准噶尔盆地南缘低煤阶煤储层可动流体及孔径分布特征

摘要

为分析准噶尔盆地南缘(简称准南)低煤阶煤储层可动流体、束缚流体以及孔径分布特征,对准南6个矿区6个煤样进行了高速离心和低场核磁共振实验.实验结果表明:准南低煤阶煤以吸附孔发育最优,其次为渗流孔和裂隙.建立束缚水状态的最佳离心力为1.380 MPa;结合饱和水状态和束缚水状态的核磁共振T2谱,得到可动流体孔隙度为0.45％～1.89％,平均1.29％;束缚流体孔隙度为1.03％～7.45％,平均4.18％,可动流体孔隙度与渗透率呈幂指数关系(R2-0.935 8).根据“离心-T2C法”得到准南低阶煤孔隙半径主要分布在0.01～1 μm,平均孔隙半径为1.771 μm.%To analyze the movable fluid,bound fluid and pore size distribution of low rank coal reservoir in southern margin of Junggar basin,the paper performed the high-speed centrifuge and low-field nuclear magnetic resonance experiment on six coal samples from six coalfields in southern margin of Junggar basin.The experimental results showed that low rank coal mainly developed adsorption pores,followed by seepage pore and fracture.The optimum centrifugal pressure for establishing irreducible water state is 1.380 MPa.The paper integrated the T2 spectra of both saturated water state and irreducible water state to calculate movable fluid porosity and residual water porosity.The movable fluid porosity ranges between 0.45％～1.89％(averaging at 1.29％),the residual water saturation ranges between 1.03％～7.45％(averaging at 4.18％).The movable fluid porosity shows exponential relationship with air permeability (R2=0.935 8).Based on the method of"centrifugal-T2c",the pore size of low rank coal in southern margin of Junggar basin was mainly distributed in 0.01～1 μm and the average of pore size is 1.771 μm.