致密砂岩气水分布特征--以鄂尔多斯盆地东部临兴地区为例

The regularity of gas and water distribution for tight sandstone:Case study of Linxing area,eastern Ordos Basin

鄂尔多斯盆地临兴地区垂向上发育多套致密砂岩气层,目前生产最大问题是大部分井产水且井间产水量差异大,研究区气水分布规律和控制因素认识不清严重制约了该区天然气勘探开发进程。水化学分析显示致密砂岩目的地层水为CaCl2型,气藏未受大规模破坏;通过岩石薄片观察、核磁实验分析,地层水赋存特征主要受不同孔隙类型组合和孔隙结构影响。可动自由水主要赋存于残余粒间孔、溶蚀粒间孔内,毛管水、束缚水主要赋存于溶蚀颗粒孔和晶间孔内;气水分布主要受生烃强度、输导体系、构造幅度、储层非均质性影响,远离源岩储层断裂输导能力差时储层自由可动水含量较高,且在一定的构造幅度下存在气水分异现象。气田开发过程中宜针对气水分布规律在开发井部署、合层开采及排采制度上进行优化。

There are some tight sandstone reservoir accumulations vertically in Linxing area,the understanding of gas and water distribution regularity and controlling factors is unclear,which result in the restricted progress of natural gas exploration and development in the area.Water chemical analysis showed that tight sandstone formation water is CaCl2 type,the gas reservoirs were not destruction on a large scale.We found the occurrence of formation water is controlled by pore type and pore structure through rock slice analysis and nuclear magnetic experiment,the free water mainly exists in intergranular pores and dissolved intergranular pores,capillary and bound water mainly exists in dissolved particle pore and intercrystalline pore.Gas and water distribution is mainly influenced by gas-generating intensity,passage system,amplitude of structure and reservoir heterogeneity.The reservoir has more free water when it is far from the source rock and conducting ability of fault is weak,and under certain structure amplitude exists the possibility of gas water differentiation.Well deployment,commingled layer production and drainage rules should be optimized according to the gas and water distribution regularity during the process of gas field development.