Taking the semi-weathered rock of unconformity of Xia9 wellblock in Junggar Basin as an example, several types of diagenesis are studied by combining a qualitative analysis with a quantitative evaluation, consisting of compaction, dissolution, cementation, replacement and fracture. The main diagenesis, which influences the physical character of the reservoirs, involves compaction, cementation, dissolution and fracturing. Compaction and cementation reduce pores, dissolution and fracturing increase pores. On the basis of numerous core observations and experimental data, a strong heterogeneity of the digenesis is found both on the plane and on the section in semi-weathered rock of unconformity. After that, the standard of several diagenesis strength parameters is established for the quantitative evaluation of diagenesis strength. The impact of compaction is strong on the original pores, whose level is high. The cement, found mostly as siderite, blocks plenty of pores,and its level is low. The proportion of the type of the dissoluted pore is high, and the dissolution level is high, and the fractureing level is low with few fractures. The order of diagenesis is made based on the strength of diagenesis on the impacts on the porosity of the semi-weathered rock. The sequences about the effect levels of the four kinds of diagenesis are as follows: compaction> dissolution> cementation> fracturing in study area.
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