CN106501151A - A kind of shale aperture measurement device and method based on imbibition and ion diffusion property - Google Patents

Abstract

The invention discloses a shale aperture measuring device and method based on imbibition and ion diffusion characteristics, comprising: high-precision analytical balance (1), support (2), flask (3), fishing line (4), magnetic stirring device (5), lifting system (6), conductivity meter (7), constant temperature and humidity box (8). The present invention makes full use of the unique high capillary force imbibition and strong ion diffusion characteristics of shale through experimental measurement, designs a high-precision shale imbibition and ion diffusion synchronous detection device, and proposes an average pore diameter suitable for shale The evaluation method further improves the scientificity and accuracy of shale pore diameter measurement; the invention has the characteristics of simple operation, little environmental impact, low test cost, and reliable results.

Description

A shale pore size measurement device and method based on imbibition and ion diffusion characteristics

technical field

The invention belongs to the technical field of shale gas development, in particular to a shale pore size measurement device and method based on imbibition and ion diffusion characteristics.

Background technique

Southern my country's marine shale gas resources are abundant. As an important alternative energy source, its commercial exploitation is of great significance to ensure my country's energy security, reduce domestic energy costs and environmental pressure. Shale gas is a typical marginal oil and gas resource, which is specifically manifested in the extremely low porosity and permeability of the reservoir, the pore roar is at the micro-nano level, and the pore structure is complex. As an important parameter to evaluate the physical characteristics of shale, pore size is often difficult to measure accurately. At present, the pore size of shale is mainly determined by means of mercury injection, gas adsorption, and nuclear magnetic resonance. However, the pore sizes obtained by several testing methods are often quite different, and the testing cost is high.

Contents of the invention

The purpose of the present invention is to provide a shale pore diameter measurement device and method based on imbibition and ion diffusion characteristics, further improve the measurement accuracy of shale pore diameter, reduce measurement cost, and provide a scientific basis for the determination of shale physical characteristic parameters.

The technical solution of the present invention is: a shale pore size measurement device based on imbibition and ion diffusion characteristics, which includes: high-precision analytical balance, support, flask, fishing line, magnetic stirrer, lifting system, conductivity meter, constant temperature Humidity chamber;

The high-precision analytical balance is placed above the support for measuring the mass change of the shale sample before and after water absorption;

The bracket is placed in the constant temperature and humidity box for carrying the high-precision analytical balance; a small hole is provided in the middle of the bracket for vertically hanging the shale sample suspended on the high-precision analytical balance. Hanging to the inside of the bracket;

The flask is placed on the upper surface of the magnetic stirrer to hold distilled water, and the shale samples that hang down on the high-precision analytical balance can enter and exit from the mouth of the flask when they rise or fall;

The fishing line is used to hang the shale sample on the high-precision balance;

The magnetic stirrer is placed on the upper surface of the lifting system for stirring the distilled water in the flask;

The lifting system is used to lift the flask to realize shale sample immersion or leave the distilled water in the flask;

The conductivity meter hangs down in the distilled water in the flask to measure the ion concentration of the distilled water in the flask;

The constant temperature and humidity box is used to keep the high-precision analytical balance, the support, the flask, the fishing line, the magnetic stirrer, the lifting system, and the conductivity meter in a constant temperature and humidity environment .

Furthermore, the precision of the high precision analytical balance is 0.0001g.

Furthermore, the flask is a 250ml flask.

Furthermore, the fishing line is No. 0.6 fishing line.

Furthermore, the accuracy of the conductivity meter is 0.1 μS/cm.

A shale pore size measurement method based on imbibition and ion diffusion characteristics, comprising the following steps:

A. Extract a cylindrical shale sample, calculate the cross-sectional area A _c , seal the cylindrical surface of the cylindrical shale sample with epoxy resin, and place it in a drying oven to dry until the quality of the cylindrical shale sample does not change;

B. Place the high-precision analytical balance on the support, hang the dried cylindrical shale sample on the high-precision analytical balance with a fishing line, and record the reading M0 of the high-precision analytical balance;

C. Place the lifting system under the support, place the flask on the magnetic stirrer, and place the magnetic stirrer on the lifting system;

D. Add volume V distilled water into the flask, and measure the conductivity G0 in the water;

E. Turn on the magnetic stirrer to raise the lifting system, so that the cylindrical shale sample is immersed in distilled water for 20 seconds;

F. Lower the lifting system so that the cylindrical shale sample is completely exposed to the water surface, record the balance reading M1, and measure the conductivity G1 in the water;

