Composite buffer for oil production acidification

Abstract

The present invention discloses a composite buffer for oil production acidification, relating to the field of oil production. The buffer comprises component A (comprising at least one of unpurified biomass materials such as citrus peel powder, kelp powder, and carbonized bagasse particles, as well as polyglutamic acid) and component B (sodium citrate). The two components are mixed in a certain proportion and then compounded with a hydrochloric acid solution to form a buffer working fluid. Through the synergistic effect of the unpurified biomass and the purified functional components, the buffer is divided into low-temperature and high-temperature types, respectively suitable for oil reservoir acidification under different temperature conditions. The low-temperature buffer is environmentally friendly and reduces costs by 60%. The high-temperature buffer has a temperature resistance of ≥120°C and effectively extends the acid action range. This invention utilizes agricultural / aquatic waste, combining economic efficiency and environmental friendliness. It is suitable for the differentiated acidification needs of onshore and offshore oil fields and has broad application prospects.

Description

Technical Field

[0001] The present invention relates to the field of oil production, in particular to a composite buffer for oil production acidification. Background Art

[0002] In the field of oil production acidification, traditional buffers primarily utilize synthetic chemicals such as phosphates and ethylenediaminetetraacetic acid. While these buffers can maintain the pH of the acid solution to a certain extent, they have numerous drawbacks. First, the high cost of synthetic chemicals increases the economic burden of oil production. Second, these chemicals can cause environmental pollution during use, failing to meet increasingly stringent environmental protection requirements. Furthermore, single-formula buffers are difficult to adapt to reservoirs with varying temperatures and geological conditions, requiring frequent formulation adjustments in practical applications.

[0003] Based on the above-mentioned deficiencies of the prior art, the present invention aims to solve the following technical problems: to provide a low-cost, environmentally friendly buffer that can adapt to different temperature conditions to meet the diverse needs for buffers in the oil production acidification process. Summary of the Invention

[0004] In view of the above-mentioned shortcomings of the prior art, the object of the present invention is to provide a composite buffer for oil production acidification to solve one or more problems in the prior art.

[0005] To achieve the above object, the technical solution of the present invention is as follows:

[0006] Composite buffer for oil production acidification, including

[0007] Component A comprises 5 to 10 parts by mass of unpurified biomass materials and 2 to 5 parts by mass of polyglutamic acid, wherein the unpurified biomass materials are citrus peel powder, kelp powder, and carbonized sugarcane bagasse particles.

[0008] Component B: 4 to 8 parts by mass of sodium citrate.

[0009] The component A and the component B are mixed in a mass ratio of 1:0.8 to 1:1.2 when in use, and compounded with the hydrochloric acid solution in a mass ratio of 1:10 to 1:20 to form a buffer working solution.

[0010] The preparation method comprises the following steps:

[0011] S1, subjecting the unpurified biomass material to acid activation treatment, soaking it in a 3% to 8% hydrochloric acid solution for 12 to 48 hours, separating the solid and liquid, and then drying it.

[0012] S2, mixing the acid-activated biomass material with polyglutamic acid to form component A.

[0013] S3, mixing component A and component B in proportion, and compounding with hydrochloric acid solution.

[0014] Furthermore, the unpurified biomass material includes citrus peel powder and kelp powder, wherein the mass ratio of citrus peel powder to kelp powder is (5-8): (3-5).

[0015] Furthermore, the unpurified biomass material includes carbonized bagasse particles, and the preparation method of the carbonized bagasse particles is to carbonize the bagasse at 250-350° C. for 1-3 hours under nitrogen protection, crush it to 150-300 mesh, and then acid wash it.

[0016] Furthermore, the mass ratio of the carbonized bagasse particles to the kelp powder is (4-8): (3-5), and the added amount of the polyglutamic acid is 3-5 parts by mass.

[0017] Furthermore, when the unpurified biomass material is citrus peel powder, the concentration of hydrochloric acid in step S1 is 5% to 6%, and the soaking time is 20 to 24 hours.

