogenization temperature of inclusions of quartz in sandstones vary mainly between 90℃ 100℃, which indicate that precipitation temperature of authigenic quartz is lower and that precipitation time is earlier. The sandstones of Shiqianfeng and Shihezi Formations show high tuffaceous materials, which is important volcanic source of cement. The average content of calcite cement, with a very negativeδ（13）^C value and high homogenization temperature （150℃or so）, is 2%, which is affected by organic acids during the formation. The precipitation of calcite cement occured later, and calcite often occupy space of feldspar dissolution.δ（13）^C values of dolomite cements are significantly higher than calcite, and close to the seawater value, and so do theδ（18）^O. the calcite precipitation temperature is lower and earlier than most of the precipitation of calcite and authigenic quartz, while dolomite cements donot occupy feldspar solution space. Kaolinite shows a positive impact on reservoir, silica and dolomite cements remain neutral in the evolution of the reservoir. However the calcite cements are the negative influence on reservoir.Dissolution of the upper Paleozoic of Ordos Basin was the main diagenesis and the dissolution fluid was mainly from the acid fluid of coal formation. The dissolving time started from the same period of the early burial diagenesis to deep burial of the late diagenetic stage which created the unique diagenetic conditions.Based on the study of the characteristics of sandstone reservoir, the formation mechanism of authigenic mineral, the impact of diagenesis on the reservoir, diagenetic history and diagenetic sequences and porosity evolution model were summarized for the different of the Paleozoic sandstone reservoir in Ordos Basin, which provides theoretical guidance for the reservoir quality prediction.更多还原