A wicking-acid spreading synergistic oil production method based on a wicking agent and a wicking agent

Abstract

The present application discloses a wicking-acid spreading synergistic oil production method based on a wicking agent. S1: Extract core samples from the target reservoir and determine the mineral composition of the target reservoir; S2: Take an anionic surfactant and an amphoteric surfactant, compound them respectively according to multiple different molar ratios and dissolve them in water respectively to obtain multiple groups of wicking agents; in each group of wicking agents, the sum of the molar proportions of the anionic surfactant and the amphoteric surfactant is 10; S3: Adjust the pH values of each group of wicking agents multiple times within the range of pH = 1.14 to 7.00. After each pH value adjustment of each group of wicking agents, soak the core samples extracted in S1 with it for 48 h, and then test the change difference of the contact angle of the core samples; S4: Select a group of wicking agents with the largest change difference of the contact angle after adjusting the pH value, and use it to carry out wicking oil production on the target reservoir. The present application also discloses a wicking agent applicable to this oil production method.

Description

Technical Field

[0001] The present invention belongs to the technical field of oilfield exploitation, and particularly relates to a wicking-acidizing synergistic oil production method based on a wicking agent and a wicking agent. Background Art

[0002] Since the initial reservoir is rich in crude oil, and the initial pore wall surface is usually oil-wet, a large amount of oil film will adhere to the pore wall surface, resulting in a decrease in the contact efficiency between the acid fluid and the rock wall surface, thus affecting the acidizing effect. In addition, the presence of crude oil in the pores shortens the effective period of acidizing and increases the difficulty of reservoir acidizing. During the chemical wicking process, the chemical wicking agent mainly acts on small and medium pores. By changing the wettability of the rock wall surface, the adhered oil film on the pore wall surface is peeled off, the interfacial energy of the oil-water and liquid-solid interfaces is changed, and the seepage resistance of the reservoir is reduced. However, due to the existence of fine pores and solid blockages, the swept volume of the chemical wicking agent is small, and it only acts near the wellbore and cannot reach the deep part of the reservoir. The consequence is low oil production efficiency, poor effect, and difficult to guarantee the output, which is not conducive to the efficient development of oilfields, especially unconventional tight reservoir oilfields. Summary of the Invention

[0003] The present application provides a wicking-acidizing synergistic oil production method based on a wicking agent, which solves the technical problems of large acidizing difficulty and small swept volume of chemical wicking in the development of unconventional tight reservoirs in the prior art, and realizes on the one hand using the wicking agent to change the wettability of the pore wall surface, so that the adhered oil film on the pore wall surface peels off, increasing the action efficiency of the acid fluid; on the other hand, using the ability of the acid fluid to dissolve the pore wall surface and blockages to improve the swept system of the wicking agent, so as to achieve the technical effect of efficient synergistic oil production of acidizing-chemical wicking. The present application also provides a wicking agent, which is a compound of an anionic surfactant and an amphoteric surfactant, and its compound system can realize real-time regulation of the formula at different pH values. Applying it to the above-mentioned wicking-acidizing synergistic oil production method based on a wicking agent can achieve an ideal oil production effect when the wicking agent is at an optimal composition and pH value.

[0004] According to the first aspect of the present application, a wicking-acidizing synergistic oil production method based on a wicking agent is provided, which includes the following steps:

[0005] S1. Extract the core sample of the target reservoir and determine the mineral composition of the target reservoir;

[0006] S2. Take an anionic surfactant and an amphoteric surfactant, and perform compounding at different molar ratios respectively and dissolve them in water respectively to obtain multiple groups of wicking agents; in each group of the wicking agents, the sum of the molar ratios of the anionic surfactant to the amphoteric surfactant is 10;

[0007] S3. Adjust the pH value of each group of the imbibition agents multiple times within the range of pH = 1.14 - 7.00. After each pH value adjustment of each group of the imbibition agents, use it to soak the core samples extracted in S1 for 48 h, and then measure the change difference in the contact angle of the core samples.

[0008] S4. Select a group of the imbibition agents with the largest change difference in contact angle after adjusting the pH value, and use it for imbibition oil recovery in the target reservoir.

