Drilling fluid treating agent for preventing asphaltene precipitation blockage

Abstract

The invention discloses a drilling fluid treating agent for preventing asphaltene precipitation blockage. The drilling fluid treating agent is formed by mixing a Tween type surfactant and an alcohol solvent, the mass ratio of the Tween type surfactant to the alcohol solvent is 1: 3-1: 10, the number of carbon atoms of a side carbon chain of the Tween type surfactant is 10-20, the number of polyoxyethylene chain segments contained in the Tween type surfactant is 5-30, and the molecular weight of the alcohol solvent is 40-120 g / mol. The asphaltene dispersant is simple in preparation process, wide in raw material source and low in cost; the asphaltene dispersant has strong adaptability and is suitable for crude oil with different water contents and different compositions; the asphaltene dispersant is small in dosage and good in inhibition effect.

Description

Technical Field

[0001] The invention relates to a drilling fluid treating agent for preventing asphaltene precipitation and clogging, belonging to the technical field of oil production. Background Art

[0002] Crude oil is a continuously distributed dynamic colloidal stable system, including saturated and aromatic colloids and asphaltenes. Generally speaking, asphaltenes refer to substances in crude oil that are soluble in toluene but insoluble in n-heptane. It is a complex mixture, the main feature of which is that it contains polycyclic aromatic hydrocarbons, with aliphatic chains connected to the polycyclic aromatic hydrocarbons, and contains certain heteroatoms. Such polycyclic aromatic hydrocarbons can be divided into single aromatic ring nuclei connected by aliphatic chains, which are called archipelago structures; or they can be kept as compact condensed polycyclic aromatic hydrocarbons, which are called continental structures. The most important feature of asphaltenes is that they tend to self-associate and produce precipitation, which is also the difference between asphaltenes and other petroleum components. Due to this characteristic, for oil products with a high asphaltene content, the production, transportation, storage and processing will be adversely affected by asphaltene precipitation.

[0003] In the process of oil production, tight and other unconventional reservoirs have problems such as poor pore connectivity and low recovery. Conventional water injection development often "cannot inject and cannot produce", so gas drive is an important way to improve the recovery of tight reservoirs. When injecting CO2 to develop asphaltene-rich reservoirs, CO2 injected into crude oil will break the initial equilibrium state of the four components (saturated fraction, aromatic fraction, colloid, and asphaltene) in the crude oil system, causing asphaltene flocculation and deposition, resulting in pore throat blockage, damage to the reservoir and thus affecting oil recovery efficiency.

[0004] Therefore, how to provide an asphaltene dispersant that has a good improvement effect on crude oil stability and a low application cost is a technical problem that needs to be solved urgently to avoid asphaltene flocculation and deposition. Summary of the invention

[0005] The purpose of the present invention is to provide an asphaltene dispersant for improving the stability of crude oil, which can effectively improve the stability of crude oil, obtain good improvement effects at a relatively low dosage, have low use costs, and avoid damage to reservoirs caused by asphaltene deposition.

[0006] The drilling fluid treating agent for preventing asphaltene precipitation and clogging provided by the invention is formed by mixing a Tween surfactant and an alcohol solvent.

[0007] Wherein, the mass ratio of the Tween surfactant to the alcohol solvent is 1:3-1:10.

[0008] Preferably, the number of carbon atoms in the side carbon chain of the Tween surfactant is 10-20; More preferably, the number of carbon atoms in the side carbon chain of the Tween surfactant is 12 to 18; Preferably, the Tween surfactant contains 5-30 polyoxyethylene segments; More preferably, the Tween-type surfactant contains 6-26 polyoxyethylene segments.

[0009] Preferably, the Tween surfactant is selected from any one of Tween-20, Tween-40 and Tween-60.

[0010] Preferably, the molecular weight of the alcohol solvent is 40 to 120 g / mol; Preferably, the alcohol solvent is selected from any one of isopropanol, n-butanol and tert-amyl alcohol.

[0011] Compared with the prior art, the advantages and positive effects of the present invention are: The asphaltene dispersant of the present invention uses a Tween surfactant as a main agent and an alcohol solvent as a co-solvent, and can effectively improve the colloidal stability of crude oil through synergistic effects; The asphaltene dispersant of the present invention has a simple preparation process, a wide range of raw material sources, and a low cost; The asphaltene dispersant of the present invention has strong adaptability and is suitable for crude oils with different water contents and different compositions; The asphaltene dispersant of the invention has a small dosage and a good inhibitory effect. DETAILED DESCRIPTION

[0012] Unless otherwise specified, the experimental methods used in the following examples are conventional methods.

[0013] Unless otherwise specified, the materials and reagents used in the following examples can be obtained from commercial sources.

[0014] The drilling fluid treating agent for preventing asphaltene precipitation and clogging provided by the present invention is prepared from a Tween surfactant and an alcohol solvent, wherein the mass ratio of the Tween surfactant to the alcohol solvent is 1:3-1:10.

