A device and method for measuring rock porosity under high hydrostatic pressure

Abstract

The application discloses a kind of measuring device and method of rock porosity under high hydrostatic pressure, it includes autoclave (5), rock sample (17) is fixed in autoclave (5), and the one end of autoclave (5) is connected with first valve (3) with plug (15);First valve (3) is connected with second valve (2);Second valve (2) connects manual liquid pressurizing pump (1);The other end plug (19) of autoclave (5) is connected with four-way valve (6);Four-way valve (6) one end connects vacuum pump (8), the other end connects second needle valve (9), and second needle valve (9) is connected with third three-way valve (11);Third three-way valve (11) is connected with third needle valve (12);Third needle valve (12) is connected with argon cylinder (14) by pressure reducing valve (13);Prior art does not have the device and method for measuring rock porosity under high hydrostatic pressure, using measurement under normal temperature and pressure environment cannot achieve the technical problems such as the like.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of rock porosity measurement, and particularly relates to a rock porosity measurement device and method under high hydrostatic pressure. BACKGROUND

[0002] Rock porosity is one of rock storage properties and is an important parameter for oil, gas and water storage calculation and evaluation. Rock porosity is usually measured under normal temperature and pressure in a laboratory or is obtained by reverse calculation through seismic wave logging, conductivity logging and empirical formula in the field. The reverse calculation through seismic wave logging, conductivity logging and empirical formula is an indirect measurement with large error and is rarely used. Rock porosity is usually measured under normal temperature and pressure in a laboratory. The measurement of rock porosity under high hydrostatic pressure can simulate the change of oil, gas and water storage in a formation and provide a more direct basis for actual resource exploitation. However, there is no device and method for measuring rock porosity under high hydrostatic pressure in the prior art, and the measurement under normal temperature and pressure cannot achieve this function. SUMMARY

[0003] The present application aims to solve the technical problem of providing a rock porosity measurement device and method under high hydrostatic pressure to solve the technical problem that there is no device and method for measuring rock porosity under high hydrostatic pressure in the prior art and the measurement under normal temperature and pressure cannot achieve this function.

[0004] The technical solution adopted by the present application is as follows:

[0005] A rock porosity measurement device under high hydrostatic pressure comprises a high-pressure kettle, a rock sample is fixed in the high-pressure kettle, one end of the high-pressure kettle is connected with a first valve through a kettle plug, the first valve is connected with a second valve, the second valve is connected with a manual liquid pressurizing pump, the other end of the high-pressure kettle is connected with a four-way valve through a kettle plug, one end of the four-way valve is connected with a vacuum pump, the other end of the four-way valve is connected with a second needle valve, the second needle valve is connected with a third three-way valve, the third three-way valve is connected with a third needle valve, and the third needle valve is connected with an argon cylinder through a pressure reducing valve.

[0006] The end of the kettle plug extending into the high-pressure kettle is connected with a fluororubber sleeve, and the rock sample is wrapped in the fluororubber sleeve; the fluororubber sleeve is fixed on the kettle plug through a metal ring.

[0007] The first valve is connected with a first three-way valve, one end of the first three-way valve is connected with the second valve, and the other end of the first three-way valve is connected with a first pressure gauge.

[0008] The vacuum pump is connected with the four-way valve through a first needle valve.

[0009] The third three-way valve is connected with a second pressure gauge.

[0010] The measurement method of the rock porosity measurement device under high hydrostatic pressure comprises the following steps:

[0011] Step 1, process a series of stainless steel cylindrical samples with the same outer diameter and height, containing different void volumes, and the porosities are 0, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, and 10%, respectively;

[0012] Step 2, wrap the stainless steel cylindrical sample with a fluororubber sleeve, fix it on the pot plug, and assemble the autoclave;

[0013] Step 3, pressurize the autoclave to 1 MPa by a manual liquid pressurizing pump as the confining pressure of the autoclave;

[0014] Step 4, close the second needle valve, and introduce 180 kPa ± 0.03 KPa argon into the standard chamber;