[0009] In a possible implementation manner,

[0010] In S2, the sum of the mass concentrations of the anionic surfactant and the zwitterionic surfactant in each group of the imbibition agents is 0.5 wt%.

[0011] In a possible implementation manner,

[0012] In S2, after taking the anionic surfactant and the zwitterionic surfactant for compounding and dissolving them in water, hydrophilic nanoparticles are further added to the water.

[0013] In the above possible implementation manner, further,

[0014] The mass concentration of the hydrophilic nanoparticles in each group of the imbibition agents is 0.05 wt%.

[0015] According to the second aspect of the present application, an imbibition agent is provided, which is characterized in that

[0016] it includes an imbibition main body and a pH regulator;

[0017] The imbibition main body includes an anionic surfactant, a zwitterionic surfactant and water;

[0018] The sum of the mass concentrations of the anionic surfactant and the zwitterionic surfactant is 0.3% - 1.0 wt%;

[0019] The molar mass ratio of the anionic surfactant to the zwitterionic surfactant is (2 - 8):(8 - 2);

[0020] The pH regulator is used to adjust the pH value of the imbibition agent within the range of pH = 1.14 - 7.00.

[0021] In a possible implementation manner,

[0022] The anionic surfactant includes one or more of carboxylic acid derivatives, sulfonates, sulfate esters, phosphate esters, and N-acylaminocarboxylate anionic surfactants, and more specifically includes one or more of sodium dodecyl sulfate, sodium polyoxyethylene fatty alcohol ether propylsulfonate, sodium lauryl sulfate, and potassium cetyl phosphate.

[0023] In a possible implementation,

[0024] The zwitterionic surfactant includes one or more of amino acid type, betaine type, and imidazoline type zwitterionic surfactants, and more specifically includes one or more of dodecyldimethylbetaine, coconut oil amide propyl betaine, erucic acid amide propyl betaine, dodecyldimethylammonium oxide, and erucic acid amide propyl ammonium oxide.

[0025] In a possible implementation,

[0026] It also includes hydrophilic nanoparticles with a particle size of 50 - 100 nm and a mass concentration of 0.01% - 0.1 wt%.

[0027] In the above possible implementation, further,

[0028] The hydrophilic nanoparticles include one or more of nano-silica, nano-molybdenum disulfide, nano-montmorillonite, and nano-coal ash.

[0029] In a possible implementation,

[0030] The pH regulator includes one or more of hydrochloric acid, hydrofluoric acid, acetic acid, and oxalic acid.

[0031] One or more technical solutions provided by the present application have at least the following beneficial effects:

[0032] (1) For the imbibition-acid spreading synergistic oil production method based on the imbibition agent provided by the present application, on the one hand, the imbibition agent is used to change the wettability of the pore wall surface, so that the adhered oil film on the pore wall surface peels off, increasing the action efficiency of the acid solution; on the other hand, the ability of the acid solution to dissolve the pore wall surface and blockages is utilized to improve the swept system of the imbibition agent, so as to achieve the technical effect of efficient synergistic oil production by acidification-chemical imbibition. The chemical imbibition effect that this method can achieve is significantly improved compared with the chemical imbibition effects of using acidification alone and in deionized water.

[0033] (2) In the imbibition agent provided by this application, the system of anion surfactant / amphoteric surfactant / nanoparticle compound shows good chemical imbibition oil production effect in a low pH environment. Moreover, this imbibition agent uses the compound of anion surfactant and amphoteric surfactant, and its compound system can realize real-time regulation of the formula at different pH values. Applying it to the above-mentioned imbibition-acid spreading synergistic oil production method based on the imbibition agent, the combination of the two can make the imbibition agent achieve an ideal oil production effect under better composition and pH value. Description of the Drawings

[0034] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the following will briefly introduce the drawings required to be used in the description of the embodiments of this application or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative work, other drawings can also be obtained based on these drawings.

