CN111205836A - Preparation method and degradation prediction method of recyclable high-density liquid rubber plug - Google Patents
Preparation method and degradation prediction method of recyclable high-density liquid rubber plug Download PDFInfo
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Abstract
The invention provides a preparation method and a degradation prediction method of a recyclable high-density liquid rubber plug, and relates to the field of oil gas chemical industry. A recyclable high-density liquid rubber plug is mainly prepared by the following components in percentage by mass through a cross-linking reaction: 30-90% of weighting agent, 0.01-0.03% of stabilizing agent, 0.2-0.6% of reinforcing material, 1.5-2.0% of polymer and 0.5-0.6% of cross-linking agent, wherein the ratio of the polymer to the cross-linking agent is 3: 1, and the balance of water. The preparation of the recyclable high-density liquid rubber plug adopts the raw materials, and the density is 1.2-1.5g/cm3The method has the advantages of good pumping performance, temperature resistance, no need of gel breaking, high-efficiency circulating flowback and the like. The degradation time of different rubber plug systems under different temperature conditions is predicted by establishing a degradation prediction linear regression equation model of the recyclable high-density liquid rubber plugThe guiding and flowback process ensures the safety, effectiveness and smoothness of the well completion and workover operation of the oil and gas well.
Description
Technical Field
The invention relates to the field of oil gas chemical industry, in particular to a preparation method and a degradation prediction method of a recyclable high-density liquid rubber plug.
Background
With the increasing of oil and gas wells such as deep wells, ultra-deep wells, unconventional wells, high temperature and high pressure wells, most wells have the problems of corrosion damage of underground pipe columns and well head devices, scaling of oil pipes, buckling of pipe columns, deformation, fracture and the like, and well repair operation is needed.
Most areas have high pressure coefficient, and high-density well killing fluid is needed for well killing during well repairing. The density of conventional organic salt and inorganic salt well killing fluid is low, and the heavy weight of barite and iron ore powder has the problems of poor settling stability, great damage to stratum and the like.
The temporary blocking kill plug technology is that a high-strength visco-elastic plug is formed in a shaft by utilizing the principle that a high-concentration polymer solution is crosslinked in the shaft, so that kill fluid is isolated from a producing zone, the kill fluid is prevented from leaking into a stratum, the pressure of a well mouth is greatly reduced, and the safety of subsequent pressurized workover operation is guaranteed.
However, the existing 'liquid rubber plug' generally has the problems of short rubber plug slow crosslinking time (several minutes), difficult pump injection (high initial viscosity) or alternative injection of a thickening agent and a crosslinking agent, complex process, poor high temperature resistance of the rubber plug, rubber breaking, unpredictable degradation time, difficult flowback and the like, and particularly, the prior crosslinking is easily caused by field application, so that the pump injection friction resistance is high, and even the pump injection into a target position is difficult.
Disclosure of Invention
The invention aims to provide a recyclable high-density liquid rubber plug which has the advantages of adjustable flowing property after gelling, adjustable density, temperature resistance, good pumping property, good stability, no need of rubber breaking, recyclability and the like.
Another objective of the present invention is to provide a method for preparing a recyclable high-density liquid rubber plug, which is intended to prepare the recyclable high-density liquid rubber plug.
The third purpose of the invention is to provide a method for predicting the degradation time of the recyclable high-density liquid rubber plug, aiming at reflecting the degradation rule and determining the reasonable flowback time.
In order to achieve the purpose, the invention adopts the following technical scheme:
the invention provides a recyclable high-density liquid rubber plug which is mainly prepared from the following components in percentage by mass through a crosslinking reaction: 30-90% of weighting agent, 0.01-0.03% of stabilizing agent, 0.2-0.6% of reinforcing material, 1.5-2.0% of polymer and 0.5-0.6% of cross-linking agent, wherein the ratio of the polymer to the cross-linking agent is 3: 1, and the balance of water.
The polymer can be one or more of polyacrylamide, acrylamide, tert-butyl acrylate copolymer, xanthan gum and guar gum. The weighting agent may be potassium formateOr one or more of sodium bromide, the density range of the rubber plug formed after the rubber plug is weighted is 1.2g/cm3-1.5g/cm3. The stabilizer can be one or more of thiourea and sodium sulfite. The reinforcing material may be one or more of hectorite, bentonite, montmorillonite, graphite powder, and sodium alginate. The cross-linking agent can be one or more of polyethyleneimine, aluminum citrate, orthoboric acid, formaldehyde, triethylene tetramine, dimethylaminopropylamine, resorcinol and phenolic resin.
