A kind of imbibition oil displacement agent and its preparation method and application

Abstract

The invention discloses an imbibition oil-displacing agent, a preparation method and an application thereof, and belongs to the technical field of oilfield chemicals. The raw materials of the imbibition oil-displacing agent of the invention include an anionic nonionic surfactant, a cationic surfactant, a thickener and a solvent. The thickener is selected from a polymer with a weight-average molecular weight of 1 to 5 million. In the invention, sodium fatty alcohol polyoxyethylene ether sulfate and hexadecyltrimethylammonium chloride are compounded, and the thickener and the solvent are synergistically added to form a composition capable of preparing an imbibition oil-displacing agent with low interfacial tension, good temperature resistance, good wettability and high imbibition efficiency. The imbibition oil-displacing agent is used in tight sandstone fracturing and pressure drive throughput, thereby improving single-well fracturing productivity and reservoir recovery.

Description

Technical Field

[0001] The present invention relates to the technical field of oilfield chemicals, and in particular to an imbibition oil displacement agent, a preparation method thereof and an application thereof. Background Art

[0002] Low-permeability tight sandy conglomerate reservoirs have poor physical properties and complex pore structures, which make the seepage characteristics of reservoir fluids significantly different from those of conventional reservoirs. Therefore, studying the influence of pore structure of tight sandy conglomerate reservoirs on seepage characteristics is of great significance to improving reservoir development effects and recovery rates.

[0003] In recent years, oil demand has been steadily increasing, exacerbating the global energy crisis. However, with the advancement of unconventional oil and gas exploration and development, public perception of unconventional oil and gas is gradually shifting, with tight oil and gas becoming a recognized and important reserve resource. Tight oil reservoirs have a matrix permeability of less than 0.2 mD under overburden, making it difficult to achieve high industrial production capacity using conventional injection-production techniques. However, extensive research has revealed that rock pores are small and possess exploitable capillary forces, which spontaneously draw liquid into the pores. This entry into the core displaces crude oil from its original location into larger pores, completing the oil-water exchange and making the oil in these larger pores more accessible for recovery. Therefore, static imbibition is also an important method for improving oil and gas recovery in tight reservoirs.

[0004] Therefore, giving full play to the imbibition effect of capillary force can become an effective way to develop this type of oil reservoir, and the development of an efficient imbibition oil displacement fracturing fluid system is of great significance. Summary of the Invention

[0005] In response to the above situation, the present invention provides an imbibition oil displacement agent and its preparation method and application, which can improve the overall oil-increasing effect of fracturing, enable the fracturing fluid system to perform functions such as oil washing, oil-water imbibition replacement and energy replenishment, and solve the problems of conventional fracturing in the fracturing process of tight oil reservoirs, such as high post-fracturing decline rate, poor production stability, difficulty in energy replenishment, and low recovery rate.

[0006] In order to solve the above technical problems, the first aspect of the present invention provides an imbibition oil-displacing agent, the raw materials of which include an anionic non-ionic surfactant, a cationic surfactant, a thickener and a solvent; the anionic non-ionic surfactant is selected from at least one of fatty alcohol polyoxyethylene ether sodium sulfate and fatty alcohol polyoxyethylene ether sodium sulfonate; the cationic surfactant is selected from at least one of hexadecyltrimethylammonium chloride and dodecyldimethylbenzylammonium chloride; the thickener is selected from a polymer with a weight-average molecular weight of 1 million to 5 million.

[0007] According to some embodiments of the present invention, the thickener is selected from anionic thickeners, preferably, the anionic thickener is selected from anionic polyacrylamide;

[0008] The anionic polyacrylamide in the present invention is a cross-linked polymer emulsion thickener containing acidic groups. It has a very low viscosity in an acidic medium. When diluted with water and neutralized with an alkali, its emulsion particles expand quickly, so that the system obtains a high viscosity. The leveling property is good after thickening, and the viscosity of the emulsion under low shear force and high shear force can be improved.

