为明确东道海子凹陷乌尔禾组凝灰岩孔隙结构与主控因素,基于低压CO2 吸附、低温N2 吸附以及高压压汞实验,对凝灰岩全尺寸孔隙孔径进行表征;基于分形理论,对凝灰岩微孔和介孔的孔隙复杂程度和非均质性进行定量表征,阐明影响与控制凝灰岩孔隙结构的主要因素.结果表明,凝灰岩主要发育锥形管孔、开口的锥形平板孔和狭窄的平行板孔等形态孔隙,孔径呈多峰分布;凝灰岩总孔体积介于0.005 4~0.047 8 cm3/g,各类孔隙发育程度差异较大,凝灰岩总孔体积主要由介孔所提供,介孔体积介于0.004 2~0.041 3 cm3/g,平均 0.026 0 cm3/g,平均占比 75.10%;其次是微孔和宏孔,微孔体积介于0.000 6~0.005 5 cm3/g,平均0.003 1 cm3/g,宏孔体积介于0.000 6~0.005 3 cm3/g,平均0.002 8 cm3/g,二者的占比分别为11.5%和13.4%;凝灰岩孔隙的比表面积主要由微孔和介孔所提供,二者的平均占比分别为53.04%和46.71%.凝灰岩微孔分形维数Dm介于2.59~2.97,介孔分形维数D1 介于2.23~2.55,介孔分形维数D2 介于2.62~2.83,反映凝灰岩孔隙非均质性较强.岩石中总有机碳与黏土矿物是凝灰岩孔隙发育的主要控制因素.
In order to clarify the characteristics and main controlling factors of the pore structure of tuffs in the Urho Formation of the Dongdaohaizi depression,the pore size of full-size pores of tuffs was characterized based on low-temperature carbon dioxide adsorp-tion,nitrogen adsorption and high-pressure mercury pressure experiments.The tuff mudstone mainly existed conical tube pores,conical plate pores with open ends and narrow parallel plate pores.Pore size has the multi-peak distribution,the total pore volume of the tuff mudstone ranges from 0.005 4 to 0.047 8 cm3/g,with a large of various types of pores.The pore volume of the tuffs is mainly provided by mesopores,which ranges from 0.004 2 to 0.041 3 cm3/g with the average of 0.026 cm3/g and accounts for 75.10%,followed by micropores and macropores.Micropores range from 0.000 6 to 0.005 5 cm3/g with the mean of 0.003 1 cm3/g,and macropore change from 0.000 6 to 0.005 3 cm3/g with the average of 0.002 8 cm3/g and account for 11.5%and 13.4%respectively.The specific sur-face area of tuffaceous mudstone is mainly provided by micropores and mesopores.The tuff microporous fractal dimension Dm ranges from 2.59 to 2.97,mesopore fractal dimension D1 from 2.23 to 2.55 and mesopore fractal dimension D2 from 2.62 to 2.83,reflecting the pore strong inhomogeneity of the tuffaceous mudstone.The TOC and clay minerals are the main controlling factors for pore in the tuffs,with quartz and feldspar being less important.