索伦—林西地区林西组成岩作用及沉积环境研究

发布时间：2018-09-11 06:28

【摘要】：索伦-林西地区位于内蒙古自治区中部,包含突泉盆地、扎鲁特盆地和乌拉盖等中小型盆地,约15万平方公里。林西组地层在研究区内分布广泛,厚度较大,在页岩气方面极具研究价值。但是本区林西组地层的岩石类型特征、成岩作用、沉积相研究还较为薄弱。本文在广泛收集前人研究成果和大量野外剖面实测基础上,利用镜下观察、全岩分析、粘土矿物分析、扫描电镜、电子探针分析、孔渗测试、粒度分析等多种手段,系统研究了研究区晚二叠世林西组的岩石学特征、成岩作用及其对地层物性的影响;在还原研究区主要研究地点沉积相基础上,并简单探讨了岩体及热液流体对岩石物性的影响。林西组的分布受控于研究区西北侧的贺根山-黑河断裂以及南部的西拉木伦河断裂,贺根山-黑河断裂西部、西拉木伦河断裂南部无林西组分布。研究区内林西组地层主要分布在索伦、扎鲁特、林西等地区。主要的岩石类型为泥页岩、岩屑长石砂岩、长石岩屑砂岩、岩屑石英砂岩及极少量的灰岩。砂岩成分中石英,长石、岩屑的含量均在30%左右,仅林西地区剖面顶部成熟度较高,石英含量达到80%。全岩分析的结果显示泥页岩中石英含量差别不大,为48%±;粘土矿物含量在突泉和扎鲁特地区较高,分别为34.9%和39.9%;林西、索伦、西乌旗地区较低,分别为19.2%、26.7%和28.0%。X-射线衍射分析表明林西地区粘土矿物主要为伊利石,平均含量为76.1%;其次为绿泥石,平均含量为14.0%。碎屑岩成岩作用类型为压实作用、胶结作用、交代作用及溶蚀作用。压实作用体现在矿物接触类型为线接触-凹凸接触,颗粒定向排列;胶结物主要为黏土矿物、硅质矿物及碳酸盐矿物,黏土胶结物以伊利石为主,绿泥石次之;碳酸盐胶结物以方解石为主;硅质胶结主要表现为石英次生加大和自生微晶石英;交代作用主要出现在林西地区,主要表现方解石交代石英;溶蚀作用表现为矿物颗粒形成铸模孔和粒内溶孔。碳酸盐岩的成岩作用主要为压实作用、胶结作用、交代作用、溶蚀作用,压实作用使颗粒定向排列,灰岩中的石英颗粒为凹凸接触;胶结物类型为碳酸盐胶结物,主要为亮晶方解石;交代作用表现为方解石交代石英,颗粒产生白云石化;溶蚀作用表现为胶结物中出现溶蚀孔隙。泥页岩镜质体反射率(Ro)67%的测试数据分布在2~4%;泥岩伊利石/蒙皂石(I/S)的S(%)含量中85%的数据15%;石英次生加大级别为一级;颗粒间以线接触为主;伊利石结晶度数据中72%位于0.2(Δ2θ)区间内。综合以上数据,显示研究区林西组碎屑岩处于晚成岩阶段。研究区林西组砂岩孔隙度和渗透率较低,孔隙度平均值为2.64%,渗透率数据中有85%的数据0.04×10-3μm2,表明索伦-林西地区为一套低孔低渗储层。砂岩储层物性与成岩作用密切相关,压实作用、胶结作用使储层孔隙度和渗透率降低;溶蚀作用使储层孔隙度提高。地球化学微量元素Sr/Ba均1,B/Ga中有93%的数据3.3;扎鲁特盆地钻井揭示深部林西组地层岩性以厚层泥岩为主;古生物化石为西伯利亚地台植物群、淡水双壳类化石以及三种淡水叶肢介;以上证据均显示索伦-林西地区林西组时期为陆相沉积环境。索伦地区林西组时期为以扇三角洲前缘相为主体,向半深湖相过渡的沉积相类型,出现正粒序砂岩和块状泥岩的组合;扎鲁特地区为扇三角洲前缘相和半深湖相的交界地带,表现为扎鲁特南部为粒序多变砂岩和较厚泥岩的组合,扎鲁特北部为整体厚度巨大的泥岩;林西地区主体为扇三角洲前缘相沉积,在半拉山村区域出现数次小规模海侵,表现为砂泥岩组合循环出现,夹突变灰岩透镜体;西乌旗地区为半深湖相沉积,剖面以厚层泥岩为主。综合分析表明,研究区整体上构成了以西拉木伦河与贺根山-黑河断裂为主要控制区的、以南北向物源供给为主的半深湖-扇三角洲沉积体系。
[Abstract]:Soren-Linxi area is located in the central part of Inner Mongolia Autonomous Region, including Tuquan Basin, Zalute Basin and Uragai Basin, about 150,000 square kilometers. The Linxi Formation strata are widely distributed and thick in the study area, which is of great value in shale gas research. On the basis of extensive collection of predecessors'research results and a large number of field profiles, this paper systematically studies the petrological characteristics and diagenesis of the Linxi Formation in the study area by means of microscopic observation, whole rock analysis, clay mineral analysis, scanning electron microscopy, electron probe analysis, pore permeability test and grain size analysis. Based on the sedimentary facies of the main research sites in the reduction area, the influence of rock mass and hydrothermal fluid on rock physical properties is briefly discussed. The distribution of the Linxi Formation is controlled by the Hegenshan-Heihe fault on the northwest side of the study area, the Xilamulun River fault in the south, the Hegenshan-Heihe fault in the west, and the Xilamu in the south. The main rock types are mud shale, lithic feldspar sandstone, feldspar lithic sandstone, lithic quartz sandstone and very small amount of limestone. The content of quartz, feldspar and lithic debris in sandstone is about 30%, only in Linxi area. The results of whole rock analysis show that the content of quartz in mudstone shale is little