CN112228019A - Method for evaluating influence of carbon dioxide flooding salt scale precipitation on recovery ratio - Google Patents
Method for evaluating influence of carbon dioxide flooding salt scale precipitation on recovery ratio Download PDFInfo
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- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 title claims abstract description 150
- 150000003839 salts Chemical class 0.000 title claims abstract description 139
- 229910002092 carbon dioxide Inorganic materials 0.000 title claims abstract description 83
- 239000001569 carbon dioxide Substances 0.000 title claims abstract description 70
- 238000011084 recovery Methods 0.000 title claims abstract description 56
- 238000000034 method Methods 0.000 title claims abstract description 39
- 238000001556 precipitation Methods 0.000 title claims description 50
- 238000006243 chemical reaction Methods 0.000 claims abstract description 67
- 230000008021 deposition Effects 0.000 claims abstract description 28
- 238000002474 experimental method Methods 0.000 claims abstract description 22
- 238000006073 displacement reaction Methods 0.000 claims abstract description 14
- 230000008569 process Effects 0.000 claims abstract description 13
- 239000011435 rock Substances 0.000 claims abstract description 5
- 150000002500 ions Chemical class 0.000 claims description 34
- 239000007787 solid Substances 0.000 claims description 28
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 23
- 239000008398 formation water Substances 0.000 claims description 22
- 239000000376 reactant Substances 0.000 claims description 18
- 230000015572 biosynthetic process Effects 0.000 claims description 14
- 230000000694 effects Effects 0.000 claims description 12
- 239000012530 fluid Substances 0.000 claims description 11
- 230000000704 physical effect Effects 0.000 claims description 7
- 230000003993 interaction Effects 0.000 claims description 6
- 230000035699 permeability Effects 0.000 claims description 6
- 230000008859 change Effects 0.000 claims description 4
- 239000011148 porous material Substances 0.000 claims description 4
- 239000003129 oil well Substances 0.000 claims description 3
- 238000011156 evaluation Methods 0.000 claims 2
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims 1
- 229910052799 carbon Inorganic materials 0.000 claims 1
- 238000004458 analytical method Methods 0.000 abstract description 4
- 238000011160 research Methods 0.000 abstract description 4
- 238000011161 development Methods 0.000 abstract description 2
- 239000003921 oil Substances 0.000 description 35
- 239000000047 product Substances 0.000 description 11
- JLVVSXFLKOJNIY-UHFFFAOYSA-N Magnesium ion Chemical compound [Mg+2] JLVVSXFLKOJNIY-UHFFFAOYSA-N 0.000 description 7
- 229910001425 magnesium ion Inorganic materials 0.000 description 7
- 238000004364 calculation method Methods 0.000 description 6
- 238000002347 injection Methods 0.000 description 6
- 239000007924 injection Substances 0.000 description 6
- BHPQYMZQTOCNFJ-UHFFFAOYSA-N Calcium cation Chemical compound [Ca+2] BHPQYMZQTOCNFJ-UHFFFAOYSA-N 0.000 description 4
- 229910001424 calcium ion Inorganic materials 0.000 description 4
- BVKZGUZCCUSVTD-UHFFFAOYSA-M Bicarbonate Chemical compound OC([O-])=O BVKZGUZCCUSVTD-UHFFFAOYSA-M 0.000 description 3
- 239000011575 calcium Substances 0.000 description 3
- 238000004519 manufacturing process Methods 0.000 description 3
- 238000012821 model calculation Methods 0.000 description 3
- 239000002244 precipitate Substances 0.000 description 3
- 238000004088 simulation Methods 0.000 description 3
- VTYYLEPIZMXCLO-UHFFFAOYSA-L Calcium carbonate Chemical compound [Ca+2].[O-]C([O-])=O VTYYLEPIZMXCLO-UHFFFAOYSA-L 0.000 description 2
- BVKZGUZCCUSVTD-UHFFFAOYSA-N carbonic acid Chemical compound OC(O)=O BVKZGUZCCUSVTD-UHFFFAOYSA-N 0.000 description 2
- 239000001095 magnesium carbonate Substances 0.000 description 2
- 229910000021 magnesium carbonate Inorganic materials 0.000 description 2
- 239000012071 phase Substances 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000033558 biomineral tissue development Effects 0.000 description 1
- 229910000019 calcium carbonate Inorganic materials 0.000 description 1
- 239000010779 crude oil Substances 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- 230000018109 developmental process Effects 0.000 description 1
- 229910017053 inorganic salt Inorganic materials 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- ZLNQQNXFFQJAID-UHFFFAOYSA-L magnesium carbonate Chemical compound [Mg+2].[O-]C([O-])=O ZLNQQNXFFQJAID-UHFFFAOYSA-L 0.000 description 1
- 230000035515 penetration Effects 0.000 description 1
- 230000036632 reaction speed Effects 0.000 description 1
- 239000013049 sediment Substances 0.000 description 1
- 239000007790 solid phase Substances 0.000 description 1
- 239000000243 solution Substances 0.000 description 1
- 238000004457 water analysis Methods 0.000 description 1
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- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
- E21B43/16—Enhanced recovery methods for obtaining hydrocarbons
- E21B43/164—Injecting CO2 or carbonated water
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Abstract