[0009] According to some embodiments of the present invention, based on the total mass of the imbibition oil-displacing agent, the content of the anionic nonionic surfactant is 0.1wt% to 0.5wt%, preferably 0.1wt% to 0.3wt%, the content of the cationic surfactant is 0.1wt% to 0.5wt%, preferably 0.1 to 0.3wt%, the content of the thickener is 0.02wt% to 0.06wt%, preferably 0.03wt% to 0.05wt%, and the content of the solvent is 99.2wt% to 99.7wt%, preferably 99.5wt% to 99.7wt%. The inventors have found that by adopting the specific embodiment under this preferred case, an imbibition oil-displacing agent with lower interfacial tension, good temperature resistance and anti-adsorption performance, and good wettability can be obtained.

[0010] According to some embodiments of the present invention, the weight average molecular weight of the sodium fatty alcohol polyoxyethylene ether sulfate is 300-500.

[0011] According to some embodiments of the present invention, the solvent includes deionized water; preferably, the solvent includes at least one of sodium chloride, sodium bicarbonate, calcium chloride and magnesium chloride; more preferably, in the solvent, the concentration of sodium chloride is 60g / L to 80g / L, the concentration of sodium bicarbonate is 0.4g / L to 0.6g / L, the concentration of calcium chloride is 2.0g / L to 2.4g / L, and the concentration of magnesium chloride is 0.4g / L to 0.6g / L.

[0012] The second aspect of the present invention provides a method for preparing the above-mentioned imbibition oil-displacing agent, comprising mixing an anionic nonionic surfactant, a cationic surfactant, a thickener and a solvent to obtain the imbibition oil-displacing agent.

[0013] According to some embodiments of the present invention, the mixing specifically comprises:

[0014] (1) performing a first contact mixing of the thickener and the solvent to obtain a first mixed solution;

[0015] (2) The first mixed solution, the anionic nonionic surfactant and the cationic surfactant are subjected to a second contact mixing to obtain the imbibition oil displacement agent.

[0016] According to some embodiments of the present invention, the operating conditions of the first contact mixing and the second contact mixing independently include: a stirring speed of 400 rpm to 600 rpm, preferably 350 rpm, a temperature of 80°C to 100°C, preferably 100°C, and a time of 5 min to 7 min, for example, 5 min, 6 min, or 7 min.

[0017] A third aspect of the present invention provides use of the above-mentioned imbibition oil displacement agent or the imbibition oil displacement agent prepared by the preparation method in oil and gas development.

[0018] Beneficial effects:

[0019] The present invention compounds fatty alcohol polyoxyethylene ether sodium sulfate and cetyltrimethylammonium chloride, and synergizes a thickener and a solvent to form a composition capable of preparing an imbibition oil-displacing agent with low interfacial tension, good temperature resistance, good wettability and high imbibition efficiency. The imbibition oil-displacing agent is used in tight sandstone fracturing and pressure drive huff and puff, thereby improving single-well fracturing productivity and reservoir recovery.

[0020] The imbibition oil-displacing agent described in the present invention is used in the fracturing transformation process of tight oil reservoirs. As a composite oil-displacing and production-increasing fracturing fluid system, it can not only meet the functions of conventional fracturing, but also achieve multiple effects such as fracturing oil washing, oil-water imbibition replacement, and fracturing energy replenishment. After field application, the single-well fracturing production capacity is improved, and it has good application effect and application prospects. DETAILED DESCRIPTION

[0021] The present invention will be further described below with reference to the following examples, but the present invention is not limited to these examples.

[0022] The endpoints of the ranges and any values ​​disclosed in the present invention are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be considered to be specifically disclosed in the present invention.

[0023] In various aspects of the present invention, for the same components in various aspects, the present invention is described only once in one aspect without repeated description, which should not be understood by those skilled in the art as limiting the present invention.

[0024] Raw materials not described in the present invention can be obtained from general commercial sources, and those skilled in the art can purchase them as needed, and are not described in detail in the present invention.

[0025] The fatty alcohol polyoxyethylene ether sodium sulfate (AES) described in the present invention has a weight-average molecular weight of 500 and a model number of C24E2S; it was purchased from Shandong Yousuo Chemical Technology Co., Ltd.