[0018] Furthermore, when the unpurified biomass material includes carbonized bagasse particles, the acid washing in S1 is performed by ultrasonic treatment with a 3% to 5% nitric acid solution for 30 to 60 minutes.

[0019] Furthermore, in the acidizing of high-temperature carbonate formations, the injection rate of the buffer working fluid is 0.5-1.2 m³ / min, and the bottom hole temperature is maintained at 100-150°C.

[0020] In order to achieve the complete technical effect described in this scheme, the concentration of the hydrochloric acid solution in this scheme is 15%~28%, and the final pH value of the buffer working solution is maintained at 2.0~5.5 for at least 2 hours.

[0021] Compared with the prior art, the beneficial technical effects of the present invention are as follows:

[0022] (1) The use of unpurified biomass materials (such as citrus peel powder, kelp powder, and carbonized sugarcane bagasse particles) in synergistic combination with purified functional components (polyglutamic acid, sodium citrate) reduces dependence on synthetic chemicals and reduces the risk of environmental pollution. At the same time, these biomass materials are derived from agricultural / aquatic waste, realizing the recycling of resources and further enhancing environmental benefits.

[0023] (2) Low-temperature and high-temperature buffer formulations are designed to adapt to different temperature conditions. Low-temperature buffers are suitable for acidizing operations at temperatures ≤80°C, while high-temperature buffers are suitable for acidizing operations at temperatures ≥100°C. This wide temperature range adaptability enables the buffers to meet the diverse temperature requirements of the oil production acidizing process, avoiding the tedious need for frequent formulation adjustments.

[0024] (3) By incorporating carbonized bagasse particles and their porous structure, the buffer in this solution exhibits improved heat resistance and sustained release. These carbonized bagasse particles not only enhance the buffer's stability in high-temperature environments but also extend the effective action range of the acid solution, making the acidizing process more durable and efficient, effectively improving the efficiency and quality of oil recovery. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 FIG. 1 is a schematic diagram of a process for preparing a buffer in an exemplary embodiment of the present invention. DETAILED DESCRIPTION

[0026] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and exemplary descriptions. It should be noted that the structures, proportions, sizes, etc. illustrated in the drawings of this specification are only used to match the contents disclosed in the specification for the understanding and reading of those familiar with this technology, and are not intended to limit the conditions for the implementation of the present invention. Any modification of the structure, change in the proportion relationship or adjustment of the size should still fall within the scope of the technical content disclosed in the present invention without affecting the efficacy and purpose of the present invention.

[0027] Test Experiment

[0028] This study designs two bio-based, two-component buffers for acidizing oil and gas wells under different operating conditions, one suitable for low-temperature (≤80°C) and the other for high-temperature (≥100°C) environments. Due to these differences in formulation, the two buffers exhibit significant differences in chemical properties and performance. To accurately quantify the performance differences resulting from these formulation changes and determine the optimal component ratio, this study will conduct a series of rigorous experimental tests, evaluating various performance indicators of buffers with different ratios. Comparative analysis of these experimental data will provide a scientific basis for optimizing the buffer formulation, ensuring its superior buffering effectiveness under diverse operating conditions.

[0029] During the experiment, the following general process settings were followed:

[0030] Regarding acid activation treatment, the acid concentration of citrus peel powder is strictly controlled between 5% and 6%, considering that its fiber structure is easily damaged when the acid concentration exceeds 6%. Furthermore, nitric acid is used instead of hydrochloric acid during the acid washing process for the carbonized bagasse particles. This improvement effectively removes metallic impurities (such as potassium and calcium ions), preventing these impurities from reacting with the acid to form precipitation, thereby ensuring the purity and stability of the buffer.

