A carbonate rock acid fracturing coupling agent screening method based on interface film formation regulation of acid rock reaction

Abstract

This invention relates to the field of oil and gas field enhancement and stimulation technology, and discloses a method for screening coupling agents for acid fracturing in carbonate rocks based on interfacial film formation to regulate acid-rock reactions. The method first conducts basic physical property tests on different types of coupling agents to evaluate their wettability and spreading ability on carbonate rock surfaces; then, it characterizes the adsorption and film-forming behavior of the coupling agents on the rock surface; it evaluates the compatibility of the coupling agents with different fracturing fluid systems; it analyzes the influence of coupling agent concentration and stirring conditions on the acid-rock reaction rate through acid-rock reaction experiments, and establishes an evaluation index for acid-rock reaction rate control; finally, it conducts reservoir adaptability evaluation under different temperature, mineral composition, and porosity conditions, and comprehensively screens out target coupling agents suitable for acid fracturing operations in carbonate rocks. This invention establishes a systematic coupling agent screening process, which can effectively reduce the acid-rock reaction rate, increase the acid interaction distance, and thus improve the acid fracturing stimulation effect of carbonate reservoirs.

Description

Technical Field

[0001] This invention relates to the field of oil and gas field production enhancement and stimulation technology, specifically to a method for screening coupling agents for acid fracturing stimulation of carbonate reservoirs, and in particular, a method for optimizing coupling agents based on interfacial film formation mechanism and acid-rock reaction rate control characteristics. Background Technology

[0002] Carbonate reservoirs are widely distributed in oil and gas reservoirs worldwide and are important target formations for oil and gas development. However, during acid fracturing operations in deep, high-temperature carbonate reservoirs, the reaction rate between the acid and the rock is usually rapid, leading to the rapid consumption of the acid in the near-wellbore area, resulting in severe dissolution and making it difficult to achieve effective deep stimulation, thus reducing the effectiveness of acid fracturing operations.

[0003] To address these issues, researchers have proposed using slow-rate acid systems or rate-controlling additives to decelerate the acid-rock reaction rate. However, most existing rate-controlling systems suffer from insufficient stability, poor adaptability, or limited rate-controlling effects.

[0004] Coupling agents are functional chemical agents with interfacial modification capabilities. They can form organic-inorganic composite films on solid surfaces, regulating the reaction behavior between fluids and rocks by altering the interfacial chemical structure and wetting properties. Studies have shown that coupling agents can adsorb and form stable films on carbonate rock surfaces, thereby blocking direct contact between acid and mineral surfaces and delaying the acid-rock reaction process. However, current research on the application of coupling agents in acid fracturing systems is still limited, especially under high-temperature carbonate reservoir conditions, and a systematic and standardized method for screening and evaluating coupling agents is lacking.

[0005] Therefore, it is necessary to establish a coupling agent screening method for acid pressure rate control requirements in order to achieve comprehensive evaluation and selection of different types of coupling agents. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for screening and comprehensively evaluating coupling agents for acid fracturing of carbonate rocks. The aim is to accurately screen coupling agents suitable for specific reservoir conditions through a multi-dimensional and multi-scale evaluation system, reveal their film-forming mechanism, optimize application parameters, and quantitatively evaluate their effects on delaying acid-rock reaction and increasing effective action distance, ultimately achieving the technical goal of significantly delaying the acid-rock reaction rate and significantly increasing the effective action distance of the acid.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] This invention provides a method for screening carbonate rock acid fracturing coupling agents based on interfacial film formation to regulate acid-rock reactions, comprising the following steps:

[0009] S1: Test the basic physical properties of the coupling agent, including apparent viscosity, surface tension, and contact angle on the carbonate rock surface. Evaluate the wettability and spreading ability of the coupling agent on the rock surface based on the test results to complete the preliminary screening of the coupling agent.

[0010] S2: Evaluate the interfacial film-forming ability of the coupling agent obtained in step S1, including: analyzing the chemical bond structure between the coupling agent and carbonate rock minerals, observing the microscopic morphological changes on the rock surface, measuring the three-dimensional morphology and roughness of the rock surface, thereby determining the adsorption and film-forming characteristics of the coupling agent on the rock surface.

[0011] S3: Conduct compatibility evaluation of the coupling agent obtained in step S2 on the fracturing fluid system. Add the coupling agent to different types of fracturing fluid systems and conduct stability tests under set temperature conditions to evaluate the compatibility performance between the coupling agent and the fracturing fluid system.

