CN102735592B - Apparatus for measuring diffusion coefficient of carbon dioxide in rock - Google Patents

Abstract

The invention relates to an apparatus used for measuring the diffusion coefficient of carbon dioxide in rock. The apparatus comprises an apparatus housing. A gas tank, a diffusion cylinder and a fluid tank are arranged vertically in parallel in the apparatus housing. A gas pipeline and a liquid pipeline are arranged outside the apparatus housing. The inlet of the gas pipeline is connected to a carbon dioxide cylinder through a booster pump. A four-way valve is arranged in series on the gas pipeline. The gas outlets of the four-way valve are respectively connected to the four-way valve, the gas tank, and a pressure sensor. The inlet of the liquid pipeline is connected with a sample tank. A four-way valve is arranged in series on the liquid pipeline. The liquid outlets of the four-way valve are respectively connected to the four-way valve, the fluid tank, and a pressure sensor. According to the invention, a gas chamber is eliminated fundamentally, and the influence caused by sampling upon the gas pressure is eliminated. Vacuum pumping, saturated formation fluid and the determination of gas diffusion coefficient are integrated. Therefore, the influences on the saturated fluid in rock during the vacuum pumping process are completely eliminated.

Description

A kind of carbon dioxide of measuring is at the device of diffusion coefficient of rock

Technical field

The present invention relates to a kind of carbon dioxide of measuring at the device of diffusion coefficient of rock, belong to the technical field of petrochemical complex.

Background technology

Carbon dioxide is as main greenhouse gases, and its reduction of discharging problem has been the hot issue of the world today.Scientists study shows, the effective ways of realizing carbon dioxide discharge-reduction are Geological storages, yet carrying out carbon dioxide geological while burying, and it is particularly important that the selection in its Geological storage place seems.This is because field operating mechanism, environment regulator and the public wish, carrying out guaranteeing when carbon dioxide geological is buried that it buries security, to guarantee that carbon dioxide can not surmount predetermined border underground, can not leak in atmosphere again.Therefore, it is buried to place before burying and carry out safety evaluation and seem particularly important carrying out carbon dioxide geological.

Carbon dioxide is when ground storage, constantly in dynamic disperse state, until reach balance.In order to assess, to bury place security and need to measure the coefficient of diffusion of carbon dioxide in rock.At present common mensurated gas composition is at the device of diffusion coefficient of rock, its principle mostly based on mensurated gas composition in the variation of rock sample two ends concentration and then calculate the coefficient of diffusion of gas in rock.These class methods need to be by carrying out real time sample to rock two ends air chamber, then each time point gaseous sample is carried out to gas chromatographic analysis, thereby calculate the variation of rock two ends gas concentration, will moment bring impact to rock two ends air chamber pressure in sampling like this, thereby affect measuring accuracy.And because needs arrange two air chambers at rock two ends, cause needing mensurated gas composition when the diffusion coefficient of rock of saturated resident fluid, will make saturated resident fluid lose in vacuum, affected the homogeneity of experiment and stratum full-scale condition.

Summary of the invention

Summary of the invention

For above technical deficiency, the present invention discloses a kind of carbon dioxide of measuring at the device of diffusion coefficient of rock.The present invention no longer measures carbon dioxide at diffusion coefficient of rock by measuring the concentration of carbon dioxide, but obtain carbon dioxide at diffusion coefficient of rock by measuring the variation of carbon dioxide gas pressure: by the carbon dioxide state equation of proofreading and correct, converse the variation of its concentration, and then determine the coefficient of diffusion of carbon dioxide in rock.The present invention has fundamentally cancelled air chamber, has eliminated the impact that sampling causes gaseous tension, and by vacuumizing, the mensuration of saturated resident fluid and gas diffusivity is integrated, thereby thoroughly eliminated the impact on saturated fluid in rock in vacuum.

Terminological interpretation:

Saturated fluid is processed: refer to by vacuumizing the whole sucking-offs of air of loading in diffusion barrel in the tiny hole of sample rock interior, then utilize constant-flux pump that Experimental Flowing Object displacement is entered in diffusion barrel, continuation injection experiments fluid can produce one and build the pressure, it is logical when pressure is suppressed 10MPa, Experimental Flowing Object in diffusion barrel is under high pressure pressed in the hole of filling sample rock, has realized whole saturated upper Experimental Flowing Objects in the hole that loads sample rock.

