【作者】 黄可可；

【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， 2010， 硕士

【摘要】 论文选取川西凹陷新场构造须家河组砂岩储层为研究对象,以中石化分公司勘探开发研究院设立的《孝-新-合地区须家河组砂岩沉积期后水-岩相互作用机制研究》项目为依托,尝试通过研究区部分砂岩样品的化学全分析结果,结合铸体薄片、扫描电镜、阴极发光、X衍射定量分析等多种基础手段,讨论了研究区须家河组砂岩储层中的重要成岩现象及其在化学组成上的表现。主要取得了以下认识:根据岩心描述和薄片分析认为,富岩屑砂岩是最主要的岩石类型,次生孔隙是主要的储集空间类型。碳酸盐是最为主要的自生矿物,高岭石仅分布在须4段。须4段较须2段具有较高的方解石胶结物及自生伊利石含量,而须2段自生石英含量、绿泥石含量、白云石胶结物含量则显著高于须4段。长石的溶解作用是须家河组砂岩储层质量改善的重要因素,局部的高溶解地层间隔是我们研究的主要目标。根据方解石胶结物的δ13C值及石英的包裹体温度认为,须4段砂岩在成岩过程中存在一定数量的有机碳的参与。根据全岩化学认为,须2段较高的SiO2含量和须4段Al2O3含量略高显示出须2段砂岩具有更高的成分成熟度,须4段SiO2多存在于富铝矿物中;须4段较高的MgO和CaO含量以及其与碳酸盐矿物(方解石和白云石之和)之间显著的正相关性说明须4段砂岩具有更高的碳酸盐矿物,须2段钙镁含量的相关系数(R2)高达0.89,揭示出了须2段的MgO主要存在于白云石中;砂岩中的钾主要存在于伊利石和钾长石中,须2段具有较高的K2O含量,因而K2O含量与伊利石、钾长石之和显示出良好的正相关性;不同的矿物具有不同的K/Al摩尔比值,其中钾长石中为1/1,伊利石中的K/Al摩尔比变化在1/3～1/4之间,而高岭石、钠长石和绿泥石则几乎不含钾。因此,砂岩中富铝矿物含量的变化会导致钾、铝相对丰度的变化,这是本论文利用砂岩化学成分进行埋藏成岩过程中长石溶解和次生孔隙形成机制研究的重要理论依据。本研究在计算K/Al摩尔比率时从Al2O3的总含量中减去Na2O,以修正斜长石的影响;须4段砂岩的K2O/(Al2O3-Na2O)指数较低,基本上都在1/4以下,显示出缺乏钾长石的富钾矿物组合特征。须2段砂岩以具有较高的K2O/(Al2O3-Na2O)指数为主要特征,多数样品都分布在1/1到1/3之间,少数样品分布在1/3到1/4之间,反映了钾长石、伊利石等富钾矿物的组合特征;高次生孔隙发育带主要出现在须4段顶部、紧靠须5段泥岩的部分,砂岩具有很低的K2O/Al2O3指数,显示在较早成岩阶段经历过较强酸性流体的作用和铝硅酸盐的溶解,并造成地层中H+的储备。在这个低钾带中,也只限于这个低钾带中,K2O/Al2O3指数与孔隙度强烈的正相关性,显示砂岩遭受强烈溶解、钾长石消失。更多还原

【Abstract】 Based on the task of“The Post-Sedimentational Water-Rock Interaction of Xujiahe Formation gas reservoir of Xiao-Xing-He Gas Field, West Sichuan Depression”and by analyzing the whole rock chemical composition of the deep Xujiahe Formation gas reservoir of Xingchang Gas Field, West Sichuan Depression , combining the Optical microscopy, XRD, CLM, SEM analyses on core samples from three wells, This thesis presents how the Chemical composition indicates the Chemical diagenesis of Xujiahe sandstone. this thesis gives some conclusions in the following:1) Based on the description of well cores, the identification of the thin section and the grain size analysis, we got the lithologies of the research area. As a result, we found that abundance of lithic sandstone occupies the absolutely superiority. Carbonate is the most major authigenic minerals, kaolinite only to be found in Xu4. Xu4 contains higher calcite cements and authigenic illite content than that of in Xu2. However, authigenic quartz content, chlorite, dolomite cement content in Xu2 was significantly higher than Xu4. Dissolution of feldspar is the most important factor to improve the Reservoir quality of Xujiahe sandstone, local stratigraphic interval of high dissolved is the main objective of our study.2) According to theδ13C values of calcite cement and the homogenization temperature of fluid inclusion in quartz cements, the diagenetic process of Xu4 sandstone involves higher degrees of organic carbon participation.3) 3)According to whole-rock chemistry, Xu2 contains higher SiO2 content and Xu4 contains higher Al2O3 content, suggestes Xu2 sandstone has a higher compositional maturity, and SiO2 present in Xu4 may exists mainly in the Al-rich minerals; the fact that MgO and CaO enriched in Xu4 is relative to the higher content of carbonate minerals, which shows a significant positive correlation between them, the related coefficient (R2) between calcium and magnesium in Xu2 up to 0.89, revealed the MgO mainly in dolomite; With the exception of kaolin and albite, the major aluminium-bearing minerals in sandstones (K-feldspar, mica and illite) also contain significant potassium, causing a strong positive correlation between potassium and aluminium. However, the K/Al molar ratio in K-feldspar is 1/1, but varies between 1/3 and 1/4 in illite.So,Variations in the abundance of these minerals cause the differences in the total potassium and aluminium content of the sandstones. This is the key theoretical point used in this thesis to investigate the chemical composition relative to the feldspar dissolution and secondary porosity formation mechanism. However, alumina content is relatively high in samples with higher plagioclase contents. Therefore, aluminium in plagioclase(albite), corresponding to the molar Na2O, is subtracted from the total Al2O3 content in the calculation of K/Al molar ratio, and this modied ratio has been used instead. The bulk K/Al molar ratios in the Xu4 sandstones basically below 1/4 shows a lack of potassium-rich feldspar mineral. However, the K/Al molar ratios are relatively high in the Xu2 sandstones, where K/Al molar ratios vary between 1/1 and 1/3. might be related to higher amounts of K-feldspar and authigenic illite.; the top of Xu4, close to X5 mudstone, with high secondary porosity , shows sandstone with low K2O/Al2O3 index, In low K zone, The K2O/Al2O3 index shows a good positive correlation with porosity, indicating the sandstone subjected to strong feldspar dissolution.更多还原