[0035] Figure 1 Schematic diagram of the influence effect of the imbibition agent with different molar ratios of anion surfactant to amphoteric surfactant on the wettability of core samples at pH 2.05 in Example 1 of this application;

[0036] Figure 2 Curve graph showing the change of rock wettability with pH when the molar ratio of anion surfactant to amphoteric surfactant in the imbibition agent with different components in Example 1 of this application is 5:5. Detailed Embodiments

[0037] The following will clearly and completely describe the technical solutions in the embodiments of this application with reference to the drawings in the embodiments of this application. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative work belong to the scope of protection of the present invention.

[0038] In the description of the embodiments of this application, it should be noted that the terms "first", "second", and "third" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance. For those of ordinary skill in the art, the specific meanings of the above terms in the embodiments of this application can be understood according to specific circumstances. Embodiment

[0039] In the first aspect, this embodiment provides an imbibition-acid spreading synergistic oil production method based on an imbibition agent, which includes the following steps:

[0040] S1. Extract core samples of the target reservoir and determine the mineral composition of the target reservoir. In practical applications, multiple core samples usually need to be extracted for subsequent use. The purpose of determining the mineral composition of the target reservoir is to facilitate the specific selection of a more suitable surfactant according to the mineral composition of the target reservoir in the subsequent steps.

[0041] S2. Take an anionic surfactant and an amphoteric ion surfactant, compound them according to multiple different molar ratios respectively, and dissolve them in water respectively to obtain multiple groups of imbibition agents. In each group of the imbibition agents, the sum of the molar percentages of the anionic surfactant and the amphoteric ion surfactant is 10.

[0042] For example, compound the anionic surfactant and the amphoteric ion surfactant according to the molar ratios of 8:2, 7:3, 6:4, 5:5, 4:6, 3:7, and 2:8 respectively, and then dissolve them in water to obtain 7 groups of imbibition agents with different component ratios. As for the specific types of the anionic surfactant and the amphoteric ion surfactant in the imbibition agent, as mentioned above, they can be specifically selected according to the mineral composition of the target reservoir.

[0043] In this embodiment, the total mass concentration of the anionic surfactant and the amphoteric ion surfactant in each group of imbibition agents is always 0.5 wt%.

[0044] In this embodiment, in order to further improve the use effect of the imbibition agent, hydrophilic nanoparticles are also added, specifically 0.01% - 0.1 wt% of nano-silica. In other examples, different types of hydrophilic nanoparticles can also be selected according to actual needs, such as nano-molybdenum disulfide, nano-montmorillonite, nano-coal ash, etc. In this embodiment, the mass concentration of nano-silica in each group of imbibition agents is always 0.05 wt%.

[0045] S3. Adjust the pH value of each group of the imbibition agents multiple times within the range of pH = 1.14 - 7.00. After each adjustment of the pH value of each group of the imbibition agents, soak one core sample extracted in S1 for 48 h, and then test the change difference of the contact angle of the core sample.

[0046] For example, a set of imbibition agents with a molar ratio of anionic surfactant to zwitterionic surfactant of 8:2 is divided into four parts, and the pH of each part of the imbibition agent is adjusted respectively. Specifically, the pH values are adjusted to pH = 1.14, pH = 2.05, pH = 4.23, and pH = 7.00 respectively; using these four parts of the imbibition agent after pH adjustment, each part is used to soak a core sample extracted from S1 for 48 hours, and then the change difference in the contact angle of the core sample is measured; for the imbibition agents with other surfactant molar ratios, the specific operation method is the same as the above method. As for the specific number of pH adjustments and the pH values for each adjustment, they can be flexibly selected according to actual needs;

[0047] S4. After the pH of each group of imbibition agents is adjusted multiple times and the change difference in the contact angle of the core sample is measured in S3, select a group of the imbibition agents after pH adjustment with the largest change difference in the contact angle, and use it for imbibition oil recovery in the target reservoir.

