A reservoir modifier for low-permeability sandstone and shale oil reservoirs and its preparation method

Abstract

The present invention relates to the field of oilfield development, and discloses a reservoir modifier for low-permeability sandstone and shale oil reservoirs and a preparation method thereof. The preparation method comprises the following steps: cleaning, freeze-drying and pulverizing usnea to obtain usnea powder; extracting active ingredients from the usnea powder with a mixed solvent composed of methanol, water and a first alkaline substance to obtain an extract; mixing the extract with column chromatography silica gel, and recovering methanol by reduced pressure distillation; extracting the silica gel with an acid solution; adding a second alkaline substance, a sulfonating agent, a modifier and water to the acid dissolution solution for reaction, and then adding a surfactant and a stabilizer; drying and packaging the chemical modification product. The present invention directly dissolves rocks with plant extracts to increase permeability, without damaging the formation; does not contain strong acids and will not produce harmful substances during use, having good environmental protection benefits; can be injected synchronously with oil production agents, with simple and fast operation and good economic benefits.

Description

Technical Field

[0001] The present invention relates to the field of oilfield development, and particularly to a reservoir modifier for low-permeability sandstone and shale reservoirs and a preparation method thereof. Background Art

[0002] The existing developable oil reservoirs are mainly low-permeability and ultra-low-permeability. Due to their dense structure and very low permeability, the remaining oil is mainly distributed in micron / sub-micron pores, and the existing chemical oil recovery agents are difficult to effectively reach. Therefore, the current development methods are acidification and fracturing, that is, using chemical substances such as hydrofluoric acid and hydrochloric acid plus pressure sufficient to damage the formation to artificially create fractures in the formation to increase permeability. However, the existing technology causes great damage to the formation, and the comprehensive recovery rate generally still cannot exceed 15%. In other words, the existing development methods for low-permeability oil reservoirs mainly aim at the problem of too low formation permeability, and use chemical agents (acidifying agents), mechanical pressure (fracturing) or a combination of both to artificially create fractures in the formation to increase formation permeability. However, these means will seriously increase the heterogeneity of the formation, and the residual chemical agents contain toxic and harmful substances and are difficult to treat (such as fluorides), which not only brings difficulties to the subsequent development of the oil reservoir, but also increases the cost of environmental protection treatment and limits the development of some oil reservoirs.

[0003] The current chemical agents for treating low-permeability rock formations mainly use fluorides to corrode silicates under acidification conditions such as hydrochloric acid / sulfuric acid to create dissolution pores. Regarding the relevant patents on oilfield acidification technology, the following are listed:

[0004] The invention patent with the application number CN202111602520.6 and the publication number CN116333717B discloses a high-viscosity slow-acidizing agent for volcanic rock reservoir acidification, a preparation method and an application thereof. The high-viscosity slow-acidizing agent is composed of HCl, HF, polymer thickening agent, acidification corrosion inhibitor, iron ion stabilizer, acidification emulsion-breaking demulsifier, high-viscosity thickening agent, hydration agent and water, etc. It has good temperature resistance, excellent rheological properties at 120°C, good slow-acidizing effect and filtration loss reduction effect, and can achieve deep penetration of acid fluid to remove deep formation pollution.

[0005] The invention patent application No. is CN202211143732.7 and the publication No. is CN117786918A, which discloses a method for acidification and reconstruction design of clay shale reservoirs. Based on the clay shale reservoir and lithological characteristics, this method gives full play to the advantages of bedding planes, maintains the rock skeleton, dredges the rock bedding, communicates pores and takes into account large-scale acidification for swelling prevention and oil washing. Taking quartz, feldspar and clay minerals as the rock skeleton, mainly dissolving calcite, dolomite, siderite and pyrite in the bedding, a design method for injection parameters of acidification and reconstruction of bedding planes is established. Taking the part of HCl-soluble rock on the bedding plane as the basis for dosage design, it is clear that the reservoir fracture pressure is the upper limit of injection pressure, and the injection displacement under this pressure is the upper limit. The overall purpose is to achieve deep treatment of acid fluid, form effective acid etching grooves and improve the permeability of bedding. In the field test of shale oil development in oilfields, good oil testing results of increasing liquid production and oil production are obtained.

