Measuring method of gas core permeability

Abstract

The invention discloses a measurement method of rock core gas logging permeability. The method comprises the following steps of inputting values of rock core diameter and length into a computing chip; putting a rack core into a rubber sleeve, and applying confining pressure by a small-sized hand-cranking hydraulic pump; pushing a piston to a minimum calibration position of an inner cavity, and closing an emptying valve; setting the moving speed of the piston, starting a piston driving device, stopping working when the piston is moved to a maximum calibration position of the inner cavity, calculating the apparent permeability of rock core gas by the computing chip, and further calculating the rock core gas logging permeability to complete first-time measurement; opening the emptying valve, and then closing the emptying valve after the pressure of the inner cavity is balanced; repeating the previous steps, moving the piston to the minimum calibration position of the inner cavity, and carrying out measurement for the second time; and calculating the average value of the twice measured values by the computing chip to obtain the final rock core gas logging permeability. According to the measurement method, the rock core gas logging permeability can be measured for two times in the back and forth movement process of the piston, so that the measurement method is high in measurement efficiency and high in measurement speed, and has an important significance for rapid evaluation of rock samples collected in the field.

Description

technical field [0001] The invention belongs to the technical field of petroleum engineering and relates to a technique for measuring rock core permeability, in particular to a method for measuring rock core gas permeability. Background technique [0002] In the petroleum industry, permeability is an important parameter to characterize the ability of oil and gas to pass through reservoir rocks, and gas or liquid is usually used as the medium to measure the permeability of cores. In indoor experiments, the experimental medium of gas permeability measurement can be helium or nitrogen, and air can also be used to measure rock permeability when the experimental accuracy is not high; the experimental medium of liquid permeability measurement is generally water or crude oil. [0003] Normally, the test results of laboratory cores are relatively accurate, but the experimental equipment is huge and has high requirements on the environment, which is not easy to carry in the field. Po...

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Problems solved by technology

This method is relatively reliable and has many applications, but the operation is more complicated, the measurement time is long and the stability of the data is affected by many factors.

In the steady-state method, it is very difficult and not accurate enough to measure the fluid flow, especially the small flow of low-permeability rocks

[0005] Steady-state gas permeability measurement method is a common method for measuring rock core permeability at present, which mainly has the following disadvantages: the equipment is huge, not only needs to be equipped with nitrogen or helium gas source, but also requires a huge constant pressure chamber and constant pressure control device, which is inconvenient Field measurement; the pressure difference between the upstream and downstream constant pressure chambers cannot be strictly controlled, and a pressure feedback control device needs to be installed between the upstream and downstream to ensure that the pressure difference between the inlet and outlet of the core is constant, and it takes too long to achieve equilibrium; gas flowmeters generally use soap bubbles Flow meter or ball rise height measurement, due to the compressibility and viscosity of gas, the accuracy of the data measured by the above equipment is low

[0007] The unsteady-state method calculates the core permeability by measuring the change of pressure with time, which avoids the disadvantage of inaccurate gas flow measurement. However, due to the need for gas source, the equipment is relatively large, which is not suitable for field operations, and continuous measurement is required. It takes time to calculate the core permeability. If the gas flow is not stable, the measurement effect of the device is not good.

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