[0048] Specifically, in this embodiment, a series of imbibition agents prepared in S1 to S3 are tested for changing the rock wettability. A contact angle measuring instrument (Kino Company, USA) is used to measure the change in the wettability of the core surface before and after soaking in the imbibition agent for 48 hours. The results are as Figure 1 and Figure 2 shown. According to the contact angle classification criterion: 0° to 75° is water-wet, 75° to 105° is neutrally wet, and 105° to 180° is oil-wet. Among them, the initial core wetting angle is 117°, which is oil-wet. Among them Figure 1 is the relationship between the wetting contact angle of the core and the compound molar ratio of anionic surfactant and zwitterionic surfactant when the pH of different imbibition agent systems is 2.05; Figure 1 In, SDS is sodium dodecyl sulfate, AEOSHS is sodium fatty alcohol polyoxyethylene ether hydroxypropyl sulfonate, EAB-40 is erucic acid amide propyl betaine, and CAB-40 is a kind of coconut oil amide propyl betaine. Figure 2 is the change curve of the wetting contact angle of the core with the pH of the imbibition agent system when the compound molar ratio of anionic surfactant and zwitterionic surfactant in different imbibition agent systems is 4:6.

[0049] From Figure 1It can be seen that, when the pH is determined, there is an optimal value for the compounding molar ratio of an anionic surfactant and an amphoteric surfactant. If the proportion of the anionic surfactant or the amphoteric surfactant is too high, the contact angle of the core will increase. This is mainly because the protonation of the amphoteric surfactant makes it exhibit the characteristics of a cationic surfactant in acidic solutions and the characteristics of an anionic surfactant in alkaline solutions. When the surfactant system acts on the rock wall, due to the mutual attraction between anions / cations, there is a synergistic effect, enhancing the effect of changing the rock wettability. When the anionic surfactant or the amphoteric surfactant is in excess, due to the electrostatic repulsion in the aqueous solution, the amount effectively acting on the rock wall is reduced, thus reducing the effect of changing the rock wettability. In addition, the ability of different anionic surfactant and amphoteric surfactant components in the imbibition agent system to change the rock wettability is also different. Generally speaking, the imbibition agent system composed of AEOSHS / CAB-40 has the best effect on changing the rock wettability. When the compounding molar ratio of AEOSHS / CAB-40 is 4:6, the contact angle of the rock can be reduced from 117° to 47°, changing the wettability of the rock from oil-wet to water-wet.

[0050] From Figure 2 It can be seen that for the imbibition agent system with a determined compounding ratio, the applicable optimal pH is different, and pH has a great influence on its ability to change the rock wettability, and the imbibition agent shows good pH sensitivity. This is mainly because the degree of protonation of the amphoteric surfactant in different acid solutions is different, and the exhibited cationic properties are also different. Therefore, when the pH changes, the molar ratio of the anionic surfactant used in the compounding is also different.

[0051] Multiple experimental data show that in this embodiment, when the pH is 2.05, the compounding molar mass ratio of AEOSHS and CAB-35 (a kind of cocoamidopropyl betaine) is 4:6, the sum of their mass concentrations is 0.5 wt%, and the imbibition agent composed of the concentration of nano-silica being 0.05 wt% has the best imbibition recovery rate (50.24%). Its imbibition recovery rate is higher than the sum of that of single acidification (15.73%) and the imbibition recovery rate (22.69%) of this imbibition agent when the pH is 7.00.

[0052] In the second aspect, this embodiment also provides an imbibition agent applicable to the oil production method in the first aspect above; the imbibition agent provided in this embodiment includes an imbibition main body and a pH regulator; wherein:

[0053] The imbibition main body includes an anionic surfactant, an amphoteric surfactant and water;

[0054] The sum of the mass concentrations of the anionic surfactant and the amphoteric surfactant is 0.3% - 1.0 wt%;

[0055] The molar mass ratio of the anionic surfactant to the zwitterionic surfactant is (2 - 8):(8 - 2);

[0056] The pH regulator is used to adjust the pH value of the imbibition agent within the range of pH = 1.14 - 7.00.

[0057] Specifically, in this embodiment, the optional anionic surfactants include one or more of carboxylic acid derivatives, sulfonates, sulfate esters, phosphate esters, and N-acyl amino carboxylates, and more specifically include one or more of sodium dodecyl sulfate, sodium polyoxyethylene fatty alcohol ether propylsulfonate, sodium lauryl sulfate, and potassium cetyl phosphate; the optional zwitterionic surfactants include one or more of amino acid type, betaine type, and imidazoline type zwitterionic surfactants, and more specifically include one or more of dodecyldimethylbetaine, coconut oil amide propyl betaine, erucic acid amide propyl betaine, dodecyldimethylamine oxide, and erucic acid amide propylamine oxide.

