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为进一步推动山东昌潍北部地区的新生代油气勘探,应用潍北、牛头镇和侯镇等3个凹陷9个层段的天文地层年龄分析,计算出新生代不整合时间和剥蚀量。天文地层学计算方法主要包括:地层分层,测井频谱分析,寻找40万年周期和旋回的对比。得到结果:孔三段-孔二段界线的年龄为61.819Ma,孔二段-孔一段界线的年龄为54.638Ma,孔一段-沙四下亚段界线的年龄为48.448Ma,沙四下-沙四上亚段界线的年龄为43.516Ma,沙四上亚段顶的年龄为40.362Ma,馆陶组-明化镇组界线的年龄大约为35.778—31.896Ma。通过剥蚀的时间和沉积环境的分析提出如下观点:1)大约在48.448Ma以前,昌潍坳陷北部的沉积是全盆地的、稳定的,其中包括:约长达4Myr期间孔三段断断续续出现玄武岩喷发,大约7Myr时间内孔二段出现沼泽和浅湖相的沉积,约6Myr时间内孔一段主要为干旱相的小水塘、水坑“红色”沉积;2)从沙河街组开始(48.448Ma)至东营组末(23.03Ma)期间,也即大约25Myr期间,潍北的昌参1、昌1等井的中心部位,仍然是不断下陷、沉积;3)馆陶组沉积期间(大约23.03—13Ma)盆地全区上升。因此在大约10Myr的剥蚀时间过程中,不仅没有沉积,而把原沉积的沙三亚段至东营组不断‘反剥’到沙四段下部;4)馆陶组末(大约13Ma)到明化镇组顶(2.588Ma)沉积期间,全区开始以河流泛滥平原相为主的泥岩和泥质粉细砂岩的沉积,形成盖层。根据天文地层方法的剥蚀量计算,潍北凹陷中有3个“反剥高点”。这些“反剥高点”在始新世末至渐新世的沉积和构造上升和剥蚀过程中,可能造成砂岩回弹和孔隙扩张,形成好的储集区。根据计算,最大的“反剥高点”是在昌36—央5—昌8井一带,剥蚀厚度约达1800—3000m,与多年油田勘探取得成果是一致的。
In order to further promote the Cenozoic oil and gas exploration in northern Changwei, Shandong, the age of unconformity and denudation of Cenozoic are calculated by using the astronomical formation ages of 9 sections of three depressions in Weibei, Niutou and Houzhen. Astronomical stratigraphy calculation methods include: stratigraphic stratification, log spectrum analysis, looking for 40 million years cycle and cycle comparison. The results show that the age of Kong3-Kong2 Member boundary is 61.819Ma, the age of Kong2-Kong1 boundary is 54.638Ma, the age of Kong1-Sha4 lower boundary is 48.448Ma, The upper limit of the Upper Es4 line is 43.516Ma. The top of the Upper Es4 line is 40.362Ma. The age of the Guantao-Minghua Line boundary is about 35.778-31.896Ma. According to the time of denudation and the analysis of sedimentary environment, the following opinions are put forward: 1) Before about 48.448Ma, the sediments in the northern part of Changwei Depression are all stable in the whole basin. Including: about 4Myr, basalt Eruption, the deposition of marsh and shallow lacustrine facies occurred in the second member of the pore in about 7Myr time, a small reservoir of water mainly in the arid phase and puddles of “red” sediment in about 6Myr time; 2) 48.448Ma) to the end of Dongying Formation (23.03Ma), that is, about 25Myr, the central part of Changshen 1 and Chang 1 wells in Weifu is still undergoing subsidence and sedimentation; 3) during the deposition of Guantao Formation 23.03-13Ma) The whole area of the basin has risen. Therefore, during the erosion time of about 10Myr, not only no sedimentation, but the original deposition of the Sansha Segment to Dongying group constantly ’stripping’ to the lower part of Sha 4; 4) the end of Guantao group (about 13Ma) to Minghua Town During the deposition at the top of the group (2.588Ma), the whole area was started with the deposition of mudstone and muddy fine sandstone dominated by river flood plains, forming the caprock. According to the calculation of the denudation of the astronomical formation method, there are 3 “anti-stripping highs” in the Weibei Depression. These “anti-stripping point” during the Eocene to Oligocene deposition and tectonic uplift and erosion process may cause sandstone rebound and pore expansion, the formation of a good reservoir area. According to the calculation, the largest “anti-stripping point” is in the Chang 36-Central 5- Chang 8 well area, the erosion thickness of about 1800-3000m, with many years of oil exploration results are consistent.