鄂南致密砂岩气藏储层孔隙特征研究

Pore Structure Characteristics of Tight Sandstone Gas Reservoirs in the Southern Ordos Basin

摘要: 致密砂岩储层因其孔隙结构相对复杂、非均质性强等原因而在非常规油气开发中面临诸多挑战。为深入探究该类储层的孔隙结构特征及其非均质性规律，本文选取鄂尔多斯盆地某区块盒一段的致密砂岩岩心，结合X射线衍射(XRD)、低温氮气吸附(BET)等实验手段对其孔隙结构特征及矿物组成进行表征。结果表明，研究区致密砂岩储层孔隙类型以介孔(2~50 nm)为主，孔径分布在8.8~33.0 nm之间，平均孔径为14.7 nm，矿物组成中黏土矿物绝对含量较高，矿物类型主要有伊利石、高岭石、伊/蒙混层等。基于低温氮气吸附的孔隙分形维数介于2.317~2.631之间，平均为2.538，反映出致密砂岩储层具有高度复杂与显著非均质的孔隙结构。本研究可为致密气藏储层评价与开发提供理论支撑。

Abstract: Tight sandstone reservoirs present numerous challenges in unconventional hydrocarbon development due to their complex pore structures and strong heterogeneity. To better understand the pore structure characteristics and heterogeneity of such reservoirs, this study investigates tight sandstone cores from the He-1 Member in a selected block of the southern Ordos Basin. A combination of X-ray diffraction (XRD) and low-temperature nitrogen adsorption (BET) techniques was employed to characterize both pore structure and mineral composition. Results indicate that mesopores (2~50 nm) dominate the pore system, with pore sizes ranging from 8.8 to 33.0 nm and an average pore diameter of 14.7 nm. The reservoir features a high clay mineral content, primarily composed of illite, kaolinite, and illite-smectite mixed layers. Fractal dimension values derived from nitrogen adsorption data range from 2.317 to 2.631, with an average of 2.538, suggesting a highly complex and significantly heterogeneous pore network. This study provides a theoretical basis for reservoir evaluation and development of tight gas reservoirs.