沁水盆地南部海陆过渡相煤系地层横波波速预测

PREDICTION OF THE SHEAR WAVE VELOCITY FOR THE SEA-LAND TRANSITIONAL FACIES COAL MEASURE STRATA IN SOUTH QINSHUI BASIN

沁水盆地南部具有复杂的构造演化史,其上古生界海陆过渡相煤系地层分布广泛,气测异常极为普遍,多种非常规气共生共存,具备形成致密砂岩气的地质条件,是当前致密砂岩气勘探的热点地区。由于致密砂岩气藏具有紧临烃源岩分布、近距离运移成藏的特点,选取具有可靠常规测井、偶极子声波测井及钻井岩心资料的单井,以包含3号煤烃源岩的山西组煤系地层为研究对象,分别采用常规经验法、多元回归法及基质模量法对研究区海陆过渡相煤系地层横波波速进行预测。结果表明,基质模量法的预测精度(相对误差2.83%)明显高于常规经验法(相对误差6.8%)及多元回归法(相对误差5.35%)。因此,优选基质模量法预测研究区煤系地层横波波速,利用基质模量法反演获得了煤系地层多个模量参数值,其代表了复杂构造演化背景条件下煤系地层致密碎屑岩及原生结构煤的岩石物理性质。

There＇s a complex tectonic evolution history for South Qinshui Basin,the sea-land transitional facies coal measure strata are widely distributed in Upper Paleozoic of this area,the gas logging abnormal is extremely common,a variety of the unconventional gases coexist here,and the geological conditions of accumulating the tight sandstone gas are well prepared,so this area has become the current hot spot of the tight sandstone gas exploration.Due to the characteristics of close distribution near the hydrocarbon source rocks,close-range migration and accu-mulation of the tight sandstone gas reservoirs,the single well was selected for possessing the reliable conventional logging,dipole acoustic logging and drilling core data,making Shanxi-Formation coal measure strata containing No. 3 coal hydrocarbon source rocks as the research object,with the help of the conventional empirical method,multivariate regression method and matrix modulus method,the shear wave velocities are predict respectively for the sea-land transition facies coal measure strata in the study area. The results show that the prediction precision of the matrix modulus method（ the relative error is 2. 83%） is significantly higher than those of the two other methods（ the relative error of the former is 6. 8%; and the one of the rest is 5. 35%）. Therefore,the former is optimized for the prediction of the shear wave velocities of the coal measures strata and presentation of the multiple modulus parameters because of the representation of the petrophysical properties of the tight clastic rocks and original structure coal in the coal measure strata under the condition of the complex tectonic evolution background.