[0012] S4: Conduct acid-rock reaction experiments in an acid-rock reaction experimental apparatus. Analyze the effect of coupling agent on the acid-rock reaction rate by measuring the reaction rate between acid and carbonate rock samples and by changing the concentration of coupling agent and stirring speed.

[0013] S5: Establish an evaluation index for the rate control of acid-rock reaction and quantitatively evaluate the acid-rock reaction rate under different coupling agent conditions;

[0014] S6: Conduct adaptability experiments under different reservoir conditions, including temperature, mineral composition and rock porosity, and comprehensively evaluate the film-forming ability, compatibility and rate control effect of the coupling agent, so as to screen out the target coupling agent suitable for acid fracturing construction in carbonate reservoirs.

[0015] Furthermore, the basic physical property parameter tests mentioned in step S1 specifically include: measuring the apparent viscosity of the coupling agent using a six-speed rotational viscometer, measuring the liquid surface tension coefficient of the coupling agent using a surface tension meter, and measuring the contact angle of the coupling agent on the surface of the carbonate rock sample using a contact angle meter via the three-point method, thereby evaluating the wettability and spreading ability of the coupling agent on the rock surface.

[0016] Furthermore, the evaluation of interfacial film-forming ability in step S2 specifically includes:

[0017] Fourier transform infrared spectroscopy was used to analyze the changes in functional groups on the surface of carbonate rocks before and after modification with coupling agents. The weakening of the hydroxyl peak and the appearance of characteristic peaks of Si-OM, Al-O-Ca and Ti-O-Ca were tracked to determine the type of chemical bonding between the coupling agent and the rock surface.

[0018] The microscopic morphological changes of the rock surface before and after modification with coupling agent were observed using scanning electron microscopy, and the uniformity, density and structural integrity of the film before and after acid etching were analyzed.

[0019] Atomic force microscopy was used to measure the three-dimensional morphology and roughness parameters of the rock surface before and after modification, including the arithmetic mean roughness Ra and the root mean square roughness Rq, to ​​quantitatively evaluate the smoothness and structural stability of the film.

[0020] Furthermore, the compatibility evaluation of the fracturing fluid system described in step S3 specifically includes: adding the coupling agent to slickwater fracturing fluid, low-viscosity fracturing fluid, and guar gum fracturing fluid respectively, observing them under set temperature conditions, and recording the phase separation time, turbidity changes, precipitation formation, and viscosity changes, thereby evaluating the compatibility performance between the coupling agent and different fracturing fluid systems.

[0021] Furthermore, the experiment on the acid-rock reaction regulation effect described in step S4 specifically includes: setting a coupling agent concentration gradient and a stirring speed gradient in the acid-rock reaction experimental device, measuring the reaction rate between the acid solution and the carbonate rock sample under different conditions, recording the changes in porosity and permeability of the core before and after the reaction and the morphological characteristics of the core end face, and analyzing the regulation effect of the coupling agent on the acid-rock reaction rate.

[0022] Furthermore, the concentration gradient of the coupling agent is in the range of 0%-10%; the stirring speed gradient is in the range of 0 r / min-500 r / min.

[0023] Furthermore, the establishment of the acid-rock reaction rate control evaluation index in step S5 specifically includes: using the acid-rock reaction rate of the untreated rock sample as a blank control, calculating the rate reduction under different coupling agent treatment conditions, plotting the concentration-reaction rate relationship curve and the rotation speed-reaction rate relationship curve, determining the optimal rate control concentration and the optimal rate control rotation speed, and establishing a quantitative evaluation index with the rate reduction as the core.

[0024] Furthermore, the reservoir adaptability experiment described in step S6 specifically includes: conducting acid-rock reaction experiments on carbonate rock samples treated with coupling agents under different temperature conditions, different calcite contents, and different rock porosities, measuring the change in reaction rate, and comprehensively screening out coupling agents suitable for the target reservoir conditions by combining the film-forming ability evaluation results of step S2, the compatibility evaluation results of step S3, and the rate control effect evaluation results of steps S4-S5.

[0025] Furthermore, the temperature range is 160℃-200℃; the calcite content includes low, medium and high content gradients; and the rock porosity includes low, medium and high porosity gradients.

[0026] Advantages and beneficial effects of the present invention:

[0027] 1. This invention constructs a multi-dimensional systematic screening platform: for the first time, it couples basic physical properties, chemical bonding, microstructure, macroscopic performance and engineering application parameters into a single screening process, overcoming the shortcomings of traditional methods that have a single evaluation dimension and are out of touch with practical applications.

