济阳坳陷沾化凹陷陡坡带始新统沙三段扇三角洲储层成岩作用与有利储层成因

Diagenesis and Genesis of Favorable Reservoir of Fan Delta in Eocene Shahejie Fm.,Zhanhua Sag Jiyang Depression,Bohai Bay Basin

15口井岩芯和众多储层实验资料研究表明,沾化凹陷北部陡坡带始新统沙河街组扇三角洲砂体由长石砂岩、岩屑长石砂岩等构成。在埋藏成岩演化过程中,该砂岩储层经历了多种成岩作用,现储层埋深1800-4000m,处于中成岩演化阶段,总体形成了中孔中渗储层（平均孔隙度为19.7%,平均渗透率为111.5×10^-3μm^2）。但在成岩演化过程中,溶蚀作用对于改善储层质量起到了重要作用,主要在2800-3300m深度段,有机酸对长石颗粒的溶蚀,形成的粒间和粒内孔隙不仅增加了孔隙度,而且提高了储层渗透率,改善了储层质量（孔隙度可达到30%,渗透率达到1000×10^-3μm^2）。可以看出,确定次生孔隙发育深度段有利于有利储层和油气富集层段预测。

Based on 15 key cores and several hundreds of reservoir analysis data,the fan delta sand bodies of Shahejie Formation in Zhanhua Sag,Jiyang Depression,Bohai Bay Basin,are consisted of feldspathic sandstone,which mainly experienced compaction,cementation,dissolution and replacement during the burial diagenetic evolution,and now the diagenetic evolution came to the middle diagenetic stage at current burial depth of 1800 -4000m. The dissolution of feldspar played a significant role in improving reservoir quality during the burial diagenetic evolution. The intergranular pores and intragranular pores,caused by the feldspar dissolution in the depth of 2800 - 3300 m,are constructive for the reservoir properties in increasing the porosity and permeability（ the porosity may be up to 30% and the permeability up to 1000 × 10^-3μm^2）. Obviously,to find the depth where the dissolutions and the secondary pores developed is favorable for predicting good quality reservoir.