The invention also provides a preparation method of the recyclable high-density liquid rubber plug, which comprises the following steps:
preparing high-density base liquid by using weighting agent, sequentially adding stabilizing agent, reinforcing material, polymer and cross-linking agent into the high-density base liquid according to the weight portion ratio, and uniformly stirring.
The invention also provides a method for predicting the degradation time, which comprises the temperature resistance test of the thermal analyzer for the recyclable high-density liquid rubber plug and the formula derivation for predicting the degradation time.
The preparation method of the recyclable high-density liquid rubber plug and the degradation prediction method thereof have the beneficial effects that: the recyclable high-density liquid rubber plug system adopts a polymerization crosslinking and intercalation filling technology, and the weighting agent ensures that the density of the rubber plug is improved while the performance of the rubber plug is not influenced, so that the aim of matching with high-density well killing fluid is fulfilled; the reinforcing material is filled in the polymer branched chain structure, so that the thermal salt stability is ensured; the stabilizer ensures the stable performance of the rubber plug at high temperature; the cross-linking agent promotes formation of the plug at high temperatures.
The recyclable high-density liquid rubber plug provided by the invention still has fluidity after being gelatinized, and can be converted into brittleness from viscoelasticity under certain temperature and time conditions to form a mixture of water and brittle particles, so that the recyclable high-density liquid rubber plug is favorable for recycling. Meanwhile, the composite material has the advantages of adjustable density, temperature resistance, pressure resistance, good pumping performance, good stability, no need of a gel breaking process, recyclability and the like. In the process of pressurized workover operation, the problems of corrosion damage of underground pipe columns and wellhead devices, scaling of oil pipes, buckling of pipe columns, deformation, fracture and the like in most wells can be effectively avoided.
The invention provides a preparation method of a recyclable high-density liquid rubber plug, which adopts the weighting agent, the stabilizing agent, the reinforcing material, the polymer, the cross-linking agent and water as raw materials, has small consumption of the raw materials, basically adopts a one-pot method as a preparation method, is remarkable in that the cross-linking agent needs to be diluted in advance, and has the advantages of simple preparation, low cost and the like. In addition, the change of the clear water volume after weighting is also considered, and a liquid volume change rule table of adding different parts of weighting agents is summarized, so that the field preparation can be guided.
The invention provides a method for predicting the degradation time of a recyclable high-density liquid rubber plug. Because the rubber plug has the characteristics of natural degradation and no need of rubber breaking, the hidden troubles of cost increase and incomplete chemical rubber breaking caused by mechanical rubber breaking are avoided. The degradation time prediction method reflects the change of the degradation rule of the rubber plug, can predict reasonable flowback time at different oil reservoir temperatures, and ensures safe, effective and smooth operation.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the embodiments will be briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present invention and therefore should not be considered as limiting the scope, and for those skilled in the art, other related drawings can be obtained according to the drawings without inventive efforts.
FIG. 1 shows the initial viscosity profiles of examples 1, 2, 3, 4, 5 of the present invention.
FIG. 2 shows the viscous modulus of inventive examples 1, 2, 3, 4, 5 after 11 hours of aging at 160 ℃.
FIG. 3 shows the modulus of elasticity after aging at 160 ℃ for 11 hours for inventive examples 1, 2, 3, 4, 5.
Figure 4 shows a DSC curve comparison with a recyclable high density plug as provided in example 1 of the present invention.
Figure 5 shows DSC plots of recyclable high density plugs provided in example 2 of the present invention.
Figure 6 shows DSC plots for recyclable high density plugs provided in example 3 of the present invention.
Figure 7 shows DSC plots for recyclable high density plugs provided in example 4 of the present invention.
Figure 8 shows DSC plots for recyclable high density plugs as provided in example 5 of the present invention.
Detailed Description
In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and perfectly described below. The examples, in which specific conditions are not specified, were conducted under conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products available commercially.
The following is a detailed description of the method for preparing the recyclable high-density liquid rubber plug and predicting the degradation of the recyclable high-density liquid rubber plug according to the embodiment of the invention.
A recyclable high-density liquid rubber plug is mainly prepared by the following components in percentage by mass through a cross-linking reaction: 30-90% of weighting agent, 0.01-0.03% of stabilizing agent, 0.2-0.6% of reinforcing material, 1.5-2.0% of polymer and 0.5-0.6% of cross-linking agent, wherein the ratio of the polymer to the cross-linking agent is 3: 1, and the balance of water.
