多资料约束下的塔里木盆地寒武系层序地层划分与对比

塔里木盆地寒武系露头分布局限、钻井数量少,给开展盆地尺度的层序地层学研究带来困难。以肖尔布拉克露头为基础,根据岩相发育特征及叠置样式完成了寒武系层序地层格架的建立。寒武系共发育8个Ⅲ级层序,18个Ⅳ级层序。井下录井岩性剖面精度低,难以满足层序划分的要求,基于Fisher判别分析,综合利用岩心及测井资料完成岩性识别;利用GR曲线的最大熵谱分析完成对泥质含量变化趋势的识别;利用地震资料上可识别的削截特征进行层序界面的识别。在多资料的综合约束下完成了井下层序划分。利用贯穿盆地东西向和南北向两条剖面上具代表性的10口钻井和1个露头剖面的资料,完成了台—盆尺度的高频层序对比,分析了等时格架下的地层沉积样式与岩相变化特征。认为总体上寒武纪地层由早至晚沉积速率逐渐增大,沉积中心向盆地方向迁移。层序类型不同,储层发育特征亦不同,层序界面处常发育优质储层。

Division and Correlation of Cambrian Stratigraphic Sequences under Multiple Data Constraint,Tarim Basin

Cambrian outcrops are rare in distribution in Tarim Basin and only a few dril ed wel s penetrated through the whole Cambrian strata. These facts make difficulty for geologists to carry out the study of basin-scaled stratigraphic sequence. On the base of the data from outcrops at Xiaoerbulake, a detailed analysis of stratigraphic sequence framework was conducted according to the lithofacies characteristics and their stacking patterns. The Cambrian strata consists of 8 Ⅲ-order sequences and 18 Ⅳ-order sequences. The lithologic sections of wel s obtained by geological logging are low in accuracy, which can't meet the requirement of sequence division. Based on the Fisher discriminant analysis, wel s were conducted on the lithology identification with core data and wel logging data. Depending on the Maximum Entropy Spectrum analysis of the GR curves, changing trends of the shale content in carbonate rocks within wel s were analyzed. Seismic data were also used to identify the sequence boundary. The data from 10 wel s and 1 outcrop that are representative to the W-E and N-S profiles across the basin were conducted on sequence division under constraint of multiple data. Combined with wel s and outcrop division, 2 sections of high-frequency sequence were correlated. It is concluded that, the depositing rate general y increased during Cambrian period, and depocenter migrated toward Tadong region. Different types of reservoirs occur in different sequence types. Sequence boundaries are favourable for developing good reservoirs.