富古地区下古生界储层孔隙结构特征分析

Characteristics of pore structure of lower Paleozoic reservoir in Fugu Area

王 旭 邓礼正 张 娟 易小燕

Wang Xu Deng Lizheng Zhang Juan Yi Xiaoyan

成都理工大学能源学院，四川 成都 610059

College of Energy Resources, Chengdu University of Technology, Chengdu 610059, China

鄂尔多斯盆地南缘富古地区下古生界马家沟组风化壳发育，储集空间类型复杂。文中利用铸体薄片、扫描电镜、物性、压汞等化验分析手段系统分析了该区奥陶系储层的微观孔隙结构特征。根据孔隙结构参数、压汞曲线的形态结合孔隙类型将该区储层分为：微孔隙、细喉道、排驱压力高的特低孔低渗致密储层，储集性很差，这种储层在该区的储层中占大部分；微裂缝发育的储层，这类储层排驱压力低，平台不明显，孔隙度低而渗透率较高；溶孔发育且连通性好的储层，此类储层排驱压力较高，平台宽缓，孔渗好；局部溶孔发育但周围被致密储层包围、封隔的储层，此类储层孔隙度较高、渗透率很低，孔隙结构、参数均为致密储层特征。储层中发育微裂缝及溶孔改善了储层的储集性，使储层非均质性增强。

Weathering crust was developed in Majiagou Formation of lower Palaeozoic era, in the south front of Fugu Area, Ordos Basin. The microscopic pore structure of Ordovician weathering crust reservoir in Fugu Area was thoroughly analyzed by using mercury injection, cast thin section, scanning electron microscope and conventional physical properties. Based on the pore structure parameters, shape of mercury injection curves combined with pore types, the rock in Fugu Formation are mainly divided into three categories. The main part is tight reservoir with low porosity and low permeability characterized by microscopic pore, small throat, high displacement pressure, which has poor reservoir quality. The reservoir with micro-fractures is characterized by low displacement pressure, unobvious plat, low porosity and high permeability. The nature of reservoir rocks is determined by the development degree and connectivity of dissolved pores. The rock with more dissolved pores and better connectivity has higher displacement pressure, more obvious and broader plat, higher porosity and permeability. However, rock with poorly developed pores and surrounded by dense rocks has higher porosity and lower permeability, and pore structure parameters are characterized as tight rock. Developments of micro-cracks and dissolved pores in the rock have improved the reservoir quality and intensified the heterogeneity of the area, which made the rock as the main reservoir in the area.