In order to ensure that the rubber plug is flowable and easy to circulate and return and has excellent temporary plugging performance, further preferably, the recyclable high-density liquid rubber plug is mainly prepared from the following components in percentage by mass through a crosslinking reaction: 36-90% of weighting agent, 0.02-0.03% of stabilizing agent, 0.2-0.4% of reinforcing material, 1.5-1.8% of polymer and 0.5-0.6% of cross-linking agent, wherein the ratio of the polymer to the cross-linking agent is 3: 1, and the balance of water.
The polymer can be one or more of polyacrylamide, tert-butyl acrylate copolymer, xanthan gum and guar gum. The weighting agent can be one or more of potassium formate or sodium bromide, and the density range of the rubber plug formed after weighting is 1.2g/cm3-1.5g/cm3. The stabilizer can be one or more of thiourea and sodium sulfite. The reinforcing material may be one or more of hectorite, bentonite, montmorillonite, graphite powder, and sodium alginate. The cross-linking agent can be one or more of polyethyleneimine, aluminum citrate, orthoboric acid, formaldehyde, triethylene tetramine, dimethylaminopropylamine, resorcinol and phenolic resin.
Preferably, in a preferred embodiment of the present invention, the polymer may be one or more of polyacrylamide, xanthan gum, guar gum, etc., wherein the polyacrylamide is a dendrimer, and the main chain and the branch chain comprise hydrophilic groups and amide groups, carboxyl groups, aldehyde groups, sulfonic acid groups, tert-butyl ester groups, etc. with a cross-linking structure; the weighting agent can be one or more of sodium bromide or potassium formate; the stabilizer is thiourea; the reinforcing material is one or more of hectorite, montmorillonite and sodium alginate; the cross-linking agent is one or more of polyethyleneimine, formaldehyde, triethylenetetramine and resorcinol.
The invention also provides a preparation method of the recyclable high-density liquid rubber plug. Specifically, the weighting agent is used for preparing a high-density base solution, the stabilizer, the reinforcing material, the polymer and the cross-linking agent are sequentially added into the high-density base solution according to the weight part ratio, the mixture is uniformly stirred, and the cross-linking agent needs to be diluted in advance. Detailed formulation methods are shown in the examples below.
The invention also provides a method for predicting the degradation time of the recyclable high-density liquid rubber plug. At present, thermogravimetric analyzer (TG) and Differential Scanning Calorimetry (DSC) are generally adopted for predicting degradation time, Arrhenius is used for calculating activation energy, and time required by different reaction degrees is deduced reversely, but most of materials are solid according to the method, the inventor thinks that high-water-content materials are easy to evaporate, most of crucibles tested by the thermogravimetric analyzer are open or small holes are punched on cover plates, and aging tanks in aging experiments are almost absolutely sealed, so that the error between a prediction formula deduced according to a thermodynamic method and an actual aging experiment is overlarge, and for materials with high water content, such as the recyclable high-density liquid rubber plugs, fitting an aging experiment data point derivation empirical formula is more appropriate.
Further, the recyclable high-density liquid plug is converted from viscoelastic to brittle and becomes a mixture of water and brittle particles, which is believed that the plug can easily flow back in this state.
Further, the time required for the recyclable high-density liquid rubber plug to change from the viscoelastic body to the water and the brittle particles under different temperature conditions is counted. It should be noted that to make the data more accurate, the experiment was repeated several times, every 1 hour on day 5.
Further, considering that the logarithm of the degradation time and the reciprocal of the temperature have a certain linear relationship, the linear regression equation for predicting the degradation time is:
in the formula (1), t is the time required for the recyclable high-density rubber plug to be converted into the mixture of the brittle fragments and the water from the viscoelastic body under different temperature conditions, and is unit: hours (h); t is the aging temperature, unit: kelvin (K); a and b are the equation constants.
In the present invention, the gel strength determination method is based on the visual code table of GelStrength Codes (GSC for short) for gel strength of Sydansk et al (1988), as shown in Table 1. All gel strength ratings in the present invention were determined according to the data provided in table 1.
Table 1 gel strength visual code standard
In the preparation of a recyclable high density liquid rubber plug, the weighting agent ratios are performed according to table 2.
Table 2 weighting agent dosage table (in 100ml of clear water).
| Density (g/cm)3) | Adding sodium bromide in weight (g) | Weighted post volume/weighted pre volume |
| 1.2 | 36 | 1.08 |
| 1.3 | 54 | 1.33 |
| 1.4 | 70 | 1.42 |
| 1.5 | 90 | 1.50 |
The characteristics, properties and prediction of degradation time of the present invention are further described in detail with reference to the following examples.
Example 1
The experimental example provides preparation of a recyclable conventional density liquid rubber plug, the density of which is 1.0g/cm3For purposes of comparison with other examples.