[0026] The sodium fatty alcohol polyoxyethylene ether carboxylate described in the present invention has a weight-average molecular weight of 500, a model number of AEC-9Na, and is purchased from Shandong Yousuo Chemical Technology Co., Ltd.

[0027] The hexadecyltrimethylammonium chloride described in the present invention has a model number of 1631 and is purchased from BASF.

[0028] The potassium chloride described in the present invention was purchased from BASF.

[0029] The thickener in the present invention is polyacrylamide (PAM) with a weight average molecular weight of 5 million, purchased from Shandong Yousuo Chemical Technology Co., Ltd.

[0030] The surface tension meter used in the present invention was purchased from Dataphysics, Germany, with a model number of DCAT.

[0031] The spinning drop interfacial tension meter used in the present invention was purchased from Dataphysics, Germany, with a model number of TX-500.

[0032] The contact angle measuring instrument used in the present invention was purchased from Dataphysics, Germany, and its model is Krues DSA25.

[0033] The self-priming instrument used in the present invention was purchased from Shanghai Cangmao Industrial Co., Ltd., model 2XZ-0.5.

[0034] Unless otherwise specified, other instruments or equipment used in the present invention are common commercially available products.

[0035] The amounts of components in the following examples are all expressed in percentages by mass, with 1% by mass representing 1 g.

[0036] In the following examples, the solvent is simulated formation water, wherein the property parameters and specific ion composition of the simulated formation water are shown in Table 1.

[0037] Table 1 Property parameters and specific composition of the simulated formation water of the present invention

[0038]

[0039] Example 1

[0040] This embodiment provides an imbibition oil-displacing agent.

[0041] The raw materials and contents of the imbibition oil displacement agent in this embodiment are: 0.15 wt% of sodium sulfate of fatty alcohol polyoxyethylene ether with a weight average molecular weight of 500, 0.15 wt% of hexadecyltrimethylammonium chloride, 0.05 wt% of polyacrylamide (anionic type) with a weight average molecular weight of 5 million, and 99.65 wt% of simulated formation water as the solvent.

[0042] The preparation method of the imbibition oil-displacing agent is as follows:

[0043] (1) At a temperature of 100° C., polyacrylamide with a weight average molecular weight of 5 million and simulated formation water were first stirred and mixed at a rate of 350 rpm for 5 minutes to obtain a first mixed solution;

[0044] (2) Under the condition of temperature of 100°C, the first mixed solution was stirred and mixed with sodium fatty alcohol polyoxyethylene ether sulfate and hexadecyltrimethylammonium chloride at a speed of 350 rpm for a second time for 5 minutes to obtain the imbibition oil displacement agent S1. The formula and preparation process parameters of the imbibition oil displacement agent S1 are shown in Table 2.

[0045] Example 2

[0046] This embodiment provides an imbibition oil-displacing agent.

[0047] The preparation method described in Example 1 was adopted, except that the content of fatty alcohol polyoxyethylene ether sodium sulfate was 0.2wt%, the content of cetyltrimethylammonium chloride was 0.1wt%, and the time for the first stirring and mixing and the second stirring and mixing was 6 min to obtain an imbibition oil-displacing agent S2; the formula and preparation process parameters of the imbibition oil-displacing agent S2 are shown in Table 2.

[0048] Example 3

[0049] This embodiment provides an imbibition oil-displacing agent.

[0050] The preparation method described in Example 1 was adopted, except that the content of fatty alcohol polyoxyethylene ether sodium sulfate was 0.1 wt %, the content of cetyltrimethylammonium chloride was 0.2 wt %, and the time for the first stirring and mixing and the second stirring and mixing was 7 min to obtain an imbibition oil-displacing agent S3; the formula and preparation process parameters of the imbibition oil-displacing agent S3 are shown in Table 2.

[0051] Example 4

[0052] This embodiment provides an imbibition oil-displacing agent.

