Method for obtaining undercompaction overpressure in stratum

Abstract

The invention discloses a method for obtaining the undercompaction overpressure in a stratum. The method comprises the steps that 1, firstly, according to the difference change characteristics of theaverage interval transit time, the average stratum density and the average neutron porosity of a mudstone section along with the average buried depth, the normal compaction section and the undercompaction section are determined; 2, then the index relation of the acoustic wave velocity and the vertical effective stress is fitted by utilizing a scatter diagram of the acoustic wave velocity and the vertical effective stress of the normal compaction section; 3, due to the fact that change of the vertical effective stress and the acoustic wave velocity of the undercompaction section needs to fall on a change trend curve of the acoustic wave velocity and the vertical effective stress of the normal compaction section, the acoustic wave velocity of the undercompaction section is substituted into the index relation obtained in the step 2, and the vertical effective stress of the undercompaction section is obtained; and 4, finally, the overpressure value in the undercompaction section is obtained by combining the relation of the vertical effective stress of the undercompaction section and the overpressure. The magnitude of the undercompaction overpressure can be accurately obtained only through logging data, the characteristics of rapidity, simpleness, convenience and accuracy are achieved, and the evaluation efficiency on the undercompaction overpressure is improved.

Description

technical field [0001] The invention relates to the field of petroleum and natural gas exploration and development, in particular to a method for obtaining overpressure due to undercompaction in formations. Background technique [0002] When the formation pressure exceeds the hydrostatic pressure of the formation, the formation is overpressured. Overpressure is common in petroleum basins, and there are many overpressure formation mechanisms, among which undercompaction is the most common formation mechanism for formation overpressure. At present, the quantitative evaluation of undercompaction and overpressure in the formation mainly uses the equilibrium depth method and the numerical simulation method. The accuracy of the numerical simulation method has a great relationship with the selected simulation parameters, and the accurate acquisition of the simulation parameters It is relatively difficult; the equilibrium depth method is more common to calculate undercompaction and...

AI Technical Summary

Problems solved by technology

At present, the quantitative evaluation of undercompaction and overpressure in the formation mainly uses the equilibrium depth method and the numerical simulation method. The accuracy of the numerical simulation method has a great relationship with the selected simulation parameters, and the accurate acquisition of the simulation parameters It is relatively difficult; the equilibrium depth method is more common to calculate undercompaction and overpressure, but the solution process of this method is relatively complicated, and there is a lack of multi-method verification of the solution results

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