Sequentially adding the stabilizer, the reinforcing material and the polymer into clear water, stirring for 2-4h to form a uniform solution, then adding the diluted cross-linking agent, and fully stirring and dissolving to obtain the initial solution of the liquid rubber plug with the circulated conventional density. Wherein, the system formula is as follows: 0.02% of thiourea, 0.2% of a mixture of hectorite and montmorillonite (mass ratio of 4: 1) + 1.5% of a mixture of polyacrylamide and xanthan gum (mass ratio of 14: 1) + 0.5% of a mixture of polyethyleneimine, formaldehyde and resorcinol (mass ratio of 8: 1: 1), the balance being water, the density being 1.0g/cm3 Total volume 100 ml.
Example 2
This experimental example provides a recyclable high-density liquid adhesivePreparation of plugs and prediction method of degradation with density of 1.2g/cm3。
Adding a weighting agent into clear water, uniformly stirring, then adding a stabilizing agent, a reinforcing material and a polymer, stirring for 2-4h to form a uniform solution, then adding a diluted cross-linking agent, and fully stirring and dissolving to obtain the initial solution of the recyclable high-density liquid rubber plug. Wherein, the system formula is as follows: 36% of a mixture of sodium bromide and potassium formate (mass ratio of 5: 1) + 0.02% of thiourea + 0.2% of a mixture of hectorite and montmorillonite (mass ratio of 7: 1) + 1.5% of a mixture of polyacrylamide and xanthan gum (mass ratio of 13: 2) + 0.5% of a mixture of polyethyleneimine, formaldehyde and resorcinol (mass ratio of 3: 1: 1), the balance being water, the density being 1.2g/cm3 Total volume 100 ml.
And pouring the prepared initial solution of the recyclable high-density liquid rubber plug system into a six-turn rotational viscometer to perform initial viscosity test.
As can be seen by comparing FIGS. 1 and 2, the system of example 2 rapidly reduced the initial viscosity of the recyclable plug from 2400mPa.s to 936.6mPa.s and increased the density to 1.2g/cm3And the injection property is ensured.
Pouring the prepared initial solution of the recyclable high-density liquid rubber plug system into an aging tank, sealing and respectively putting into ovens at 140 ℃, 150 ℃ and 160 ℃, and inspecting the gelling condition and the degradation condition of the system. The specific gelling is shown in Table 3.
Table 3 example 2 gel formation
Through the gelling test, the recyclable high-density rubber plug obtained in the example 2 has gelling time of 8-11 hours and final setting strength of H grade.
The high density recyclable liquid rubber plug aged at 160 ℃ for 11 hours was dropped into a HAAKERS model 600 rheometer for viscoelasticity testing.
As can be seen by comparing example 1 and example 2 in FIG. 2, the viscous modulus of the rubber plug of the system of example 1 is 19.6 to 28.6Pa, and the viscous modulus of the rubber plug of the system of example 2 is reduced to 10.0 to 14.7 Pa.
As can be seen from the comparison of examples 1 and 2 in FIG. 3, the elastic modulus of the rubber plug in the system of example 1 is 4.74-15.1Pa, and the elastic modulus of the rubber plug in the system of example 2 is increased to 28-38.1 Pa.
Compared with the figures 2 and 3, the rubber plug of the system in the embodiment 1 has high viscosity and low elasticity, mainly viscosity and poor cyclability, and the rubber plug of the system in the embodiment 2 has high elasticity and low viscosity, mainly elasticity, so that the reservoir protection effect and the stratum pressure-bearing capacity of the rubber plug are improved.
Through degradation tests, the recyclable high-density rubber plug obtained in example 2 hardly undergoes dehydration in the early stage of degradation, is aged for a certain time, and is converted from a viscoelastic body into a mixture of brittle fragments and water. The statistical time required for the high density plug to reach this state at different temperatures is given by the following data points: (T, T) ═ 140 ℃, 154h), (150 ℃, 135h), (160 ℃, 118h) is substituted into equation (1) to derive the degradation time prediction equation:
the correlation coefficient R of the formula (2) is in the range of 140-160 DEG C20.99 has an excellent linear relationship, predicting the maximum error in degradation time: and +/-0.95 h.
Comparing fig. 4 and fig. 5, in the DSC test, the rubber plug of the system of example 1 has only one degradation process and the decomposition temperature is 109 ℃. The system rubber plug of the embodiment 2 has two degradation processes, the decomposition temperatures are 109 ℃ and 127.4 ℃, and the temperature resistance is improved.