different, which is 48%+ and the clay mineral content is 34.9% and 39.9% respectively in Tuquan and Zalut areas, while that in Linxi, Solon and Xiwuqi areas is 19.2%, 26.7% and 28.0% respectively. The clay minerals in this area are mainly illite with an average content of 76.1%, followed by chlorite with an average content of 14.0%. The diagenesis of clastic rocks is characterized by compaction, cementation, metasomatism and dissolution. The clay cements are mainly illite, followed by chlorite; the carbonate cements are mainly calcite; the siliceous cements are mainly quartz secondary enlargement and authigenic microcrystalline quartz; the metasomatism mainly occurs in Linxi area, mainly calcite metasomatism quartz; and the dissolution is mineral particle formation and casting. The diagenesis of carbonate rocks is mainly compaction, cementation, metasomatism, dissolution and compaction, which make the grain aligned directionally and the quartz grains in limestone are in concave-convex contact; the cements are carbonate cements, mainly sparkling calcite; the metasomatism is calcite metasomatism quartz, and the grains are produced. Raw dolomitization; dissolution is characterized by the presence of dissolution pores in cements. The test data of vitrinite reflectance (Ro) 67% of mudstone shale are distributed between 2 and 4%; the data of S (%) content of mudstone illite/smectite (I/S) are 15%; the quartz secondary enlargement grade is first order; the line contact between particles is dominant; and 72% of illite crystallinity data are located at 0.2 (2). In the study area, the sandstone porosity and permeability of Linxi formation are low, the average porosity is 2.64%, and 85% of the permeability data is 0.04 Reservoir porosity and permeability are reduced by close correlation, compaction and cementation; porosity is increased by dissolution; data of 93% of geochemical trace element Sr/Ba is 1, B/Ga is 3.3; drilling in Zalut Basin reveals that the lithology of deep Linxi Formation is mainly thick mudstone; paleontological fossils are Siberian platform flora. Freshwater bivalve fossils and three kinds of freshwater phyllodes; all the above evidences show that the Linxi Formation in the Solon-Linxi area was a continental sedimentary environment; the Linxi Formation in the Solon area was a sedimentary facies type with fan delta front facies as the main body and transited to the semi-deep lacustrine facies, and there was a combination of orthorhombic sandstone and massive mudstone; The boundary zone between delta front facies and semi-deep lacustrine facies is characterized by the combination of sandstone and thick mudstone in the south of Zahrut, and the mudstone in the north of Zahrut with huge thickness as a whole. The study area consists of a semi-deep lake-fan delta sedimentary system dominated by the Xilamulun River and the Hegenshan-Heihe fault and mainly by the North-South provenance.
【学位授予单位】：吉林大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：P618.13;P512.2

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