A new method for provenance analysis in sedimentary basins based on logging data

Provenance analysis is a critical connection between the sedimentary basin and the orogenic belt. Methods such as petrological analysis of clastic rocks, heavy mineral analysis, geochemical analysis, and isotopic dating methods are all based on core analysis. However, core analysis is expensive and limited in quantity.

Well logging data are easy to obtain and can reflect much information. Moreover, the logging data has longitudinal continuity, which can record the formation properties continuously. A new quantitative method for provenance analysis based on well logging data is proposed. The new method mainly relies on the assumption that terrigenous clastic rocks are the products of weathering, fragmentation, transport, and deposition of the original rocks in the provenance area, and the composition and combination of clastic minerals in the rocks can reflect the characteristics of the source area. Then, different clastic minerals have different physical properties, and logging responses, so clastic rocks from different provenances may have different logging responses. The difference in logging response can be used to analyze the source-sink system.

A case study is introduced. Jiyang Depression of the Bohai Bay Basin is a faulted lake basin in the Paleogene. The northern part of Dongying sag is the Chenjiazhuang uplift, and the western part is the Binxian uplift, both parts are important provenance areas. Sedimentary systems such as near-shore subaqueous fan and fan delta are widely developed in the steep slope zone of the faulted lacustrine basin. The logging and drilling lithology analysis shows that well A has a 50m conglomerate layer in Shahejie Formation. The logging data show that the logging response of the top 30m conglomerate layer is different from that of the bottom 20m conglomerate layer. The core analysis shows that the top conglomerate is dominated by granitic gneiss rock, while the bottom conglomerate is dominated by carbonate rock. two provenance systems are developed in Dongying Sag.

This method can achieve good results on coarse-grained sediments, but this method may be restricted to deposits mainly composed of fine sandstone, silty, and shale. In the future, multiple methods should be combined to improve the result of provenance analysis.