CN101587055A - Standard test piece based on calibration permeability test - Google Patents

Abstract

The invention discloses a standard test piece based on a calibration penetration experiment. The shape of the standard test piece is a solid cylinder, which is composed of a solid skeleton, pores and channels; the solid skeleton has a firm structure, stable material performance, and the material has high hardness and toughness. Good, corrosion-resistant, rust-resistant, heat-resistant, and pressure-resistant; the pore shape is spherical, the pore size is uniform, the pore size is controlled within the range of 1-50 μm, and the pores are evenly distributed inside and on the surface of the test piece; The average opening degree of the communicating channels on the end face is controlled within the range of 0.1% to 5%. After long-term penetration testing, the present invention has constant permeability parameters, high effectiveness, high reliability and strong practicability. Taking the permeability coefficient of the present invention as a reference benchmark, a detection means and tool as a benchmark are provided for the global penetration experiment technology. The standard test piece based on the calibrated permeation test is suitable for various permeation tests, especially for calibrating the accuracy and range of low permeation test methods and devices.

Description

Standard specimens based on calibrated penetration experiments

technical field

The invention relates to the technical field of porous medium standard test pieces, and more specifically relates to a standard test piece based on a calibration permeation experiment, which is suitable for calibrating the accuracy and range of a permeation experiment, especially for calibrating the accuracy and range of a low-permeability experiment.

Background technique

Permeability is an important property of porous media, and permeability coefficient is a parameter characterizing the permeability of porous media. For a long time, people have gradually recognized and used permeability coefficient parameters to evaluate the permeability of rock formations. Generally speaking, the fields of petroleum engineering and hydrogeology focus on aquifers and reservoir rock formations with high permeability; the fields of seismic and structural geology focus on non-sedimentary rock formations with low permeability; in recent years, more and more research fields Pay attention to rock formations with ultra-low permeability or even impermeable permeability. These rock formations are often in a state of high geostress and high pore pressure. etc.) reservoir evaluation and mining, waste (nuclear waste, greenhouse gas, garbage pollutants, etc.) geological storage formation evaluation and construction design research. It can be seen that efficient and accurate permeability coefficient measurement methods and devices can provide reliable basis and powerful means for the development of the above research fields and engineering projects. At present, most measurement methods of rock permeability coefficient can be divided into two categories according to the measurement method: one is direct measurement, such as rock sample permeability test, formation test, etc.; the other is indirect measurement, through measurement and rock permeability Related petrophysical property parameters, using the relationship between the two to determine the permeability coefficient. Relatively speaking, the accuracy of direct measurement is higher, so most researchers tend to use laboratory experiments to conduct permeability experiments on rock samples to obtain the permeability coefficient.

Since the advent of Darcy's law in the middle of the nineteenth century, people officially called the proportional constant "K" in Darcy's law the permeability coefficient in the twentieth century. In fact, it is more accurate to call the permeability coefficient according to Darcy's experiment, because the permeability coefficient is related to The parameters related to the geometric shape and structure of rock particles and the properties of the seepage medium. The permeability coefficient mentioned in this paper is the inherent property parameter of porous media, and the unit is Darcy D (D=μm ² ). There is an approximate conversion relationship, which is 1D=1×10 ^-3 cm/s=1×10 ^-5 m/s. Note that liquid water must be used as the seepage medium under normal conditions. Based on Darcy's law and Darcy's infiltration experiment method and device, later generations have developed indoor infiltration suitable for various research objects in order to study the material properties of research objects in various fields, or to provide key parameters for evaluating the development and construction design of various engineering projects. Measuring methods and measuring devices. So far, indoor infiltration experiments can be divided into two categories according to the measurement principle: one is the conventional infiltration experiment, including the constant water level method and the variable water level method, and the Darcy infiltration experiment belongs to the constant water level method; the other is the Low permeability experiments include four kinds of transient pressure pulse method (constant volume pulse method), constant flow pump method, pressure oscillation method and the recently proposed variable volume pressure pulse method. Conventional infiltration experiments mainly measure flow parameters in a steady flow state, while low-permeability experiments mainly measure pressure (water head) parameters in an unsteady flow state.