Example 3
The experimental example provides preparation and degradation prediction of a recyclable high-density liquid rubber plug, and the density is 1.3g/cm3。
Adding a weighting agent into clear water, uniformly stirring, then adding a stabilizing agent, a reinforcing material and a polymer, stirring for 2-4h to form a uniform solution, then adding a diluted cross-linking agent, and fully stirring and dissolving to obtain the initial solution of the recyclable high-density liquid rubber plug. Wherein, the system formula is as follows: 54% of a mixture of sodium bromide and potassium formate (9: 1 by mass) + 0.03% of thiourea, 0.4% of laponite and sodium alginateThe mixture (mass ratio is 3: 1) + 1.5% polyacrylamide and guar gum mixture (mass ratio is 13: 2) + 0.5% polyethyleneimine and triethylenetetramine mixture (mass ratio is 9: 1), the balance is water, and the density is 1.2g/cm3 Total volume 100 ml.
And pouring the prepared initial solution of the recyclable high-density liquid rubber plug system into a six-turn rotational viscometer to perform initial viscosity test.
As can be seen by comparing FIGS. 1 and 3, the system of example 3 rapidly reduced the initial viscosity of the recyclable plug from 2400mPa.s to 920.6mPa.s and increased the density to 1.3g/cm3And the injectability is ensured, and compared with example 2 and example 3, the formula of example 3 is better in viscosity reduction.
Pouring the prepared initial solution of the recyclable high-density liquid rubber plug system into an aging tank, sealing and respectively putting into ovens at 140 ℃, 150 ℃ and 160 ℃, and inspecting the gelling condition and the degradation condition of the system. The specific gelling conditions are shown in Table 4.
Table 4 example 3 gel formation
Through the gelling test, the recyclable high-density rubber plug obtained in example 3 has gelling time of 8-11 hours and final setting strength of H grade.
The high density recyclable liquid rubber plug aged at 160 ℃ for 11 hours was dropped into a HAAKERS model 600 rheometer for viscoelasticity testing.
As can be seen by comparing examples 1 and 3 in FIG. 2, the viscous modulus of the plug in the system of example 1 is between 19.6 Pa and 28.6Pa, and the viscous modulus of the plug in the system of example 3 is reduced to between 8.47 Pa and 11.4Pa, which is slightly lower than that in the system of example 2.
Figure 3 comparing examples 1 and 3 it can be seen that the modulus of elasticity of the plug for the system of example 1 is between 4.74 and 15.1Pa and the modulus of elasticity of the plug for the system of example 3 rises between 7.26 and 16.5Pa, slightly lower than for the system of example 2.
Compared with the system in the embodiment 1, the rubber plug of the system in the embodiment 1 has high viscosity and low elasticity, mainly viscosity, and poor cyclability, and the system in the embodiment 3 has reduced viscosity and increased elasticity, thereby improving the reservoir protection effect and the stratum bearing capacity of the rubber plug compared with the system in the embodiment 1.
Through degradation tests, the recyclable high-density liquid rubber plug obtained in example 3 hardly undergoes dehydration in the early stage of degradation, is aged for a certain time, and is converted from a viscoelastic body into a mixture of brittle fragments and water. The statistical time required for the high density plug to reach this state at different temperatures is given by the following data points: (T, T) ═ 140 ℃, 152h), (150 ℃, 130h), (160 ℃, 116h) is substituted into equation (1) to derive the degradation time prediction equation:
the correlation coefficient R of the formula (3) is in the range of 140-160 DEG C20.98 has an excellent linear relationship, predicting the maximum error in degradation time: and +/-1.5 h.
Comparing fig. 4 and fig. 6, in the DSC test, the system of example 1 has only one degradation process and a decomposition temperature of 109 ℃, and the system of example 3 has two degradation processes with decomposition temperatures of 106.6 ℃ and 125 ℃, respectively, and the temperature resistance is improved.
Example 4
The experimental example provides preparation and degradation prediction of a recyclable high-density liquid rubber plug, and the density is 1.4g/cm3。
Adding a weighting agent into clear water, uniformly stirring, then adding a stabilizing agent, a reinforcing material and a polymer, stirring for 2-4h to form a uniform solution, then adding a diluted cross-linking agent, and fully stirring and dissolving to obtain the initial solution of the recyclable high-density liquid rubber plug. Wherein, the system formula is as follows: 70 percent of sodium bromide and potassium formate (the mass ratio is 6: 1) +0.03 percent of thiourea +0.4 percent of mixture of hectorite, montmorillonite and sodium alginate (the mass ratio is 6: 1: 1) +1.8 percent of polyacrylamide, guar gum and xanthan gum (the mass ratio is 16: 1: 1) +0.6 percent of mixture of polyethyleneimine and triethylenetetramine (the mass ratio is 5: 1), the balance of water and the density is 1.3g/cm3 Total volume 100 ml.