Detailed Description Of The Invention

Technical scheme of the present invention is as follows:

Measure carbon dioxide at a device for diffusion coefficient of rock, it comprises crust of the device 4, at the interior tile vertically of described crust of the device 4, is provided with gas tank 5, diffusion barrel 6 and fluid tank 9; In crust of the device 4 outer setting, there are gas pipeline and fluid pipeline, the entrance of described gas pipeline is connected with dioxide bottle 3 by supercharge pump 32, on described gas pipeline, series connection is provided with four-way valve 30, and the gas outlet of described four-way valve 30 is connected with four-way valve 25, gas tank 5 and pressure transducer 28 respectively; The entrance of described fluid pipeline is connected with sample tank 15, and on described fluid pipeline, series connection is provided with four-way valve 19, and the liquid outlet of described four-way valve 19 is connected with four-way valve 25, fluid tank 9 and pressure transducer 18 respectively; Described gas tank 5 is for the carbon dioxide at splendid attire experimental pressure and temperature; Described fluid tank is for formation pore fluid or simulated formation fluid at splendid attire experimental pressure and temperature;

Top in the top of gas tank 5, the top of diffusion barrel 6 and fluid tank 9 is respectively arranged with temperature sensor, the bottom of described gas tank 5 is connected with constant-flux pump 1 by needle-valve 2, the bottom of described diffusion barrel 6 is connected with check valve 13 by needle-valve 12, and the bottom of described fluid tank 9 is connected with constant-flux pump 11 by needle-valve 10;

Described four-way valve 25 is connected with pressure transducer 22 by T-valve 23, and described T-valve 23 is connected with molecular pump 27 by needle-valve 24;

In described gas tank 5 axially on be provided with piston; In fluid tank 9 axially on be provided with piston; In described gas tank 5, fluid tank 9 and diffusion barrel 6, be provided with well heater.Described well heater heats and heat insulation function for gas tank 5, fluid tank 9 and diffusion barrel 6 provide.

Preferred according to the present invention, at described measurement carbon dioxide, at the device of diffusion coefficient of rock, also comprise computing machine, described constant-flux pump, needle-valve, check valve 13, sample tank 15, temperature sensor, pressure transducer, four-way valve, T-valve, molecular pump 27, supercharge pump 32 and well heater are connected with computing machine respectively.By the running parameter of the above-mentioned parts of computer acquisition, control the normal work of above-mentioned parts simultaneously.

Preferred according to the present invention, on described crust of the device, be provided with control panel, on control panel, comprise gas tank pressure display unit, fluid tank pressure display unit, diffusion barrel pressure display unit, temperature control panel, total power switch, heating source switch and computer operated switch; Described temperature control panel is for arranging the heating-up temperature of well heater, pressure display unit is connected with each pressure transducer, dynamically show that in experimentation, the pressure in each tank body changes, computer operated switch is for controlling and being connected of computer data acquiring, computer operated switch is when open mode, and computing machine can each pressure transducer of Real-time Collection and temperature sensor data.Operating personnel can set basic experiment parameter intuitively by described control panel, and read relevant temperature and pressure numerical value.Pressure transducer in the present invention, for monitoring in real time each tank body internal pressure, and is transferred to control panel and computing machine; Described temperature sensor, for monitoring in real time temperature in each tank body, and is transferred to control panel and computing machine; Described T-valve, four-way valve, needle-valve, check valve, for connecting line and pilot piping switch.

Preferred according to the present invention, at described diffusion barrel inner top and bottom, be provided with a pair of fixedly snap ring.Described diffusion barrel is used for loading rock sample, and set fixedly snap ring is used for fixedly rock sample.

Preferred according to the present invention, in described sample tank, stirrer is installed.The formation pore fluid that described sample tank provides for splendid attire scene or according to actual formation pore fluid configuration simulation fluid.

The present invention adopts 3 kinds of power supply devices, be respectively constant-flux pump, supercharge pump and molecular pump, constant-flux pump 1 is connected with dioxide bottle, for the carbon dioxide displacement of gas tank 5 is entered in diffusion barrel 6, constant-flux pump 14 is connected with sample tank 15, for the Experimental Flowing Object displacement of fluid tank 9 is entered in diffusion barrel 6, after supercharge pump 32 is connected to dioxide bottle 3, for dioxide bottle 3 carbon dioxides are delivered in gas tank 5, be pressurized to requirement of experiment pressure, molecular pump 27 is for vacuumizing diffusion barrel 6 and the inner rock sample that loads.