According to the gas-water two-phase seepage theory, calculate the relationship between the water absorption per unit area V _imb and the solution conductivity G caused by ion diffusion during the imbibition process; the physical parameters involved are x, k _w , P _c , S _wf , S _wi , μ _w , B, C, n do not need to be measured, B and C are obtained by analyzing the test curve in the later stage, and other parameters are eliminated by means of mathematical transformation in the later stage;

According to the Handy imbibition model, the position x of the water phase imbibition front changes with the imbibition time t as follows:

where k _w is the water permeability mD, P _c is the capillary force Pa, is the porosity, S _wf is the water saturation of the front, and S _wi is the initial water saturation;

Because the cylindrical shale samples are dense, the water saturation at the front is relatively high, and the cylindrical shale samples have been dried, so the difference between them is about 1;

During the imbibition process of a cylindrical shale sample, the volume of absorbed water per unit area changes with time as follows:

In the formula: B is the retention of water per unit area g/cm ² , μ _w is the viscosity of water

Then the change in conductivity of the solution caused by ion diffusion is:

In the formula: C is the ion attachment amount per unit area mg/cm ² , n is the capillary number;

G. Make the lifting system rise again, so that the cylindrical shale sample is completely immersed in distilled water for 20 seconds;

H. repeat step F and step G, obtain the change of M～M0 and G～G0 with time t, can obtain the change of water absorption volume V _imb and solution conductivity G with time t;

I. Draw the water absorption volume per unit surface area and the change curve of conductivity with t ^0.5 , and calculate the slope of the curve, the imbibition rate A and the ion diffusion rate D respectively, calculate the obtained A and D and obtain the A/D ratio ratio;

According to the water absorption per unit area V _imb and the theoretical formula of the solution conductivity G changing with time caused by ion diffusion during the imbibition process, the ratio of the imbibition rate A to the ion diffusion D is calculated, and the process is as follows:

The ratio of the imbibition rate to the ion diffusion rate is:

J. The intercept between the extension line of the conductivity curve and the vertical axis is C/V, and the average pore diameter r of the shale is obtained.

By means of experimental measurement, the present invention makes full use of the unique high capillary force imbibition and strong ion diffusion characteristics of shale, designs a high-precision shale imbibition and ion diffusion synchronous detection device, and proposes an average The pore size evaluation method can be used as an effective supplement to conventional pore size testing methods. The invention is simple in operation, less affected by the environment, low in test cost and reliable in results, and also provides a brand-new idea for the analysis of the physical characteristics of shale.

Description of drawings

Fig. 1 is a schematic diagram of the device of the present invention;

Fig. 2 is a flow chart of the method of the present invention.

1--high-precision analytical balance, 2--stand, 3-- sesame cake, 4--fishing line, 5--magnetic stirrer, 6--lifting system, 7--conductivity meter, 8--constant temperature and humidity box

detailed description

Embodiment 1: Referring to Fig. 1, a kind of shale aperture measurement device based on imbibition and ion diffusion characteristics is characterized in that it comprises: high-precision analytical balance 1, support 2, flask 3, fishing line 4, magnetic force stirrer 5. Lifting system 6. Conductivity meter 7. Constant temperature and humidity box 8;

The high-precision analytical balance 1 is placed above the support 2 for measuring the mass change of the shale sample before and after water absorption; the precision of the high-precision analytical balance 1 is 0.0001g;

The support 2 is placed in the constant temperature and humidity box 8 for carrying the high-precision analytical balance 1; the middle of the support 2 is provided with a small hole for hanging the high-precision analytical balance 1 The shale sample is vertically suspended inside the support 2;

The flask 3 is placed on the upper surface of the magnetic stirrer 5 for containing distilled water, and the shale sample hanging down on the high-precision analytical balance 1 can enter and exit from the mouth of the flask 3 when it rises or falls; Said flask 3 is a 250ml flask;

The fishing line 4 is used to drop the shale sample on the high-precision balance 1; the fishing line 4 is No. 0.6 fishing line

The magnetic stirrer 5 is placed on the upper surface of the lifting system 6 for stirring the distilled water in the flask 3;

The lifting system 6 is used to lift the flask 3 to realize shale sample immersion or leave the distilled water in the flask 3;

The conductivity meter 7 hangs down in the distilled water in the flask 3 to measure the ion concentration of the distilled water in the flask 3; the conductivity meter 7 has an accuracy of 0.1 μS/cm;

The constant temperature and humidity box 8 is used to make the high-precision analytical balance 1, the support 2, the flask 3, the fishing line 4, the magnetic stirrer 5, the lifting system 6, the conductance The rate meter 7 is in a constant temperature and humidity environment.