[0031] The injection rate and method of the buffer working fluid have been optimized for acidizing operations in different oil and gas well conditions. For shallow reservoirs (temperature ≤ 80°C), the buffer working fluid injection rate is set at 0.8-1.0 m³ / min, with a preferred positive circulation injection method to ensure efficient acidizing operations. For deep wells with high-temperature formations (temperature ≥ 100°C), the injection rate is adjusted to 0.5-0.7 m³ / min. In conjunction with a wellhead cooling device, the acid fluid temperature rise rate is strictly controlled to no more than 10°C / min to prevent excessive acid temperatures from affecting the buffer performance and acidizing effectiveness.

[0032] The injection rate of the buffer working fluid is 0.5~1.2 m³ / min, and the bottom hole temperature is maintained at 100~150℃.

[0033] During the experiment, the following test standards were followed:

[0034] Corrosion inhibition rate: SY / T5405-2019 specifies the performance test methods and evaluation indicators of corrosion inhibitors for acidification.

[0035] pH stability: ASTM G51-18 "Standard Test Method for Measurement of Soil pH for Corrosion Testing".

[0036] Dissolution uniformity: Evaluated through core dissolution testing according to SY / T5405-2019, using Berea sandstone cores. Laboratory testing procedures for dissolution uniformity testing can be designed in conjunction with HG / T3523 (Technical Requirements for Corrosion Specimens).

[0037] High temperature corrosion inhibition rate: SY / T7025-2014 specifies the laboratory evaluation method of corrosion inhibitors for acidic oil and gas fields at high temperatures (such as 120°C), including the determination of corrosion rate and corrosion inhibition efficiency.

[0038] pH maintenance time: Refer to the test requirements for pH stability in ISO10523:2008. Usually, the pH change over time is recorded under constant temperature conditions. For example, high temperature experiments require that the pH fluctuation is ≤0.5 for ≥6 hours.

[0039] Corrosion rate: In the oil and gas field, the corrosion rate is measured using N80 steel sheets under high temperature and high pressure conditions according to SY / T5405-2019.

[0040] Recipe Consistency:

[0041] In all experimental groups, the ratio of polyglutamic acid to hydrochloric acid solution was fixed (low temperature: 3.00 parts by mass + 1:15; high temperature: 3-5 parts by mass + 1:18), and only the amount of the main biomass component (citrus peel powder / carbonized sugarcane bagasse particles) and auxiliary agents (kelp powder, sodium citrate) was adjusted.

[0042] Variable Control:

[0043] The core variables of low temperature conditions are citrus peel powder (5.00-8.00), kelp powder (3.00-5.00), and sodium citrate (4.00-6.00);

[0044] The core variables of high-temperature working conditions are carbonized sugarcane bagasse particles (4.00~8.00), kelp powder (3.00~5.00), sodium citrate (5.00~8.00), and polyglutamic acid (3.00~5.00).

[0045] Compounding process:

[0046] The stirring time of the low-temperature buffer working solution was fixed at 10 minutes (500 rpm) and that of the high-temperature buffer working solution was 15 minutes (400 rpm) to ensure uniform dispersion.

[0047] Low temperature conditions:

[0048] Test Subject:

[0049] Experimental group: low-temperature biomass buffer (citrus peel powder + kelp powder + sodium citrate + polyglutamic acid).

[0050] Control group 1: conventional phosphate buffer (10% sodium dihydrogen phosphate + 5% EDTA);

[0051] Control group 2: blank group (15% hydrochloric acid solution only).

[0052] Test indicators and weights:

[0053]

[0054] Experimental data:

[0055]

[0056] After a simple data analysis, it can be seen that the formula of experimental group 3 has the highest weighted total score and is the best ratio.

[0057] Performance change trends:

[0058] Corrosion inhibition rate: It first increases and then decreases with the increase of citrus peel powder content (5→8 parts), and the optimal value is 6 parts;

[0059] pH stability: first increases and then decreases with the increase of sodium citrate ratio (4→6 parts);

[0060] Dissolution uniformity: positively correlated with the content of kelp powder, but excessive amount (>5 parts) leads to decreased dispersibility.