Above-mentioned measurement carbon dioxide, in a method of work for the device of diffusion coefficient of rock, comprises that step is as follows:

(1) utilize well heater respectively gas tank 5, fluid tank 9 and diffusion barrel 6 to be dried;

(2) utilize constant-flux pump 1 and constant-flux pump 11 respectively that the piston upper space of gas tank 5 and fluid tank 9 is emptying stand-by;

(3) will sample cylinder rock core or artificial cylinder rock core as filling sample rock, described filling sample rock is dried, with packing in diffusion barrel 6 after will the filling sample rock upper and lower both ends of the surface sealing of fluid sealant, utilize in diffusion barrel 6 up and down fixedly snap ring 8 will load the vertical fixed placement of sample rock;

(4) check the impermeability of whole device;

(5) by supercharge pump 32, the carbon dioxide in dioxide bottle 3 is delivered in gas tank 5, is pressurized to and wants simulated formation pressure, stand-by;

(6) Experimental Flowing Object is packed in sample tank 15, stand-by; Described Experimental Flowing Object is formation pore fluid or simulated formation fluid, and described simulated formation fluid configures in sample tank 15 by previous exploration gained formation pore fluid data and obtain, the simulation fluid identical with formation pore fluid character;

(7) utilize constant-flux pump 14 that the Experimental Flowing Object in sample tank 15 is pumped in fluid tank 9, and utilize constant-flux pump 11 that the Experimental Flowing Object in fluid tank 9 is forced into and wants simulated formation pressure;

(8) utilize molecular pump 27 that diffusion barrel 6 is vacuumized;

(9) utilize well heater respectively gas tank 5, fluid tank 9, diffusion barrel 6 to be heated, constant temperature is to wanting simulated formation pressure, stand-by;

(10) utilize constant-flux pump 11 that Experimental Flowing Object in fluid tank 9 is pumped in diffusion barrel 6, then utilize constant-flux pump 11 by exert pressure in diffusion barrel 6 to 10MPa, to loading rock sample, carry out saturated fluid processing;

(11) continue to utilize constant-flux pump 11 to carry out pressurized operation by 9 pairs of inner Experimental Flowing Objects of diffusion barrel 6 of fluid tank, be forced into and want simulated formation pressure;

(12) adjust the set pressure of check valve 13, described set pressure is compared with the little 0.1MPa of diffusion barrel internal pressure;

(13) utilize constant-flux pump 1 that carbon dioxide in gas tank 5 is pumped in diffusion barrel 6, due to the effect of check valve 13, the Experimental Flowing Object in emptying diffusion barrel 6;

(14) close needle- valve 12,20,26, utilize pressure transducer 22 to gather original pressure P0, utilize the pressure P 1-Pn of n time point t1～tn of pressure transducer 22 collections, (n is more than or equal to 2);

(15) Δ P be n time point pressure P 1-Pn respectively with the pressure differential of original pressure P0, as, Δ P 1=P1-P0, Δ P 2=P2-P0, Δ P n=Pn-P0; By the pressure drop Δ P 1 ~ Δ P n calculating with respectively with the corresponding mapping of time point t1～tn, obtain Δ P with

curve map, calculate the slope k of described curve map cathetus section part;

(16) bring the k in step (15) into formula 1.,

$\mathrm{\ΔP}=\frac{4M_{\∞}\mathrm{ZRT}\sqrt{D_{\mathrm{eff}}}}{r_{0}V\sqrt{\mathrm{\π}}}\sqrt{t}=k\sqrt{t}$ ①

Formula 1. in, Δ P be n time point pressure P 1-Pn respectively with the pressure differential of original pressure P0, as, Δ P 1=P1-P0, Δ P 2=P2-P0, Δ P n=Pn-P0; M _∞-the time levels off to carbon dioxide when infinite and diffuses into the amount in filling sample rock, mol; Z-compressibility factor is determined by the pressure and temperature of testing; R-universal gas constant, 8.314Pam ³k ^-1mol ^-1; T-experimental temperature, K; D _eff-carbon dioxide diffusion coefficient; r ₀the xsect radius of-filling sample rock, m; Annular volume between V-rock sample and diffusion barrel, m ³; T-time point, comprises t1～tn; K-Δ P and t ^1/2the slope of the straight-line segment that forms part;

By formula, 1. obtained,

can obtain the diffusion coefficient D of carbon dioxide in filling sample rock _eff.

