| The wettability of reservoir is a comprehensive reflection of the interaction between reservoir fluids with rocks,which affects the migration and accumulation of petroleum in tight sandstone reservoirs.In this paper,the wettability of reservoir is evaluated through the contact angle measurement,and influencing factors are analyzed from two angles of mineral compositions and the content of the petroleum polarity component.Based on the petroleum accumulation and simulation experiment,the starting pressure gradient and final petroleum content in tight sandstone can be obtained to analysis how wettability would influence the process of petroleum migration and accumulation.The results show that:(1)the contact angle of tight sandstones are mainly from 70 to110 degrees.The wettability of reservoir is mainly neutral wetting type,water and oil wetting type is less.(2)The wettability of tight reservoir is affected by relative content of hydrophily,neutral and lipophilicity mineral.And the higher content of quartz,the stronger water wetting of tight sandstone;the higher content of illite mixed layers and chlorite,the stronger petroleum wetting of tight sandstone.(3)The content of polar components(colloid and asphaltene)increased,and the wettability of tight reservoirs changes from water wet to neutral,even to petroleum wet.(4)The order of starting pressure gradient of tight reservoir is: oil-wet type < neutral-wet type < water-wet type,oil wetting condition is the most conducive to petroleum migration.(5)The final petroleum saturation is the highest in petroleum-wet reservoir,followed by the neutral wetting type and water wetting type.Oil-wet reservoir is the most conducive to petroleum accumulation. |
