Device and method for testing low-permeability core starting pressure gradient at high temperature and high pressure with unsteady state method

Abstract

The invention discloses a device and a method for testing a low-permeability core starting pressure gradient at the high temperature and the high pressure with an unsteady state method. The method comprises steps as follows: a to-be-tested low-permeability core sample is prepared and placed in a core holder; an automatic water pump is used for providing required confining pressure and return pressure for the core holder; a third valve is closed, and a gas pressurization device is used for pressurizing a standard bottle; after a second pressure sensor stably reads, the third valve is opened, and gas in the standard bottle permeates an inlet of the core holder; a controller records a pressure value, changing over time, read by the second pressure sensor and stops recording until the change rate of a reading number of the second pressure sensor is lower than a threshold value; and the core starting pressure gradient is calculated according to the reading number, changing over time, of the second pressure sensor. According to the device and the method, all that is required is to add a high-precision pressure sensor at an outlet of the standard bottle for recording pressure of the outlet, the high-precision pressure sensor has characteristics of low cost, high test precision, large range and the like, and the measurement problem of low flow speed is solved.

Description

technical field [0001] The invention relates to the technical field of laboratory testing of rock core parameters in the field of basic research on oil and gas field development, in particular to a device and method for testing low-permeability rock core start-up pressure gradients at unsteady high temperature and high pressure. Background technique [0002] At present, most of the laboratory testing techniques for the starting pressure gradient of domestic test cores still use the steady-state method for testing. The steady-state method uses a stable displacement pressure to drive gas or liquid into the porous medium. The velocity at the outlet of the medium is the measured fluid velocity as the stable displacement velocity corresponding to the displacement pressure difference of the porous medium at a certain laboratory temperature and confining pressure. The corresponding displacement velocity is obtained by setting multiple sets of displacement pressures, and finally the...

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Problems solved by technology

[0016] To sum up, the Forchheimer equation of gas seepage cannot effectively reflect the phenomenon of low-velocity non-Darcy seepage and the existence of the real threshold pressure gradient

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