The present invention is that the carbon dioxide state equation by proofreading and correct converses the variation of its concentration, and then determines the coefficient of diffusion of carbon dioxide in rock, and described formula derivation is 1. as follows:

From Fick the first diffusion law, when coefficient of diffusion is constant, the diffusion differential equation passive in rectangular coordinate system, remittance item is: (i), wherein C is gas concentration, the coefficient of diffusion that D is gas, and t is the time, x, y, z is rectangular coordinate system coordinate;

By by the expression-form that (i) formula obtains under cylindrical coordinate by mathematical coordinate transform being:

$\frac{\∂C}{\∂t}=\frac{1}{r}\{\frac{\∂}{\∂r}\left(\mathrm{rD}\frac{\∂C}{\∂r}\right)+\frac{\∂}{\∂\mathrm{\θ}}\left(\frac{D}{r}\frac{\∂C}{\∂\mathrm{\θ}}\right)+\frac{\∂}{\∂z}\left(\mathrm{rD}\frac{\∂C}{\∂z}\right)\}$ （ii）；

Because experiment rock core used is column type rock core, upper and lower two butt-end packings, gas can only enter rock core in radial diffusion, by the one dimension radial diffusion differential equation that (ii) formula is reduced under cylindrical coordinate, is therefore:

(iii);

According to boundary condition, in conjunction with equation, (iii) carry out following simultaneous $\left\{\begin{array}{c}\frac{\&PartialD;C}{\&PartialD;t}=D_{\mathrm{eff}}(\frac{{\&PartialD;}^{2}C}{\&PartialD;{\mathrm{<figure-callout\; id="2"\; label="r"\; filenames="HDA00001832447200011.png"\; state="\{\{state\}\}">r</figure-callout>}}^2}+\frac{1}{r}\frac{\&PartialD;C}{\&PartialD;r}),0<r<{\mathrm{<figure-callout\; id="0"\; label="r"\; filenames="HDA00001832447200022.png,HDA00001832447200031.png"\; state="\{\{state\}\}">r</figure-callout>}}_0,t\&GreaterEqual;0\\ C{|}_{t=0}=\mathrm{0,0}<r<r_0\\ C{|}_{r={\mathrm{<figure-callout\; id="0"\; label="r"\; filenames="HDA00001832447200022.png,HDA00001832447200031.png"\; state="\{\{state\}\}">r</figure-callout>}}_0}={\mathrm{<figure-callout\; id="0"\; label="C"\; filenames="HDA00001832447200022.png,HDA00001832447200031.png"\; state="\{\{state\}\}">C</figure-callout>}}_0,t\&GreaterEqual;0\end{array}\right.,$ Solve and obtain equation solution (iii) and be:

(iv), J wherein ₀(r α _n) be zeroth order Bessel function of the first kind, J ₁( _r0 α _n) be single order Bessel function of the first kind, α _nfor J ₀(r ₀α _nthe positive root of)=0;

With Mt, be illustrated in gas in time t and diffuse into the amount of substance in rock core; Use M _∞the expression time levels off to gas when infinite and diffuses into the amount of substance in rock core.By formula (iv) pair radius r integration, obtain the relational expression between Mt and time t:

$\frac{M_r}{M_{\&infin;}}=1-\underset{n=1}{\overset{\&infin;}{\mathrm{\&Sigma;}}}\frac{4}{{\mathrm{<figure-callout\; id="0"\; label="r"\; filenames="HDA00001832447200022.png,HDA00001832447200031.png"\; state="\{\{state\}\}">r</figure-callout>}}_0^2{\mathrm{\&alpha;}}_{\mathrm{<figure-callout\; id="2"\; label="n"\; filenames="HDA00001832447200011.png"\; state="\{\{state\}\}">n</figure-callout>}}^2}\exp (-D_{\mathrm{eff}}{\mathrm{\&alpha;}}_n^{2}t)$ （v）；

When

time, (v) formula can be reduced to:

(vi)

By real gas state equation Δ PV=Z Δ nRT and M _tin=Δ n substitution (vi), obtain $\mathrm{\&Delta;P}=\frac{4M_{\&infin;}\mathrm{ZRT}\sqrt{D_{\mathrm{eff}}}}{r_{0}V\sqrt{\mathrm{\&pi;}}}\sqrt{t}=k\sqrt{t}$ (vii), this formula is 1. formula.

