利用负胶结物投点图评价西湖凹陷古近系砂岩储层

Using minus-cement point diagram to evaluate Paleogene sandstone reservoir in Xihu Depression

王春梅1 裴昌蓉

成都理工大学沉积地质研究院，四川 成都 610059 大庆油田有限责任公司勘探开发研究院，黑龙江 大庆 163712

Institute of Sedimentary Geology, Chengdu University of Technology, Chengdu 610059, China Research Institute of Exploration and Development, Daqing Oilfield Limited Company, CNPC, Daqing 163712, China)

基于D W Housekencht提出的胶结物质量分数-负胶结物孔隙度投点图原理，对西湖凹陷古近系砂岩颗粒环边或孔隙衬里方式产出的铁白云石胶结物、连生方解石胶结物和分散的粒状方解石胶结物3种不同碳酸盐胶结物质量分数、粒间体积进行计算和统计，作出胶结物质量分数-负胶结物孔隙度投点图，并基于投点图作出判定，认为具连生结构方解石和粒状环边铁白云石的岩石初始孔隙度降低的第一重要因素是胶结作用；粒状结构方解石粒间体积的减少主要是由压实作用控制的；投点位于图的右上角的以颗粒环边或孔隙衬里方式产出的铁白云石胶结物是在较早成岩阶段形成的，提高了岩石的机械强度和抗压实能力，使储集空间得以保护，因此，对储层演化影响是正面的；投点位于图的左下角的连生方解石胶结物和分散的粒状方解石胶结物，形成于岩石已经历有效压实作用的较晚成岩阶段，占据了有限的残余粒间孔隙和由长石等铝硅酸盐溶解作用形成的次生孔隙，对储层的影响是负面的。

Based on cement content - minus-cement pore point diagram principle proposed by David W. Housekencht, this article calculates the content and intergranular volume of ankerite cement, intergrowth calcite cement and dispersive granular calcite cement, which are produced from Xihu Depression paleogene sandstone granular rim or pore lining mode. Cement content-minus-cement pore point diagram is made out and several conclusions are drawn from this point diagram. It is considered that cementation is the first important factor to rock initial porosity reduction of intergrowth calcite and granular rim ankerite cements, granular calcite intergranular volume reduction is mainly controlled by the compaction, ankerite cements which are produced by granule rim or pore lining mode with their points in the upper right corner in the diagram are formed at an early diagenetic stage, which have a positive effect on the reservoir because they can improve rock mechanical strength and resistance to compaction and protect space for storing and gathering. Meanwhile, when the point is in the lower left corner, and intergrowth calcite cement and dispersive granular calcite cements are formed at a late diagenetic stage, during which rock has undergone an effective compaction and occupied limited residual intergranular pore and secondary pores formed by feldspar and other aluminosilicate dissolution. The effect to reservoir is negative.