[0058] In a preferred technical solution, it further includes hydrophilic nanoparticles with a particle size of 50 - 100 nm, specifically nanosilica particles in this embodiment, and its mass concentration is 0.01% - 0.1 wt%; other optional hydrophilic nanoparticles include one or more of molybdenum disulfide nanoparticles, montmorillonite nanoparticles, and coal ash nanoparticles.

[0059] This embodiment takes an imbibition agent as an example to illustrate the preparation method of the above-mentioned imbibition agent:

[0060] Take a certain amount of anionic surfactant, specifically any proportion mixture of SDS and AEOSHS; take a certain amount of zwitterionic surfactant, specifically any proportion mixture of EAB-40 and CAB-35; compound the above anionic surfactant and zwitterionic surfactant according to the molar ratios of 8:2, 7:3, 6:4, 5:5, 4:6, 3:7, and 2:8 respectively, and then dissolve them in water to obtain 7 groups of imbibition main bodies; add nanosilica to each group of imbibition main bodies, and then adjust the pH of each group of imbibition main bodies between 1.14 and 7.00 through hydrochloric acid, such as pH being 1.14, 2.05, 4.23, and 7.00; obtain multiple groups of imbibition agents. In the above-mentioned groups of imbibition agents, the total mass of the anionic surfactant and the zwitterionic surfactant always accounts for 0.5 wt% of the mass concentration of the imbibition agent, and the mass of the nanosilica always accounts for 0.05 wt% of the mass concentration of the imbibition agent. Example

[0061] This example investigated the synergistic oil production performance when the different imbibition agents provided in Example 1 were combined with an acidic pH regulator. In the imbibition agents used, the molar ratio of the anionic surfactant to the zwitterionic surfactant was 4:6, and the total mass concentration of the anionic surfactant and the zwitterionic surfactant was always 0.5 wt%, and the mass concentration of nano-silica was always 0.05 wt%, specifically as follows:

[0062] Simulated formation water with a salinity of 3698.0 mg / L was used, and its specific ion composition is shown in Table 1.

[0063] Table 1:

[0064] Ion <![CDATA[Sodium + + Potassium + > <![CDATA[Mg 2+ > <![CDATA[Ca 2+ > <![CDATA[Cl – > <![CDATA[SO4 2- > <![CDATA[HCO3 - > <![CDATA[CO3 2- > Total salinity Ion concentration (mg / L) 931.9 64.2 179.6 899.5 62.3 133.2 1427.3 3698.0

[0065] Core imbibition recovery experiment:

[0066] Natural outcrop cores (average cross-sectional diameter of 2.5 cm; length of about 8 cm; average permeability of 1 mD) were used for the imbibition recovery experiment. The experimental design and results are shown in Table 2. In Table 2, the column of "Scheme" represents the specific components of the anionic surfactant and the cationic surfactant in the imbibition agent, and pH represents the overall pH value of the adjusted imbibition agent.

[0067] Table 2:

[0068] Scheme pH Imbibition recovery rate (%) SDS / EAB-40 2.05 39.16 SDS / CAB-40 2.05 42.35 AEOSHS / EAB-40 2.05 45.23 AEOSHS / CAB-35 2.05 50.24 AEOSHS / CAB-35 7.00 22.69 No addition 2.05 15.73

[0069] It can be seen from Table 2 that compared with the acidic pH regulator system without addition, the imbibition recovery rates of the compounded imbibition agent systems have been greatly improved, increasing the imbibition recovery rates of the cores from 15.73% to 39.16%, 42.35%, 45.23% and 50.24% respectively, all increasing by more than 20%. It shows that the imbibition agent composed of anionic surfactant + zwitterionic surfactant and the acidic pH regulator has a good synergistic effect and is suitable for the imbibition-acidizing synergistic oil production method. In addition, the imbibition agent composed of AEOSHS / CAB-35 has good pH sensitivity and has a good imbibition recovery rate effect at pH = 2.05, and the recovery rate reaches 50.24%. Compared with the imbibition recovery rate at pH = 7.00 and the imbibition recovery rate during single acidification, there are significant improvements, and the imbibition recovery rate is higher than their sum, indicating that the AEOSHS / CAB-35 system has a good synergistic effect with the acid solution.

