Calculation of Formation Overpressure and Its Role in Hydrocarbon Accumulation

Based on the acoustic time difference data of more than 200 Wells, the equilibrium depth method is used to calculate the recovery of overpressure. According to the average excess pressure of a single well, the excess pressure plane and section maps of Chang 7-Chang 8 of Yanchang formation in Ordos Basin were drawn up. The results show that during the maximum burial period, high pressure anomalies start from the upper and lower strata of Chang 6 member of Yanchang formation, and the amplitude of abnormal pressure varies with different regions. The Tianchi-Baibao line in the northwest of the study area and the Qingcheng-Ningxian line in the west formed two high value areas, which spread from northwest to southeast, and the excess pressure difference (length 7-length 8) was mostly 10-20 Mpa. The area with large formation excess pressure difference is a potential favorable exploration area for Chang 8 reservoir. At present, large Chang 8 reservoirs are found in the southwest of the basin, and most of them are located in areas with high abnormal pressure. This method has strong theoretical value and practical guiding significance in basin oil and gas exploration, and is expected to be widely applied and promoted.