The invention has the advantages that:

The present invention no longer measures carbon dioxide at diffusion coefficient of rock by measuring the concentration of carbon dioxide, but obtain carbon dioxide at diffusion coefficient of rock by measuring the variation of carbon dioxide gas pressure: by the carbon dioxide state equation of proofreading and correct, converse the variation of its concentration, and then determine the coefficient of diffusion of carbon dioxide in rock.The present invention has fundamentally cancelled air chamber, has eliminated the impact that sampling causes gaseous tension, and by vacuumizing, the mensuration of saturated resident fluid and gas diffusivity is integrated, thereby thoroughly eliminated the impact on saturated fluid in rock in vacuum.

Accompanying drawing explanation

Fig. 1 is the structural representation of device of the present invention;

Fig. 2 is the schematic diagram of the control panel on crust of the device of the present invention;

Fig. 3 maps by the corresponding time t1～tn of the P1 in his-and-hers watches 1～Pn, i.e. pressure temporal evolution figure;

Fig. 4 is for to map to the arithmetic square root of time t1～tn by the pressure differential deltap P 1～Δ P n in his-and-hers watches 1, i.e. the pressure reduction variation diagram of arithmetic square root in time.

In Fig. 1,2,1, constant-flux pump; 2, needle-valve; 3, dioxide bottle; 4, crust of the device; 5, gas tank; 6, diffusion barrel; 7, load rock sample; 8, fixing snap ring; 9, fluid tank; 10, needle-valve; 11, constant-flux pump; 12, needle-valve; 13, check valve; 14, constant-flux pump; 15, sample tank, 16, needle-valve; 17, temperature sensor; 18, pressure transducer; 19, four-way valve; 20, needle-valve; 21, temperature sensor; 22, pressure transducer; 23, T-valve; 24, needle-valve; 25, four-way valve; 26, needle-valve; 27, molecular pump; 28, pressure transducer; 29, temperature sensor; 30, four-way valve; 31, needle-valve; 32, supercharge pump.

Embodiment

According to embodiment and Figure of description, the present invention is described in detail below, but is not limited to this.

Embodiment,

As illustrated in fig. 1 and 2.

Measure carbon dioxide at a device for diffusion coefficient of rock, it comprises crust of the device 4, at the interior tile vertically of described crust of the device 4, is provided with gas tank 5, diffusion barrel 6 and fluid tank 9; In crust of the device 4 outer setting, there are gas pipeline and fluid pipeline, the entrance of described gas pipeline is connected with dioxide bottle 3 by supercharge pump 32, on described gas pipeline, series connection is provided with four-way valve 30, and the gas outlet of described four-way valve 30 is connected with four-way valve 25, gas tank 5 and pressure transducer 28 respectively; The entrance of described fluid pipeline is connected with sample tank 15, and on described fluid pipeline, series connection is provided with four-way valve 19, and the liquid outlet of described four-way valve 19 is connected with four-way valve 25, fluid tank 9 and pressure transducer 18 respectively;

Top in the top of gas tank 5, the top of diffusion barrel 6 and fluid tank 9 is respectively arranged with temperature sensor, the bottom of described gas tank 5 is connected with constant-flux pump 1 by needle-valve 2, the bottom of described diffusion barrel 6 is connected with check valve 13 by needle-valve 12, and the bottom of described fluid tank 9 is connected with constant-flux pump 11 by needle-valve 10;

Described four-way valve 25 is connected with pressure transducer 22 by T-valve 23, and described T-valve 23 is connected with molecular pump 27 by needle-valve 24;

In described gas tank 5 axially on be provided with piston; In fluid tank 9 axially on be provided with piston;

At described measurement carbon dioxide, at the device of diffusion coefficient of rock, also comprise computing machine, described constant-flux pump, needle-valve, check valve 13, sample tank 15, temperature sensor, pressure transducer, four-way valve, T-valve, molecular pump 27, supercharge pump 32 and well heater are connected with computing machine respectively.