[0070] Multiple experimental data show that when the pH is 2.05 and the nanoparticle concentration is 0.05 wt%, the imbibition agent with a compounding ratio of SDS / EAB-40 to AEOSHS / CAB-35 of 4:6 has the strongest ability to change the wettability of the rock; on the contrary, when the compounding ratio is 2:8, the imbibition agent has a relatively poor effect on changing the wettability of the rock compared to other imbibition agents. Therefore, it can be seen that the imbibition agent in this embodiment exhibits good pH sensitivity, and the ratio of anionic surfactant to zwitterionic surfactant needs to be adjusted according to the pH of the acid solution during use.

[0071] The various embodiments in this specification are described in a progressive manner. For the same or similar parts between the various embodiments, reference can be made to each other, and the key points of each embodiment are the differences from other embodiments.

[0072] The above embodiments are only used to illustrate the technical solutions of the present application, rather than limiting the present application; although the present application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the present application.

Claims

1. A wicking-acidizing synergistic oil production method based on a wicking agent, characterized in that It includes the following steps: S1. Extract the core samples of the target reservoir and determine the mineral composition of the target reservoir; S2. Take an anionic surfactant and an amphoteric surfactant, compound them according to multiple different molar ratios respectively, and dissolve them in water respectively to obtain multiple groups of imbibition agents; in each group of the imbibition agents, the sum of the molar proportions of the anionic surfactant and the amphoteric surfactant is 10; S3. Adjust the pH values of each group of the imbibition agents multiple times in the range of pH = 1.14 - 7.

00. After each adjustment of the pH value of each group of the imbibition agents, use it to soak the core samples extracted in S1 for 48 hours, and then test the change difference of the contact angle of the core samples; S4. Select a group of the imbibition agents with the largest change difference of the contact angle after adjusting the pH value, and use it to carry out imbibition oil production on the target reservoir.

2. A synergistic imbibition-acidizing oil production method based on an imbibition agent according to claim 1, characterized in that in S2, the sum of the mass concentrations of the anionic surfactant and the amphoteric surfactant in each group of the imbibition agents is 0.5 wt%.

3. A synergistic imbibition-acidizing oil production method based on an imbibition agent according to claim 1, characterized in that in S2, after taking the anionic surfactant and the amphoteric surfactant for compounding and dissolving them in water, hydrophilic nanoparticles are also added to the water.

4. A synergistic imbibition-acidizing oil production method based on an imbibition agent according to claim 3, characterized in that the mass concentration of the hydrophilic nanoparticles in each group of the imbibition agents is 0.05 wt%.

5. An imbibition agent, characterized in that it includes an imbibition main body and a pH regulator; the imbibition main body includes an anionic surfactant, an amphoteric surfactant and water; the anionic surfactant specifically includes sodium dodecyl sulfate and / or sodium fatty alcohol polyoxyethylene ether propyl sulfonate; the amphoteric surfactant specifically includes cocoamidopropyl betaine and / or erucylamidopropyl betaine; the sum of the mass concentrations of the anionic surfactant and the amphoteric surfactant is 0.3% - 1.0 wt%; the molar mass ratio of the anionic surfactant to the amphoteric surfactant is (2 - 8):(8 - 2); the pH regulator is used to adjust the pH value of the imbibition agent in the range of pH = 1.14 - 7.

00.

6. An imbibition agent according to claim 5, characterized in that it further includes hydrophilic nanoparticles with a particle size of 50 - 100 nm and a mass concentration of 0.01% - 0.1 wt%.

7. An imbibition agent according to claim 6, characterized in that the hydrophilic nanoparticles include one or more of nano-silica, nano-molybdenum disulfide, nano-montmorillonite, and nano-coal ash.

8. An imbibition agent according to claim 5, characterized in that the pH regulator includes one or more of hydrochloric acid, hydrofluoric acid, acetic acid, and oxalic acid.

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