煤层气藏核磁共振技术实验研究

The Experimental Study on Coalbed Gas Reservoir Using Nuclear Magnetic Resonance Technique

本文利用低磁场核磁共振仪测试了四个区块不同渗透率煤样的核磁共振T2弛豫时间谱,给出了渗透率、孔隙度和可动流体百分数等测试参数,并分析了泥浆滤液对煤样的伤害程度。研究表明:核磁共振所测试的孔隙度和渗透率与实验室常规所测试的孔隙度和渗透率基本一致,两者的相关性很好。测出的典型煤样的T2弛豫时间谱大都以双峰型为主,两谱峰间连续性差,前峰表征的流体处于束缚状态,主要反映煤层的微孔隙特征;后峰表征的流体处于可动状态,主要反映煤层的裂缝(割理)特征。

Some coal samples with different permeability were selected in four blocks, and the amplitude of T2 spectrum of these coal samples were tested with the nuclear magnetic resonance. Based on the test, some testing parameters were got, such as the permeability, porosity and the percentage of movable fluid. The damage degree of the coal samples caused by mud filtrate was analyzed. The results show that the permeability and porosity tested with the nuclear magnetic resonance are basically identical with the result tested by the conven- tional experiment in laboratory, which have a very good correlation. The measured T2 relaxation time speetnans of typical coal samples are mainly two-peak patterns, and the continuity of the two spectral peaks is bad. The prepeak shows that the fluid is irreducible which reflects the micro pores characters of coal bed; The post- peak shows that the fluid is movable which reflects the fractures （cleats） characters of coal bed.