基于测井曲线的小波变换定量层序地层单元划分

盆地中沉积地层具有明显的旋回性，对应不同的测井曲线特征，可以用它来进行层序地层划分。为降低在一个视觉层次上划分地层的人为主观性，使得层序地层单元的划分更加科学，将一维的测井曲线运用小波变换技术拓展为二维时频域，将不同时间( 深度) 尺度的沉积旋回清晰地展现出来。以梅河盆地钻井为例，选取a 值在0. 25 ～ 0. 5 amax区间利用小波时频能量图识别三—五级层序地层学单元特征明显。在小波时频能量图中，层序顶底高能量向中部减弱，进而划分出三级层序界面; 层序内部能量从向大尺度转移--向小尺度转移--趋于稳定--向大尺度转移，反映了体系域从低水位--水进－高水位--水退的垂向变化过程; 其内部每个小的能量团又可以看作是一个准层序。由此建立应用小波变换划分层序地层单元的模型，为层序地层学的定量划分提供了一种新手段。

Quantitative division of sequence stratigraphic units based on wavelet inversion of logging curve

The sedimentary strata are obvious in cyclicity in the basin，which can be used to distinguish the sequence stratigraphy，responsing to different characters of the logging date． In order to avoid the subjectivity of division of strata in a visual level，and make the division of sequence stratigraphic units more scientificly，we use the wavelet transform technique to expand 1-D level logging curves to 2-D time-frequency domain，which would show the sedimentary cycles clearly in different times or depth scales． Based on the logging date of the Meihe Basin，by taking the value rang 0. 25 to 0. 5 amax ，the third to fifth scale sequence sedimentary units have distinctive characteristics in wavelet time-frequency power imaging． In the wavelet power imaging，the high power site with the characteristics of power reduced upwardly and downwardly，which helps to define the third sequence boundary． In thethird sequence，from the bottom to the top，the features of power imaging is changed from large scale to small scale then to the stability and finally，to the reversal of large scale，and this four states correspond to the system tracts vertical evolution of LST，TST，HST and RST． The smaller power imaging could also be recognized as a parasequence． The model of sequence stratigraphic division based on the wavelet transform technique offers a new method for identifying sequence．