CN103267710A - Measurement and calculation method for effective viscosity of VES (viscoelastic surfactant) variable-viscosity acid in porous medium - Google Patents

Abstract

The invention relates to a measurement and calculation method for the effective viscosity of VES (viscoelastic surfactant) variable-viscosity acid in a porous medium. The method comprises the following steps of: testing the influence of a pH value, the cation concentration, the VES concentration and a shearing rate on the viscosity of the VES variable-viscosity acid by a rheometer; then testing the effective viscosity of the VES variable-viscosity acid in the porous medium by an artificial rock core with a more uniform particle size; building a shearing rate calculation formula in the porous medium by comparing the effective viscosity with the viscosity tested by the rheometer; and building a viscosity calculation formula of the VES variable-viscosity acid based on a relation between the pH value, the cation concentration, the VES concentration as well as the shearing rate and the viscosity of the VES acidic liquid. According to the method for measuring the effective viscosity of the VES variable-viscosity acid in the porous viscosity under a formation condition, a reliable basis is supplied to evaluation of a VES variable-viscosity acid diversion effect and a filtration reduction effect; and the problem that the effective viscosity of the VES variable-viscosity acid under the formation condition and the calculation method cannot be obtained in the prior art is solved.

Description

VES mensuration and the computing method of virtual viscosity of acid in porous medium that become sticky

Technical field

The present invention relates to a kind of VES mensuration and the computing method of virtual viscosity of acid in porous medium that become sticky, belong to technical field of petroleum extraction.

Background technology

In the petroleum engineering field, the VES(viscoelastic surfactant) acid that becomes sticky turns to for acidifying or leak-off falls in acid fracturing, and bright sour viscosity is lower, becomes sticky after reacting with carbonatite, and the viscosity after becoming sticky determines its turning efficiency or falls the filter effect.Because acidifying, acid fracturing act in the porous medium of stratum, need to measure the virtual viscosity of acid in the porous medium of stratum that become sticky.Adopt flow graph (liquid viscosity test all-purpose instrument) to measure the sour viscosity that becomes sticky at present, this viscosity is the viscosity under macroscopical shearing condition, can not represent the virtual viscosity in the porous medium, the viscosity of measuring with this method can't be used for the turning efficiency under analog computation and the evaluation formation condition or fall filtration effect.

Summary of the invention

For solving the problems of the technologies described above, the object of the present invention is to provide a kind of VES of mensuration become sticky the virtual viscosity of acid under formation condition method and set up VES viscosity calculations formula based on pH value, VES concentration, cation concn and shear rate.

For achieving the above object, the invention provides a kind of VES mensuration and the computing method of virtual viscosity of acid in porous medium that become sticky, this method is earlier with rheometer test pH value, cation concn, VES concentration and shear rate become sticky the influence of sour viscosity (when testing the influencing of every kind of parameter to VES, other parameter is fixed), again with the particle diameter synthetic core test VES virtual viscosity of sour residual acid in porous medium that become sticky uniformly, by contrasting the viscosity of this virtual viscosity and rheometer test, set up porous medium medium shear rate computing formula, again based on the pH value, cation concn, relation between VES concentration and shear rate and the VES acid liquid viscosity, set up VES become sticky acid the viscosity calculations formula.

According to specific embodiments of the present invention, above-mentioned VES virtual viscosity assay method and the computing method of acid in porous medium that become sticky may further comprise the steps:

(1) utilize rheometer test VES become sticky relation and opening relationships curve between sour viscosity and pH value, cation concn, VES concentration and the shear rate, when measuring a kind of relation curve of parameter, other parameters are fixed.

(2) synthetic core is prepared: prepare the synthetic core of different permeabilities with the uniform propping agent of particle diameter, the diameter of this synthetic core is 1 inch, and length is 5-15cm, and permeability is the 1-300 millidarcy, measures factor of porosity and the permeability of every synthetic core;

(3) VES becomes sticky sour residual sour the preparation: become sticky sour and the pure CaCO of analysis with VES ₃Reaction prepares the VES sour residual acid that becomes sticky, wherein, and HCl and CaCO ₃Mol ratio be 2:1;

(4) set up relation curve between viscosity and shear rate: the become sticky viscosity of sour residual acid of the VES that obtains with step (3) under the rheometer measurement different shear rate, be plotted on the semilog coordinate, obtain the relation curve between viscosity and the shear rate, wherein, the scope of shear rate is 1-5000s ^-1