The invention belongs to the technical field of oil and gas field development, and provides a method for evaluating the influence of carbon dioxide flooding salt deposit on recovery ratio2On the basis of theoretical analysis and experimental research of salt scale deposition caused by flooding, a one-dimensional numerical model is established by using numerical simulation software to simulate CO of rock core2And (4) displacement experiment. Using a chemical reaction model, taking into account CO2Influence of salt deposit on the core during flooding. Continuously adjusting parameters in a numerical model, correcting by using an object model experiment result, and establishing CO suitable for researching a sample2The salt deposit one-dimensional model is used for analyzing the influence of the salt deposit on the final recovery ratio in the flooding process, so that whether the influence of the salt deposit needs to be considered or not in the subsequent recovery ratio prediction can be determined, the recovery ratio prediction is facilitated, and meanwhile, the prediction accuracy is improved。
Description
Technical Field
The invention belongs to the technical field of oil and gas field development, and particularly relates to a method for evaluating the influence of carbon dioxide flooding salt deposit on recovery ratio.
Background
In CO2During the displacement, CO is injected2Meets with formation water in the formation, and a small part of CO2React with water to form carbonic acid, but most of the CO2With CO in water2In molecular form, CO2Dissolving in the formation water to produce carbonic acid. CO 22Water solubility is much faster in water than in oil, but CO2The solubility in crude oil is 4-10 times that in water, so that CO dissolved in water2Can be converted into oil. CO 22The solubility in water becomes lower with increasing temperature and higher with increasing pressure. Meanwhile, the salt content in water is to CO2The solubility of (a) also affects the fact that the higher the salt content, the lower the solubility.
If the formation water itself contains high concentration of scale forming ions such as calcium ions and magnesium ions, along with CO2The injection of the method is to increase the concentration of carbonate and bicarbonate ions in formation water, the carbonate and bicarbonate ions react with calcium ions and magnesium ions to generate calcium carbonate and magnesium carbonate solid-phase deposition, and pore throats are blocked, so that the permeability of a reservoir is reduced, and the oil displacement effect of carbon dioxide is influenced.
Disclosure of Invention
The invention aims to provide a method for evaluating the influence of carbon dioxide flooding salt deposit on recovery ratio, and the method can be used for overcoming the technical problems in the prior art.
Therefore, the technical scheme provided by the invention is as follows:
a method for evaluating the influence of carbon dioxide flooding salt deposit precipitation on recovery ratio comprises the following steps:
step 1) collecting water samples of a plurality of oil wells of a target oil reservoir stratum, and analyzing to obtain scaling ion types and scaling ion content M;
step 2) carrying out interaction reaction experiments of carbon dioxide and formation water at different temperatures and different pressure differences to obtain the salt deposit amount generated by the carbon dioxide and the formation water, and establishing a relational expression of the temperature T, the pressure difference delta P, the content M of scale forming ions and the salt deposit amount;
step 3) obtaining salt deposit quantities corresponding to different pressure differences under the target oil reservoir temperature and the content of the scale forming ions according to the temperature T, the pressure difference delta P and the relation of the content M of the scale forming ions and the salt deposit quantity;
step 4) establishing a one-dimensional numerical model of the physical properties of the target oil reservoir and the properties of the formation fluid by using Eclipse software;
step 5) inputting different pressure differences into the one-dimensional numerical model, and obtaining salt scale precipitation amounts under different pressure differences according to a chemical reaction module in Eclipse software;
step 6) fitting the salt scale precipitation amount obtained in the experiment in the step 3) and the salt scale precipitation amount obtained by the one-dimensional numerical model in the step 5) to obtain a numerical model of carbon dioxide salt displacement salt scale precipitation, and judging that the numerical model of carbon dioxide salt displacement salt scale precipitation can be used for evaluating the recovery ratio of the target oil reservoir when the fitting degree is not less than 0.9;
step 7) calculating a salt deposit considering model and a salt deposit not considering model by using a numerical model of the carbon dioxide flooding salt deposit, respectively outputting a salt deposit considering recovery ratio curve and a salt deposit not considering recovery ratio curve, and then calculating the correlation of the two curves;
and 8) when the correlation degree of the two curves is not less than 0.9, indicating that the salt deposit has no influence on the recovery efficiency, and otherwise, indicating that the salt deposit has influence on the recovery efficiency.
