Effect of Alkaline Diagenetic Environment of Lower Jurassic on Reservoir Property in Kuqa Depression

Diagenetic evolution of the coal measure strata usually results in the acidic diagenetic environment,but the quartz and analcime dissolutions in the coarse clastic rocks of Ahe formation of the Lower Jurassic in Tugeerming anticlinal structural belt in eastern Kuqa depres-sion suggest that the stronger alkaline diagenetic environment probably exists during its early stage of diagenetic evolution.Calcite cement formed in the alkaline environment holds the original interstice between the clastic grains and strengthens the compactibility-resistance of the clastic rocks.In the late stage,calcite cements are dissolved due to weathering and eluviation,and the original interstices are released and the reservoir property of Ahe formation becomes better.For this reason,the alkaline diagenetic environment in the early stage plays an important role in improving the reservoir property of Ahe clastic rocks.