[0061] Microscopic mechanism analysis:

[0062] Adsorption and fiber structure of citrus peel powder: Optimal range (5-6 parts): After acid activation, citrus peel powder forms a porous fiber network (SEM observation, pore size of about 50-200 nm), which can adsorb and Fe² + , inhibiting corrosion reactions; excessive (>7 parts): fiber accumulation leads to pore blockage, a decrease in specific surface area (BET test reduces by 30%), and a decrease in adsorption efficiency.

[0063] Ion exchange effect of kelp powder: kelp is rich in calcium alginate (Ca-Alg), which releases Ca² in an acidic environment + and with exchange, delaying the pH drop; excessive kelp powder (>5 parts) is easy to agglomerate, hindering the synergistic buffering with sodium citrate (FTIR shows a reduction in carboxyl binding sites).

[0064] The dual role of sodium citrate: appropriate amount (5 servings): citrate chelates Fe³ + Formation of a stable complex (Fe-Citrate complex detected by XRD), inhibiting Precipitation; Excessive (>6 parts): High ionic strength destroys the double layer structure and accelerates local corrosion (electrochemical impedance spectroscopy shows a 40% decrease in charge transfer resistance).

[0065] High temperature conditions:

[0066] Test Subject:

[0067] Experimental group: high-temperature biomass buffer (carbonized bagasse particles + kelp powder + sodium citrate + polyglutamic acid);

[0068] Control group 1: conventional high-temperature buffer (12% polyacrylic acid);

[0069] Control group 2: blank group (28% hydrochloric acid solution only);

[0070] Control group 3: low temperature formula buffer (ratio of experimental group 3).

[0071] Test indicators and weights:

[0072]

[0073] Experimental data:

[0074]

[0075] After a simple analysis of the experimental data, it was found that the best ratio was experimental group 13 (carbonized bagasse particles 6.00 + kelp powder 4.00 + sodium citrate 6.00 + polyglutamic acid 4.00);

[0076] Performance change trends:

[0077] High temperature corrosion inhibition rate: with the increase of sugarcane bagasse carbonized particle content (4→8 parts), it first increases and then decreases, with the peak at 6 parts;

[0078] Corrosion rate: negatively correlated with polyglutamic acid content, but excessive (>5 parts) causes the rate to increase;

[0079] pH maintenance time: Affected by the synergistic effect of sodium citrate and carbonized sugarcane bagasse particles, the optimal ratio is 6 parts.

[0080] Microscopic mechanism analysis:

[0081] Loading and pore control of bagasse carbonized particles:

[0082] Optimal range (5-6 parts): After nitric acid activation, the carbonized bagasse particles form a hierarchical porous structure (TEM shows a micropore-mesopore distribution) with a specific surface area of ​​800 m² / g, which can load polyglutamic acid and slowly release it.

[0083] Excessive (>7 parts): The carbon skeleton collapses at high temperature (TG-DSC shows a 15% increase in weight loss at 600°C), and the pores close, resulting in the explosive release of the corrosion inhibitor.

[0084] Thermal stability and complexing ability of polyglutamic acid:

[0085] Appropriate amount (4 parts): The carboxyl group (-COOH) of polyglutamic acid reacts with Fe² at high temperature. + / Fe³ + Formation of thermally stable chelates (Fe-OC bonds detected by EDS);

[0086] Excessive (>5 parts): The molecular chain breaks at high temperature (GPC shows the molecular weight drops from 500kDa to 200kDa), and the complexing ability is lost.

[0087] Synergistic buffering of sodium citrate and carbonized bagasse particles:

[0088] Sodium citrate maintains pH stability through ionization equilibrium;

[0089] Adsorption of oxygen-containing functional groups (CO and C=O bonds detected by XPS) on the surface of carbonized bagasse particles , delaying acid consumption.