And pouring the prepared initial solution of the recyclable high-density liquid rubber plug system into a six-turn rotational viscometer to perform initial viscosity test.
As can be seen by comparing example 1 and example 4 in FIG. 1, the system of example 4 rapidly reduced the initial viscosity of the recyclable plug from 2400mPa.s to 895.4mPa.s and increased the density to 1.4g/cm3The injectability was ensured, and the viscosity was lower than in examples 2 and 3.
Pouring the prepared initial solution of the recyclable high-density rubber plug system into an aging tank, sealing and respectively putting into ovens at 140 ℃, 150 ℃ and 160 ℃, and inspecting the gelling condition and the degradation condition of the system. The specific gelling conditions are shown in Table 5.
Table 5 example 4 gel formation
Through the gelling test, the recyclable high-density rubber plug obtained in the example 4 has gelling time of 8-11 hours and final setting strength of H grade.
The high density recyclable liquid rubber plug aged at 160 ℃ for 11 hours was dropped into a HAAKERS model 600 rheometer for viscoelasticity testing.
As can be seen by comparing example 1 with example 4 in FIG. 2, the viscous modulus of the plug in the system of example 1 is between 19.6 Pa and 28.6Pa, and the viscous modulus of the plug in the system of example 4 is reduced to between 6.85 Pa and 11.7Pa, which is slightly lower than that in examples 2 and 3.
As can be seen by comparing example 1 and example 4 in FIG. 3, the modulus of elasticity of the rubber plug of the system of example 1 is between 4.74 and 15.1Pa, and the modulus of elasticity of the rubber plug of the system of example 4 is increased to between 26.1 and 37.2Pa, higher than that of example 3 and lower than that of example 2.
Compared with the figures 2 and 3, the rubber plug of the system in the embodiment 1 is mainly viscous and has poor cyclability, and the rubber plug of the embodiment 4 is mainly elastic and has high elasticity and low viscosity, so that the reservoir protection effect and the stratum bearing capacity of the rubber plug are improved.
Through degradation tests, the recyclable high-density liquid rubber plug obtained in example 4 hardly undergoes dehydration in the early stage of degradation, and is aged for a certain time to be converted from a viscoelastic body into a mixture of brittle fragments and water. The statistical time required for the high density plug to reach this state at different temperatures is given by the following data points: (T, T) ═ 140 ℃, 184h), (150 ℃, 168h), (160 ℃, 150h) is substituted into equation (1) to derive the degradation time prediction equation:
the formula (4) has a correlation coefficient R in the range of 140-160 DEG C20.98 has an excellent linear relationship, predicting the maximum error in degradation time: and +/-1.6 h.
Comparing fig. 4 and fig. 7, the rubber plug of the system of example 1 has only one degradation process and a decomposition temperature of 109 ℃ in the DSC test, and the rubber plug of the system of example 4 has two degradation processes with decomposition temperatures of 110.61 ℃ and 126.6 ℃, respectively, and the temperature resistance is improved and is higher than that of examples 2 and 3.
Example 5
The experimental example provides preparation and degradation prediction of a recyclable high-density liquid rubber plug, and the density is 1.5g/cm3。
Adding a weighting agent into clear water, uniformly stirring, then adding a stabilizing agent, a reinforcing material and a polymer, stirring for 2-4h to form a uniform solution, then adding a diluted cross-linking agent, and fully stirring and dissolving to obtain the initial solution of the recyclable high-density liquid rubber plug. Wherein, the system formula is as follows: 90 percent of sodium bromide and potassium formate (the mass ratio is 8: 1) +0.03 percent of thiourea +0.4 percent of laponite, a mixture of montmorillonite and sodium alginate (the mass ratio is 6: 1: 1) +1.8 percent of polyacrylamide, guar gum and xanthan gum (the mass ratio is 7: 1: 1) +0.6 percent of polyethyleneimine, triethylenetetramine, a mixture of formaldehyde and resorcinol (the mass ratio is 7: 1: 1), the balance of water and the density of 1.5g/cm3 Total volume 100 ml.
And pouring the prepared initial solution of the recyclable high-density liquid rubber plug system into a six-turn rotational viscometer to perform initial viscosity test.
As can be seen by comparing example 1 and example 5 in FIG. 1, the example 5 system rapidly reduced the initial viscosity of the recyclable plug from 2400mPa.s to 796.9mPa.s and increased the density to 1.5g/cm3And the injection property is ensured.
