渤海海域古近系—新近系不整合剥蚀量恢复研究

Study on the Recovery of Erosion Quantity of Unconformities of Paleogene—Neogene in Bohai Sea Area

应用盆地波动过程分析方法,对渤海海域9个不同坳陷内的18口典型井古近系和新近系进行了沉积—剥蚀过程分析,分解出了760Ma、220Ma、70Ma和30Ma四个低频波动周期,以及18Ma、8Ma和2Ma三个高频波动周期。通过分析反映"组"、"段"级别的、以18Ma和8Ma为周期的波动曲线特征,预测了孔店期—沙河街期沉积—剥蚀过程;系统地计算出了古近纪—新近纪地层中主要不整合的剥蚀量,确定了与油气成藏密切相关的孔店组末期、东营组末期和馆陶组末期地层剥蚀厚度分别为:0～516m、0～213m和0～682m。通过波动曲线特征对比分析,确定了研究区构造转换带分别是孔店期位于渤中、沙河街期和东营期位于BZ13-1-2井区和LD10-1-1井区、馆陶期位于LD10-1-1井区、明化镇期位于BZ3-1-3D井区;定量地恢复了与油气运聚密切相关的孔店晚期、东营晚期和馆陶晚期不整合剥蚀量平面分布,再现了关键时期沉降沉积区和隆起剥蚀区区域分布规律。上述认识对于深入研究渤海海域古近系—新近系油气分布规律,开拓沙河街组及其以下层系油气勘探新领域具有重要意义。

By the application of wave process method, the process of sedimentary-erosion of the Paleogene and Neogene have been analyzed. On the 18 typical wells in 9 different depressions of the Bohai sea area, writers decomposed out 4 low frequency wave cycles and 3 high-frequency wave periods as follows： 760Ma, 220Ma, 70Ma, 30Ma and 18Ma, 8Ma, 2Ma. Based on the analysis of the wave characteristics cycled 18Ma and 8Ma which reflects the ＂Formation＂ and ＂Member＂ level, writers predicted the process of sedimentary-erosion of the time of Kongdian Formation--Shahejie Formation, calculated the erosion quantity of the main unconformities in the Paleogene-Neogene strata and identified the strata erosion quantity at the end of the Kongdian Fm. , Dongying Fro. and Guantao Fro. , i.e. , 0 -516m, 0 N213m and 0 -682m respectively; which were closely related to the oil and gas accumulation. By comparative studying the wave characteristics, the tectonic transition belt have been identified in the study area. The tectonic transition belt during the Kongdian stage was located in the center of Bohai sea area; those duringthe Shahejie and Dongying stage were located in the BZ13-1-2 and LD10-1-1well areas respectively. The tectonic transition belts during the Guantao stage and Minghuazhen stage were located in the LD10-1-1 well area and BZ3-1-3D Well area respectively. And the horizontal distribution of erosion quantities of the unconformities at the ends of the Kongdian, Dongying and Guantao stage, which were closely related to the hydrocarbon migration and accumulation, also have been quantitatively recovered; the distribution regularities of subsidence--sediment areas and uplift--denudation areas in the key stages are reproduced. The understanding mentioned above have important significances to the research on the Paleogene--Neogene oil and gas distribution regularity and to exploration oil and gas in the Shahejie Formation and underlying formations.