Abstract:

Lowabnormally low pressure in the sandstones and overpressure in the mudstones were developed in the Paleocene of the Southern Liaohe West Sag. The diagenesis were accelerated by the low pressure in the sandstones and retarded by the overpressure in the mudstones. A new numerical model was built, which could be used to simulate the diagenetic history and predict diagenetic stages and facies under abnormal pressure systems. The results show that the synrift stage is characterized by intensive fault activities, high heat flow and high diagenesis rate, contrasting to the weak tectonic activity, low heat flow and low diagenesis rate of postrift stage. The part of Shahejie Formation at the deep sag has entered the phase B of middle diagenetic stage to late diagenetic stage, forming tight reservoirs, while part of Shahejie Formation at the slope area is mainly at early diagenetic stage to phase A of middle diagenetic stage, forming conventional reservoirs.

Key words: tight sandstone, unconventional oil and gas, abnormally low pressure, overpressure, diagenetic history, Southern Liaohe West Sag