[0015] Step 5, vacuumize the sample chamber to make the pressure in the sample chamber less than 1 KPa;

[0016] Step 6, open the second needle valve to connect the standard chamber and the sample chamber, and record the reading of the second pressure gauge;

[0017] Step 7, replace the stainless steel cylindrical sample, repeat steps 2-6 to obtain a quadratic function curve fitted by different void volumes corresponding to different pressure drops, and obtain the fitting formula p = -2*10 -5 *V 2 +0.0343*V+69.55; p is the pressure drop; V is the void volume;

[0018] Step 8, measure the porosity of the rock sample: place the rock sample in the fluororubber sleeve, repeat the measurement steps of steps 2-6, record the pressure drop in the standard chamber, and substitute the recorded pressure drop into the fitting formula to obtain the void volume of the rock sample and the porosity.

[0019] The standard chamber refers to the space between the second needle valve and the second valve.

[0020] The sample chamber refers to the space between the first needle valve, the second needle valve, and the sample in the autoclave.

[0021] It also comprises: repeating steps 2-6 with copper cylindrical samples containing different void volumes, substituting the obtained gas pressure drop into the fitting formula to obtain a comparison between the measured void volume and the actual void volume of the sample to verify the accuracy of the fitting formula.

[0022] The calculation method of the porosity is to add different confining pressures to the autoclave, to obtain the void volume of the rock under different confining pressures, and then to obtain the porosity of the rock under different hydrostatic pressures.

[0023] The beneficial effects of the present application are as follows:

[0024] The present application first calibrates the system by a series of 304 stainless steel cylindrical samples with different void volumes under 1MPa hydrostatic pressure; that is, the pressure drop of 304 stainless steel cylindrical samples with different void volumes is different under the same initial gas pressure, and a formula is fitted according to the void volume and the dropped pressure; the reliability of the system is verified by comparing the void volume measured by the above method with the actual measured volume using red copper samples with different voids; when the actual rock sample is tested, the pressure drop of the actual rock sample is brought into the fitted formula to obtain the void volume of the rock. Finally, the void volume of the rock is divided by the total volume of the rock to obtain the void fraction of the rock sample under high hydrostatic pressure.

[0025] Compared with the prior art, the beneficial effects of the present application are as follows: a formula of void volume and pressure drop is fitted under 1MPa confining pressure, the total deformation of the rock under high hydrostatic pressure is ignored (the elastic modulus of the rock is much greater than the hydrostatic pressure), the pressure drop under high hydrostatic pressure is brought into the fitted formula to obtain the void fraction of the rock. The in-situ measurement of the void fraction under high hydrostatic pressure is realized.

[0026] The present application solves the technical problems that the prior art does not have a device and method for measuring the void fraction of rock under high hydrostatic pressure, and the measurement under normal temperature and pressure environment cannot achieve the same effect. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 The figure is a structural schematic diagram of the present application;

[0028] Figure 2 The figure is a structural schematic diagram of the fixation of the sample in the autoclave. DETAILED DESCRIPTION

[0029] A device for measuring the void fraction of rock under high hydrostatic pressure, which comprises an autoclave 5, a rock sample 17 fixed in the autoclave 5, an autoclave plug 15 at one end of the autoclave 5 connected with a first valve 3; the first valve 3 is connected with a second valve 2; the second valve 2 is connected with a manual liquid pressurizing pump 1; an autoclave plug 19 at the other end of the autoclave 5 is connected with a four-way valve 6; one end of the four-way valve 6 is connected with a vacuum pump 8, and the other end is connected with a second needle valve 9, which is connected with a third four-way valve 11; the third four-way valve 11 is connected with a third needle valve 12; the third needle valve 12 is connected with an argon cylinder 14 through a pressure reducing valve 13.

[0030] The autoclave plug 19 extends into the autoclave 5 and is connected with a fluororubber sleeve 16 fixed at one end, and the rock sample 17 is wrapped in the fluororubber sleeve 16; the fluororubber sleeve 16 is fixed on the autoclave plug 19 by a metal ring 18.

