Present‐day Geothermal Field and Thermal History of the Zhanhuadong Block, Jiyang Depression

Abstract

AbstractIn the Zhanhuadong block, Jiyang depression, present‐day geothermal field is analyzed based on available borehole temperature data and thermal history is reconstructed using tectonothermal modeling costrained by vitrinite reflectance (Ro) data. The results indicate that, (1) the average present geothermal gradient is 35.8°C/km, showing a decreasing trend with depth; higher geothermal gradients more than 37°C/km in Gudao and Kendong area are observed. (2) The thermal evolution shows a heat flow evolution associated with multi‐episodic rifting processes. Palaeo‐heat flow reached the maximum about 83.6mW/m2 in the early Paleocene corresponding to the major rifting stage, and then cooled down with pulsant variation corresponding to minor rifting to the present‐day regional average heat flow 63mW/m2. (3) Since the main oil bearing layers experienced a long‐term slowly heating process under a reasonable burial depth, they are still in the “oil‐generating window" with a wide depth range. The geothermal evolution in the Zhanhuadong block, Jiyang depression, is good for oil generation. The reconstructed thermal history results support the viewpoint that Bohai bay basin is a rift basin and is of practical significance to the oil exploration in the study area.