Dating method for fault zone fluid activity history under low-temperature background condition

Abstract

The invention relates to a dating method for fluid curtain type fluid activity history. The dating method comprises the following steps: 100. measuring temperature in a current fault zone; 200. selecting apatite mineral from the fault zone based on the measured temperature; 300. performing (U-Th)/He chronological testing on the selected apatite; 400. analyzing a thermal history superposing process in the fault zone based on the test result; and 500. analyzing fluid activity stage and age based on the analysis result. Compared with the prior art, the dating method has the advantages that the accuracy and the resolution are high, the method is not limited to the authigenic mineral formed by fluid activity, the problem of non-uniform capture of the fluid is solved, the object for fluid research is expanded, multiple temperature limitations can be provided for the fluid activity history, and the distinguishing of the fluid activities at different curtains and different stages is made possible objectively.

Description

technical field [0001] The patent of the present invention relates to a dating method for the episodic fluid activity history of fluid in fault zones, in particular, to a dating method for the episodic fluid activity history of fluid along fault zones under low temperature background conditions (0-30°C). Background technique [0002] There are two flow modes of subsurface fluid, steady state and unsteady state. Take the article "New Development of Petroleum Non-Darcy Seepage" published in "Petroleum Drilling and Production Technology" Volume 25, Issue 5, Page 40-42 in 2003 Model" as an example, it is considered that steady flow refers to a continuous seepage process, and the parameters of the fluid do not change with time, so the migration of fluid can be described by Darcy's law. Corresponding to it is unsteady-state fluid activity, which refers to the flow process in which underground fluid suddenly starts to flow rapidly and ends in a short period of time. Various paramet...

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Problems solved by technology

Wan Junwei and others emphasized the method of using trace elements or rare gas isotopes in fluids for dating in "The Theory and Practice of Isotope Hydrology" published by China University of Geosciences Press. The precondition is that "Fluid is in a closed system", and the frequent fluid mixing of overpressure fluid breaks the relatively closed environment in different fluid dynamic systems, leading to the failure of the isotope dating method using trace components and rare gases in the fluid

[0014] In summary, existing techniques cannot be applied to accurate dating of episodic fluid activity histories in fault zones

The reason is that the episodic fluid activity in the fault zone has a large flow rate and a very short duration during the active period; the fluid in the fault zone generally exhibits multi-stage and multi-episode activities, and the multi-stage and multi-episode fluid activities will lead to the formation of authigenic minerals. Multi-period or inherited development, the age of authigenic minerals reflects the comprehensive age of multi-episode fluid activities, but cannot distinguish the age of each episode of fluid activity; when the fluid in the fault zone enters the overlying formation, it is usually accompanied by Abnormal high temperature and high pressure will produce strong boiling effect after entering the overlying relatively low-temperature and low-pressure formation, resulting in the formation of fluid inclusions (boiling inclusions) captured by authigenic minerals that cannot represent the actual temperature and pressure conditions for fluid formation; fracture The frequent fluid mixing of fluids in the belt breaks the relatively closed environment in different hydrodynamic systems, leading to the failure of the isotopic dating method using trace components and noble gases in the fluids

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