利用三维数字岩心技术评价低渗透砂砾岩储层孔隙结构

Evaluation of pore structure of low permeability glutenite reservoir by 3D digital core technology

为更直观、准确地分析准噶尔盆地陆梁隆起二叠系下乌尔禾组低渗透砂砾岩储层微观孔隙特征,利用CT扫描成像技术对砂砾岩样品开展岩心三维空间的孔洞、裂缝和高密度填隙物发育特征评价,从图像灰度、均质性和孔喉连通性的角度分析岩石孔隙结构。在此基础上,根据最大球算法提取并建立了储层数字岩心孔隙网络模型,研究了不同岩样的孔隙半径、喉道半径、孔喉比以及岩心孔喉配位数等概率分布特征。研究认为:1)研究区样品的储集空间以溶蚀孔和微裂缝为主,孔隙半径为0.1~10.0μm,喉道半径为0.1~7.0μm,孔喉比为0~4,配位数为0~7,岩石总体孔喉比和喉道半径小、喉道连通差,是导致研究区岩心渗透率低的主要原因。2)常规渗透率为0.330×10^(-3)μm^(2)样品的孔隙半径主要为2.5μm,喉道半径主要为1~3μm,孔喉比多为2,配位数为0~3;常规渗透率为0.441×10^(-3)μm^(2)样品的孔隙半径主要为5.5μm,喉道半径主要为1~5μm,孔喉比大部分为2.5,配位数为1~6。渗透率越高,三维数字岩心技术计算的孔隙结构参数越好,这与常规试验分析结果具有较好的一致性。

In order to more intuitively and accurately analyze the micro pore characteristics of low-permeability sandy conglomerate reservoir of lower Wuerhe Formation of Permian in Luliang Uplift,Junggar Basin,CT scanning imaging technology is used to evaluate the development characteristics of pores,fractures and high-density interstitial materials in core 3D space of glutenite samples,and the rock pore structure is analyzed from the perspective of image gray,homogeneity and pore throat connectivity.On this basis,according to the maximum sphere algorithm,the digital core pore network model is extracted and established,and the probability distribution characteristics of pore radius,throat radius,pore throat ratio and core pore throat coordination number of different rock samples are studied.The results show that:1)The reservoir space of the samples in the study area is mainly composed of dissolution pores and micro fractures,and the pore radius is distributed in the range of 0.1~10.0μm,with throat radius ranging from 0.1 to 7.0μm,the pore throat ratio is 0~4,the coordination number is 0~7,the overall pore throat ratio and throat radius of the rock are small,and the throat connectivity is poor,which is the main reason for the low core permeability in the study area.2)The pore radius of the sample with conventional permeability of 0.330×10^(-3)μm^(2) is mainly 2.5μm,the throat radius is mainly 1~3μm,the pore throat ratio is mostly 2,and the coordination number is 0~3;The pore radius of the sample with conventional permeability of 0.441×10^(-3)μm^( 2) is mainly 5.5μm,the throat radius is mainly 1~5μm,the pore throat ratio is mostly 2.5,and the coordination number is 1~6.The higher the permeability is,the better the pore structure parameters calculated by three-dimensional digital core technology are.This is in good agreement with the results of conventional test analysis.