[0090] In summary, the optimal ratio and its micro advantages are as follows:

[0091] Low temperature conditions:

[0092]

[0093] High temperature conditions:

[0094]

[0095] Summarize:

[0096] The core of low-temperature performance: the adsorption capacity of citrus peel powder and the chelation effect of sodium citrate need to be balanced between fiber network integrity and ionic strength;

[0097] Core of high-temperature performance: The pore stability of carbonized bagasse particles and the thermal degradation threshold of polyglutamic acid determine the long-term corrosion inhibition effect;

[0098] General rule: The function of biomass materials is jointly restricted by the microstructure (pores, functional groups) and thermal / chemical stability, and the optimal ratio is the result of the synergistic effect of multiple factors.

[0099] The above analysis combines material characterization methods (SEM, XPS, FTIR, etc.) with corrosion electrochemical testing, and complies with the relevant standards requirements of SY / T5405-2019 and ASTM.

[0100] Example

[0101] Example 1: Low-temperature applicable buffer (shallow oil reservoir)

[0102] 1. Formula composition

[0103]

[0104] 2. Preparation Method

[0105] Citrus peel pretreatment:

[0106] Raw material cleaning: Rinse the citrus peels three times with deionized water to remove surface impurities;

[0107] Drying and crushing: drying in an oven at 60℃ until the moisture content is ≤5%, then crushing through an 80-mesh sieve;

[0108] Acid activation: Soak in 5% hydrochloric acid solution (solid-liquid ratio 1:10) for 24 hours, filter, wash with water until neutral, and dry at 80℃.

[0109] Kelp powder pretreatment:

[0110] Acidification treatment: kelp pieces were soaked in a citric acid solution with a pH of 3 and magnetically stirred for 2 hours (300 rpm);

[0111] Drying: vacuum drying at 60℃ until the moisture content is ≤3%.

[0112] Component mixing:

[0113] Put the processed citrus peel powder, kelp powder, polyglutamic acid and sodium citrate into a double-helix cone mixer;

[0114] Mixing parameters: speed 200 rpm, time 30 minutes, mixing uniformity ≥ 98% (detected by NIR spectroscopy).

[0115] Preparation of buffer working solution:

[0116] Mix the total amount of buffer and 15% hydrochloric acid solution in a mass ratio of 1:15;

[0117] Stirring conditions: titanium alloy stirring paddle, speed 500 rpm, time 10 minutes, temperature controlled at 25±2°C.

[0118] Example 2: High-temperature applicable buffer (deep well acidizing).

[0119] 1. Formula composition

[0120]

[0121] 2. Preparation method:

[0122] Preparation of bagasse carbonized particles:

[0123] Carbonization treatment: Bagasse was heated to 300°C at a rate of 10°C / min in a tube furnace (nitrogen flow rate 50 mL / min) and kept at this temperature for 2 h.

[0124] Acid washing and activation: The carbonized product was crushed and passed through a 200-mesh sieve, ultrasonically treated with a 5% nitric acid solution for 40 minutes (power 200 W, frequency 40 kHz), and washed with water until neutral.

[0125] Component mixing:

[0126] Carbonized bagasse particles, kelp powder, polyglutamic acid and sodium citrate are placed in a V-type mixer;

[0127] Mixing parameters: speed 150 rpm, time 40 minutes, mixing uniformity ≥ 97%.

[0128] Preparation of buffer working solution:

[0129] Prepare according to the mass ratio of total amount of buffer: 28% hydrochloric acid solution = 1:18;

[0130] Stirring conditions: Hastelloy reactor, rotation speed 400 rpm, stirring time 15 minutes, pre-cooled to 10 ° C to control the reaction exotherm.

[0131] How it works

[0132] Acid activation and carbonization mechanism:

[0133] Citrus peel acid activated the porous structure to form a pore size of 50-200nm (BET specific surface area 320 m² / g), enhancing adsorption;

[0134] The mesoporous structure (pore size 2-50 nm) of carbonized bagasse particles is loaded with polyglutamic acid, and the sustained release rate is reduced by 30% at high temperature.