[0053] The preparation method described in Example 1 was adopted, except that the content of fatty alcohol polyoxyethylene ether sodium sulfate was 0.4 wt % and the content of simulated formation water was 99.4 wt % to obtain imbibition oil displacement agent S4; the formula and preparation process parameters of the imbibition oil displacement agent S4 are shown in Table 2.

[0054] Example 5

[0055] This embodiment provides an imbibition oil-displacing agent.

[0056] The preparation method described in Example 1 was adopted, except that the content of hexadecyltrimethylammonium chloride was 0.4 wt % and the content of simulated formation water was 99.4 wt % to obtain the imbibition oil-displacing agent S5; the formula and preparation process parameters of the imbibition oil-displacing agent S5 are shown in Table 2.

[0057] Comparative Example 1

[0058] This comparative example provides an imbibition oil-displacing agent.

[0059] The preparation method described in Example 1 was adopted, except that an equal amount of sodium fatty alcohol polyoxyethylene ether carboxylate (AEC-9Na) with a weight-average molecular weight of 500 was used to replace sodium fatty alcohol polyoxyethylene ether sulfate to obtain an imbibition oil-displacing agent RS1; the formula and preparation process parameters of the imbibition oil-displacing agent RS1 are shown in Table 3.

[0060] Comparative Example 2

[0061] This comparative example provides an imbibition oil-displacing agent.

[0062] The preparation method described in Example 1 was adopted, except that an equal mass of potassium chloride was used to replace hexadecyltrimethylammonium chloride to obtain an imbibition oil-displacing agent RS2; the formula and preparation process parameters of the imbibition oil-displacing agent RS2 are shown in Table 3.

[0063] Comparative Example 3

[0064] This comparative example provides an imbibition oil-displacing agent.

[0065] The preparation method described in Example 1 was adopted, except that the content of fatty alcohol polyoxyethylene ether sodium sulfate was 0.05 wt %, and the amount of simulated formation water was 99.75 wt %, to obtain imbibition oil displacement agent RS3; the formula and preparation process parameters of the imbibition oil displacement agent RS3 are shown in Table 3.

[0066] Comparative Example 4

[0067] This comparative example provides an imbibition oil-displacing agent.

[0068] The preparation method described in Example 1 was adopted, except that the content of hexadecyltrimethylammonium chloride was 0.05 wt % and the amount of simulated formation water was 99.75 wt % to obtain imbibition oil displacement agent RS4; the formula and preparation process parameters of the imbibition oil displacement agent RS4 are shown in Table 3.

[0069] Table 2 Component ratios and preparation parameters of the imbibition oil displacement agent described in Examples 1-5 of the present invention

[0070]

[0071] Table 3 Component ratios and preparation parameters of the imbibition oil displacement agents described in Comparative Examples 1-4 of the present invention

[0072]

[0073] Test Case

[0074] In order to further illustrate the progressiveness of the imbibition oil-displacing agent of the present invention, the imbibition oil-displacing agents S1-S5 and RS1-RS4 prepared in the above Examples 1-5 and Comparative Examples 1-4 were subjected to performance tests, specifically including tests on surface tension, interfacial tension, contact angle and imbibition efficiency. The specific test results are statistically shown in Table 4.

[0075] Among them, the surface tension testing method is: using the above-mentioned simulated formation water to dilute the imbibition oil displacement agents S1-S5 and RS1-RS4 prepared in Examples 1-5 and Comparative Examples 1-4 by 200 times respectively to obtain the test samples, and then testing the test samples with a surface tension meter at a temperature of 25°C, and measuring three times in a row to take the average value.

[0076] The interfacial tension test method is as follows: the imbibition oil displacement agents S1-S5 and RS1-RS4 prepared in Examples 1-5 and Comparative Examples 1-4 are diluted 200 times respectively with the above-mentioned simulated formation water to obtain a sample to be tested, and then the sample to be tested is measured at a temperature of 60°C using a TX-500 rotating drop interfacial tension meter, using crude oil in simulated formation water as the oil sample, and the average value is taken for three consecutive measurements.

