莲花油层中粘土矿物分布规律研究

辽河高升油田莲花油层富含稠油,搞清储层中粘土矿物的类型、含量、平面和纵向分布规律对整个稠油油藏开发方案的设计、油层保护、提高采收率等开发措施实施和稠油油藏形成条件等研究都具有极其重要的意义。本文利用X-衍射、电镜、热反应实验对高升油田莲花油层中的粘土矿物进行了系统研究。研究表明,莲花油层中的粘土矿物以蒙脱石为主,粘土矿物类型、含量分布主要受岩石类型和沉积相控制,含油饱和度大小对粘土矿物类型影响不大。蒸汽驱采油会导致储层中蒙脱石的含量减少,增加储层的微观非均质性.

The Study of Clay Minerals Distribution in Lianhua Reservoir

The Lianhua reservoir of Shahejie group(geology period E1) in Gaosheng Oil field , located in Liaohe granen faulting basin, is rich in heavy crude oil, with the burial depth being 1　450～1　700　m.The reservoirs have been under development for 22 years. The company has made great profit from the reservoir development by means of steam-flooding technology, but some problems have been found in the reservo i r with the technology application, because the difficulty in reservoir developme nt is increasing with the frequency of applying the technology. By the end of 19 98 the average steam flooding for every well has been four times, but the more s team-flooding, the less satisfactory the efforts to increase the production. 　　Therefore, a more comprehensive study of the types, content, and the horizonta l and vertical distribution characteristics of the clay minerals in the reservoi r is of most important consequence to the design of the heavy crude oil developme nt, reservoir protection, reservoir evaluation, and enhanced oil recovery (EOR) etc. The clay minerals in Lianhua reservoir are systematically studied by means of X-ray diffraction, scan electronic microscope and heat simulation experiment s. 　　The Lianhua reservoir is a sediment by gravity flow, with the rock types bein g gravel, sandstone, and mudstone, and the sedimentary depth being 50～600　m. L ian hua reservoir has excellent physical property, with the porosity being 20%～26% and the permeability being 1～4 μm2. 　　The studies show that the major clay minerals in Lianhua reservoir are montmoril lonite(60%～85%), illite (8%～20%), kaolinite (5%～25%), and chlorite (<5%). T he montm orillonite content decreases with the increase of the burial depth, but the kaol inite and illite content are just the opposite, because the porosity fluid in sa ndstone and gravels more easily circulative than that in mudstone, and the mont morillonite in sandstone can more easily convert into other clays. 　　For the study of the relationship between oil saturation and clay types, the rock is divided into two groups according to the oil saturation degree: the oil -saturated and non-saturated. The statistical result shows that the clay mi nera ls content and clay types have nothing to do with the oil saturation percentage. 　　The types, contents and distributions of clay minerals are mainly controlled by rock types and sedimentary facies. In general, the absolute content of the mo ntmorillonite increases with decrease of the sedimentary rock grains. The montmo rillonite in gravel and sandstone has a relatively lower content than that in mu dston e, but there is no much difference between the gravel and sandstone in their co ntents of montmorillonite. The relative content of montmorillonite in gravel and sandstone is 53.88%～85.99%, with an average of 67.94%, while the content in mu d stone is 69.54%～86.59%, with an average of 79.02%. The relative contents of kao li nite distribution decrease in the sequence of gravel, sandstone, and mudstone. But that of the illite is just the opposite. Lianhua reservoir is a turbidity cu rrent deposit in lake facies. Sandstone and gravel are mainly distributed in gro ove and branch groove facies, mudstone and aleurolite in deep lake , groove fron t margin and interlayer branch groove facies. During the evolving process of the facies from the main groove to branch groove, to the groove front margin, to th e interlayer branch groove, and finally to deep lake, the absolute content of cl ay minerals and the relative content of montmorillonite in Lianhua reservoir inc reases with the decline of the primary hydraulics. 　　By heat simulation experiments and a comparative study of the distribution c haracteristics of clay minerals before and after the steam flooding , it is foun d that the montmorillonite in the reservoir can increase because of kaolinite 's reaction to carbonate grains. But because the heavy crude oil carries the montm orillonite grains out, there finally is an approximately 1% deduction of the abs olute amount of montmorillonite in the reservoir after steam flooding. Because t he steam flooding can destroy the clay microstructure to a large degree, some cl ay minerals disperse and migrate to increase the micro-heterogeneity parameters of reservoir. According to the types, contents and distributions of the sensitiv e minerals, the main mechanism of formation damage during steam flooding is part icle migration and swelling of montmorillonite .Steam has a strong effect to the microstructure of the clay minerals.