[0031] The fluorine rubber sleeve is used for wrapping the sample to avoid damage of the sample and ensure that the pressure is not lost and transmitted to the sample.

[0032] The first valve 3 is connected with a first three-way valve, one end of the first three-way valve is connected with the second valve 2, and the other end is connected with the first pressure gauge 4.

[0033] The vacuum pump 8 is connected with the four-way valve 6 through the first needle valve 7.

[0034] The third three-way valve 11 is connected with the second pressure gauge 10.

[0035] The measuring method of the rock porosity measuring device under high hydrostatic pressure comprises the following steps:

[0036] Step 1, a series of 304 stainless steel cylindrical samples with different void volumes and the same outer diameter and height are processed, and the porosities are 0, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9% and 10% respectively;

[0037] Step 2, the stainless steel cylindrical sample is wrapped with a fluorine rubber sleeve, fixed on a kettle plug and loaded into an autoclave.

[0038] Step 3, the autoclave is pressurized to 1 MPa by a manual liquid pressurizing pump, and the pressure is observed by the first pressure gauge to stop pressurizing and close the second valve 2 after the pressure reaches; the confining pressure of the autoclave is used as the hydrostatic pressure applied to the sample. The confining pressure of the present application is 1 MPa, which is much larger than 180 KPa, which helps to ensure that the rubber sleeve is tightly attached to the sample, and only when the confining pressure is greater than this value, the internal expansion of the rubber sleeve will not be caused.

[0039] Step 4, the second needle valve is closed, and 180 kPa±0.03 KPa of argon is introduced into the standard cavity; the initial pressure of the gas is 180 KPa, that is, 0.18 MPa, and the initial pressure is 180 KPa, and the change amplitude with time is the smallest after equilibrium, that is, the stability is good after equilibrium.

[0040] Step 5, the sample cavity is vacuumized to be less than 1 KPa; according to the theory, the smaller the better, but it takes a lot of time; the sample cavity is vacuumized to be less than 1 KPa in the present application, which can be basically realized in 75s, greatly saving time and meeting the effect.

[0041] Step 6, the second needle valve is opened to connect the standard cavity and the sample cavity, and the reading of the second pressure gauge is recorded; the pressure drop in the standard cavity is obtained by subtracting the reading of the second pressure gauge from the initial pressure.

[0042] Step 7, replace the stainless steel cylinder sample, repeat steps 2-6 to get different void volume of the sample corresponding to different pressure drop, the void volume of all samples and the corresponding pressure drop fitted out a quadratic function curve, get the fitting formula p = -2*10 -5 *V 2 +0.0343*V+69.55; p is the pressure drop; V is the void volume;

[0043] Step 8, measure the porosity of the rock sample: the rock sample is put into the fluorine rubber sleeve, repeat the measurement steps of steps 2-6, record the pressure drop in the standard cavity, the recorded pressure drop is substituted into the fitting formula, the void volume of the rock sample can be calculated, and the porosity is obtained.

[0044] The standard cavity refers to the void between the second needle valve and the second valve.

[0045] The sample cavity refers to the void between the first needle valve, the second needle valve and the sample in the autoclave.

[0046] It also includes: using copper cylinder samples with different void volumes, repeating steps 2-6, bringing the obtained gas pressure drop into the fitting formula, obtaining a comparison of the measured void volume and the actual void volume of the sample to verify the accuracy of the fitting formula.

[0047] Considering that the skeleton deformation of the rock under certain hydrostatic pressure is very small and can be ignored, that is, the total volume of the rock does not change; the measured value of the standard cavity after pressure drop is also applicable to the above formula when different confining pressures are added to the autoclave, the void volume of the rock under different confining pressures can be calculated, and the porosity of the rock under different hydrostatic pressures can be measured.