(5) the VES residual sour displacement test of acid that becomes sticky: carry out displacement test, record experiment pressure reduction and discharge capacity with become sticky sour residual acid and synthetic core of VES;

(6) become sticky sour virtual viscosity of VES is calculated: pressure reduction, discharge capacity and core permeability are according to the anti-VES of asking of the following formula virtual viscosity μ e of sour residual acid in pore media (being synthetic core) that become sticky by experiment:

μ e=A Δ pk/qL, wherein, k is core permeability, and q is the discharge capacity of displacement in the experiment, and A is that core section is long-pending, and L is rock core length, Δ p is rock core two ends displacement pressure reduction;

(7) shear rate is calculated: by the corresponding shear rate of sour virtual viscosity that becomes sticky of the anti-VES of looking on viscosity and shear rate relation curve

Flow velocity VD=q/A, core porosity and permeability are by experiment set up the shear rate computing formula:

$\stackrel{\·}{r}=\frac{{2.9V}_D}{\sqrt{\mathrm{k\φ}}}$

In the formula, V _DBe the Darcy velocity in the displacement test, k is core permeability, and φ is core porosity;

(8) the VES sour viscosity calculations formula that becomes sticky: in conjunction with VES become sticky the relation curve between acid concentration, cation concn and the shear rate of sour viscosity and pH value, VES that becomes sticky, set up the become sticky viscosity calculations formula of acid of VES:

When pH＜a, μ=μ 0;

When pH 〉=a, $\mathrm{\μs}=\min (\max ({\mathrm{\μ}}_0,48561{\stackrel{\·}{r}}^{0.883}),b),$ This formula is returned and is obtained by the become sticky viscosity of sour residual acid and the relation curve between the shear rate of VES;

μ=μ S * 0.5 * [erf (c * (C _VES-d)/e)+1] * 0.5 * [erf (f * (C _Cation-g))+1], this formula is returned and is obtained by become sticky relation curve between sour viscosity and pH value, cation concn, VES concentration and the shear rate of VES;

A=0 in the formula, b=2391, c=7, d=3.3%, e=5%, f=1.8, g=1.5;

Wherein, μ ₀Be the bright sour viscosity of VES, the unit of viscosity is mPas, C _VESBe become sticky VES concentration in the acid of VES, unit is wt%, C _CationBe become sticky cation concn in the acid of VES, unit is mol/L.

Formula method for building up: obtain relation between shear rate and residual sour viscosity by the become sticky viscosity of sour residual acid and the relation curve regression formula between the shear rate of VES; According to the VES indicated pH value of relation curve between sour viscosity and pH value, cation concn, VES concentration and the shear rate, cation concn, the VES concentration influence to viscosity that becomes sticky, by its Changing Pattern, structure viscosity calculations formula, the coefficient in the formula obtains by the data homing method.

In said method, the VES acid that becomes sticky is the potpourri of VES, HCl and water, and preferably, VES becomes sticky, and the content of HCl is 20wt% in the acid, and the content of VES is 1-6wt%, and surplus is water.

In said method, preferably, in step (3), VES becomes sticky, and the concentration of HCl is 20wt% in the acid, and the concentration of VES is 6wt%.

In said method, preferably, step (1) can be carried out in such a way: when test VES became sticky sour viscosity and pH value relation curve, VES concentration was controlled to be 6wt%, and HCl concentration is controlled to be 20wt%, regulated HCl and CaCO ₃Mol ratio obtain the acid solution of different pH values, detect at 170s with flow graph again ^-1Shear rate under viscosity, set up the relation curve between viscosity and the pH value then; When test VES became sticky viscosity and the cation concn relation curve of acid, the VES sour concentration that becomes sticky was 6wt%, adds CaCl ₂Regulate Ca ²⁺Concentration detects at 170s with flow graph to the cation concn numerical value of different needs again ^-1Shear rate under viscosity, set up the relation curve between viscosity and the cation concn then; When test VES became sticky the viscosity of acid and the concentration relationship curve of VES, HCl concentration was controlled to be 20wt%, HCl and CaCO ₃Mol ratio be controlled to be 2:1, change the concentration of VES, detect at 170s with flow graph again ^-1Shear rate under viscosity, set up the relation curve between viscosity and the VES concentration then; When test VES became sticky sour viscosity and shear rate relation curve, VES concentration was controlled to be 6wt%, and HCl concentration is controlled to be 20wt%, regulated HCl and CaCO ₃Mol ratio be controlled to be 2:1, detect viscosity under different shear rates with flow graph again, set up the relation curve between viscosity and the shear rate then.