At present, there is no standard specimen with a known permeability coefficient at home and abroad, and the permeability coefficient is constant under various experimental conditions. It is difficult to clearly explain the accuracy and error of the above-mentioned various permeability coefficient measurement methods and measurement devices. , most researchers use the repeatability of measurement results to evaluate its objectivity. Since the measurement results of indoor and on-site permeability experiments are not strictly and uniformly defined, and there is no standard or standardized calibration statement for the global permeability measurement technology, the following problems arise: for the same rock sample, its permeability coefficient should be constant, However, if different penetration measurement methods or different measurement devices are used, the measurement results will be different, even by several orders of magnitude. Even if the same experimental method and device are used, there will be a problem of repeatability deviation of the measurement results. , there are two reasons for this problem: on the one hand, the permeability coefficient of the rock sample itself will change due to various reasons, such as the dissolution of the solid skeleton, the blockage of pores caused by microbial reproduction, the erosion of particles under pressure gradients or seepage, The rock samples themselves have problems of heat sensitivity and water sensitivity, etc., so the permeability coefficients of the rock samples themselves are not equal in different periods or under different external conditions, and even vary across orders of magnitude; The parameters (flow or pressure) monitored by the measuring device are different, or the performance of the device (leakage rate, measurement accuracy, etc.) is different, or the external conditions of the control (temperature, pore pressure, pressure gradient, etc.) are different. Different permeability coefficient values are measured for the same rock sample. So for different rock samples, under different external conditions, which measuring method or measuring device is more accurate, there is no strict reference standard at home and abroad, and most of them are judged based on common sense; The measurement method or measurement device is superior, and it is difficult to evaluate and check; if the measurement method and measurement device need to be improved, the degree of improvement cannot be accurately quantified. It can be seen that the standard specimen with known reference permeability parameters based on the calibration permeability experiment is indispensable for experimental research and device development. Using the permeability coefficient of the standard specimen as a reference standard, it is possible to clearly illustrate the permeability of various rock samples. Accurately calibrate the accuracy and range of the permeation experiment, which is helpful to the optimization of the experimental method and the improvement of the experimental device.

Contents of the invention

The purpose of the present invention is exactly in order to make up for the gap in the strict standardization and standardization requirements of the permeability coefficient measurement technology described above. The penetration parameters that can be used as benchmarks provide a means and basis for standardizing research in the field of scientific research and evaluating the development of engineering projects. The standard test pieces of the present invention have permeability parameters that can be used as benchmarks. With their permeability coefficients as reference standards, other materials can be accurately described, such as the permeability of rock formation samples and the law of permeability changes, and the permeability measurement method and device can also be clearly calibrated. The accuracy and range of the current penetration test can not be quantified and the accuracy can not be explained accurately, which can only be characterized by experience or repeatability. The invention is the most effective calibration tool for establishing technical norms or standards for measuring permeability coefficient, has originality, reliability, practicability and unity, and has wide application prospects.

In order to achieve the above object, the present invention adopts the following technical measures:

Aiming at the shortcoming that the permeability of the rock sample itself is sensitive to external conditions, the present invention successfully develops a standard test piece based on a calibration permeability experiment. After long-term penetration testing and testing under various penetration conditions, it has been confirmed that its permeability performance is constant. It is very effective and reliable as a reference basis for the permeability of other materials. It is also very effective as a means and tool for calibrating the accuracy and range of penetration experiments. Reliable and practical, so as to evaluate the quality of penetration tests and improve the performance of penetration tests.

The standard test piece is a porous medium standard test piece, which is composed of solid skeleton, pores and channels; its connection relationship is: the end face and the side face are vertically connected, and the end face and the side face are smooth surfaces; the pore size is too small and generally controlled at 1-50 μm within the range; the cut plane is connected with the cross section, the cut plane shows the longitudinal structure of the pore skeleton, and the cross section shows the transverse structure of the pore skeleton; the standard part is in the shape of a solid cylinder with a size of Φ50×100mm; the solid skeleton The structure is firm and integrated into a whole; the shape of the pores is spherical or spherical, the pore size is uniform, the pore size is controlled within the range of 1-50 μm, and the pores are evenly distributed inside and on the surface of the test piece; the pores and the solid skeleton form an intricate and organic structure. A certain regular channel network, in which the average through-hole degree of the through-hole channel on the section is controlled within the range of 0.1% to 5%; the overall shape of the test piece is a solid cylinder, the size is Φ50×100mm, and the dimensional accuracy is ±0.01 mm. The physical, mechanical and chemical properties of the solid skeleton of the standard test piece are stable. The material of the solid skeleton has high hardness, good toughness, corrosion resistance, rust resistance, heat resistance, and pressure resistance. Stainless steel alloys, titanium alloys, ceramics, etc. can be used.

After long-term penetration experiments and tests under various penetration conditions, the permeability of the standard test piece remains constant and is not affected by external conditions, effectively solving the problems caused by the defects of rock materials such as stress sensitivity, heat sensitivity, and water sensitivity. The problem of permeability coefficient changes. As a standard specimen for calibrating permeability experiments, it has known permeability parameters that can be used as benchmarks. Based on their permeability coefficients, it can accurately illustrate the permeability of other rock materials, and can accurately calibrate the accuracy range and effect of permeability experiments. Remarkable, functional excellence.