[0006] The above acidification technologies all rely on strong acids and hydrofluoric acid to dissolve rocks, require complex equipment and subsequent treatment, and involve harmful substances and environmental protection issues, and cannot be injected synchronously with existing oil production agents.

[0007] At present, there is no relevant research and technology on using plant extracts to corrode silicate rocks. Summary of the Invention

[0008] To overcome the defects of the prior art, the present invention provides a reservoir modifier for low-permeability sandstone and shale oil reservoirs and a preparation method thereof. The technical scheme is as follows:

[0009] A preparation method of a reservoir modifier for low-permeability sandstone and shale oil reservoirs, which includes the following steps:

[0010] (1) Raw material treatment: Using usnea as the raw material, successively carry out cleaning, freeze-drying and pulverization treatment to obtain usnea powder;

[0011] (2) Methanol extraction: Extract the active ingredients from the usnea powder obtained in step (1) with a mixed solvent composed of methanol, water and a first alkaline substance to obtain an extract; wherein: the mass ratio of usnea powder, methanol, water and the first alkaline substance is 20:(100-200):(30-60):(2-10); the first alkaline substance includes one or more of sodium hydroxide, potassium hydroxide, ammonia water, triethylamine, triethanolamine, ethanolamine, diethanolamine and pyridine;

[0012] (3) Column chromatography silica gel adsorption: Mix the extract obtained in step (2) with column chromatography silica gel according to a mass ratio of 100:(10-20), and then recover methanol by vacuum distillation and adsorb the product on the silica gel;

[0013] (4)Acid solution extraction: Extract the silica gel of the adsorption product in step (3) with an acid solution having a mass concentration of 1-5%, so that the product is dissolved in the acid solution to form an acid dissolution solution; the acid solution is an aqueous solution of formic acid, acetic acid, citric acid, oxalic acid, hydrochloric acid or sulfuric acid;

[0014] (5)Chemical modification: Add a second basic substance, a sulfonating agent, a modifier and water to the acid dissolution solution formed in step (4) for reaction, and then add a surfactant and a stabilizer to the reaction product solution to obtain a chemically modified product; wherein: the mass ratio of the acid dissolution solution, the second basic substance, the sulfonating agent, the modifier and water is 100:(2-15):(20-30):(10-20):(50-100); the mass ratio of the reaction product solution, the surfactant and the stabilizer is 100:(5-10):(3-5); the second basic substance includes one of sodium hydroxide, potassium hydroxide and ammonia water; the sulfonating agent includes one of sulfamic acid, propanesultone, butanesultone, pyridine sulfur trioxide, butyrolactone, valerolactone, chloroacetic acid and its salts, bromoacetic acid and its salts, sodium formaldehyde sulfoxylate; the modifier includes one of glutaraldehyde, formaldehyde, hexamethylenetetramine, hydroxymethylacrylamide, dimethylolurea, dimethylolmelamine, trimethylolmelamine, dimethylolphenol, trimethylolphenol;

[0015] (6)Drying and packaging: Dry the chemically modified product obtained in step (5), and then package it.

[0016] Further, the extraction temperature in step (2) is 20-50°C, and the extraction time is 2-6 hours.

[0017] Further, the specification of the column chromatography silica gel in step (3) is 200-400 mesh.

[0018] Further, the acid solution extraction time in step (4) is 1-5 hours.

[0019] Further, the reaction temperature in step (5) is 60-100°C, and the reaction time is 6-24 hours.

[0020] Further, the stabilizer in step (5) includes one of sodium thiosulfate, sodium dithionite, sodium sulfite, sodium formaldehyde sulfoxylate, D / L-(iso)ascorbic acid and its salts and esters, gallic acid and its salts and esters, tert-butylhydroquinone, sorbitol, maltitol.

[0021] Further, the surfactant in step (5) has the following characteristic structure:

[0022] ;

[0023] Wherein: Cx is a carbon chain, x = 5 - 18, including an alkyl chain with a saturated structure, a carbon chain with a branched structure, and a carbon chain with a cyclic structure, and also including a mixed raw material carbon chain extracted from natural oils and fats and petroleum; n = 4 - 18.