On described crust of the device, be provided with control panel, on control panel, comprise gas tank pressure display unit, fluid tank pressure display unit, diffusion barrel pressure display unit, temperature control panel, total power switch, heating source switch and computer operated switch; Described temperature control panel is for arranging the heating-up temperature of well heater, pressure display unit is connected with each pressure transducer, dynamically show that in experimentation, the pressure in each tank body changes, computer operated switch is for controlling and being connected of computer data acquiring, computer operated switch is when open mode, and computing machine can each pressure transducer of Real-time Collection and temperature sensor data.

At described diffusion barrel inner top and bottom, be provided with a pair of fixedly snap ring.In described sample tank, stirrer is installed.

Measure as described in Example 1 carbon dioxide in a method of work for the device of diffusion coefficient of rock, comprise that step is as follows:

(1) utilize well heater respectively gas tank 5, fluid tank 9 and diffusion barrel 6 to be dried;

(2) utilize constant-flux pump 1 and constant-flux pump 11 respectively that the piston upper space of gas tank 5 and fluid tank 9 is emptying stand-by;

(3) will sample cylinder rock core or artificial cylinder rock core as filling sample rock, described filling sample rock is dried, with packing in diffusion barrel 6 after will the filling sample rock upper and lower both ends of the surface sealing of fluid sealant, utilize in diffusion barrel 6 up and down fixedly snap ring 8 will load the vertical fixed placement of sample rock;

(4) check the impermeability of whole device;

(5) by supercharge pump 32, the carbon dioxide in dioxide bottle 3 is delivered in gas tank 5, is pressurized to and wants simulated formation pressure, stand-by;

(6) Experimental Flowing Object is packed in sample tank 15, stand-by; Described Experimental Flowing Object is formation pore fluid or simulated formation fluid, and described simulated formation fluid configures in sample tank 15 by previous exploration gained formation pore fluid data and obtain, the simulation fluid identical with formation pore fluid character;

(7) utilize constant-flux pump 14 that the Experimental Flowing Object in sample tank 15 is pumped in fluid tank 9, and utilize constant-flux pump 11 that the Experimental Flowing Object in fluid tank 9 is forced into and wants simulated formation pressure;

(8) utilize molecular pump 27 that diffusion barrel 6 is vacuumized;

(9) utilize well heater respectively gas tank 5, fluid tank 9, diffusion barrel 6 to be heated, constant temperature is to wanting simulated formation pressure, stand-by;

(10) utilize constant-flux pump 11 that Experimental Flowing Object in fluid tank 9 is pumped in diffusion barrel 6, then utilize constant-flux pump 11 by exert pressure in diffusion barrel 6 to 10MPa, to loading rock sample, carry out saturated fluid processing;

(11) continue to utilize constant-flux pump 11 to carry out pressurized operation by 9 pairs of inner Experimental Flowing Objects of diffusion barrel 6 of fluid tank, be forced into and want simulated formation pressure;

(12) adjust the set pressure of check valve 13, described set pressure is compared with the little 0.1MPa of diffusion barrel internal pressure;

(13) utilize constant-flux pump 1 that carbon dioxide in gas tank 5 is pumped in diffusion barrel 6, due to the effect of check valve 13, the Experimental Flowing Object in emptying diffusion barrel 6;

(14) close needle- valve 12,20,26, utilize pressure transducer 22 to gather original pressure P0, utilize pressure transducer 22 to gather the pressure P 1-Pn of n time point t1～tn, (n is more than or equal to 2), fills in into table 1,

Table 1: utilize pressure transducer 22 to gather the pressure P 1-Pn of each time point and the pressure reduction calculating

By the pressure in his-and-hers watches 1, the time is mapped, obtain pressure temporal evolution figure, see Fig. 3;

(15) Δ P be n time point pressure P 1-Pn respectively with the pressure differential of original pressure P0, as, Δ P 1=P1-P0, Δ P 2=P2-P0, Δ P n=Pn-P0; By the pressure reduction in his-and-hers watches 1, the arithmetic square root of time is mapped, obtains the pressure reduction variation diagram of arithmetic square root in time, see Fig. 4, obtain Δ P with

curve map, slope k=19.0220 of calculating the part of curve map cathetus section in described Fig. 4; As can be seen from Figure 4 spread initial period pressure drop very fast, not linear, this is mainly because this stage is diffusion unstable state state; When reaching diffusion lower state, the arithmetic square root of pressure drop and time is linear;

