Estimation of the amount of erosion at unconformities in the last stage of the Eocene Sanduo period in the Subei Basin, China |
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Authors: | Chen Liqiong |
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Affiliation: | Jiangsu Oilficld Company, SINOPEC, Jiangsu 225009, China |
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Abstract: | Strata erosion is a widespread phenomenon in sedimentary basins. The generation, migration, and accumulation of hydrocarbon
is influenced by the scale of erosion, so estimating the amount of erosion is essential in the analysis of oil and gas bearing
basins. According to the geological features in the Subei Basin and the actual data, using the integrated method, we estimated
the level of erosion at the unconformities caused by the Sanduo event. By using the mudstone interval transit time method
and the vitrinite reflectance method on data from typical wells, it can be concluded that the Gaoyou, Jinhu, and Hongze depressions
suffered strong strata erosion from the late Eocene to Oligocene, and the total strata erosion thickness was 300–1,100 m.
Different tectonic units in the same depression have extremely uneven erosion intensity: the low convex regions have the maximum
erosion thickness, amounting to 800–1,100 m; the slope regions have an erosion thickness of generally 600–800 m; the erosion
thickness of the slope-hollow transition zone is 300–500 m. For the whole basin, we used the strata thickness trend analysis
method combined with the interval transit time and vitrinite reflectance methods to estimate the erosion thickness in the
Sanduo period. The results show that the most severe erosion of the Sanduo event in the Subei Basin is between 1,000 m to
1,200 m, mainly located in depressions around the Jianhu Uplift; the deep hollow area has the least erosion, generally about
300–600 m, and the erosion in the slope area is about 600–900 m. Compared with the northern part, the southern part has relatively
little erosion. It is also proved that the Sanduo movement has heterogeneous intensity, and the western region has greater
intensity than the eastern region. |
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Keywords: | Unconformity estimation of erosion mudstonc interval transit time method vitrinitereflectance method Subci Basin |
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