The relationship among the temperature T, the pressure difference delta P, the content M of the scale forming ions and the precipitation amount of the salt scale in the step 2) is as follows:
y＝ae(bT+cΔp+dM)
wherein a, b, c and d are constants; t is temperature, DEG C; delta P is differential pressure, MPa; m is the content of scaling ions, mg/L.
The process of establishing the one-dimensional numerical model of the physical properties of the target oil reservoir and the properties of the formation fluid by using Eclipse software in the step 4) is as follows:
and inputting the average porosity, permeability, original oil saturation, original pressure and formation temperature of a target oil reservoir into Eclipse software to generate a one-dimensional numerical model.
The specific process for obtaining the salt deposit precipitation amount under different pressure differences according to the chemical reaction module in the Eclipse software in the step 5) is as follows:
(1) inputting initial chemical reaction rate constant, reactant carbon dioxide coefficient and product solid coefficient, determining chemical reaction rate by using chemical reaction module, and obtaining salt scale deposition M under different pressure differences1i；
(2) Adjusting the chemical reaction rate constant, the carbon dioxide coefficient of the reactant and the solid coefficient of the product, and obtaining the salt deposit precipitation M under different pressure differences by using the chemical reaction moduleni(ii) a n represents the number of adjustments and i represents the number of pressure differential sets.
When the salt deposit amount under different pressure differences is obtained according to a chemical reaction module in Eclipse software in the step 5), assuming that the fluid saturation comprises the solid saturation:
So+Sg+Sw+Ss＝1
in the formula, SOOil saturation without dimension; sgThe gas saturation is zero dimension; swThe water saturation is zero dimension; ssIs solid saturation without dimension.
The expression of the chemical reaction rate in step 5) is as follows:
Rr＝Vb·Ar·exp(-Er/RT)·Πcrinri
in the formula: vbIs the rock pore volume, m3；ArIs a chemical reaction rate constant without dimension; erAs reaction energykJ/kg-M; r is a gas constant and has no dimension; t is temperature, DEG C; n isriIs a component index, 0 or 1, the component reacts to 1, does not react to 0; criIs the saturation of the components in the reaction phase.
The specific process of the step 6) is as follows:
respectively comparing the salt scale precipitation amount obtained in the experiment in the step 3) with the salt scale precipitation amount M obtained by the one-dimensional numerical model in the step 5)1iAnd MniAnd fitting, and selecting the chemical reaction rate constant, the reactant carbon dioxide coefficient and the product solid coefficient corresponding to the maximum value with the fitting degree of more than 0.9 as input parameter values in the numerical model of the carbon dioxide salt-flooding scale deposition.
The initial chemical reaction rate constant and the carbon dioxide coefficient of the reactant are obtained through experiments.
The process of obtaining the salt scale precipitation amount under different pressure differences by utilizing the chemical reaction module is as follows:
before the reaction, the solid saturation S is containedsIs 0, oil saturation SOGas saturation SgAnd water saturation SwAre the original parameters of the target oil before being hidden in carbon dioxide flooding;
when reacting, the oil saturation S is changed by the pressure difference in the one-dimensional numerical modelOGas saturation SgAnd water saturation SwAll change and finally output the saturation S containing solidsAnd obtaining the salt deposit amount.
The invention has the beneficial effects that:
the method for evaluating the influence of the carbon dioxide flooding salt deposit on the recovery ratio provided by the invention fully combines the oil reservoir geological research result, and analyzes the influence of the carbon dioxide flooding salt deposit on the recovery ratio by combining theoretical analysis and experimental research and adopting numerical simulation calculation.
