鄂尔多斯盆地东部盒8段致密砂岩储层特征及低产地质原因分析

Characteristics of tight sandstone reservoirs and analysis of geological causes of low yield of He8 Member in eastern Ordos Basin

鄂尔多斯盆地东部是长庆油田公司实现油气当量5000×10^4t目标的重要接替领域，上古生界石盒子组盒8段是该地区天然气勘探的主要目的层，储层舍气普遍，单井产量低，储层渗透率普遍小于1mD。储集砂岩类型以岩屑石英砂岩为主，与鄂尔多斯盆地西部苏里格气田盒8段储层相比，具有石英含量低、软组分含量高、喉道半径小和可动流体饱和度低的特点，是比苏里格气田盒8储层更致密的致密砂岩储层。应力敏感性和气水相渗实验分析结果表明，鄂尔多斯盆地东部盒8段致密砂岩储层地层条件下应力敏感性强、储层水锁损害大、气相渗透率降低幅度大是造成单井产量低的主要地质原因。

Eastern Ordos Basin is an important successive region for the Changqing Oilfield Company to achieve the goal of the 50-million-ton oil-gas equivalent weight. The He8 Member of Shihezi Formation, Upper Paleozoic, is the main target zone of natural gas exploration in the region. Its reservoirs are generally gas-bearing with low production rate per well, and the reservoir permeability is generally less than lml）. The reservoir sandstone types are dominated by lithic quartz sandstone, with characteristics of low quartz content, high soft component content, small throat radius, and low movable fluid saturation, compared with those of the He8 Member rservoirs in the western Ordos Basin＇s Sulige gasfield. Therefore, they are tighter sandstone reservoirs than the He8 reservoirs of Sulige gasfieht. Stress sensitivity and gas-water relative permeability experiment analysis show that the strong stress sensitivity, large water blocking damage to reservoirs, and big amplitude of gas-permeability reduction, under the tight sandstone reservoir conditions of the He8 Member in the eastern Ordos Basin, are major geological reasons that cause low production per well