[0015] In the asphaltene dispersant of the present invention, the Tween surfactant is used as the main agent for dispersing, which has a strong polarity and can selectively interact with the strongly polar asphaltene molecules in crude oil. Otherwise, if the main agent does not have a sufficiently strong polarity, since the content of the weak polar components (aromatic and saturated components) in crude oil and the number of molecules per unit volume are far greater than the asphaltene molecules, a large amount of the main agent will interact with the aromatic and saturated components, which will greatly reduce the dispersing effect of the main agent on the asphaltene molecules. Further, an alcohol solvent is added as a co-solvent to mix with the main agent. Since the alcohol solvent can dissolve the Tween surfactant and has a small polarity, it is easy to dissolve with the dispersion medium of crude oil, so that the main agent with a strong polarity dissolved in the alcohol solvent can better migrate in the crude oil, and enter the interior of the crude oil colloid to interact with asphaltene, playing a role in stabilizing asphaltene.

[0016] It should also be noted that, in the present invention, the Tween surfactant and the alcohol solvent are compounded in a mass ratio of 1:3 to 1:10, and the obtained crude oil asphaltene dispersant has a suitable polarity and has an ideal improvement effect on crude oil stability. If the mass ratio of the Tween surfactant and the alcohol solvent in the crude oil asphaltene dispersant is higher than 1:3, the polarity of the obtained crude oil asphaltene dispersant is too strong and cannot be well dissolved in crude oil; if the mass ratio of the Tween surfactant and the alcohol solvent in the crude oil asphaltene dispersant is lower than 1:10, the main agent contained in the crude oil asphaltene dispersant is too little, and the ideal improvement effect cannot be obtained.

[0017] In the present invention, the carbon number of the side carbon chain of the Tween surfactant is 12 to 18, and the number of polyoxyethylene segments contained in the Tween surfactant is 5 to 26. The reason why the present invention further limits the carbon number of the side carbon chain in the Tween surfactant is that when the number of atoms in the side carbon chain of the Tween surfactant exceeds 18, its polarity is too large and it is extremely difficult to disperse; when the number of atoms in the side carbon chain is less than 12, the carbon chain is shorter and the stabilizing effect is weakened. In this preferred embodiment, the number of polyoxyethylene ether segments (i.e., -OCH2CH2-) in the Tween-type surfactant is further limited. This is because: the hydrophilic groups in the Tween-type surfactant are mainly polyoxyethylene ether bonds. The more polyoxyethylene ether segments there are, the stronger the hydrophilicity. When the number of polyoxyethylene ether segments is less than 5, the surfactant has a weaker polarity and has a weaker effect on the highly polar components such as colloids and asphaltene in the crude oil, and the dispersion and stabilization effect on the crude oil is not obvious; when the number of polyoxyethylene ether segments is greater than 26, the surfactant will be difficult to disperse in the crude oil, and the stabilization effect it can have will be greatly reduced.

[0018] In the present invention, the Tween surfactant is selected from any one of Tween-20, Tween-40 and Tween-60. The embodiment of the present invention lists three kinds of Tween surfactants, among which the carbon number of the side carbon chain of Tween-20 is 12, and the number of polyoxyethylene ether segments contained is in the range of 21-22; the carbon number of the side carbon chain of Tween-40 is 16, and the number of polyoxyethylene ether segments contained is in the range of 18-22; the carbon number of the side carbon chain of Tween-60 is 18, and the number of polyoxyethylene ether segments contained is in the range of 18-22. The polarity of these three Tween surfactants is similar to that of the colloid in crude oil, and they can react with the colloid and adsorb on the surface of asphaltene together with the colloid. At the same time, the Tween surfactant adsorbed on the surface of asphaltene can form hydrogen bonds with heteroatoms such as S and N in asphaltene molecules, hinder the self-association between asphaltene molecules, and disperse asphaltene aggregates to achieve the effect of improving the stability of crude oil colloids. At the same time, these three Tween surfactants are commercial products with mature production processes. They are high in purity, reliable in quality, cheap and easy to obtain, and are non-toxic, harmless and environmentally friendly.

[0019] In the present invention, the molecular weight of the alcohol solvent is 40 to 120 g / mol. When the molecular weight of the alcohol solvent is within the above range, it has good solubility for Tween surfactants, and its polarity is small, which is close to the polarity of aromatic components in crude oil, and it is easy to dissolve with aromatic components, and can carry Tween surfactants into the crude oil colloid system.

[0020] In the present invention, the alcohol solvent is selected from any one of isopropanol, n-butanol and tert-amyl alcohol. Three specific alcohol solvents are listed in the embodiment of the present invention, and these three alcohol solvents can dissolve Tween surfactants, and their polarity is similar to the aromatic components in crude oil, and can carry Tween surfactants into the crude oil colloid system, especially isopropanol and n-butanol have the best effect. It should be noted that the embodiment of the present invention is not limited to the alcohol solvents listed above, and those skilled in the art can also select other suitable alcohol solvents, as long as they have good solubility for Tween surfactants and can be soluble in crude oil.

[0021] In order to more clearly and in detail introduce the crude oil asphaltene dispersant for improving crude oil stability provided by the embodiments of the present invention, it will be described below in conjunction with specific embodiments.

