Prediction of Paleogene reservoirs based on structural evolution analysis: taking Shahejie Formation in the middle part of Liaoxi Uplift as example

Two problems are encountered in the middle part of Liaoxi Uplift, with regard to the reservoir prediction for Shahejie Formation: the lack of large-scale traps and the rapid lateral variation in reservoirs, which have made reservoir prediction difficult and limited the progress of rolling exploration. In order to solve these problems, we turned the way of research to carry out the Paleogene reservoir prediction upon structural evolution. Using the methods of fission track structure inversion and space balance profiling, detailed study of structural evolution was conducted. This approach abandoned the traditional stratigraphic deposition model, and proposed a new way of thinking for the Shahejie Formation. It is assumed that the Shahejie Formation might occur as well in the high part of Liaoxi uplift. Based on the new understanding, new exploration strata and favorable targets in Shahejie Formation are re-selected. Combined with the pre-stack synchronous inversion technology under structural constraints, the development area of the dominant reservoirs in Shahejie Formation was accurately predicted, and the well position deployment and drilling were effectively performed. The exploration practice in recent years has proved the effectiveness of the new understanding. Two new gas oil-bearing structures of ten million cubic meters of reserves have been discovered in the study area, which strongly supported the increase in oil and gas reserve and production of the Bohai Oilfield, and also provided a reference for the study of Paleogene reservoirs in similar areas.