The Characteristics And Distribution Of Clay Minerals From The Jurassic Ahe Formation In Northern Tectonic Zone,Kuqa Depression

Due to the exploration of oil and natural gas,one of the key areas in recent years,tight sandstone has the characteristics of complex reservoir structure and wide distribution of clay minerals.The study on the distribution characteristics and control factors of different types of clay minerals is of great significance in the protection of tight sandstone reservoirs.This paper takes the Jurassic Ahe Formation in the northern tectonic belt of the Kuqa Depression in the Tarim Basin as an example.Based on a large number of core samples,log data analysis and previous studies,through thin section observation,scanning electron microscopy and X-ray diffraction of clay minerals experiments and other methods to explore the type,content and distribution characteristics of clay minerals in the reservoirs of the study area,and have a good guiding role in oilfield development and reservoir sensitivity prediction.Firstly,the characteristics of the reservoir should be mastered as a whole.The characteristics of reservoir petrology and physical properties should be analyzed through slice identification.The rock types in the study area are mainly lithic sandstone,and the skeleton components are mainly quartz and cuttings.Typical ultra-low porosity and low permeability sandstone.On the basis of reservoir characteristics research,the use of scanning electron microscopy,clay mineral X-ray diffraction and other analytical experiments to carry out research on clay minerals.Statistics on the results of X-ray diffraction experiments show that the clay minerals in the reservoirs in the study area include illite,Iraqi/Mongolian mixed layer,kaolinite and chlorite.The most important clay mineral is illite.The intergranular filling is mainly silky and flaky;followed by chlorite,and the content of mixed yttrium/montmorillonite and kaolinite is low.According to the research on the combination relationship of predecessors,the clay mineral combination in the study area is divided into five kinds.The key content of this paper is the distribution characteristics of clay minerals in the study area,and the distribution of absolute content of different kinds of clay minerals on the plane and the vertical distribution.Upward relative content variation characteristics;combined with the distribution characteristics of clay minerals,the influencing factors of clay minerals were analyzed.Studies have shown that the distribution of clay minerals is controlled by many factors.The occurrence of clay minerals is different.The main controlling factors for controlling the distribution of clay minerals are different: the plane distribution of illite is controlled by the source conditions,along the source direction.The illite content is reduced,and the vertical distribution of illite is controlled by the particle size and depth.The content of illite decreases with the increase of the particle size and increases with the increase of the buried depth.The plane distribution of kaolinite is mainly controlled by the buried depth.The vertical distribution is controlled by the dissolution and depth.The stronger the dissolution,the higher the kaolinite content,and the relative content of kaolinite with the increase of the buried depth.Gradually decreases.The plane distribution of chlorite is not much different.The vertical distribution is controlled by diagenesis.With the increase of burial depth and temperature,kaolinite gradually changes to chlorite,kaolinite content decreases,and chlorite content increases.