Pouring the prepared initial solution of the recyclable high-density rubber plug system into an aging tank, sealing and respectively putting into ovens at 140 ℃, 150 ℃ and 160 ℃, and inspecting the gelling condition and the degradation condition of the system. The specific gelling conditions are shown in Table 6.
Table 6 example 5 gel formation
Through the gelling test, the recyclable high-density rubber plug obtained in example 5 has gelling time of 8-11 hours and final setting strength of H grade.
The high density recyclable liquid rubber plug aged at 160 ℃ for 11 hours was dropped into a HAAKERS model 600 rheometer for viscoelasticity testing.
As can be seen by comparing example 1 with example 5 in FIG. 2, the viscous modulus of the rubber plug of the system of example 1 is 19.6 to 28.6Pa, and the viscous modulus of the rubber plug of the system of example 5 is reduced to 3.34 to 6.05Pa, which is lower than that of examples 2, 3 and 4.
As can be seen by comparing example 1 with example 5 in FIG. 3, the elastic modulus of the rubber plug of the system of example 1 is between 4.74 and 15.1Pa, and the elastic modulus of the rubber plug of the system of example 5 is increased to between 32.8 and 43.7Pa, which is higher than that of the systems of examples 2, 3 and 4.
Compared with the figures 2 and 3, the rubber plug of the system in the embodiment 1 has high viscosity and low elasticity, mainly viscosity and poor cyclability, and the rubber plug of the system in the embodiment 5 has high elasticity and low viscosity, mainly elasticity, so that the reservoir protection effect and the stratum bearing capacity of the rubber plug are improved.
Through degradation tests, the recyclable high-density liquid rubber plug obtained in example 5 hardly undergoes dehydration in the early stage of degradation, is aged for a certain time, and is converted from a viscoelastic body into a mixture of brittle fragments and water. The statistical time required for the high density plug to reach this state at different temperatures is given by the following data points: (T, T) — (140 ℃, 210h), (150 ℃, 190h), (160 ℃, 168h) is substituted into equation (1) to derive the degradation time prediction equation:
the formula (4) has a correlation coefficient R in the range of 140-160 DEG C20.98 has an excellent linear relationship, predicting the maximum error in degradation time: and +/-1.9 h.
Comparing fig. 4 and 8, the rubber plug of the system of example 1 has only one degradation process and the decomposition temperature is 109 ℃ in the DSC test, while the rubber plug of the system of example 5 has three degradation processes, the decomposition temperatures are 101.01 ℃, 125.81 ℃ and 136.2 ℃, respectively, and the temperature resistance is improved.
It can be seen from the performance tests of the recyclable high density liquid rubber plugs obtained in examples 2 to 5 that: the density of the recyclable high-density liquid rubber plug can be controlled to be 1.2-1.5g/cm3(ii) a The initial rubber plug solution has good fluidity and is convenient for pumping; the gelling time is 8-11 hours, and the final setting strength is H grade; the gel has certain flow property after being gelatinized, has the characteristics of high elasticity and low viscosity, can be converted into brittle particles and water from a viscoelastic body after being aged for a period of time at a certain temperature, has cyclability and can be efficiently flowback; and various systems have a plurality of degradation reaction processes, and the temperature resistance is strong.
The degradation time prediction methods of examples 2-5 reflect the degradation law of the recyclable high density liquid rubber plug. Regression equation correlation coefficient R for predicted degradation time inferred from aging experimental data points in each example2Are all above 0.98, have excellent linear relationship. And the 4 prediction degradation time equations can accurately predict the degradation state of the rubber plug in the stratum so as to guide the flowback process.
The raw materials of the recyclable high-density liquid rubber plug provided by the invention comprise the weighting agent, the stabilizer, the reinforcing material, the polymer, the cross-linking agent and water, the consumption of the raw materials is small, the preparation method basically adopts a one-pot method, and the cross-linking agent needs to be diluted in advance, so that the recyclable high-density liquid rubber plug has the advantages of simplicity in preparation, low cost and the like.
The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (10)
1. A preparation method and a degradation prediction method of a recyclable high-density liquid rubber plug are characterized by being mainly prepared from the following components in percentage by mass through a crosslinking reaction: 30-90% of weighting agent, 0.01-0.03% of stabilizing agent, 0.2-0.6% of reinforcing material, 1.5-2.0% of polymer and 0.5-0.6% of cross-linking agent, wherein the ratio of the polymer to the cross-linking agent is 3: 1, the balance being water;
further preferably, the adhesive is mainly prepared from the following components in percentage by mass through a crosslinking reaction: 36-90% of weighting agent, 0.02-0.03% of stabilizing agent, 0.2-0.4% of reinforcing material, 1.5-1.8% of polymer and 0.5-0.6% of cross-linking agent, wherein the ratio of the polymer to the cross-linking agent is 3: 1, and the balance of water.
