高能河道砂体特征及勘探意义——以元坝地区须三段为例

Characteristics of high-energy channel sandstone and its exploration significance:A case from Xujiahe Formation in Yuanba area

元坝地区须三段钙屑砂岩气藏具有"源储共生、高效运聚、成藏条件优越和整体含气"的岩性气藏的特征,储层主要发育在辫状河三角洲高能河道砂体中。元坝地区西北部须三段富钙屑高能河道砂体具有低伽马(伽马曲线均呈光滑箱型或微齿化箱型)、高电阻,碳酸盐岩岩屑含量高、石英含量低,溶蚀孔隙和裂缝十分发育的特点。富钙屑高能河道砂体沉积厚度大,是须三段天然气富集高产的基础;近物源,碳酸盐岩屑含量高,抗压实程度强,可溶蚀程度强,是须三天然气富集高产的关键。须三段钙屑砂岩气藏的勘探应以钙屑砂岩单层厚度大、钙屑含量高、石英含量低的近源高能河道砂体为主要对象。

The calcarenaceous sandstone reservoirs in the 3rd member of the Xujiahe Formation in the Yuanba area are lithologic ones featured by source and reservoir coexistence, high migration efficiency, favorable accu- mulation condition and overall gas-bearing capacity. Reservoirs mainly develop in the high-energy channel sand- stones of braided river delta. The calcarenaceous high-energy channel sandstones in the 3rd member of the Xujia- he Formation in the northwestern Yuanba area are characterized by low GR （smooth box-like or toothed box-like gamma curves）, high resistance, high carbonate debris content, low quartz content, and wide spread of dissolu- tion pores and cracks. The big thickness of cal high-energy channel sandstones provides the basement for the enrichment of natural gas in the 3rd member of the Xujiahe Formation. Near source, high carbonate debris content, high compression strength and high dissolution degree are the keys for the enrichment of natural gas in the 3rd member of the Xujiahe Formation. The explorations of cal sandstone reservoirs in the 3rd member of the Xujiahe Formation should be focused on the near-source and high-energy channel sandstones with thick calcareous debris sandstone, high calcareous content and low quartz content.