[0024] A reservoir modifier for low-permeability sandstone and shale oil reservoirs, which is obtained by preparing according to the preparation method of a reservoir modifier for low-permeability sandstone and shale oil reservoirs described above.

[0025] The main components in the prepared reservoir modifier have the following typical structures:

[0026] ;

[0027] Compared with the prior art, the present invention mainly has the following beneficial technical effects:

[0028] 1. The present invention uses plant extracts to directly dissolve rocks to improve permeability without damaging the formation.

[0029] 2. The reservoir modifier of the present invention does not contain strong acids and will not produce harmful substances during use, having good environmental benefits.

[0030] 3. The reservoir modifier of the present invention can be injected synchronously with the oil production agent, with simple and fast operation and good economic benefits.

[0031] 4. The present invention has broad application prospects in the development of low-permeability sandstone and shale oil reservoirs.

[0032] In addition, to enable those skilled in the art to better understand the present invention, the following examples extract the chemical reaction process (this process is a conventional chemical reaction, and the reaction type and process itself do not involve innovation):

[0033] . Specific Embodiments

[0034] The present invention will be described in detail below with reference to the embodiments. Example 1

[0035] 1. Preparation method of the reservoir modifier:

[0036] Usnea powder: The mass ratio of methanol, water, and ethanolamine is 20:120:30:5. Heat at 50°C for 6 hours. Mix the extract with 400-mesh column chromatography silica gel at a mass ratio of 100:10. Remove methanol by vacuum distillation and add 1% formic acid for extraction. The mass ratio of the acid dissolution solution, sodium hydroxide, propanesultone, 40% formaldehyde solution, and water is 100:5:20:12:100. The reaction time is 18 hours at a temperature of 95°C. After the reaction, add 5 parts by mass of NP-10 and 3 parts by mass of D-sodium erythorbate to every 100 parts by mass of the reaction solution, and then dry and package.

[0037] 2. Performance characterization results of the reservoir modifier:

[0038] For sandstone cores with a water permeability of 1.4 mD, the main rock type is quartz. After continuously injecting the product at a concentration of 0.3% (pH = 7.2) and heating at 80°C for 24 hours, the permeability of the sandstone core increases from 1.4 mD to 2.6 mD. Example 2

[0039] 1. Preparation method of the reservoir modifier:

[0040] Usnea powder: The mass ratio of methanol, water, diethanolamine, and sodium hydroxide is 20:150:40:5:2. Heat at 40°C for 3 hours. Mix the extract with 400-mesh column chromatography silica gel at a mass ratio of 100:15. Remove methanol by vacuum distillation and add 1% acetic acid for extraction. The mass ratio of the acid dissolution solution, sodium hydroxide, aminosulfonic acid, 40% formaldehyde solution, and water is 100:4:25:12:100. The reaction time is 12 hours at a temperature of 85°C. After the reaction, add 6 parts by mass of OP-7 and 2 parts by mass of sodium dithionite to every 100 parts by mass of the reaction solution, and then dry and package.

[0041] 2. Performance characterization results of the reservoir modifier:

[0042] For sandstone with a water permeability of 5 - 8 mD, the main rock types are quartz and feldspar. After treating with the product at a concentration of 0.5% (pH = 7.2) and heating in a sealed state at 100°C for 72 hours, dissolution cracks and pores with a size of 2 - 3 μm increase on the sandstone surface. At the same time, the surface roughness Ra increases from 0.6 μm to 2.3 μm. Example 3

[0043] 1. Preparation method of the reservoir modifier:

[0044] Usnea powder: The ratio of methanol, water, 25% ammonia water, and triethylamine is 20:180:50:10:3. Heat at 35°C for 5 hours. Mix the extract with 300-mesh column chromatography silica gel at a mass ratio of 100:20. Remove methanol by vacuum distillation, and add 1% citric acid for extraction. The mass ratio of the acid dissolution solution, 25% ammonia water, sodium formaldehyde sulfoxylate, 40% formaldehyde solution, and water is 100:15:30:20:80. The reaction time is 6 hours and the temperature is 100°C. After the reaction, add 10 parts of alkyl polyoxypropylene ether and 5 parts of sorbitol to every 100 parts of the reaction solution, and then dry and package.

