不整合半风化岩石成岩作用特征

 以准噶尔盆地夏9 井区三叠系顶部不整合半风化岩石为例，通过定性分析与定量评价相结合的方法，对其压实作用、溶蚀作用、胶结作用、交代作用和破裂作用等多种成岩作用特征进行了研究，认为压实、胶结、溶蚀和破裂作用对研究区三叠系顶部不整合半风化岩石的物性影响作用明显，其中压实、胶结作用与孔隙度呈负相关，溶蚀、破裂作用与孔隙度呈正相关，而交代作用对半风化岩石物性的影响效果较小。基于大量岩心观察和分析化验数据，发现不整合半风化岩石各种成岩作用特征在平面上与剖面上均具有较强的非均质性。通过建立多种成岩作用强度参数的判别标准，对不同类型成岩作用的作用强度进行了定量评价，认为三叠系顶部不整合半风化岩石的压实作用对原生孔隙破坏作用较大，强度级别为强；以菱铁矿为主要类型的胶结物堵塞了大量孔隙，其胶结强度级别为弱；视相对溶蚀孔隙度较高，溶蚀强度级别为强；可见少量微裂缝，破裂作用级别弱。按照对半风化岩石孔隙度影响的强弱顺序将成岩作用进行了排序，认为研究区成岩作用对三叠系顶部半风化岩石孔隙度影响程度的先后顺序为压实作用>溶蚀作用>胶结作用>破裂作用。

Diagenesis Characteristics of Semi-weathered Rock of Unconformity

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.