Quantitative simulation method for contributions of three origins of overpressure in sandstone

A quantitative simulation method for contributions of three origin of overpressure in sandstone, comprising:

• collecting analytical testing data, well logging data, geological data, and seismic data of sandstone of a target horizon, wherein the analytical testing data comprises conventional core analysis, cast thin section, and scanning electron microscope image data, and organic geochemical data;
• and the geological data comprises well drilling stratification data, formation pressure data, formation temperature data, vitrinite reflectance data, and formation age data;
• establishing a formation pressure profile according to the formation pressure data, analyzing a formation pressure characteristic of the sandstone of the target horizon in a target region, and establishing a numerical model of pressure simulation, wherein the numerical model of pressure simulation is established based on an actual formation characteristic and actual geological data of the target horizon and relates to a burial history, a thermal history, and a pressure history;
• burial history reconstruction:
• establishing a one-dimensional burial history of the sandstone of the target horizon based on geological stratification, the formation age data, and a period and a thickness of denudation;
• thermal history reconstruction:
• implanting the formation temperature data and geothermal gradient data of the sandstone of the target horizon into the numerical model of pressure simulation to reconstruct the thermal history of the sandstone of the target horizon;
• and when a simulated formation temperature value is consistent with a measured formation temperature value, indicating that the reconstructed thermal history is accurate;
• quantitatively simulating an undercompacted pore pressure evolution history;
• quantitatively simulating an undercompacted and hydrocarbon generation pressurized pore pressure evolution history;
• quantitatively simulating a total pore pressure evolution history;
• quantitative analysis of contributions of three origin of overpressure:
• when the total pore pressure evolution history is greater than the undercompacted and hydrocarbon generation pressurized pore pressure evolution history, the overpressure in the sandstone of the target horizon being contributed by undercompaction, pressurization by hydrocarbon generation, and a third origin, and quantitatively analyzing contributions of the undercompaction, the pressurization by hydrocarbon generation, and the third origin to total overpressure;
• and when the total pore pressure evolution history is equal to the undercompacted and hydrocarbon generation pressurized pore pressure evolution history, the overpressure in the sandstone of the target horizon being contributed by two origins, namely undercompaction and pressurization by hydrocarbon generation, and quantitatively analyzing contributions of the undercompaction and the pressurization by hydrocarbon generation to total overpressure;
• and
• determining an exploration region of an oil and gas reservoir according to the origins of overpressure, which specifically comprises:
• when the undercompaction is a dominant origin of overpressure, representing that an overpressured reservoir has an obvious water-bearing characteristic;
• and
• when the undercompaction and the pressurization by hydrocarbon generation are dominant origins of overpressure, representing that the overpressured reservoir has an obvious gas-bearing characteristic, wherein natural gas exploration in the reservoir is concentrated in a moderately overpressured region and a region having a high gas saturation and having a fault, a crack, and matrix pores;
• and reserves of natural gas are low in regions having lowest overpressure and highest overpressure.