(16) bring the k in step (15) into formula 1.,

$\mathrm{\&Delta;P}=\frac{4M_{\&infin;}\mathrm{ZRT}\sqrt{D_{\mathrm{eff}}}}{r_{0}V\sqrt{\mathrm{\&pi;}}}\sqrt{t}=k\sqrt{t}$ ①

Formula 1. in, Δ P be n time point pressure P 1-Pn respectively with the pressure differential of original pressure P0, as, Δ P 1=P1-P0, Δ P 2=P2-P0, Δ P n=Pn-P0; M _∞-the time levels off to carbon dioxide when infinite and diffuses into the amount in filling sample rock, mol; Z-compressibility factor is determined by the pressure and temperature of testing; R-universal gas constant, 8.314Pam ³k ^-1mol ^-1; T-experimental temperature, K; D _eff-carbon dioxide diffusion coefficient; r ₀the xsect radius of-filling sample rock, m; Annular volume between V-rock sample and diffusion barrel, m ³; T-time point, comprises t1～tn; K-Δ P and t ^1/2the slope of the straight-line segment that forms part;

By formula, 1. obtained,

can obtain the diffusion coefficient D of carbon dioxide in filling sample rock _eff=1.65 * 10 ^-10m ²/ s, fills in into table 2.

Table 2

Claims (4)

1. measure carbon dioxide at a device for diffusion coefficient of rock, it is characterized in that, it comprises crust of the device (4), and in described crust of the device (4), tile vertically is provided with gas tank (5), diffusion barrel (6) and fluid tank (9); In crust of the device (4) outer setting, there are gas pipeline and fluid pipeline, the entrance of described gas pipeline is connected with dioxide bottle (3) by supercharge pump (32), on described gas pipeline, series connection is provided with four-way valve (30), and the gas outlet of described four-way valve (30) is connected with four-way valve (25), gas tank (5) and pressure transducer (28) respectively; The entrance of described fluid pipeline is connected with sample tank (15), and on described fluid pipeline, series connection is provided with four-way valve (19), and the liquid outlet of described four-way valve (19) is connected with four-way valve (25), fluid tank (9) and pressure transducer (18) respectively;

Top in the top of gas tank (5), the top of diffusion barrel (6) and fluid tank (9) is respectively arranged with temperature sensor, the bottom of described gas tank (5) is connected with constant-flux pump (1) by needle-valve (2), the bottom of described diffusion barrel (6) is connected with check valve (13) by needle-valve (12), and the bottom of described fluid tank (9) is connected with constant-flux pump (11) by needle-valve (10); Described four-way valve (25) is connected with pressure transducer (22) by T-valve (23), and described T-valve (23) is connected with molecular pump (27) by needle-valve (24); In described gas tank (5) axially on be provided with piston; In fluid tank (9) axially on be provided with piston; In described gas tank (5), fluid tank (9) and diffusion barrel (6), be provided with well heater; At described measurement carbon dioxide, at the device of diffusion coefficient of rock, also comprise computing machine, described constant-flux pump, needle-valve, check valve (13), sample tank (15), temperature sensor, pressure transducer, four-way valve, T-valve, molecular pump (27), supercharge pump (32) are connected with computing machine respectively with well heater.

2. a kind of carbon dioxide of measuring according to claim 1 is at the device of diffusion coefficient of rock, it is characterized in that, on described crust of the device, be provided with control panel, on control panel, comprise gas tank pressure display unit, fluid tank pressure display unit, diffusion barrel pressure display unit, temperature control panel, total power switch, heating source switch and computer operated switch; Described temperature control panel is for arranging the heating-up temperature of well heater, pressure display unit is connected with each pressure transducer, dynamically show that in experimentation, the pressure in each tank body changes, computer operated switch is for controlling and being connected of computer data acquiring, computer operated switch when open mode, each pressure transducer of computer real-time acquisition and temperature sensor data.

3. a kind of carbon dioxide of measuring according to claim 1, at the device of diffusion coefficient of rock, is characterized in that, at described diffusion barrel inner top and bottom, is provided with a pair of fixedly snap ring.

4. a kind of carbon dioxide of measuring according to claim 1, at the device of diffusion coefficient of rock, is characterized in that, in described sample tank, stirrer is installed.

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