Low-permeability rock particle penetration rate measuring system and measuring method

Abstract

The invention discloses a low-permeability rock particle penetration rate measuring system and measuring method. The penetration rate measuring system comprises a high-pressure air source device, a reference cavity, a sample cavity, an inlet pressure intensity detecting device, an automatic valve, a ball valve, a pressure difference detecting device and a control device, wherein the automatic valve and the ball valve are sequentially arranged on a pipeline communicating the reference cavity and the sample cavity; the pressure difference detecting device and the automatic valve are connected in parallel; the control device is respectively connected with the automatic valve and the pressure difference detecting device; an output pipeline of the high-pressure air source device communicates with the reference cavity or the sample cavity; the inlet pressure intensity detecting device is arranged on the output pipeline of the high-pressure air source device; an air exhaust opening is formed in a pipeline of the inlet pressure intensity detecting device and the high-pressure air source device. The high-pressure air source device is connected with the reference cavity or the sample cavity; the change of the pressure intensity inside the reference cavity and the sample cavity can be controlled; the pressure intensity difference is detected through the pressure difference detecting device, so that the control device can accurately obtain a pressure intensity change curve and the particle penetration rate of rock to be measured.

Description

technical field [0001] The invention relates to the technical field of rock permeability measurement, in particular to a permeability measurement system and method for low-permeability rock particles. Background technique [0002] With the continuous advancement of science and technology, unconventional natural gas resources represented by tight gas, coalbed methane and shale gas have gradually become the key objects of exploration and development in countries all over the world. The main feature of this type of natural gas reservoir is that the reservoir has extremely low permeability, usually below 1mD. Among them, coalbed methane and shale gas have the characteristics of self-generation and self-storage. The space for the storage and migration of natural gas in the reservoir matrix is ​​micro- and nano-scale cracks and pores. The porosity is less than 10%, and the matrix permeability is as low as 1nD ~ 1μD , belonging to ultra-low permeability porous media. Permeability...

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Problems solved by technology

The disadvantages of this experimental system are: 1. Since the cylindrical shale samples are naturally coupled with natural fractures and matrix pores, the permeability of natural fractures is high, and the matrix permeability cannot be decoupled; 2. Confining pressure assistance must be introduced into the experimental system system, which increases the complexity of the system, and the design and processing requirements of the core holder are relatively high

However, there are serious common problems in the system design, which make the measurement results less reliable: (1) In order to reproduce the pressure conditions of rock reservoirs, the gas in the experiment is under high pressure, so the range of the selected ambient pressure sensor is usually 10MPa Above, while the lower limit of precision of common high-pressure pressure sensors on the market is 0.08%, which means that the confidence resolution of the sensor is about 8kPa

On the other hand, due to the low porosity of the rock, the absolute volume of the pores is small, if the ratio of the gas environment volume in the system to the sample pore volume cannot be well controlled, the total amount of gas environment pressure attenuation may be in the range of the confidence resolution. of the same magnitude, which gives less confidence in the pressure decay curve

(2) If the smaller environment / pore volume ratio is excessively pursued, the specific heat capacity of the system will be lower, the influence of ambient temperature fluctuations will increase, and the pressure decay process of the system will be greatly disturbed by temperature fluctuations, which will also make the pressure decay curve Confidence decreases for

[0005] To sum up, the experimental system based on the principle of pressure decay of rock particle samples and the high-pressure pressure sensor as the core measurement equipment has essential defects in the experimental accuracy, which makes the permeability measurement value of low-permeability rock samples less reliable. Low

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