The working principle of the present invention:

The permeability coefficient of the standard specimen based on the calibration permeability experiment is a known constant, such as 5mD. Using this reference parameter, a certain permeability experiment (such as transient pressure pulse method and device) is performed on the standard specimen to measure the permeability coefficient. , the reference permeability coefficient of the standard specimen can be expressed by the true value K _t , the permeability coefficient measured by a certain permeability experiment is often different from the true value, and can be expressed by the measured value K _f , that is to say, the difference between the measured value and the true value If there are errors, analyze the error between them and combine the measurement time limit of the penetration experiment to effectively calibrate the accuracy and range of the penetration experiment.

The present invention has the following advantages and positive effects:

① The overall physical properties of the standard test piece are superior, with the characteristics of linearity, homogeneity and isotropy.

②The physical, mechanical and chemical properties of the solid skeleton of the standard test piece are stable, and the material has high hardness, good toughness, corrosion resistance, rust resistance, heat resistance, and pressure resistance, so it avoids stress sensitivity, heat sensitivity, and water sensitivity that will occur in rock samples. question.

③ The standard test piece is a porous medium standard test piece, which is composed of solid skeleton, pores and channels, which is consistent with the structure of rock samples, and its permeability parameters are very reliable as a reference.

④ The shape of the standard test piece is a solid cylinder with a size of Φ50×100mm, which meets the rock sample size standard required by the experimental specification and is suitable for most penetration test devices.

⑤ The solid skeleton structure of the standard test piece is firm, fused with each other into a whole, and does not react with the seepage medium, so problems such as particle erosion and dissolution under long-term experimental operation of rock samples are avoided.

⑥The standard specimen has known permeability parameters that can be used as benchmarks, such as 5mD. Under long-term permeability experiments, or under various permeability conditions, such as high temperature, high pore pressure, high pressure gradient, etc., the permeability parameters Constant and unaffected by external conditions, it is very reliable as a penetration reference.

In a word, the present invention overcomes the shortcomings and deficiencies that the accuracy of the existing permeation experiments cannot be clearly stated and the measuring range of the measuring device cannot be accurately calibrated, and solves the problem of validity and reliability of the measurement results. The present invention provides a standard specimen of porous media, using its known constant and accurate permeability parameters to calibrate the accuracy and range of the permeability experiment, thereby indirectly obtaining the true value permeability coefficient of the rock sample to be tested, and finally realizing Research on the standardization and standardization of permeability coefficient measurement technology, rather than relying on rough evaluation and judgment based on experience. The invention is mainly used in the field of indoor permeation experiments, and is helpful for optimizing measurement methods, improving measurement devices, clarifying measurement results, and evaluating experimental principles.

Description of drawings

Fig. 1 is a schematic diagram of a standard specimen based on a calibration penetration experiment;

Fig. 2 is a kind of schematic diagram of the cross-sectional structure of the standard specimen based on the calibration penetration experiment;

Fig. 3 is a schematic diagram of a cross-sectional structure of a standard specimen based on a calibration penetration experiment.

in:

1 - end face;

2 - side;

3——section plane,

3.1—solid skeleton, 3.2—pore, 3.3—channel, 3.4—through channel;

4—cross section,

4.1 - Solid skeleton, 4.2 - Porosity.

Detailed ways

Below in conjunction with accompanying drawing and implementation example the present invention is further described:

1. Description of the structure of the standard test piece

1. The shape, size and surface texture of the standard test piece

As shown in Figure 1: the end face 1 is connected vertically to the side face 2, the end face 1 (including the upper end face and the lower end face) and the side face 2 are smooth and clean, and only the whole material of the test piece, that is, the solid skeleton material, is not seen. texture. In fact, the end face 1 is also composed of solid skeleton 3.1, 4.1 and pores 3.2, 4.2. Since the surface of the standard test piece is polished, and the size of pores 3.2, 4.2 is too small, generally controlled within the range of 1-50 μm, so the naked eye Invisible, only visible under magnification or in a microscopic state.

The surface finish of the standard test piece is required, because the standard test piece is placed in a flexible pressure chamber during use, and the outer surface of the test piece is wrapped with a flexible rubber sleeve. The rough surface will cause the deformation error of the rubber sleeve.

