多资料约束下的塔里木盆地寒武系层序地层划分与对比

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

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。

Cambrian outcrops are rare in distribution in Tarim Basin and only a few drilled wells pen^rated through the wholeCambrian strata. These facts make difficulty for geologists to carry out the study of basin-scaled stratigraphic sequence. On the baseo f the data from outcrops at Xiaoerbulake, a detailed analysis o f stratiyaphic sequence framework was conducted according to thelithofacies characteristics and their stacking patterns. The Cambrian strata consists o f 8 n -order sequences and 18 I\^ - ordersequences. The lithologic sections o f wells obtained by geological logging are low in accuracy, which can't me^; the requirement ofsequence division. Based on the Fisher disaiminant analysis, wells were conducted on the lithology identification with core data andwell logging data. Depending on the Maximum Entropy Spectaim analysis o f the GR curves, changing trends of the shale contentin carbonate rocks within wells were analyzed. Seismic data were also used to identify the sequence boundary. The data from 10wells and 1 outcrop that are representative to the W -E and N -S profiles aaoss the basin were conducted on sequence divisionunder constraint of multiple data. Combined with wells and outcrop division, 2 sections of high-frequency sequence were correlated.It is concluded that, the depositing rate generally inaeased during Cambrian period, and depocenter migrated toward Tadong region.Different types of reservoirs occur in different sequence types. Sequence boundaries are favoirable for developing good reservoirs.