[0022] Embodiment 1, The crude oil asphaltene dispersant for improving crude oil stability is prepared by mixing Tween-40 and isopropanol, wherein the mass ratio of Tween-40 to isopropanol is 1:4.

[0023] Embodiment 2, The crude oil asphaltene dispersant used for improving crude oil stability is prepared by mixing Tween-20 and tert-amyl alcohol, wherein the mass ratio of Tween-20 to tert-amyl alcohol is 1:9.

[0024] Embodiment 3, The crude oil asphaltene dispersant for improving crude oil stability is prepared by mixing Tween-60 and n-butanol, wherein the mass ratio of Tween-60 to n-butanol is 1:9.

[0025] In order to illustrate the improvement effect of the crude oil asphaltene dispersant provided in Examples 1-3 on crude oil stability, the inhibitory effect of the asphaltene dispersant will be evaluated using the following measurement method.

[0026] Determination method: Based on the property that asphaltene is insoluble in n-hexane, an excess amount of precipitant n-hexane is added to the crude oil to cause flocculation and precipitation of the crude oil. The asphaltene deposition inhibitor for oil recovery of the present invention is added. Since it has the ability to disperse asphaltene, it can inhibit the occurrence of asphaltene precipitation. This method is used to evaluate the inhibitory effect of the asphaltene deposition inhibitor for oil recovery of the present invention on asphaltene deposition.

[0027] The specific steps for determining the inhibition rate are as follows: 1) Preparation of inhibitor-toluene solution Weigh 0.600 g (accurate to 0.001 g) of sample in a 100 mL volumetric flask, dilute to 100 mL with toluene solution, cover the volumetric flask with a stopper, and shake the volumetric flask by hand for 30 seconds to fully dissolve the sample in toluene, thereby preparing a 0.6% inhibitor-toluene solution for use, wherein the samples are the asphaltene dispersants obtained in Examples 1 to 3 of the present invention, respectively.

[0028] 2) Determination of inhibition rate 0.50 g (accurate to 0.01 g) of crude oil preheated to 30° C. was added to three 100 mL stoppered pointed-bottom graduated centrifuge tubes respectively. Then, 1.2 mL of the above-prepared inhibitor-toluene solution was pipetted into each centrifuge tube using a pipette (wherein, the inhibitor-toluene solution prepared in Example 1 was added to centrifuge tube 1, the inhibitor-toluene solution prepared in Example 2 was added to centrifuge tube 2, and the inhibitor-toluene solution prepared in Example 3 was added to centrifuge tube 3). The upper end of the centrifuge tube was held by hand, the centrifuge tube was tilted 45° to 60°, and shaken for 120 seconds to fully and evenly mix the crude oil and the inhibitor-toluene solution.

[0029] Then add preheated n-hexane at 30°C until the mark on the centrifuge tube reaches 75mL, plug the centrifuge tube with a stopper, tighten it, and shake the centrifuge tube vigorously back and forth for about 200 times until there is no obvious black crude oil attached to the bottom and wall of the centrifuge tube.

[0030] Place the centrifuge tube vertically in a 30℃ water bath. After 60 minutes of constant temperature, slowly remove the centrifuge tube in a vertical state and read the volume of the sediment at the bottom under strong light. At the same time, replace the inhibitor-toluene solution with toluene as a blank experiment.

[0031] 3) Calculation

[0032] Where: S —Inhibition rate, %; V 0—the volume of sediment at the bottom of the blank experiment centrifuge tube, mL; V —Volume of sediment at the bottom of the centrifuge tube after adding inhibitor, mL.

[0033] Table 1 Asphaltene dispersant inhibition effect

[0034] Comparative results: As shown in Table 1, when the asphaltene dispersant of the present invention is added to crude oil, the inhibition rate can reach more than 90%, indicating that the asphaltene dispersant of the present invention has a good inhibitory effect on asphaltene deposition.

[0035] In summary, in the process of CO2 injection exploitation in tight reservoirs, attention should be paid to the deposition of asphaltene, and a suitable CO2 injection method should be selected to reduce the degree of damage to reservoir permeability and improve crude oil recovery.

Claims

1. A drilling fluid treatment agent for preventing asphaltene precipitation and clogging, which is formed by mixing a Tween surfactant and an alcohol solvent.

2. The drilling fluid treating agent according to claim 1, characterized in that: The mass ratio of the Tween surfactant to the alcohol solvent is 1:3-1:

10.

3. The drilling fluid treating agent according to claim 1 or 2, characterized in that: The number of carbon atoms in the side carbon chain of the Tween surfactant is 10-20; The Tween surfactant contains 5-30 polyoxyethylene segments.

4. The drilling fluid treating agent according to any one of claims 1 to 3, characterized in that: The Tween surfactant is selected from any one of Tween-20, Tween-40 and Tween-60.

5. The drilling fluid treating agent according to any one of claims 1 to 4, characterized in that: The molecular weight of the alcohol solvent is 40 to 120 g / mol.

6. The drilling fluid treating agent according to claim 5, characterized in that: The alcohol solvent is selected from any one of isopropanol, n-butanol and tert-amyl alcohol.

7. Use of the drilling fluid treating agent according to any one of claims 1 to 6 in oil field exploitation.

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