Claims

1. A method for measuring the porosity of rock under high hydrostatic pressure using a measuring device, the device comprising an autoclave (5), characterized in that: A rock sample (17) is fixed inside an autoclave (5). One end of the autoclave (5) is plugged (15) and connected to a first valve (3); the first valve (3) is connected to a second valve (2); the second valve (2) is connected to a manual liquid pressurization pump (1); the other end of the autoclave (5) is plugged (19) and connected to a four-way valve (6); one end of the four-way valve (6) is connected to a vacuum pump (8), and the other end is connected to a second needle valve (9); the second needle valve (9) is connected to a third three-way valve (11); the third three-way valve (11) is connected to a third needle valve (12); the third needle valve (12) is connected to an argon cylinder (14) via a pressure reducing valve (13); the measurement method includes: Step 1: Process a series of stainless steel cylindrical samples with the same outer diameter and height, containing different void volumes, with porosities of 0, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, and 10%, respectively. Step 2: Wrap the stainless steel cylindrical sample with a fluororubber sleeve, fix it on the stopper, and install the autoclave. Step 3: Pressurize the autoclave to 1 MPa using a manual liquid pressurization pump, which serves as the confining pressure for the autoclave. Step 4: Close the second needle valve (9) and introduce argon gas at 180 kPa ± 0.03 kPa into the standard chamber; Step 5: Evacuate the sample chamber to make the pressure in the sample chamber less than 1 kPa; Step 6: Open the second needle valve (9) to connect the standard chamber and the sample chamber, and record the reading of the second pressure gauge (10); Step 7: Replace the stainless steel cylindrical sample and repeat steps 2-6 to obtain a quadratic function curve for different pressure drops corresponding to different void volumes. The fitting formula is p = -2 * 10. -5 *V 2 +0.0343*V+69.55; p is the pressure drop; V is the void volume; Step 8: Measure the porosity of the rock sample: Place the rock sample inside the fluororubber sleeve, repeat the measurement steps 2-6, record the pressure drop in the standard cavity, substitute the recorded pressure drop into the fitting formula, and the porosity of the rock sample can be calculated.

2. The measurement method of the rock porosity measuring device under high hydrostatic pressure according to claim 1, characterized in that: The end of the stopper (19) that extends into the autoclave (5) is connected and fixed with a fluororubber sleeve (16), and the rock sample (17) is wrapped inside the fluororubber sleeve (16); the fluororubber sleeve (16) is fixed to the stopper (19) by a metal ring (18).

3. The measurement method of the device for measuring rock porosity under high hydrostatic pressure according to claim 1, characterized in that: The first valve (3) is connected to a first three-way valve. One end of the first three-way valve is connected to the second valve (2), and the other end is connected to the first pressure gauge (4).

4. The measurement method of the rock porosity measuring device under high hydrostatic pressure according to claim 1, characterized in that: The vacuum pump (8) is connected to the four-way valve (6) through the first needle valve (7).

5. The measurement method of the rock porosity measuring device under high hydrostatic pressure according to claim 1, characterized in that: The third three-way valve (11) is connected to the second pressure gauge (10).

6. The method for measuring rock porosity under high hydrostatic pressure according to claim 1, characterized in that: The standard cavity refers to the gap between the second needle valve (9) and the third needle valve (12).

7. The measurement method of the rock porosity measuring device under high hydrostatic pressure according to claim 1, characterized in that: The sample chamber refers to the gap between the first needle valve (7), the second needle valve (9), and the sample inside the autoclave.

8. The method for measuring rock porosity under high hydrostatic pressure according to claim 1, characterized in that: It also includes: using copper cylindrical samples with different void volumes, repeating steps 2-6, substituting the obtained gas pressure drop into the fitting formula, and comparing the measured void volume with the actual void volume of the sample to verify the accuracy of the fitting formula.

9. The method for measuring rock porosity under high hydrostatic pressure according to claim 1, characterized in that: The porosity is calculated by applying different confining pressures to the autoclave, determining the void volume of the rock under different confining pressures, and then obtaining the porosity of the rock under different hydrostatic pressures.

Images