基准面变化幅度半定量分析技术及其应用

基准面是抽象的、非物理的、一个变化的势能面，其通过制约可容空间变化控制着地层的沉积与保存作用。湖相沉积受构造控制作用强，地震上超点法难以用来确定基准面的变化幅度。通过录井岩性资料中沉积物类型及其叠加特征可以反推相对可容空间的变化幅度。依据砂岩—泥岩旋回的厚度分布，选取丰度最高值区间的中值厚度或平均旋回厚度为统计区间，自目的层底部向顶部统计各区间内砂岩、泥岩厚度，计算泥岩百分含量，并赋以不同泥岩百分含量相应的基准面变化值，可半定量分析基准面变化幅度。应用该方法可明确不同地区可容空间的变化特征，识别转换面和划分基准面旋回，并分析基准面旋回变化对沉积相分配的控制作用。该方法在滨浅湖滩坝相砂、泥岩薄互层的基准面旋回划分和对比中应用，建立了高精度等时地层格架。

Semiquantitative Analytic Technique on Base Level Variation Range and Its Application

Base level is an imaginary level surface and as a matter of fact, a very physical potential energy level at the same time, which controls stratum depositional and conservation by increasing or decreasing accommodation space. Lacustrine sedimentation is mainly controlled by tectonic action. Seismic onlap pinch out boundary is difficult to be used for confirming excursion of the base level. The sediment types and their superimposed features in log data can conversely verify the rangeability of relative accommodation space. In the light of thickness distribution of the sand shale sequence cycle, we can semiquantitatively analysis rangeability of the base level by selecting middle thickness or average thickness of the maximal bearing value area as statistics area, then accounting thickness of sand and shale of every area from bottom to top, and calculating percentage of the mudstone which endowed with different "base level variety numerical value". The method is suitable to make definite the changing features of accommodation space, to recognize transform surfaces and base level cycle, and to analysis the dominance for precipitation facies partition. It is applied in base level cycle division and comparison of offshore sedimentation sand or sand shale alternate layer to establish high resolution equitime framework.