The invention is in the treatment of CO2On the basis of theoretical analysis and experimental research of salt scale deposition caused by flooding, a one-dimensional numerical model is established by using numerical simulation software to simulate CO of rock core2And (4) displacement experiment. Using a chemical reaction model, taking into account CO2In the driving processEffect of salt deposit on core. Continuously adjusting parameters in a numerical model, correcting by using an object model experiment result, and establishing CO suitable for researching a sample2And analyzing the influence of the salt scale deposition on the final recovery ratio by the one-dimensional model of the salt scale deposition in the flooding process, so that whether the influence of the salt scale deposition needs to be considered or not in the subsequent recovery ratio prediction can be determined, the recovery ratio prediction is facilitated, and meanwhile, the prediction accuracy is improved.
The following will be described in further detail with reference to the accompanying drawings.
Drawings
FIG. 1 is a graph comparing the results of salt scale precipitation model calculation with the results of experiment;
figure 2 is a plot of model calculations for salt scale-considered versus non-considered sediment recovery.
Detailed Description
The following description of the embodiments of the present invention is provided for illustrative purposes, and other advantages and effects of the present invention will become apparent to those skilled in the art from the present disclosure.
The exemplary embodiments of the present invention will now be described with reference to the accompanying drawings, however, the present invention may be embodied in many different forms and is not limited to the embodiments described herein, which are provided for complete and complete disclosure of the present invention and to fully convey the scope of the present invention to those skilled in the art. The terminology used in the exemplary embodiments illustrated in the accompanying drawings is not intended to be limiting of the invention.
Unless otherwise defined, terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Further, it will be understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense.
Example 1:
the embodiment provides a method for evaluating the influence of carbon dioxide flooding salt deposit on recovery ratio, which comprises the following steps:
step 1) collecting water samples of a plurality of oil wells of a target oil reservoir stratum, and analyzing to obtain scaling ion types and scaling ion content M;
step 2) carrying out interaction reaction experiments of carbon dioxide and formation water at different temperatures and different pressure differences to obtain the salt deposit amount generated by the carbon dioxide and the formation water, and establishing a relational expression of the temperature T, the pressure difference delta P, the content M of scale forming ions and the salt deposit amount;
step 3) obtaining salt deposit quantities corresponding to different pressure differences under the target oil reservoir temperature and the content of the scale forming ions according to the temperature T, the pressure difference delta P and the relation of the content M of the scale forming ions and the salt deposit quantity;
step 4) establishing a one-dimensional numerical model of the physical properties of the target oil reservoir and the properties of the formation fluid by using Eclipse software;
step 5) inputting different pressure differences into the one-dimensional numerical model, and obtaining salt scale precipitation amounts under different pressure differences according to a chemical reaction module in Eclipse software;
step 6) fitting the salt scale precipitation amount obtained in the experiment in the step 3) and the salt scale precipitation amount obtained by the one-dimensional numerical model in the step 5) to obtain a numerical model of carbon dioxide salt displacement salt scale precipitation, and judging that the numerical model of carbon dioxide salt displacement salt scale precipitation can be used for evaluating the recovery ratio of the target oil reservoir when the fitting degree is not less than 0.9;
step 7) calculating a salt deposit considering model and a salt deposit not considering model by using a numerical model of the carbon dioxide flooding salt deposit, respectively outputting a salt deposit considering recovery ratio curve and a salt deposit not considering recovery ratio curve, and then calculating the correlation of the two curves;
and 8) when the correlation degree of the two curves is not less than 0.9, indicating that the salt deposit has no influence on the recovery efficiency, and otherwise, indicating that the salt deposit has influence on the recovery efficiency.
The principle of the invention is as follows:
developing an experiment of salt scale precipitation generated by the reaction of carbon dioxide and formation water, establishing a one-dimensional numerical model based on experimental data, target reservoir physical properties and formation fluid properties, and simulating core CO by using numerical simulation software2Displacement experiment to evaluate the most carbon dioxide precipitation of salt scaleThe impact of the final recovery.