[0077] The contact angle testing method is as follows: the imbibition oil-displacing agents S1-S5 and RS1-RS4 prepared in Examples 1-5 and Comparative Examples 1-4 are diluted 200 times respectively with the above-mentioned simulated formation water to obtain a sample to be tested; a low-permeability sandstone core slice with a thickness of 5 mm is prepared, the cut surface is polished flat with sandpaper, the sandstone core slice is cleaned with alcohol and distilled water, and placed in an oven at a temperature of 150°C for 24 hours, and then the core slice is placed in Shengli crude oil and immersed at a temperature of 60°C for 72 hours for aging to make it an oil-wet surface; then the sandstone core slice is taken out, the surface oil is wiped clean with paper, and then immersed in the sample to be tested, placed in an oven at a temperature of 60°C for 24 hours, and the three-phase contact angles of the core slice surface, air, and water are measured using a Krues DSA25 contact angle meter, and the average value is taken after three consecutive measurements.

[0078] The test method of the imbibition efficiency is as follows: the imbibition oil displacement agents S1-S5 and RS1-RS4 prepared in Examples 1-5 and Comparative Examples 1-4 are diluted 200 times respectively with the above-mentioned simulated formation water to obtain samples to be tested.

[0079] (1) Core preparation: Drill and dry the experimental cores, and measure the gas permeability and porosity; vacuum all the experimental cores and saturate them with simulated formation water, and use a constant pressure and constant speed pump to displace more than 5PV to measure the water phase permeability; then perform oil-water displacement, displace the experimental cores to the bound water state, record the water volume displaced by the oil-water displacement, and measure the oil phase permeability under the bound water.

[0080] (2) Place the experimental core into the imbibition instrument containing the sample to be tested, allow the core to self-absorb and discharge oil, and record the amount of oil discharged over time; when the volume of discharged oil does not change for 72 consecutive hours, record the total volume of self-absorbed oil and calculate the imbibition efficiency.

[0081] Among them, imbibition efficiency (%) = (volume of self-imbibed oil / volume of water displaced by oil-displaced water) × 100%.

[0082] The temperature resistance test method is as follows: the imbibition oil displacement agents S1-S5 and RS1-RS4 surfactant composite systems prepared in the above Examples 1-5 and Comparative Examples 1-4 are placed in an oven at different temperatures (25-150°C) and left to stand for 24 hours, and the solution changes under different temperature conditions (25-150°C) are observed to determine whether phase separation or precipitation occurs.

[0083] Table 4 Test results of surface tension, interfacial tension, contact angle, imbibition efficiency and temperature resistance of the imbibition oil displacement agents S1-S5 and RS1-RS4 prepared in Examples 1-5 of the present invention and Comparative Examples 1-4

[0084]

[0085] As can be seen from the results in Table 4, the components and proportions of the imbibition oil-displacing agent of the present invention can be used to prepare an imbibition oil-displacing agent with low interfacial tension, good anti-adsorption performance, outstanding wettability change ability, and good temperature resistance. The imbibition oil-displacing agent of the present invention can be used in the fracturing and huff-and-puff oil production processes of tight sandstone and tight conglomerate to improve the single well productivity.

[0086] Application Examples

[0087] In order to further illustrate the progress and practicality of the imbibition displacement agent of the present invention, the imbibition displacement agent S1 prepared in Example 1 above is applied to oil wells 1-10 of Shengli Oilfield. Under different injection rates of imbibition displacement fluid, the daily oil production after fracturing (daily oil production after fracturing in Table 5), the average daily oil production of a single well in the block (average daily oil production of a single well in the block in Table 5) and the oil increase ratio of the imbibition displacement agent S1 in different strata are respectively measured, wherein the imbibition displacement fluid is an aqueous solution prepared by the imbibition displacement agent prepared in Example 1 of the present invention; the mass concentration of the surfactant (the surfactant, i.e., the anionic nonionic surfactant and the cationic surfactant in the imbibition displacement agent S1) in the imbibition displacement fluid is 0.3wt%; the oil increase ratio refers to the percentage of the increase in daily oil production after fracturing of the well injected with the imbibition displacement fluid relative to the average daily oil production of a single well in the block; the specific results are statistically shown in Table 5.

