Characteristics and control factors of tight sandstone reservoirs inmarine-continental transitional coal measures

Abundant unconventional gas resources were stored in tight sandstone reservoir,which deposited in marine-continental transitional coal measures.In order to make great breakthrough in tight sandstone gas in coal measures,the characteristics of tight sandstone reservoirs in coal measure in Linxian area were analyzed and the diagenetic process and its impacts on reservoir properties were also discussed,which were based on thin sections,scanning electron microscope,X-ray diffraction,porosity and permeability test,which will make great .The results show that the sandstonesare mostly sublithareniteandhas entered the middle diagenetic Stage B.The types of pores are dominated byresidual intergranular pore,intergranular dissolution pores,intragranular dissolved pores and kaolinite intercrystallinepores.The content of clay minerals in sandstones is high,including kaolinite,illite,chlorite and mix-layerillite/smectite.And the kaolinite contents have a positive relationship with porosity and permeability,indicating that the existence of kaolinite have a positive influence on reservoir qualities.Compaction play a leading role in reducing reservoir porosity and permeability.There exist abundant organic matters in coal measure,which resulted in organic acid formed in diagenetic process.the organic acid not only promote the dissolution,but also provided material andthe room for authigenic quartz growing.