Embodiment 2: Referring to Fig. 2, a method for measuring shale pore size based on imbibition and ion diffusion characteristics comprises the following steps:

A. Extract a cylindrical shale sample, calculate the cross-sectional area A _c , seal the cylindrical surface of the cylindrical shale sample with epoxy resin, and place it in a drying oven to dry until the quality of the cylindrical shale sample does not change;

B. Place the high-precision analytical balance on the support, hang the dried cylindrical shale sample on the high-precision analytical balance with a fishing line, and record the reading M0 of the high-precision analytical balance;

C. Place the lifting system under the support, place the flask on the magnetic stirrer, and place the magnetic stirrer on the lifting system;

D. Add volume V distilled water into the flask, and measure the conductivity G0 in the water;

E. Turn on the magnetic stirrer to raise the lifting system, so that the cylindrical shale sample is immersed in distilled water for 20 seconds;

F. Lower the lifting system so that the cylindrical shale sample is completely exposed to the water surface, record the balance reading M1, and measure the conductivity G1 in the water;

According to the gas-water two-phase seepage theory, calculate the relationship between the water absorption per unit area V _imb and the solution conductivity G caused by ion diffusion during the imbibition process; the physical parameters involved are x, k _w , P _c , S _wf , S _wi , μ _w , B, C, n do not need to be measured, B and C are obtained by analyzing the test curve in the later stage, and other parameters are eliminated by means of mathematical transformation in the later stage;

According to the Handy imbibition model, the position x of the water phase imbibition front changes with the imbibition time t as follows:

where k _w is the water permeability mD, P _c is the capillary force Pa, is the porosity, S _wf is the water saturation of the front, and S _wi is the initial water saturation;

Because the cylindrical shale samples are dense, the water saturation at the front is relatively high, and the cylindrical shale samples have been dried, so the difference between them is about 1;

During the imbibition process of a cylindrical shale sample, the volume of absorbed water per unit area changes with time as follows:

In the formula: B is the retention of water per unit area g/cm ² , μ _w is the viscosity of water

Then the change in conductivity of the solution caused by ion diffusion is:

In the formula: C is the ion attachment amount per unit area mg/cm ² , n is the capillary number;

G. Make the lifting system rise again, so that the cylindrical shale sample is completely immersed in distilled water for 20 seconds;

H. repeat step F and step G, obtain the change of M～M0 and G～G0 with time t, can obtain the change of water absorption volume V _imb and solution conductivity G with time t;

I. Draw the water absorption volume per unit surface area and the change curve of conductivity with t ^0.5 , and calculate the slope of the curve, the imbibition rate A and the ion diffusion rate D respectively, calculate the obtained A and D and obtain the A/D ratio ratio;

According to the water absorption per unit area V _imb and the theoretical formula of the solution conductivity G changing with time caused by ion diffusion during the imbibition process, the ratio of the imbibition rate A to the ion diffusion D is calculated, and the process is as follows:

The ratio of the imbibition rate to the ion diffusion rate is:

J. The intercept between the extension line of the conductivity curve and the vertical axis is C/V, and the average pore diameter r of the shale is obtained.

Claims (6)

1. a kind of shale aperture measurement device based on imbibition and ion diffusion property, it is characterised in that it includes：High accuracy point Analysis balance (1), support (2), flask (3), fishing line (4), magnetic stirring apparatus (5), jacking system (6), conductivity meter (7), constant temperature Constant humidity cabinet (8)；

High accuracy analysis balance (1) is placed in above the support (2), is become for measuring the quality before and after shale samples absorb water Change；

Support (2) are placed in the climatic chamber (8), for carrying high accuracy analysis balance (1)；The support (2) aperture is provided with the middle of, for the shale samples being suspended on high accuracy analysis balance (1) are suspended vertically described Frame (2) is internal；

Flask (3) are placed in the magnetic stirring apparatus (5) upper surface, for containing distilled water, hang down in the high accuracy point Shale samples in analysis balance (1) can come in and go out from the flask (3) oral area when rising or falling；

Described fishing line (4) are used for hanging down in the high accuracy balance (1) shale samples；

Magnetic stirring apparatus (5) are placed in the jacking system (6) upper surface, for stirring the distilled water in the flask (3)；

Described jacking system (6) are used for lifting the flask (3), realize shale samples submergence or leave in the flask (3) Distilled water；

Conductivity meter (7) hang down in the interior distilled water of the flask (3), for determining the interior distilled water of the flask (3) Ion concentration；

Described climatic chamber (8) are used for making high accuracy analysis balance (1), the support (2), the flask (3), described Fishing line (4), the magnetic stirring apparatus (5), the jacking system (6), the conductivity meter (7) are in constant-temperature constant-humidity environment.

2. a kind of shale aperture measurement device based on imbibition and ion diffusion property as claimed in claim 1, its feature exist In：The precision of high accuracy analysis balance (1) is 0.0001g.

