Method for measuring dynamic capillary pressure of core under conditions of reservoir temperature and pressure

Abstract

The invention discloses a method for measuring a dynamic capillary pressure of a core. The method comprises the following steps of: washing, drying and evacuating the core; saturating the core with a first fluid; putting the saturated core into a core clamp holder by using core displacement equipment; setting an experimental temperature; completely saturating dead volume parts of pipelines at an upstream end and a downstream end of the core with the first fluid; simultaneously setting a return pressure as a strata pressure; keeping a constant pressure and injecting the first fluid; after the upstream and downstream differential pressure of the core is stable, stopping injecting the first fluid; injecting a second fluid, wherein the second fluid is injected into a pipeline at the upstream end of the core under the same differential pressure as that of the first fluid; displacing the first fluid in a dead volume of the pipeline at the upstream end and making the first fluid enter the core; recording the change of the accumulated flow at the outlet end of the core along with time in the process of injecting the second fluid; and measuring the dynamic capillary pressure by calculating. The method of the invention has a simple process, is easy to operate, and is rapid and accurate.

Description

technical field [0001] The invention relates to a method for measuring rock core capillary pressure, in particular to a method for measuring rock core dynamic capillary pressure under the condition of oil reservoir temperature and pressure. Background technique [0002] Capillary pressure refers to the pressure difference between the non-wetting phase and the wetting phase on both sides of the curved liquid surface. It is the additional pressure to balance the pressure difference on both sides of the curved liquid surface, and its direction points to the concave direction of the curved surface. [0003] Studies by foreign scholars have shown that in porous media, the static capillary pressure is equal to the pressure difference between the non-wet phase and the wet phase only when the immiscible fluid interface is in a static state or equilibrium state ([1] Hassanizadeh S, Gray W. Thermodynamic basis of capillary pressure in porous media [J]. Water Resources Research, 1993, ...

AI Technical Summary

Problems solved by technology

[0008] The semi-permeable diaphragm method, mercury injection method, and centrifugation method have a big defect in the capillary pressure test: they cannot accurately reflect the capillary pressure generated by the oil-water interface in a moving state during the oil-water two-phase seepage process under actual formation conditions

The semi-permeable diaphragm method requires a long test time, the test pressure is low, and cannot simulate the pressure conditions of the formation; the mercury intrusion method cannot simulate the temperature and pressure conditions of the formation, and the rock sample cannot be reused because it has been polluted after the test. Mercury is poisonous, and once it leaks, it will endanger the health of operators. Therefore, it is necessary to be careful and take necessary protective measures when performing mercury injection experiments; the centrifugation method is cumbersome to calculate, and the equipment required is relatively complicated.

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