In said method, when in step (2), preparing rock core, can obtain the rock core of different permeabilities by the particle diameter that changes propping agent.When preparing every rock core, make particle diameter even as far as possible, pore size is more even like this, and the shear rate that is subjected to during the acid solution displacement is more even.

In said method, in step (2), adopt factor of porosity, the permeability method of testing of petroleum engineering field standard to carry out for the test of factor of porosity and permeability.

In said method, in step (5), this displacement test can carry out according to the experimentation of routine, with pump the VES acid that becomes sticky is pumped into rock core, gives fixed displacement, reaches stable back record displacement pressure reduction.

In said method, in step (7), the formula that calculates shear rate is based on the Littmann formula and obtains with better adaptation experimental data by adjusting coefficient.

The become sticky method of acid virtual viscosity in the porous medium of stratum of test provided by the invention VES has been set up the VES sour viscosity calculations method that becomes sticky, for analog computation provides the viscosity calculations formula.By adopting this method can obtain the virtual viscosity of VES acid solution in pore media under the typical displacement condition, estimate VES acid solution turning efficiency or fall filter effect (before becoming sticky by contrast VES acid solution and the viscosity differences evaluation after becoming sticky).

VES provided by the invention become sticky acid under formation condition the assay method of the virtual viscosity in the porous medium for VES becomes sticky sour turning efficiency and fall the filter effect assessment reliable foundation is provided, solved prior art and can't obtain VES become sticky virtual viscosity under the sour formation condition and the problem of computing method.

Description of drawings

Fig. 1 is the become sticky relation curve of viscosity and shear rate of sour residual acid of VES among the embodiment;

Fig. 2 is become sticky relation curve between sour viscosity and the pH value of VES among the embodiment;

Fig. 3 is the become sticky relation curve of viscosity and pH value of sour residual acid of VES under the different VES concentration among the embodiment;

Fig. 4 is 7 o'clock for pH value among the embodiment, VES the become sticky viscosity of sour residual acid and the relation curve between the VES concentration;

Fig. 5 is VES among the embodiment the become sticky viscosity of sour residual acid and the relation curve of calcium ion concentration.

Embodiment

Understand for technical characterictic of the present invention, purpose and beneficial effect being had more clearly, existing technical scheme of the present invention is carried out following detailed description, but but can not be interpreted as restriction to practical range of the present invention.

Embodiment

This example provides a kind of VES mensuration and the computing method of virtual viscosity of acid in porous medium that become sticky, and it is the VES of the 20wt% acid that becomes sticky that present embodiment adopts HCl concentration.This method may further comprise the steps:

1, four different synthetic cores of preparation are measured its factor of porosity, and concrete numerical value is as shown in table 5;

2, utilize normal saline solution that the synthetic core of preparation is carried out displacement test, measure the permeability of synthetic core, concrete numerical value is as shown in table 5;

3, measure become sticky relation curve between sour viscosity and shear rate, pH value, VES concentration, kation (calcium ion) concentration of VES:

(1) measure VES become sticky between the residual sour viscosity of acid and the shear rate relation and set up curve: HCl concentration is 20wt%, HCl and CaCO ₃Mol ratio be 2:1, probe temperature is 90 ℃, VES becomes sticky, and the concentration of VES is 6wt% in the acid, change shear rate, utilize the become sticky viscosity number (specifically as shown in table 1) of sour residual acid of VES under the rheometer measurement different shear rate, draw according to the data in the table 1 and to obtain VES the become sticky viscosity of sour residual acid and the relation curve between the shear rate, as shown in Figure 1.

(2) measure VES become sticky acid viscosity and the relation between the pH value and set up curve: be 170s with fixed shear rate in the test process ^-1, probe temperature is 90 ℃, and VES becomes sticky, and the concentration of VES is 6wt% in the acid, and HCl concentration is 20wt%, adds CaCO in becoming sticky acid to VES ₃Regulate the pH value, regulate CaCO ₃Dosage is to the pH value that needs, and utilizes the become sticky viscosity number (as shown in table 2) of acid of VES under the rheometer measurement different pH condition, and drafting obtains become sticky relation curve between sour viscosity and the pH value of VES, as shown in Figure 2.