Because the carbon dioxide is injected into the stratum to displace oil, the injected carbon dioxide reacts with the stratum water to form carbonic acid solution after being dissolved in the stratum water, and H is dissociated+And HCO3 -、CO3 2-If the formation water itself contains high concentration of scale-forming ions such as calcium ions, magnesium ions, CO2The injection of the carbon dioxide and the formation water interaction experiment must be carried out to determine the relationship between the temperature, the pressure, the content of scale forming ions and the precipitation amount of salt scale.
Ca with initial formation water2+、Mg2+Is subtracted from Ca in the reacted liquid2+、Mg2+To obtain Ca of the formation water under different temperature and pressure conditions2+、Mg2+The amount of change in the concentration of (A) is calculated from the molecular weight of the precipitate3、MgCO3The quality of the precipitate.
Example 2:
on the basis of example 1, this example provides a method for evaluating the influence of carbon dioxide flooding salt scale deposition on recovery ratio, and the relationship between the temperature T, the pressure difference Δ P and the content M of scale forming ions in step 2) and the deposition amount of salt scale is as follows:
y＝ae(bT+cΔp+dM)
wherein a, b, c and d are constants; t is temperature, DEG C; delta P is differential pressure, MPa; m is the content of scaling ions, mg/L.
According to the embodiment, a salt deposit precipitation calculation expression after the carbon dioxide acts on the formation water is established according to experimental data. The precipitation amount of salt scale is in exponential relation with temperature, pressure difference and content of scale forming ions. Four groups of data are substituted in the formula, and four constant values of a, b, c and d can be obtained.
Example 3:
on the basis of the example 1, the embodiment provides a method for evaluating the influence of carbon dioxide flooding salt deposit precipitation on the recovery ratio, and the process of establishing a one-dimensional numerical model of the target reservoir physical property and the formation fluid property by using Eclipse software in the step 4) is as follows:
and inputting the average porosity, permeability, original oil saturation, original pressure and formation temperature of a target oil reservoir into Eclipse software to generate a one-dimensional numerical model.
As shown in table 3, the parameters are input by Eclipse software, and then a one-dimensional numerical model is automatically generated.
Example 4:
on the basis of example 1, this example provides a method for evaluating the influence of carbon dioxide flooding salt deposit on recovery ratio, and the specific process of obtaining the salt deposit amount under different pressure differences according to the chemical reaction module in Eclipse software in step 5) is as follows:
(1) inputting initial chemical reaction rate constant, reactant carbon dioxide coefficient and product solid coefficient, determining chemical reaction rate by using chemical reaction module, and obtaining salt scale deposition M under different pressure differences1i；
(2) Adjusting the chemical reaction rate constant, the carbon dioxide coefficient of the reactant and the solid coefficient of the product, and obtaining the salt deposit precipitation M under different pressure differences by using the chemical reaction moduleni(ii) a n represents the number of adjustments and i represents the number of pressure differential sets.
Wherein, the initial chemical reaction rate constant and the carbon dioxide coefficient of the reactant are obtained through experiments.
Using chemical reaction modules, taking into account CO2Influence of salt deposit on the core during flooding. Continuously adjusting parameters (chemical reaction rate constant and reactant carbon dioxide coefficient) in the numerical model, correcting by using the experimental result of the physical model, and establishing CO suitable for researching samples2And (3) a one-dimensional model of salt scale deposition in the flooding process (a numerical model of salt scale deposition in carbon dioxide flooding).
Example 5:
on the basis of example 1, this example provides a method for evaluating the effect of carbon dioxide flooding salt deposit on recovery efficiency, and when salt deposit precipitation amounts under different pressure differences are obtained according to a chemical reaction module in Eclipse software in step 5), the assumed fluid saturation comprises the solid saturation:
So+Sg+Sw+Ss＝1
in the formula, SOOil saturation without dimension; sgThe gas saturation is zero dimension; swThe water saturation is zero dimension; ssIs solid saturation without dimension.
According to the invention, the solid-containing saturation is introduced, and the solid saturation is set to be 0 in the initial stage of the model, so that after different pressure differences are input, the solid saturation is finally output after the model calculation, and the salt scale precipitation amount is obtained.
Example 6:
on the basis of example 4, this example provides a method for evaluating the effect of carbon dioxide flooding salt deposit on recovery efficiency, and the expression of the chemical reaction rate is as follows:
Rr＝Vb·Ar·exp(-Er/RT)·Πcrinri
in the formula: vbIs the rock pore volume, m3；ArReaction rate constant, dimensionless; erkJ/kg-M is reaction energy; r is a gas constant and has no dimension; t is temperature, DEG C; n isriIs a component index, 0 or 1, the component reacts to 1, does not react to 0; criIs the saturation of the components in the reaction phase.
