鄂尔多斯盆地上古生界致密砂岩气田储集层特征与成因*

鄂尔多斯盆地上古生界致密砂岩储集层普遍以低孔低渗为主要特征，但在低孔低渗的背景上发育相对优质储集层。应用偏光显微镜、恒速压汞等技术手段，从碎屑岩的粒度、碎屑组分、孔隙结构等分析入手，对比神木气田、榆林气田和苏里格气田3个大气田的储集层特点，并对致密砂岩中相对优质储集层的成因进行了分析。研究认为：高石英类矿物含量、适量的可溶性组分(包括长石、火山岩岩屑及凝灰质等）及残余少量粒间孔形成的酸性流体的渗流通道是形成相对优质储集层的必要条件；而较高含量的千枚岩屑、泥板岩等软组分，在上覆地层压力作用下被压实变形、充填孔隙，造成残余粒间孔全部丧失和酸性流体渗流通道的缺乏，因而形成低孔低渗的致密砂岩储集层。

Characteristics and origin of reservoirs of gas fields in the Upper Paleozoic tight sandstone,Ordos Basin

The reservoirs in the Upper Paleozoic of Ordos Basin are generally characterized by low porosity and low permeability，but reservoirs with relatively high quality developed in the background of low porosity and low permeability. By means of the polarizing microscope，rate-controlled mercury penetration and other technical methods，based on the analysis of clastic rock granularity，detrital composition and pore structure，comparison and origin analysis of the tight sandstone reservoirs in gas fields，including Shenmu Gas Field，Yulin Gas Field and Sulige Gas Field，were carried out.We concluded that higher content of quartz kind of minerals and adequate amount of soluble components(including feldspar minerals，volcanic rock debris and tuffaceous materials，etc)and the seepage channels for acidic fluid formed by remnants of intergranular pore-space are requirements for relatively high quality reservoirs;higher content of phyllites rock fragments and argillaceous slates，which were deformed under the overlying strata pressure，led to the intense decrease of intergranular pore-space and the lack of seepage channel for acidic fluid，and thus tight sandstone reservoirs with low porisity and low permeability were developed.