Formation pressure prediction and high pressure formation mechanisms of shale reservoirs in Fuling area, Sichuan Basin

Formation pressure is one of the important indicators to reflect shale gas preservation conditions, and is also an important factor affecting shale gas production. In the Fuling shale gas field, which has complex structure characteristics and variable formation pressure distribution, it is particularly important to accurately predict the formation pressure in shale gas exploration and development. The Eaton method was a preferred method for the prediction of formation pressure in the Fuling shale gas field based on the systematic analysis of the existing prediction methods. Combined with the geologic characteristics of Fuling area, the established method for normal compaction trend (NCT) lines was improved through vertical segmentation, plane partitioning and multi-well combination. It improved the accuracy of single well pressure prediction. The accuracy of 3D formation pressure prediction was improved by high-precision seismic layer velocity processing with generalized linear inversion. Based on the acoustic velocity-density intersection diagram and organic matter evolution characteristics and structural features, the paper explored the high pressure formation mechanisms of shale intervals in the Fuling area. It was concluded that the abnormal pressure in the Silurian shale formations in the Fuling area was the result of the combined effect of three mechanisms:undercompaction, hydrocarbon generation and tectonic compression.