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为了进一步提高沉积盆地残余地层古厚度的计算精度,对传统方法进行了改进,以地层压实过程中孔隙度与深度遵循指数关系为前提,提出了适用于中、新生代残余地层古厚度恢复的等效孔隙度法。首先,根据沉积压实原理,以钻井岩心和测井数据为基础,划分各井地层压实单元,并通过测试确定适用于研究区不同岩性地层的压实参数;然后,将地层压实单元等效看作不同岩性地层匀速沉降的均质体,按岩性比例确定各地层压实单元的初始孔隙度、压实系数和偏移常量,并建立其孔隙度一深度关系模型;最后,依据地层骨架厚度不变原理、沉积环境古水深的变化以及压实单元所处地层的相对位置,回剥反演计算残余地层古厚度。将等效孔隙度法应用惠民凹陷沙三段残余地层古厚度恢复,一定程度上校正了岩性差异、构造活动、异常压实作用和古水深的影响,恢复结果明显小于传统方法的结果,与实际地质情况吻合性较好,具有较高的准确性和可信度。
In order to further improve the calculation precision of the paleo-thickness of residual stratum in the sedimentary basin, the traditional method was improved. Based on the exponential relationship between porosity and depth in the compaction of the stratum, the paleopore thickness restoration suitable for the residual stratum in the Meso-Cenozoic Equivalent porosity method. First of all, based on the principle of sedimentation and compaction, based on the drilling core and well logging data, the strata compaction unit of each well is divided and tested to determine the compaction parameters applicable to different lithology strata in the study area. Then, the compaction unit Equivalently, it is considered as a homogeneous body of uniform settlement in different lithology formations. The initial porosity, compaction coefficient and migration constant of each compaction unit are determined according to the lithology ratio, and a porosity-depth model is established. Finally, Based on the principle of the constant thickness of the stratigraphic skeleton, the change of the paleo-water depth in the sedimentary environment and the relative position of the strata in which the compaction unit is located, the paleo-thickness of the residual strata is calculated by back-stripping inversion. The equivalent porosity method is applied to restore the paleo-thickness of remnant stratum in the third member of the Huimin Depression, to a certain extent, the influence of lithologic differences, tectonic activities, anomalous compaction and paleo-water depth is corrected. The recovery results are obviously smaller than those of the traditional methods. Good agreement with the actual geological conditions, with high accuracy and credibility.