The chemical reaction equation is realized by adjusting the chemical reaction coefficient of the reactant and the product.
Chemical reaction equation:
∑(SRri·Ci)→∑(SPri·Ci)
in the formula: sRriAs a reactant CiThe reaction coefficient of (3) is dimensionless; sPriTo produce a product CiThe reaction coefficient of (a) is dimensionless.
Example 7:
on the basis of example 4, this example provides a method for evaluating the effect of carbon dioxide flooding salt deposit on recovery efficiency, and the specific process of step 6) is as follows:
respectively comparing the salt scale precipitation amount obtained in the experiment in the step 3) with the salt scale precipitation amount M obtained by the one-dimensional numerical model in the step 5)1iAnd MniAnd fitting, and selecting the chemical reaction rate constant, the reactant carbon dioxide coefficient and the product solid coefficient corresponding to the maximum value with the fitting degree of more than 0.9 as input parameter values in the numerical model of the carbon dioxide salt-flooding scale deposition.
The carbon dioxide salt deposit displacement model needs to be capable of accurately representing the generation of salt deposit after the target oil reservoir is injected with carbon dioxide, mainly needs to calculate the deposition amount under different pressures, and fits the calculation result with the interaction experiment result of carbon dioxide and formation water. The fitting parameters mainly comprise a chemical reaction rate constant, a reactant carbon dioxide coefficient and a product solid coefficient.
Example 8:
on the basis of example 5, this example provides a method for evaluating the influence of carbon dioxide flooding salt scale deposition on recovery ratio, and the process of obtaining the salt scale deposition amount under different pressure differences by using the chemical reaction module is as follows:
before the reaction, the solid saturation S is containedsIs 0, oil saturation SOGas saturation SgAnd water saturation SwAre the original parameters of the target oil before being hidden in carbon dioxide flooding;
when reacting, the oil saturation S is changed by the pressure difference in the one-dimensional numerical modelOGas saturation SgAnd water saturation SwAll change and finally output the saturation S containing solidsAnd obtaining the salt deposit amount.
Example 9:
based on example 1, this example will explain the present invention in detail by taking a certain reservoir as an example, and the steps are as follows:
step 1) formation water analysis: and collecting a target oil reservoir stratum water sample, and analyzing the types and the content of scale forming ions. See table 1.
TABLE 1 ion analysis table for formation water scaling
| Ion species | 1 well ion content mg/L | 2 well ion content mg/L | 3 well ion content mg/L |
| Mg2+ | 132 | 34.8 | 241.2 |
| Ca2+ | 450 | 333 | 2650 |
| Ba2+ | 0.006 | 0.057 | 0.028 |
| Sr2+ | 19.4 | 25.4 | 18.8 |
| Total degree of mineralization | 5880 | 8900 | 16900 |
Step 2) interaction experiment of carbon dioxide and formation water
Measuring the same CO at different temperatures and pressures of a formation water sample2And (4) the amount of salt scale deposition under the injection amount. See table 2.
TABLE 2 sample reaction results Table
| Temperature (. degree.C.) | Pressure difference (MPa) | Amount of precipitate (mg/L) |
| 80 | 16 | 639 |
| 80 | 12 | 494 |
| 80 | 8 | 90 |
| 80 | 5 | 60 |
| 50 | 16 | 712 |
| 30 | 16 | 799 |
| 20 | 16 | 836 |
The inorganic salt precipitation amount has an exponential relation with temperature, pressure difference and scaling ion content, and a salt scale precipitation amount calculation expression after the carbon dioxide and formation water act is established according to experimental data.
y＝151.7967e(-0.03016T+0.059643Δp+0.000106M)
Wherein T is temperature, DEG C; delta P is differential pressure, MPa; m is the content of scaling ions, mg/L.
Step 3) calculating the salt deposit precipitation of the target oil reservoir
Calculating the salt deposit precipitation amount corresponding to different pressures under the conditions that the target oil reservoir temperature is 80 ℃ and the content of scale forming ions is 2900mg/L according to the relational expression generated in the step 2).
