A inversion method based on wave impedance and geochemistry and its application in the inversion of organic rich rocks

Yaoting Li ¹ Shijia Chen ^1* Lin Chen ² Li Jiang ² Xiangdong Yin ¹

• ¹ Southwest Petroleum University, Chengdu, China
• ² CNOOC, Zhanjiang, China

Wave impedances, once heralded as a breakthrough in exploration applications, have remained a focal point in seismic inversion studies. The integration of geophysical and geochemical methodologies in exploration has emerged as an increasingly significant challenge. This research endeavors to amalgamate organic geochemical analysis of rocks with seismic inversion techniques. A comprehensive dataset comprising 48 rock samples from 10 wells, alongside three-dimensional seismic data, was employed to evaluate organic-rich rocks within the Pearl River Mouth Basin. Three distinct geochemical characteristics of organic-rich rocks were identified within the basin, revealing rocks with fair to excellent source potential and advanced thermal maturity. Furthermore, significant heterogeneity was observed in the organic-rich rocks across different sedimentary facies. An inversion model for organic-rich rock thickness and total organic carbon (TOC) content was developed. Initially, the wave impedance of the basin was constructed using seismic wavelets and reflection coefficients, subjected to stringent wavelet quality control and logging calibration. Subsequently, the organic-rich rock model was established by segmenting the study area into multiple regions based on sedimentary facies. By examining the relationship between TOC and wave impedance within individual wells, a TOC estimation model for various sags was formulated. The development of this model introduces an innovative approach for integrating the geochemical characteristics of organic-rich rocks with geophysical methodologies, thereby presenting new opportunities for geological exploration in basins.