鄂尔多斯盆地富县探区延长组长6—长8段超低渗砂岩储集层孔喉特征

采用恒速压汞、原油边界层测试及分形几何方法，精细描述鄂尔多斯盆地伊陕斜坡富县探区延长组长6—长8段超低渗砂岩储集层微观孔隙结构及喉道分布，定量表征超低渗储集层微观孔隙结构特征及其对渗流能力的控制作用。研究表明，研究区延长组长6—长8段砂岩储集层孔隙喉道弯曲迂回程度强烈，孔喉大小悬殊，分布形式以单峰正偏态型和双峰偏粗态型为主；储集层为大孔细喉型，喉道半径的大小及其分布是低渗储集层渗流能力的决定性因素；储集层具有良好的分形几何结构，沉积环境和成岩作用差异使得储集层具多重分形特性；超低渗储集层原油吸附层厚度占孔隙体积15%~23%，原油吸附层的形成是储集层渗流能力变差的主要原因。

Pore and Throat Characteristics of Chang6-Chang8 Ultra-Low Permeability Sandstone Reservoirs of Yanchang Formation in Fuxian Exploration Area,Ordos Basin

The micro?pore structures and throat distribution of Chang6-Chang8 reservoirs of Yanchang formation in Fuxian exploration area of Yishan slope in Ordos basin are described in detail by means of constant speed mercury injection test, crude oil boundary layer test and fractal geometry method, and the control effect of micro?pore structure features on the percolation capacity is quantitatively characterized.Result shows that the sandstone reservoirs of Chang6-Chang8 members in this area are characterized by big pores and fine throats with strongly curved pore throat and size disparity, and dominated by distribution patterns of single?peak positive skewness and double?peak coarse skewness, for which the size and distribution of the throat radius could be decisive factor controlling the low?permeability reservoir’s fluid flow capacity. Also, they have good fractal geometry structures, and the sedimentary environment and diagenetic differences allow the reser?voirs to be of multi?fractal properties, while crude oil adsorption layer thickness in the extra?low permeability reservoirs accounts for 15%~23% of pore volume, and it is the formation of crude oil adsorption layer that could make the reservoir percolation capacity become poor