Step 4) establishing a one-dimensional numerical model of the physical properties of the target oil reservoir and the properties of the formation fluid by using Eclipse software;
inputting parameters such as average porosity, permeability, original oil saturation, original pressure, formation temperature and the like of the target oil reservoir to generate a one-dimensional numerical model, which is shown in table 3.
TABLE 3 one-dimensional numerical model base parameters
| Parameter name | Parameter value |
| Number of cells | 50*50*5 |
| Grid spacing | 30m |
| Simulation time | 50 years |
| Component type | |
| 8*SOLID | |
| Average porosity | 0.12 |
| Permeability rate of penetration | 0.28mD |
| Original oil saturation | 58％ |
| Original pressure | 15.8MPa |
| Formation temperature | 80℃ |
Step 5) establishing a numerical model of carbon dioxide salt-flooding scale deposition
And (3) adjusting a chemical reaction speed constant, a reactant carbon dioxide coefficient and a product solid coefficient (see table 4) by using a chemical reaction module, and fitting numerical simulation to calculate the salt deposit precipitation amount under different pressures and the experimental data of the step 3).
TABLE 4 carbon dioxide flooding salt scale precipitation model parameters
| Parameter name | Parameter value |
| Number of gas injection wells | 1 mouth |
| Number of production wells | 8-port |
| Type of injection and production | Reverse nine points |
| Gas injection well | 2500m3/d |
| Production well | 10MPa |
| Number of chemical reactions | 1 is provided with |
| Rate constant of chemical reaction | 1.2×10-5 |
| Reactant CO2Coefficient of performance | 95 |
| Product solid coefficient | 1 |
As shown in figure 1, the experimental data are consistent with the digital-analog calculation results, which shows that the model established in the step 5) can quantitatively and accurately represent the carbon dioxide flooding salt deposit, so that the model can be used for obtaining a recovery factor curve.
Step 6) influence of carbon dioxide flooding salt scale precipitation on recovery ratio:
and 5) outputting a recovery factor curve under the condition of considering the salt scale deposition and not considering the salt scale deposition by using the model established in the step 5), and evaluating the influence of the salt scale deposition on the recovery factor.
See fig. 2. According to the calculation of example data, the correlation degree between the recovery curve of the salt scale considered and the recovery curve of the salt scale not considered reaches 0.9999, which shows that the influence of the salt scale on the recovery efficiency is small, and the precipitation amount of the salt scale does not need to be calculated in the recovery efficiency prediction.
The above examples are merely illustrative of the present invention and should not be construed as limiting the scope of the invention, which is intended to be covered by the claims and any design similar or equivalent to the scope of the invention.
Claims (9)
1. A method for evaluating the influence of carbon dioxide flooding salt deposit on recovery ratio is characterized by comprising the following steps:
step 1) collecting water samples of a plurality of oil wells of a target oil reservoir stratum, and analyzing to obtain scaling ion types and scaling ion content M;
step 2) carrying out interaction reaction experiments of carbon dioxide and formation water at different temperatures and different pressure differences to obtain the salt deposit amount generated by the carbon dioxide and the formation water, and establishing a relational expression of the temperature T, the pressure difference delta P, the content M of scale forming ions and the salt deposit amount;
step 3) obtaining salt deposit quantities corresponding to different pressure differences under the target oil reservoir temperature and the content of the scale forming ions according to the temperature T, the pressure difference delta P and the relation of the content M of the scale forming ions and the salt deposit quantity;
step 4) establishing a one-dimensional numerical model of the physical properties of the target oil reservoir and the properties of the formation fluid by using Eclipse software;
step 5) inputting different pressure differences into the one-dimensional numerical model, and obtaining salt scale precipitation amounts under different pressure differences according to a chemical reaction module in Eclipse software;
step 6) fitting the salt scale precipitation amount obtained in the experiment in the step 3) and the salt scale precipitation amount obtained by the one-dimensional numerical model in the step 5) to obtain a numerical model of carbon dioxide salt displacement salt scale precipitation, and judging that the numerical model of carbon dioxide salt displacement salt scale precipitation can be used for evaluating the recovery ratio of the target oil reservoir when the fitting degree is not less than 0.9;
step 7) calculating a salt deposit considering model and a salt deposit not considering model by using a numerical model of the carbon dioxide flooding salt deposit, respectively outputting a salt deposit considering recovery ratio curve and a salt deposit not considering recovery ratio curve, and then calculating the correlation of the two curves;
and 8) when the correlation degree of the two curves is not less than 0.9, indicating that the salt deposit has no influence on the recovery efficiency, and otherwise, indicating that the salt deposit has influence on the recovery efficiency.
