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随着油气勘探的不断深入,在渤海海域陡坡带古近系相继发现了一些大中型油气藏,但陡坡带的地层划分十分困难,其一是新老化石分子共存,一般认为出现新的化石组合意味着钻遇新的地层,但这种地层划分方法有时与周边地层矛盾,在地震上无法跟踪对比;二是边界断层下降盘巨砾岩年代归属问题,由于岩石碎屑粒径远远大于钻头直径,获取的岩屑见不到原始颗粒面,很难确定钻入的是否风化壳、基底本体。陡坡带地层分析技术是一门新兴的地层分析技术,包括3项技术即钻时岩屑复合技术、电测井岩屑复合技术和化石组合和保存状态复合技术,根据钻井取样中发现的化石保存状态及其组合关系、岩性和配置关系,结合钻时、岩屑录井及其测井响应,识别再沉积、巨砾岩、风化壳和底砾岩。解决地层归属问题有助于陡坡带构造演化和成藏研究,对现场施工也有重要意义,同时,也为凸起区地层缺失原因研究提供了新的思路和方法。
With the deepening of oil and gas exploration, some large and medium-sized reservoirs have been discovered successively in the Paleogene in the steep slope belt of the Bohai Sea. However, the stratigraphic division of the steep slope belt is very difficult. One is the coexistence of new and old fossil molecules and the new fossil assemblage Which means drilling new earth strata. However, this method of stratigraphic division sometimes contradicts the surrounding strata and can not be tracked and compared in earthquakes. Second, the problem of the ownership of the boulder rocks of the boundary fault drop plate is much larger than that of the drill bit The diameter of the obtained cuttings can not be seen on the original grain surface and it is difficult to determine whether the weathered shell or base body was drilled into. The steep slope stratigraphic analysis technology is a new stratigraphic analysis technology, which includes three technologies, namely, drilling chip composite technology, electrical logging composite technology and fossil combination and storage state composite technology. Based on the fossil preservation found in drilling sampling The state and its combination, lithology and configuration relationships, combined with drilling, cuttings logging and their log responses, identify redepositions, boulders, weathered crusts and base conglomerates. Solving the problem of formation attribution helps to study the tectonic evolution and accumulation of steep slope belt, which is of great significance to on-site construction. Meanwhile, it also provides new ideas and methods for the study of the causes of the lack of formation in the raised area.