[0045] 2. Performance characterization results of the reservoir modifier:

[0046] For sandstone with a water permeability of 5 - 10 mD, the main rock types are feldspar and clay. After heat treatment at 100°C for 48 hours in a sealed state using this product with a concentration of 1.5% (pH = 7.2), dissolution cracks and pores of 3 - 4 μm are increased on the sandstone surface. At the same time, the surface roughness Ra increases from 0.7 μm to 3.9 μm.

Claims

1. A preparation method of a reservoir modifier for low-permeability sandstone and shale oil reservoirs, characterized in that, It includes the following steps: (1) Raw material treatment: Using Usnea as the raw material, successively carry out cleaning, freeze-drying and pulverization treatments to obtain Usnea powder; (2) Methanol extraction: Extract the active ingredients from the Usnea powder obtained in step (1) with a mixed solvent composed of methanol, water and a first basic substance to obtain an extract; wherein: the mass ratio of Usnea powder, methanol, water and the first basic substance is 20:(100 - 200):(30 - 60):(2 - 10); the first basic substance is one or more of sodium hydroxide, potassium hydroxide, ammonia water, triethylamine, triethanolamine, ethanolamine and diethanolamine; (3) Column chromatography silica gel adsorption: Mix the extract obtained in step (2) with column chromatography silica gel according to a mass ratio of 100:(10 - 20), then recover methanol by vacuum distillation and adsorb the product on the silica gel; (4) Acid solution extraction: Extract the silica gel with the adsorbed product in step (3) with an acid solution with a mass concentration of 1 - 5% to dissolve the product in the acid solution to form an acid dissolution solution; the acid solution is an aqueous solution of formic acid, acetic acid, citric acid, oxalic acid, hydrochloric acid or sulfuric acid; (5) Chemical modification: Add a second basic substance, a sulfonating agent, a modifier and water to the acid dissolution solution formed in step (4) for reaction, and then add a surfactant and a stabilizer to the reaction product solution to obtain a chemically modified product; wherein: the mass ratio of the acid dissolution solution, the second basic substance, the sulfonating agent, the modifier and water is 100:(2 - 15):(20 - 30):(10 - 20):(50 - 100); the mass ratio of the reaction product solution, the surfactant and the stabilizer is 100:(5 - 10):(3 - 5); the second basic substance is one of sodium hydroxide, potassium hydroxide and ammonia water; the sulfonating agent is one of aminosulfonic acid, propanesultone, butanesultone, sodium formaldehyde sulfoxylate; the modifier is one of glutaraldehyde, formaldehyde, hydroxymethylacrylamide; (6) Drying and packaging: Dry the chemically modified product obtained in step (5), and then package it; The surfactant in step (5) has the following characteristic structure: ； wherein: Cx is a carbon chain, x = 5 - 18, which is an alkyl chain with a saturated structure, a carbon chain with a branched structure and a carbon chain with a cyclic structure; The stabilizer in step (5) is one of sodium thiosulfate, sodium dithionite, sodium sulfite, sodium formaldehyde sulfoxylate, D / L-(iso)ascorbic acid and its salts, sorbitol, maltitol.

2. The preparation method of a reservoir modifier for low-permeability sandstone and shale oil reservoirs according to claim 1, characterized in that, The extraction temperature in step (2) is 20 - 50 °C, and the extraction time is 2 - 6 hours.

3. The preparation method of a reservoir modifier for low-permeability sandstone and shale oil reservoirs according to claim 1, characterized in that, The specification of the column chromatography silica gel in step (3) is 200 - 400 mesh.

4. The preparation method of a reservoir modifier for low-permeability sandstone and shale oil reservoirs according to claim 1, characterized in that, The acid solution extraction time in step (4) is 1 - 5 hours.

5. The preparation method of a reservoir modifier for low-permeability sandstone and shale oil reservoirs according to claim 1, characterized in that, The reaction temperature in step (5) is 60 - 100 °C, and the reaction time is 6 - 24 hours.

6. A reservoir modifier for low-permeability sandstone and shale oil reservoirs, characterized in that, This reservoir modifier is prepared by the preparation method of a reservoir modifier for low-permeability sandstone and shale oil reservoirs according to any one of claims 1 - 5.

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