准噶尔盆地东道海子凹陷北斜坡上二叠统梧桐沟组储集层成岩作用与孔隙演化

Diagenesis and pore evolution of Upper Permian Wutonggou Formation reservoir in the north slope of Dongdaohaizi Sag,the Junggar Basin

准噶尔盆地东道海子凹陷油气资源十分丰富,构造背景有利,开展优质储层的预测能够有效地指导井位优选,实现油气新发现。复杂成岩作用的改造决定了岩石物性和孔隙结构的演化,利用岩石薄片、铸体薄片、扫描电镜、X射线衍射等微观实验分析技术对东道海子凹陷北斜坡上二叠统梧桐沟组进行成岩作用研究,划分成岩阶段,并定量计算各阶段孔隙的改变量,明确孔隙度降低的主要影响因素。研究结果认为:(1)梧桐沟组成岩作用主要包括压实作用、胶结作用、交代作用及后期的溶蚀作用,目前主要处于中成岩A期;(2)压实减孔是梧桐沟组孔隙度损失的主要原因,平均减少23.59%,胶结作用所损失的孔隙度平均为3.30%,溶蚀作用较弱,平均增加孔隙度为2.36%;(3)叠后相干能量梯度属性方法裂缝预测认为梧桐沟组裂缝发育区与构造断裂特征有相关性;(4)有利储层受岩性、构造作用、成岩作用共同控制,滴南8井扇三角洲前缘断块群为有利储层发育区。该研究成果对该区下一步的勘探开发工作具有指向作用。

In the Dongdaohaizi Sag, the Junggar Basin, hydrocarbon resources are quite abundant and tectonic setting is favorable. The prediction of high quality reservoir plays an important role in the well location selection and the new oil and gas discovery. The petrophysics and pore evolution are dominated by the reworking of complex diagenesis. In this paper, the diagenesis of Wutonggou Formation in the north slope of Dongdaohaizi Sag was analyzed and divided by using petrographic thin section, cast thin section, SEM and X ray diffraction. Then, the variation of porosity in each stage was calculated, and the main factors leading to the reduction of po- rosity were confirmed. It is indicated that the diagenesis of Wutonggou Formation mainly includes compaction, cementation, replace- ment and later denudation. At present, it is at stage A of middle diagenesis. Compaction is the main cause for the reduction of porosity of Wutonggou Formation, making the porosity reduce averagely by 23.59%. The porosity reduction caused by cementation is 3.30% on average. Denudation is weaker, and it increases the porosity by 2.36% on average. Fractures were predicted by means of post-stack coherent energy gradient attribute method, indicating that the fracture development zone of Wutonggou Formation is correlative with fracture characteristics of structures. Favorable reservoirs are controlled jointly by lithology, tectonics and diagenesis. The fault block groups of fan delta front in Well Dinah 8 are the favorable reservoir development areas. The research results can be used as the refer- ence for the future exploration and development in this area.