2. The internal pore skeleton structure of the standard test piece

As shown in Fig. 2 and Fig. 3: the cut plane 3 is connected with the cross section 4, the cut plane 3 shows the longitudinal structure of the pore skeleton, and the cross section 4 shows the transverse structure of the pore skeleton. The white area in the figure represents the solid skeleton 3.1 and 4.1, because the solid skeleton 3.1 and 4.1 are fused together, the skeleton structure 3.1 and 4.1 are firm and stable, and constitute the skeleton system of the standard test piece; the black dots and lines in the figure represent the pores 3.2 and 4.2 , channels 3.3, pores 3.2 and 4.2 are very evenly distributed on the longitudinal and transverse planes of the test piece, and many pores are connected to each other to form channel 3.2, so the channels 3.2 are also evenly distributed inside the test piece, and many channels 3.2 are intricate Intersection forms the channel 3.2 network; only interconnected channels, such as the ones that run through the upper and lower ends as shown in Figure 2, and are connected by many channels, are the through-hole channels 3.4.

As a standard specimen based on calibration permeability experiments, its permeability parameters mainly depend on the number and size of through-hole channels. The number of through-hole channels is characterized by the average through-hole degree of through-hole channels on the cross-section. Controlled within the range of 0.1% to 5%, the size of the through-hole channel is related to the size of the aperture and the length of the test piece. That is to say, the smaller the pore size, the fewer pores, the thinner the pore network, the smaller the through-pore, the lower the permeability, the higher the density, and the greater the strength; the larger the pore size, the more channels, the greater the through-pore, The greater the permeability, the lower the density and the lower the strength.

2. How to use

1. Place the 5μD standard specimen in the core holder or pressure chamber of the permeability measurement device (such as the transient pressure pulse measurement device), and use the corresponding permeability test method (such as the transient pressure pulse method) to conduct the measurement experiment , analyze the measurement data to obtain the measured permeability coefficient value of the standard specimen, which is denoted as K _f1 .

2. Place the 50μD standard test piece in the core holder or pressure chamber of the permeability measurement device, use the corresponding permeability test method to carry out the measurement experiment, analyze the measurement data to obtain the measured permeability coefficient value of the standard test piece, record is K _f2 .

3. Place the 0.5mD standard test piece in the core holder or pressure chamber of the permeability measurement device, use the corresponding permeability test method to carry out the measurement experiment, analyze the measurement data to obtain the measured permeability coefficient value of the standard test piece, Denote it as K _f3 .

4. Place the 5mD standard test piece in the core holder or pressure chamber of the permeability measurement device, use the corresponding permeability test method to carry out the measurement experiment, analyze the measurement data to obtain the measured permeability coefficient value of the standard test piece, record is K _f4 .

5. Place the 50mD standard test piece in the core holder or pressure chamber of the permeability measurement device, use the corresponding permeability test method to carry out the measurement experiment, analyze the measurement data to obtain the measured permeability coefficient value of the standard test piece, record is K _f5 .

6. Place the 0.5D standard test piece in the core holder or pressure chamber of the permeability measurement device, use the corresponding permeability test method to carry out the measurement experiment, analyze the measurement data to obtain the measured permeability coefficient value of the standard test piece, Denote as K _f6 .

7. Draw the error curves E ₁ -K _t and E ₂ -K _t between the measured value K _f of the above-mentioned standard test piece and its corresponding true value K _t on the logarithmic coordinates, where E ₁ =K _f /K _t , E ₂ =(K _f −K _t )/K _t .

8. Considering the limitation of the measurement time of the permeation experiment, and controlling the error accuracy according to the error curve, the accuracy of the permeation experiment method and the range of the measuring device can be effectively calibrated.

9. If the conditions of use do not allow it, you can also select appropriate 2 or more operations from the above 1-6 operation steps.

Claims (3)

1. A standard test piece based on a calibration penetration test, consisting of a solid skeleton (3.1, 4.1), pores (3.2, 4.2) and channels (3.3); it is characterized in that: the end surface (1) is vertically connected to the side surface (2) , the end surface (1) and the side surface (2) are smooth surfaces, the size of the pores (3.2, 4.2) is controlled at 1-50 μm, the section plane (3) is connected with the cross section (4), and the section surface (3) is the structure of the pore skeleton Longitudinal structure, cross-section (4) is the transverse structure of the pore skeleton, the standard part is in the shape of a solid cylinder, and the size is Φ50×100mm. 2. A standard test piece based on a calibration penetration experiment according to claim 1, characterized in that: the shape of the pores (3.2, 4.2) is spherical or spherical, the pore size is uniform, and the pore size is controlled within 1-2. 50 μm, the pores (3.2, 4.2) are evenly distributed inside and on the surface of the specimen. 3. A standard test piece based on a calibration penetration experiment according to claim 1, characterized in that: the pores (3.3) and the solid skeleton (3.1, 4.1) form a regular network of pores, and the through-hole channels (3.4) are in the cross section The average through-hole degree on the surface is controlled at 0.1% to 5%.

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