[0135] Verification of synergistic effect:

[0136] Low temperature formula: When the molar ratio of polyglutamic acid to sodium citrate is 1:1.2, the complexed Fe 3+ The strongest ability (the absorption peak at 615nm disappears in UV spectrum detection);

[0137] High-temperature formula: When the mass ratio of carbonized bagasse particles to polyglutamic acid is 1.5:1, the pore filling rate is optimal (the porosity measured by mercury intrusion porosimetry is 72%).

[0138] Device Compatibility:

[0139] Conventional carbon steel equipment can be used for low-temperature buffer working fluid, while titanium alloy or nickel-based alloy pipelines must be used for high-temperature buffer working fluid to prevent acid corrosion.

[0140] Comparison of implementation effects:

[0141]

[0142] in conclusion:

[0143] Example 1 achieves a balance between low cost and high corrosion inhibition efficiency by optimizing the ratio of citrus peel powder to polyglutamic acid.

[0144] Example 2 utilizes the mesoporous loading of carbonized bagasse particles and the high temperature stability of polyglutamic acid.

[0145] Both types of formulas meet differentiated reservoir acidizing needs through precise component ratios and microstructure control.

[0146] The various technical features described in the above exemplary embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the various technical features in the above exemplary embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

Claims

1. A composite buffer for oil production acidification, characterized by: include Component A: comprising 5 to 10 parts by mass of unpurified biomass material and 2 to 5 parts by mass of polyglutamic acid, wherein the unpurified biomass material is citrus peel powder, kelp powder, or carbonized sugarcane bagasse particles; Component B: 4 to 8 parts by mass of sodium citrate; The components A and B are mixed in a mass ratio of 1:0.8 to 1:1.2 when in use, and compounded with hydrochloric acid solution in a mass ratio of 1:10 to 1:20 to form a buffer working solution; The preparation method comprises the following steps: S1, subjecting the unpurified biomass material to acid activation treatment by soaking it in a 3% to 8% hydrochloric acid solution for 12 to 48 hours, separating the solid and liquid, and then drying; S2, mixing the acid-activated biomass material with polyglutamic acid to form component A; S3, mixing component A and component B in proportion, and compounding with hydrochloric acid solution.

2. The buffer according to claim 1, wherein: The unpurified biomass material includes citrus peel powder and kelp powder, wherein the mass ratio of citrus peel powder to kelp powder is (5-8): (3-5).

3. The buffer according to claim 1, wherein: The unpurified biomass material includes carbonized bagasse particles. The preparation method of the carbonized bagasse particles is to carbonize the bagasse at 250-350° C. for 1-3 hours under nitrogen protection, crush it to 150-300 mesh, and then acid wash it.

4. The buffer according to claim 3, wherein: The mass ratio of the carbonized bagasse particles to the kelp powder is (4-8): (3-5), and the added amount of the polyglutamic acid is 3-5 parts by mass.

5. The buffer according to claim 1, wherein: When the unpurified biomass material is citrus peel powder, the concentration of hydrochloric acid in step S1 is 5% to 6%, and the soaking time is 20 to 24 hours.

6. The buffer according to claim 1, wherein: When the unpurified biomass material includes carbonized bagasse particles, the acid washing in S1 is performed by ultrasonic treatment with a 3% to 5% nitric acid solution for 30 to 60 minutes.

7. The buffer according to claim 1, wherein: In the acidizing of high-temperature carbonate formations, the injection rate of the buffer working fluid is 0.5-1.2 m³ / min, and the bottom hole temperature is maintained at 100-150°C.

8. The buffer according to any one of claims 1 to 7, characterized in that: The concentration of the hydrochloric acid solution is 15% to 28%, and the final pH value of the buffer working solution is maintained at 2.0 to 5.5 for at least 2 hours.

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