鄂尔多斯盆地致密砂岩气藏微观孔喉球棍模型表征方法

Micro nano pore throat CT imaging ball stick model of tight sandstone gas reservoir in Ordos Basin

以鄂尔多斯盆地J地区下石盒子组致密砂岩气藏储层为研究对象,利用Avizo软件的数据处理和数值模拟功能,处理多尺度三维CT成像技术提供的图像信息.提出核磁阈值分割法,应用该方法对研究区目的层岩石样品进行多尺度三维孔喉分维数重构,建立非常规致密砂岩气藏储层纳米级三维孔喉分布和孔喉球棍模型.利用数字岩心分析模块对孔隙空间进行计算,获得喉道半径、孔隙半径、配位数、喉道长度、喉道形状因子、孔隙形状因子等定量参数,进而应用上述表征参数进行孔喉结构定量评价.研究表明,纳米尺度下致密砂岩储层孔隙呈球状,喉道呈杆状、棍状和管束状分布,孔喉分布随机性强.多尺度三维CT成像技术具有无损、高分辨率等特点,能够在多个分辨率和不同视域获得较为清晰的二维、三维图像.建立的球棍模型,能够直观、定量表征孔喉大小、几何形态、空间分布、连通性等,对微细观尺度储层孔喉研究具有重要意义.

Taking the tight sandstone gas reservoir of Lower Shihezi formation in J area of Ordos Basin as the research object,the image information provided by multiscale 3D CT imaging technology is processed by using the data processing and numerical simulation functions of Avizo software.The multi-scale 3D pore throat fractal dimension reconstruction of the target rock samples in the study area is carried out,and the nano scale 3D pore throat distribution and pore throat ball stick model of unconventional tight sandstone gas reservoir are established.A threshold segmentation method is proposed,the multi-scale three-dimensional pore throat fractal dimension reconstruction of the target rock samples in the study area is carried out,and the nanometer three-dimensional pore throat distribution and pore throat club model of unconventional tight sandstone gas reservoir are established.Using the digital core analysis module to calculate the pore space,the quantitative parameters such as throat radius,pore radius,coordination number,throat length,throat shape factor and pore shape factor are obtained,and then the above characterization parameters are used to quantitatively evaluate the pore throat structure.The results show that the pores of tight sandstone reservoir are spherical,and the throat is rod-shaped,rod-shaped and pipe bundle shaped,and the distribution of pore throat is random.Multi scale three-dimensional CT imaging technology has the characteristics of non-destructive and high-resolution.It can obtain clear two-dimensional and three-dimensional images in multiple resolutions and different fields of view.The established ball stick model can directly and quantitatively characterize the pore throat size,geometry,spatial distribution,connectivity,etc.,which is of great significance to the study of pore throat in micro scale reservoir.