2. The method for evaluating the effect of carbon dioxide on the recovery ratio of salt scale displacement according to claim 1, wherein the relationship among the temperature T, the pressure difference Δ P, the content M of scale forming ions and the amount of salt scale deposition in step 2) is as follows:
y＝ae(bT+cΔp+dM)
wherein a, b, c and d are constants; t is temperature, DEG C; delta P is differential pressure, MPa; m is the content of scaling ions, mg/L.
3. The method for evaluating the effect of carbon dioxide flooding salt scale deposition on recovery factor according to claim 1, wherein the Eclipse software is applied in the step 4) to establish a one-dimensional numerical model of the target reservoir properties and the formation fluid properties as follows:
and inputting the average porosity, permeability, original oil saturation, original pressure and formation temperature of a target oil reservoir into Eclipse software to generate a one-dimensional numerical model.
4. The method for evaluating the influence of carbon dioxide-driven salt scale deposition on the recovery ratio according to claim 1, wherein the specific process for obtaining the salt scale deposition amount under different pressure differences according to the chemical reaction module in Eclipse software in the step 5) is as follows:
(1) inputting initial chemical reaction rate constant and reactant carbon dioxideCoefficient and resultant solid coefficient, determining chemical reaction rate by chemical reaction module, and obtaining salt deposit amount M under different pressure differences1i；
(2) Adjusting the chemical reaction rate constant, the carbon dioxide coefficient of the reactant and the solid coefficient of the product, and obtaining the salt deposit precipitation M under different pressure differences by using the chemical reaction moduleni(ii) a n represents the number of adjustments and i represents the number of pressure differential sets.
5. The method for evaluating the effect of carbon dioxide flooding salt deposit on recovery efficiency according to claim 1, wherein in the step 5), when the deposition amount of the salt deposit under different pressure differences is obtained according to a chemical reaction module in Eclipse software, the assumed fluid saturation comprises the solid saturation:
So+Sg+Sw+Ss＝1
in the formula, SOOil saturation without dimension; sgThe gas saturation is zero dimension; swThe water saturation is zero dimension; ssIs solid saturation without dimension.
6. The method of claim 4, wherein the evaluation of the effect of carbon dioxide flooding salt scale precipitation on recovery factor comprises: the chemical reaction rate is expressed as follows:
Rr＝Vb·Ar·exp(-Er/RT)·∏crinri
in the formula: vbIs the rock pore volume, m3；ArIs a chemical reaction rate constant without dimension; erkJ/kg-M is reaction energy; r is a gas constant and has no dimension; t is temperature, DEG C; n isriIs a component index, 0 or 1, the component reacts to 1, does not react to 0; criIs the saturation of the components in the reaction phase.
7. The method for evaluating the effect of carbon dioxide flooding salt deposit on the recovery factor according to claim 4, wherein the concrete process of the step 6) is as follows:
respectively comparing the salt scale precipitation amount obtained in the experiment in the step 3) with the salt scale precipitation amount M obtained by the one-dimensional numerical model in the step 5)1iAnd MniAnd fitting, and selecting the chemical reaction rate constant, the reactant carbon dioxide coefficient and the product solid coefficient corresponding to the maximum value with the fitting degree of more than 0.9 as input parameter values in the numerical model of the carbon dioxide salt-flooding scale deposition.
8. The method of claim 4, wherein the evaluation of the effect of carbon dioxide flooding salt scale precipitation on recovery factor comprises: the initial chemical reaction rate constant and the carbon dioxide coefficient of the reactant are obtained through experiments.
9. The method for evaluating the effect of carbon dioxide on the recovery ratio of salt scale displacement according to claim 5, wherein the precipitation of salt scale under different pressure differences is obtained by using the chemical reaction module according to the following steps:
before the reaction, the solid saturation S is containedsIs 0, oil saturation SOGas saturation SgAnd water saturation SwAre the original parameters of the target oil before being hidden in carbon dioxide flooding;
when reacting, the oil saturation S is changed by the pressure difference in the one-dimensional numerical modelOGas saturation SgAnd water saturation SwAll change and finally output the saturation S containing solidsAnd obtaining the salt deposit amount.
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