Shear rate and the viscosity numerical value of table 1 test

Shear rate, s -1	Viscosity, mPas
		1.05	2392.72
12.08	2956.66
		56.98	1500.25
101.01	907.51
		208.94	366.94
417.42	199.74
		834.27	112.38
1042.11	95.02
		2083.94	55.56
3125.67	39.91
		4167.78	33.70
5000.11	28.33

PH value and the viscosity numerical value of table 2 test

The pH value	Viscosity, mPas
		-1	15.23
-0.7	25.30
		-0.5	320.43
0	350.55
		1	360.50
2	370.71
		4	330.27
6	320.13
		8	300.28
10	280.39

(3) measure become sticky relation curve between acid and pH value and the VES concentration of VES: be 170s with fixed shear rate in the test process ^-1, probe temperature is 90 ℃, and VES becomes sticky, and the concentration of VES is 2-6wt% in the acid, and the concentration of HCl is 20wt%; For each VES concentration, in becoming sticky acid to VES, add CaCO ₃Regulate the pH value, by regulating CaCO ₃Dosage obtains the acid solution of different pH values, with its viscosity of rheometer measurement (as shown in table 3), is depicted as curve shown in Figure 3 then, the corresponding curve of each VES concentration.Simultaneously, be 7 o'clock according to the pH value, the become sticky viscosity of sour residual acid of VES is set up curve with the relation between the different VES concentration, as shown in Figure 4.

PH value, VES viscosity and the viscosity numerical value of table 3 test

(4) measure become sticky relation curve between sour viscosity and the calcium ion concentration of VES: be 170s with fixed shear rate in the test process ^-1, the pH value is 7, and probe temperature is 90 ℃, and VES becomes sticky, and the concentration of VES is 6wt% in the acid; In becoming sticky acid to VES, add CaCl ₂Regulate the pH value, regulate CaCl ₂The addition VES that obtains the different calcium ion concentration acid that becomes sticky, utilize then rheometer measurement VES under the different calcium ion concentration become sticky acid viscosity number (as shown in table 4), draw VES the become sticky viscosity of acid and the relation curve between the calcium ion concentration, as shown in Figure 5.

Calcium ion concentration and the viscosity numerical value of table 4 test

Calcium ion concentration, mol/L	Viscosity, mPas
		0	5.04
0.5	10.76
		1	50.64
1.5	168.92
		2	360.48
2.5	379.88
		3	395.75

4, under 90 ° of C, making HCl concentration is that 20wt% and VES concentration are become sticky acid and CaCO of the VES of 6wt% ₃(analyzing pure) reaction obtains VES become sticky sour residual acid (HCl and CaCO ₃Mol ratio be 2:1), adopt the rock core of step 1 preparation to carry out displacement test then, by the anti-virtual viscosity (concrete numerical value as shown in table 5) of residual acid in pore media of asking of pressure reduction, discharge capacity and core permeability:

μ _e=A Δ pk/qL, k are core permeability, and q is the discharge capacity of displacement in the experiment, and A is that core section is long-pending, and L is rock core length, and Δ p is rock core two ends displacement pressure reduction.

5, according to the above-mentioned virtual viscosity that calculates, searching corresponding shear rate (concrete numerical value is shown in " shear rate " in the table 5) among Fig. 1.

6, calculate displacement rate VD=q/A, result of calculation is as shown in table 5.

7, by permeability, factor of porosity and displacement rate match shear rate computing formula, it is formula (1):

$\stackrel{\·}{r}=\frac{{2.9V}_D}{\sqrt{\mathrm{k\φ}}}---\left(1\right)$

In the formula, V _DBe the Darcy velocity in the displacement test, k is core permeability, and φ is core porosity.

8, pass through the shear rate of formula (1) calculating shown in " formula (1) calculates shear rate " in the table 5.

9, the become sticky viscosity of sour residual acid of VES is influenced by pH value, VES concentration, cation concn, shear rate mainly, according to experimental result (Fig. 1-5, table 1-5), for used acid fluid system in this experiment, sets up following viscosity calculations formula:

When pH＜a, μ=μ ₀(2)

When pH 〉=a, $\mathrm{\μs}=\min (\max ({\mathrm{\μ}}_0,48567{\stackrel{\·}{r}}^{-0.883}),b);---\left(3\right)$

μ=μS×0.5×[erf(c×(C _VES-d)/e)+1]×0.5×[erf(f×(C _cation-g))+1]；（4）

A=0 in the formula, b=2391, c=7, d=3.3%, e=5%, f=1.8, g=1.5;

μ ₀Be the become sticky viscosity of the bright acid of acid of VES, formula (3) is the formula of Fig. 1 recurrence, and viscosity unit is mPas, C _VESBe VES concentration (wt%), C _CationBe cation concn (mol/L).

