Storage Space Distribution And Controlling Factors Of Jurassic Ahe Formation In The Northern Structural Belt Of Kuqa Depression

As a typical deep tight sandstone reservoir in western China,the micro-pores and micro-cracks of the Lower Jurassic Ahe Formation in the Dibei section of the northern Kuqa depression are widely developed and are typical reservoir types of tight sandstones in this block.It has an important influence on the migration and accumulation of oil and gas.At the same time,micro-cracks and micro-pores are important factors causing reservoir stress sensitivity,water sensitivity and salinity sensitivity,but their scale distribution and main controlling factors have not received sufficient attention.Therefore,in-depth study on the scale distribution and main controlling factors of micro-pores and micro-cracks will be of great significance for the prediction and prevention of reservoir performance and sensitivity prediction of deep tight sandstone reservoirs.In order to reveal the genetic types,distribution rules and main controlling factors of the micro-pores and micro-cracks in the Lower Jurassic sandstone reservoirs in the northern tectonic belt of Kuqa depression.The is based on rock and mineral data analysis.Multi-disciplinary knowledge such as reservoir geology,petroleum geology and sedimentary petrology is the theoretical guidance.Through the observation methods such as polarized light microscopy,scanning electron microscopy,X-ray diffraction,micro-CT scanning,and laser confocal microscopy,the micro-pores and micro-cracks distribution characteristics and main control factors were studied in Ahe Formation in the Dibei section of the northern tectonic belt in Kuqa Depression.The main genetic type of micro pores is weak corrosion pores in muddy matrix and a small amount of intercrystalline micro pores of clay minerals.The development of micro-pores is not affected by the grain size of rock particles.Compaction effect and erosion strength are the main controlling factors that lead to differences in micropore development characteristics.Depth,tectonic stress and shale content are the main factors affecting the compaction effect.In the plane,the high value of micro pores is mainly distributed in the dissolution intensity,the compaction effect is smaller in the Tuzi well area and the Yinan 4 well area,and the low value distribution is less in the dissolution strength and the compaction effect is larger in the Dibei 102 well area.In the vertical direction,the distribution of micro pores in the Dibei section is mainly affected by the dissolution strength and compaction effect.The high value is mainly distributed in the J₁a² with middle dissolution and the weaker compaction effect.The vertical distribution of micro pores in the Tuge section is mainly restricted by the corrosion intensity,and the high value of micro pores is mainly distributed in the J₁a¹ and J₁a³where the corrosion intensity is relatively weak.The main genetic types of micro-cracks are structural micro-cracks,dissolution micro-cracks and so on,and the structural micro-cracks account for the majority of micro-fractures.This time,the distribution characteristics and control factors of structural micro-cracks are mainly studied.On the whole,the development of micro-cracks is affected by the grain size of rock particles.The coarser the grain size,the higher the content of structural micro-cracks.On the plane,the development of structural micro-fractures is controlled by structural deformation strength and structural style.The tectonic micro-cracks have a large scale in the Kezi section and the Dibei section where the structural deformation strength is large,and a small scale in the Tuzi section and the Tuge section with weak structural deformation strength is small.The degree of development of micro-fractures in the Dibei section is strongly influenced by structural styles.The content of structural micro-cracks in the Yinan 4 and Yinan 5 wells with small construction amplitude is high.The development scale of the Yinan 2 and Dibei 102 wells with large construction range is relatively small.In the vertical direction,the development of structural micro-cracks is mainly affected by the tectonic style and shalecontent:（1）The development of the structural micro-cracks in the vertical direction of the Yinan 4 and Yinan 5 wells with relatively stable tectonic style is mainly affected by the shale content.The second section of the Ahe Formation with low shale content has a high degree of development;（2）The structural micro-cracks development in the Dibei 102 and Yinan 2 well areas is mainly affected by the neutralization surface effect.The structural micro-cracks content in the Yinan 2 well area at the turning end of the anticline changes with the buried depth.Large and small,the structural micro-cracks content of the Dibei 102 well located at the turning end is increased with the increase of the buried depth.