摘要
煤层顶板砂岩富水性影响煤层回采安全.为了提高煤层顶板砂岩富水性的解译精度和可靠性,综合样品X射线粉末衍射分析、测井曲线约束岩石物理建模和交会图分析等技术方法,以神东矿区1-2煤的直罗组顶板富水砂岩为例,研究顶板富水砂岩的地震岩石物理特征及解译方法.结果表明,建模的岩石物理参数与测井实测值一致性高,可用于分析顶板砂岩的相关参数变化规律.顶板砂岩的岩石物理参数受孔隙度和水饱和状态影响明显,用纵横波阻抗和模量分析时效果较优.在纵波阻抗-纵横波速度比交会图中,顶板砂岩散点呈放射状分区分布.据此制作的解译模板,可以定量解译顶板砂岩的孔隙度和水饱和状态.该研究成果可为煤层顶板砂岩的地震岩石物理特征分析和富水性解译提供关键参数支撑和理论依据.
Abstract
Water enrichment in roof sandstones affects the mining safety of coalbeds.In order to improve the interpretation accuracy and reliability,the authors have taken the water-rich roof sandstone of the 1-2 coalbed of Zhiluo Formation in the Shendong mining area as an example and studied its petrophysical characteristics and seismic interpretation methods,incorporating X-ray powder diffraction analysis,wireline-log constrained petrophysical modeling,and cross-plot analysis.The results show that the mineral composition of the sandstone is complex and mainly includes quartz(35.6％),calcite(28.5％),kaolinite(19.1％),albite(11.0％),and illite(5.8％).Following the proposed rock physical modeling strategy,the modeled P-wave velocity and density of water-saturated roof sandstone are consistent with the corresponding measured wireline logs.These consistencies have mutually verified the proposed rock physical modeling strategy and the wireline logging.With the strategy,one can use the modeled petrophysical parameters to analyze the porosity variations and water-saturation states.Generally,both porosity and water-saturation states significantly affect the petrophysical parameters.Seismic velocities,moduli,impedances,and density gradually decrease with increasing porosity,while velocity and modulus ratios show opposite trends.In the low porosity range(＜0.1),seismic velocity,moduli,and impedances vary rapidly with porosity change,while velocity and modulus ratios change slowly.In contrast,the variation trends in the high porosity range(＞0.2)are completely different.The petrophysical parameters under the water-saturated state have higher magnitudes and variation ranges than the dry state.Among all petrophysical parameters,acoustic impedances and velocity ratio are probably the preferred parameters for analyzing roof sandstone.In the P-wave impedance vs.velocity ratio cross-plot,the scattered points of roof sandstone are distributed in radial partitions,and the interpretation template made from the cross-plot can quantitatively and simultaneously interpret the porosity variation and water-saturation states.The research results can provide parameter support and theoretical guidance for analyzing petrophysical characteristics and water-rich interpretation of coalbed roof sandstones.
维普
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