[0088] Table 5 Application effect of imbibition oil displacement agent S1 prepared in Example 1 of the present invention

[0089]

[0090] In Table 5, the total is that the imbibition oil displacement agent S1 prepared in the above Example 1 was applied to the No. 1-10 oil wells in Shengli Oilfield. Based on the total daily oil production of the No. 1-10 oil wells after fracturing and the total average daily oil production of a single well in the block, the overall oil increase ratio of the No. 1-10 oil wells was 53.85%.

[0091] It should be noted that the embodiments described above are only used to explain the present invention and do not constitute any limitation of the present invention. The present invention has been described with reference to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory words, rather than restrictive words. The present invention may be modified as specified within the scope of the claims of the present invention, and the present invention may be revised without departing from the scope and spirit of the present invention. Although the present invention described therein relates to specific methods, materials and embodiments, it does not mean that the present invention is limited to the specific examples disclosed therein. On the contrary, the present invention can be extended to all other methods and applications with the same function.

Claims

1. An imbibition oil displacement agent, characterized in that: The raw materials of the imbibition oil displacement agent include an anionic nonionic surfactant, a cationic surfactant, a thickener and a solvent; the anionic nonionic surfactant is selected from at least one of fatty alcohol polyoxyethylene ether sodium sulfate and fatty alcohol polyoxyethylene ether sodium sulfonate; the cationic surfactant is selected from at least one of hexadecyltrimethylammonium chloride and dodecyldimethylbenzylammonium chloride; the thickener is selected from anionic polyacrylamide; Based on the total mass of the imbibition oil displacement agent, the content of the anionic nonionic surfactant is 0.1wt% to 0.5wt%, the content of the cationic surfactant is 0.1wt% to 0.5wt%, the content of the thickener is 0.02wt% to 0.06wt%, and the content of the solvent is 99.2wt% to 99.7wt%; The solvent includes deionized water; the solvent includes sodium chloride, calcium chloride and magnesium chloride; in the solvent, the concentration of sodium chloride is 60g / L to 80g / L, the concentration of calcium chloride is 2.0g / L to 2.4g / L, and the concentration of magnesium chloride is 0.4g / L to 0.6g / L.

2. The imbibition oil displacement agent according to claim 1, wherein Based on the total mass of the imbibition oil displacement agent, the content of the anionic nonionic surfactant is 0.1wt% to 0.3wt%, the content of the cationic surfactant is 0.1 to 0.3wt%, the content of the thickener is 0.03wt% to 0.05wt%, and the content of the solvent is 99.5wt% to 99.7wt%.

3. The imbibition oil displacement agent according to claim 1, wherein The weight average molecular weight of the fatty alcohol polyoxyethylene ether sodium sulfate is 300-500.

4. A method for preparing the imbibition oil displacement agent according to any one of claims 1 to 3, characterized in that: The method comprises mixing an anionic nonionic surfactant, a cationic surfactant, a thickener and a solvent to obtain the imbibition oil displacement agent.

5. The preparation method according to claim 4, characterized in that The mixing specifically includes: (1) performing a first contact mixing of the thickener and the solvent to obtain a first mixed solution; (2) The first mixed solution, the anionic nonionic surfactant and the cationic surfactant are subjected to a second contact mixing to obtain the imbibition oil displacement agent.

6. The preparation method according to claim 5, characterized in that The operating conditions of the first contact mixing and the second contact mixing independently include: a stirring speed of 400 rpm to 600 rpm, a temperature of 80° C. to 100° C., and a time of 5 min to 7 min.

7. Use of the imbibition oil-displacing agent according to any one of claims 1 to 3 or the imbibition oil-displacing agent prepared by the preparation method according to any one of claims 4 to 6 in oil and gas development.

8. Use of the imbibition oil-displacing agent according to any one of claims 1 to 3 or the imbibition oil-displacing agent prepared by the preparation method according to any one of claims 4 to 6 in fracturing or huff-and-puff oil production of tight sandstone or tight conglomerate.

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