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从1977年开始,地质部第四海洋地质调查大队在南海北部的珠江口盆地先后打了七口深井,大都钻迂基底(花岗岩或变质岩),初步建立了地层层序,证实了下第三系的存在,见到了多层含油砂岩;并在珠五井获得了优质工业性油气流。 该盆地上第三系共分四组,自上而下为万山组、粤海组、韩江组和珠江组,化石以有孔虫为主,其次有介形类和孢粉等。下第三系目前暂划分为两个组:珠海组和宝安组,仅见孢粉化石。 对于珠江口盆地是否存在下第三系过去是有争论的。通过珠七井的钻探,进一步证实了下第三系的存在。在珠七井的下部,见到了一套岩性较特殊、孢粉化石数量丰富、种类繁多且时代编老的地层,这套地层已揭示的厚度有336米,我们命名为宝安组。 宝安组可分两段: 上段:厚211.5米。上下为浅灰、灰白色细砂岩,间夹页岩,白云质砂岩及砂砾岩,中部为钙质砂岩及页岩互层,底部为10米厚的褐灰色钙质砂岩。
Since 1977, the Fourth Marine Geological Survey of the Ministry of Geology has successively hit seven deep wells in the Pearl River Mouth Basin in the northern part of the South China Sea, most of them drilling the basement (granite or metamorphic rocks) and initially established stratigraphic sequences, confirming the third The existence of the system, saw the multi-layer oil-bearing sandstone; and in the Pearl Well received high-quality industrial oil and gas flow. The Tertiary in the basin is divided into four groups, with Wanshan Formation, Yuehai Formation, Hanjiang Formation and Zhujiang Formation from top to bottom. The fossils are dominated by foraminifera, followed by ostracods and sporopollen. The Tertiary is currently divided into two groups: Zhuhai Formation and Baoan Formation, only sporopollen fossils. It is debatable whether there is any Tertiary past in the Pearl River Mouth Basin. Drilling through the Chu Bei well further confirmed the existence of the next Tertiary. In the lower part of the Pearl 7 wells, we saw a set of special lithology, sporo-pollen fossils of a large number, a large variety of epoch-making strata, this formation has revealed the thickness of 336 meters, we named Baoan group. Baoan group can be divided into two sections: the upper section: 211.5 meters thick. Upper and lower as light gray, gray fine sandstone, inter-folder shale, dolomitic sandstone and glutenite, the middle of calcareous sandstone and shale interbed, the bottom is 10 meters thick brown-gray calcareous sandstone.