The various data of test in table 5 experiment

Can calculate the become sticky viscosity of acid of VES under different pH values, VES concentration, cation concn, the shear rate according to the formula that obtains in the step 9, be become sticky sour turning efficiency and fall the filter effect assessment reliable foundation is provided of VES, solved prior art and can't obtain VES become sticky virtual viscosity under the sour formation condition and the problem of computing method.

Claims (3)

1. the VES virtual viscosity of acid in porous medium that become sticky measured and computing method, and it may further comprise the steps:

(1) utilize rheometer test VES become sticky acid viscosity and relation and the opening relationships curve between its pH value, cation concn, VES concentration and the shear rate;

(2) synthetic core is prepared: the synthetic core for preparing different permeabilities more than 4 with the uniform propping agent of particle diameter, the diameter of this synthetic core is 1 inch, length is 5-15cm, and permeability is the 1-300 millidarcy, measures factor of porosity and the permeability of every synthetic core;

(3) the VES residual acid preparation of acid that becomes sticky: with VES become sticky acid and CaCO ₃Reaction prepares the VES sour residual acid that becomes sticky, wherein, and HCl and CaCO ₃Mol ratio be 2:1;

(4) set up the relation curve of viscosity and shear rate: with the become sticky viscosity of sour residual acid of VES under the rheometer measurement different shear rate, be plotted on the semilog coordinate, obtain viscosity and shear rate relation curve, wherein, the scope of shear rate is 1-5000s ^-1

(5) the VES residual sour displacement test of acid that becomes sticky: become sticky sour residual acid and synthetic core of the VES that use prepares above carries out displacement test, record experiment pressure reduction and discharge capacity;

(6) become sticky sour virtual viscosity of VES is calculated: pressure reduction, discharge capacity and core permeability are according to the anti-VES of asking of the following formula virtual viscosity μ of sour residual acid in pore media that become sticky by experiment _e:

μ _e=A Δ pk/qL, wherein, k is core permeability, and q is the discharge capacity of displacement in the experiment, and A is that core section is long-pending, and L is rock core length, Δ p is rock core two ends displacement pressure reduction;

(7) shear rate is calculated: by the anti-corresponding shear rate of virtual viscosity of looking on viscosity and shear rate relation curve

Flow velocity VD=q/A, core porosity and permeability are by experiment set up the shear rate computing formula:

$\stackrel{\·}{r}=\frac{{2.9V}_D}{\sqrt{\mathrm{k\φ}}}$

In the formula, V _DBe the Darcy velocity in the displacement test, k is core permeability,

Be core porosity;

(8) the VES sour viscosity calculations formula that becomes sticky: in conjunction with VES become sticky the relation curve between acid concentration, cation concn and the shear rate of acid and pH value, VES that becomes sticky, set up the VES sour viscosity calculations formula that becomes sticky:

When pH＜a, μ=μ ₀

When pH 〉=a, $\mathrm{\μs}=\min (\max ({\mathrm{\μ}}_0,48567{\stackrel{\·}{r}}^{-0.883}),b),$

μ=μS×0.5×[erf(c×(C _VES-d)/e)+1]×0.5×[erf(f×(C _cation-g))+1]；

A=0 in the formula, b=2391, c=7, d=3.3%, e=5%, f=1.8, g=1.5;

Wherein, μ ₀Be the become sticky viscosity of the bright acid of acid of VES, unit is mPas, C _VESBe become sticky VES concentration in the acid of VES, unit is wt%, C _CationBe become sticky cation concn in the acid of VES, unit is mol/L.

2. method according to claim 1, wherein, by weight percentage, described VES becomes sticky in the acid, and the content of HCl is 20wt%, and the content of VES is 1-6wt%, and surplus is water.

3. method according to claim 1, wherein, in step (3), in described VES became sticky acid, the concentration of HCl was 20wt%, and the concentration of VES is 6wt%, and surplus is water.

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