3. a kind of shale aperture measurement device based on imbibition and ion diffusion property as claimed in claim 1, its feature exist In：Described flask (3) are 250ml flasks.

4. a kind of shale aperture measurement device based on imbibition and ion diffusion property as claimed in claim 1, its feature exist In：Described fishing line (4) are No. 0.6 fishing line.

5. a kind of shale aperture measurement device based on imbibition and ion diffusion property as claimed in claim 1, its feature exist In：Conductivity meter (7) precision is 0.1 μ S/cm.

6. a kind of shale bore diameter measuring method based on imbibition and ion diffusion property, it is characterised in that comprise the following steps：

A. cylindrical shale samples are extracted, sectional area A is calculated_c, with epoxy resin by cylindrical shale samples cylinder sealing, it is placed in Dry in drying baker, until cylindrical shale samples quality no longer changes；

B. high accuracy analysis day is flat on support, using fishing line by drying after cylindrical shale samples hang on high accuracy On assay balance, high accuracy analysis balance reading M0 is recorded；

C. jacking system is placed in below support, flask is placed on magnetic stirring apparatus, and magnetic stirring apparatus is placed on jacking system；

D. volume is added into flask for the distilled water of V, and determines electrical conductivity G0 in water；

E. magnetic stirring apparatus is opened, jacking system is increased, cylindrical shale samples is immersed in 20 seconds in distilled water；

F. decline jacking system so that cylindrical shale samples are completely exposed the water surface, recording balance reading M1, and determine in water Electrical conductivity G1；

Theoretical, unit of account area water absorption V according to air water two phase fluid flow_imbThe solution caused with the diffusion of imbibition process intermediate ion Electrical conductivity G relation over time；The physical parameter x being directed to, k_w, P_c,S_wf,S_wi, μ_w, B, C, n need not be carried out Determine, B and C is obtained by the test curve in analysis later stage, and other parameters disappear this by the means of the mathematic(al) manipulation in later stage The impact of a little parameters；

According to Handy imbibitions models, the position x of water phase imbibition leading edge with the variation relation of imbibition time t is：

$x=\sqrt{\frac{2k_w{p}_{c}t}{{\mathrm{\φ\μ}}_{{}_w}(S_{wf}-S_{wi})}}$

K in formula_wFor water penetration rate mD；P_cFor capillary force Pa,For porosity, S_wfFor leading edge water saturation, S_wiFor initially containing Water saturation；

As cylindrical shale samples are fine and close, therefore leading edge water saturation is higher, and cylindrical shale samples have passed through drying Process, then difference between the two is approximately equal to 1；

During cylindrical shale samples imbibition, the volume change over time of unit area suction water is turned to：

$V_{imb}/A_c=B+\sqrt{\frac{2k_w{p}_c\mathrm{\φ}(S_{wf}-S_{wi})t}{{\mathrm{\μ}}_w}}$

In formula：Hold-ups g/cm of the B for unit area water², μ_wViscosity for water

The electrical conductivity of solution change that then ion diffusion causes is turned to：

$G/A_c=2\frac{C}{V}+\frac{4\mathrm{\π}rnC}{V}\sqrt{\frac{2k_w{p}_c}{{\mathrm{\φ\μ}}_{{}_w}(S_{wf}-S_{wi})}}\·\sqrt{t}$

In formula：C is unit area ion adhesion amount mg/cm², n is capillary number；

G. jacking system is made to increase again so that cylindrical shale samples are totally submerged 20 seconds in distilled water；

H. repeat step F and step G, obtain the change of M～M0 and G～G0 t over time, you can obtain water suction volume V_imbWith The change of electrical conductivity of solution G t over time；

I. the water suction volume of drafting per surface area, electrical conductivity are with t^0.5Change curve, ask for the slope of curve, imbibition respectively Speed A and ion diffusion rates D, the A and D of acquisition are calculated and can be obtained the ratio of A/D；

According to unit area water absorption V_imbThe electrical conductivity of solution G caused with the diffusion of imbibition process intermediate ion changes over time Theoretical formula, calculates the ratio that imbibition speed A and ion spread D, and process is as follows：

$V_{imb}/A_c=B+A\sqrt{t}$

$G/A_c=2\frac{C}{V}+D\sqrt{t}$

Imbibition speed with the ratio of ion diffusion rates is：

$\frac{A}{D}=\frac{Vr(S_{wf}-S_{wi})}{4C}=\frac{Vr}{4C}$

J. conductance profile extended line is C/V with the intercept of the longitudinal axis, obtains average pore size r of shale.

$r=4\·\frac{A}{D}\·\frac{C}{V}$