2. A recyclable high density liquid rubber plug according to claim 1 wherein the polymer is one or more of polyacrylamide, t-butyl acrylate copolymer, xanthan gum, guar gum;
the weighting agent can be one or more of potassium formate or sodium bromide, and the density range of the rubber plug formed after weighting is 1.2g/cm3-1.5g/cm3；
The stabilizer can be one or more of thiourea and sodium sulfite;
the reinforcing material must contain hectorite and can be matched with one or more of bentonite, montmorillonite, graphite powder and sodium alginate;
the cross-linking agent can be one or more of polyethyleneimine, aluminum citrate, orthoboric acid, formaldehyde, triethylene tetramine, dimethylaminopropylamine, resorcinol and phenolic resin;
further preferably, the polymer can be one or more of polyacrylamide, xanthan gum and guar gum; the weighting agent can be one or more of sodium bromide or potassium formate; the stabilizer is thiourea; the reinforcing material must contain hectorite and can be matched with one or more of montmorillonite and sodium alginate; the cross-linking agent is one or more of polyethyleneimine, formaldehyde, triethylenetetramine and resorcinol.
3. The recyclable high-density liquid plug as described in claims 1-2, wherein the polyacrylamide is a dendrimer with a molecular weight of 800 x 104g/mol, wherein the main chain and the branched chain comprise hydrophilic groups and amide groups, carboxyl groups, aldehyde groups, sulfonic groups, tert-butyl ester groups and the like with a crosslinking structure; the hectorite is a multi-layered silicate with a particle size of 60 meshes.
4. A recyclable high density liquid plug according to claims 1-3 characterized by low initial viscosity for easy pumping; after aging and gelling, the rubber still has certain fluidity and has the characteristics of high elasticity and low viscosity; aging at 140-160 deg.C for a period of time, converting from viscoelastic body into brittle particles and water, without breaking gel, and circulating and flowing back efficiently; also has the advantages of adjustable density, temperature resistance and the like.
5. The preparation method of the recyclable high-density rubber plug as claimed in claims 1 to 3, characterized in that the raw materials comprise the weighting agent, the stabilizer, the reinforcing material, the polymer, the cross-linking agent and water, the consumption of the raw materials is small, the preparation method basically adopts a one-pot method, the cross-linking agent needs to be diluted in advance, and the preparation method has the advantages of simple preparation, low cost and the like.
6. The method for preparing a recyclable high-density rubber plug as described in claims 1-3, wherein the change in clear water volume after weight is added is taken into account, and a table of the change in volume of liquid with different parts of weight additive is summarized to guide the on-site preparation.
7. A degradation prediction method comprising the temperature resistance detection and degradation time prediction of the recyclable high-density liquid rubber plug as described in claims 1 to 3.
8. The method of claim 7, wherein the plug of recyclable high-density liquid is considered to be efficiently recycled when converted from viscoelastic to brittle and in a state of a mixture of water and brittle particles.
9. The degradation prediction method of claim 8, wherein the degradation time is not calculated using thermodynamic parameters, and an empirical formula is derived using fitted aging experimental data points.
10. The degradation prediction method of claim 9, wherein the logarithm of degradation time and the reciprocal of temperature have a linear relationship, and a degradation time prediction regression equation is established:
the equation for predicting the degradation time of the recyclable high-density liquid rubber plug prepared in example 1 is:
the correlation coefficient R of the formula (2) is in the range of 140-160 DEG C20.99 has an excellent linear relationship, predicting the maximum error in degradation time: +/-0.95 h;
the equation for predicting the degradation time of the recyclable high-density liquid rubber plug prepared in example 2 is:
the correlation coefficient R of the formula (3) is in the range of 140-160 DEG C20.98 has an excellent linear relationship, predicting the maximum error in degradation time: +/-1.5 h;
the equation for predicting the degradation time of the recyclable high-density liquid rubber plug prepared in example 3 is:
the formula (4) has a correlation coefficient R in the range of 140-160 DEG C20.98 has an excellent linear relationship, predicting the maximum error in degradation time: +/-1.6 h;
the equation for predicting the degradation time of the recyclable high-density liquid rubber plug prepared in example 4 is:
the formula (4) has a correlation coefficient R in the range of 140-160 DEG C20.98 has an excellent linear relationship, predicting the maximum error in degradation time: and +/-1.9 h.
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