四川盆地二叠系—三叠系碳酸盐岩核磁共振实验测量及分析

doi:10.3969/j.issn.1672-7703.2020.03.015

摘要/Abstract

摘要： 碳酸盐岩储层类型多样，基质孔隙度普遍偏低，储层缝洞发育，孔隙结构复杂。孔隙结构及物性是储层和含油气评价的关键因素。为了研究孔隙结构的特征，针对四川盆地三叠系雷口坡组白云岩、二叠系茅口组致密石灰岩两类碳酸盐岩岩心等共计45 块柱塞样品开展了常规孔渗、岩电实验、核磁共振等测量，从多角度分析了岩心样品的孔隙类型及在储层中的孔隙结构分布规律。研究结果表明，对于雷口坡组白云岩储层，整体岩心核磁T 2 谱呈现明显的单峰、双峰、三峰特征，表明岩心存在三重孔隙介质（基质孔隙、裂缝、溶蚀孔洞），孔隙结构非均质性强，整体物性较差。致密石灰岩核磁共振测量表明，T 2 谱呈现显著的双峰形态，储集空间为基质晶间孔及溶蚀孔，且不同岩心T 2 谱左边峰值基本稳定0.1ms 左右，表明孔隙尺寸比雷口坡组白云岩小。采用SDR 模型反演的核磁共振渗透率与气测法测量的渗透率最大绝对误差为0.31mD，一致性较好。同时，核磁共振测量结果也可以在一定程度上反映泥质含量，泥质含量较高的岩心，核磁共振T 2 谱前端信号很强，分布宽度也较大，而且核磁共振孔隙度通常大于气测孔隙度。文章所提供的实验测量及分析方法对于四川盆地碳酸盐岩缝洞储层具有普遍适用性。

关键词: 碳酸盐岩, 核磁共振, 孔隙结构, 孔隙度, 渗透率, SDR 模型

Abstract: There are various types of carbonate reservoirs, generally with low matrix porosity, well developed fractures and cavities, and complex pore structures. Pore structure and physical properties are the key factors for evaluation of reservoirs and their oil and gas-bearing properties. In order to study the pore types of core samples and the distribution laws of pore structure in reservoirs from multiple perspectives, a total of 45 core plugs, sampled from dolomite in the Triassic Leikoupo Formation and from tight limestone in the Lower Permian Maokou Formation in the Sichuan Basin, were tested for conventional porosity and permeability, and also subjected to rock-electrical experiments and Nuclear Magnetic Resonance testing. The results show that, for the dolomite reservoir of the Leikoupo Formation, the overall NMR T2 spectrum of the core samples shows obvious single-peak, double-peak and triple-peak characteristics, indicating that there are triple-porous media in the cores (matrix pores, fractures and dissolution vugs). The pore structure is of strong heterogeneity, and the overall physical properties are poor. NMR measurements of tight limestones show that the T2 spectrum presents a significant ‘double peak’ shape. The reservoir space is matrix intercrystalline pores and dissolution pores. The left peaks of the T2 spectra of different cores are basically stable at about 0.1ms, indicating that the pore size is smaller than that of dolomite in the Leikoupo Formation. The maximum absolute error between NMR permeability inverted by the SDR model and permeability measured by gas measurement is 0.31 mD, which shows good consistency. Meanwhile, the NMR results also reflect shale content to a certain extent. For cores with higher shale content, the front-end signal of the NMR T2 spectrum is strong, the distribution width is large, and NMR porosity is usually larger than gas porosity. The experimental measurement and analysis methods used in this paper are generally applicable to carbonate fractured-vuggy reservoirs throughout the Sichuan Basin.

Key words: carbonate rocks, Nuclear Magnetic Resonance, pore structure, porosity, permeability, SDR model

中图分类号:

冯庆付, 翟秀芬, 冯周, 刘朱睿鸷, 刘英明. 四川盆地二叠系—三叠系碳酸盐岩核磁共振实验测量及分析[J]. 中国石油勘探, 2020, 25(3): 167-174.

Feng Qingfu, Zhai Xiufen, Feng Zhou, Liuzhu Ruizhi, Liu Yingming. NMR experimental measurement and analysis of Permian-Triassic carbonate rocks in the Sichuan Basin[J]. China Petroleum Exploration, 2020, 25(3): 167-174.

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