[0028] 2. This invention reveals the deep-seated mechanism of coupling agents: through multi-scale characterization methods such as FTIR, SEM, and AFM, the macroscopic slowing effect of coupling agents is linked to their microscopic film-forming mechanism and chemical bonding state, clarifying the reaction mechanism between different types of coupling agents and carbonate rock surfaces (silanes form Si-O-Ca bonds, aluminates form Al-O-Ca bonds, and titanates form Ti-O-Ca bonds), providing a scientific basis for the rational design and screening of coupling agents.

[0029] 3. This invention achieves refined optimization of key process parameters: it clarifies the decisive influence of coupling agent concentration and injection rate on the final effect, and determines the optimal parameter range (2% concentration, 100 r / min) through experiments, providing direct guidance for on-site construction design.

[0030] 4. This invention establishes a comprehensive reservoir adaptability evaluation system: it systematically evaluates the influence of key reservoir parameters such as temperature, calcite content, and porosity on the retardation effect of coupling agents, and clarifies the applicable conditions of coupling agents (the retardation effect is best at a high temperature of 180℃, with a reaction rate reduction of 73.03%; the lower the calcite content and the lower the porosity, the better the retardation effect).

[0031] 5. This invention significantly improves the effect of deep reservoir stimulation: The coupling agent NXH-311w selected by the method of this invention, when combined with gelling acid, can reduce the acid-rock reaction rate by more than 70% under high temperature conditions of 180℃. The effective action distance is increased by 72.01% compared with conventional diverting acid, 102.27% compared with thickened acid, and 11.43% compared with crosslinking acid, which greatly expands the technical boundary of acid fracturing stimulation of deep high temperature reservoirs. Attached Figure Description

[0032] Figure 1 This is a flowchart of the method of the present invention;

[0033] Figure 2 The apparent viscosity for different coupling agents;

[0034] Figure 3 The surface tension of different coupling agents;

[0035] Figure 4 The contact angle changes after different coupling agents were applied to the rock sample surface for modification and coating.

[0036] Figure 5Infrared spectra of carbonate rocks modified with silane coupling agents (a-unmodified, b-KH550 modified, c-KH561 modified, d-KH563 modified, e-KH1861 modified).

[0037] Figure 6 Infrared spectroscopy of carbonate rocks modified with aluminate coupling agent (a-unmodified, b-Al-822 modified).

[0038] Figure 7 Infrared spectra of carbonate rocks modified with titanate coupling agents (a-unmodified, b-NXH-501 modified, c-NXH-311w modified).

[0039] Figure 8 This is a scanning electron microscope image of the original sample before acid etching.

[0040] Figure 9 This is a scanning electron microscope image of the original sample after acid etching.

[0041] Figure 10 Scanning electron microscope image of KH-550 after coating and before acid etching;

[0042] Figure 11 Scanning electron microscope image of KH-550 coated material after acid etching;

[0043] Figure 12 Scanning electron microscope image of KH-561 before acid etching after coating;

[0044] Figure 13 This is a scanning electron microscope image of KH-561 after acid etching and coating.

[0045] Figure 14 Scanning electron microscope image of KH-563 after coating and before acid etching;

[0046] Figure 15 This is a scanning electron microscope image of KH-563 after acid etching and coating.

[0047] Figure 16 This is a scanning electron microscope image of KH-1861 before acid etching after coating;

[0048] Figure 17 Scanning electron microscope image of KH-1861 after acid etching;

[0049] Figure 18 Scanning electron microscope image of Al-822 coating before acid etching;

[0050] Figure 19 Scanning electron microscope image of Al-822 coating after acid etching;

[0051] Figure 20 Scanning electron microscope image of NXH-501 before acid etching after coating;

[0052] Figure 21 This is a scanning electron microscope image of NXH-501 after acid etching and coating.

[0053] Figure 22 This is a scanning electron microscope image of the NXH-311w after coating and before acid etching;

[0054] Figure 23 Scanning electron microscope image of NXH-311w after coating and acid etching;

[0055] Figure 24 This is a three-dimensional morphological image of the original sample obtained by atomic force microscopy.

[0056] Figure 25 Three-dimensional morphology of KH-550 after coating by atomic force microscopy;

[0057] Figure 26 Three-dimensional morphological image of KH-561 after coating by atomic force microscopy;

[0058] Figure 27 Three-dimensional morphological image of KH-563 after coating by atomic force microscopy;

[0059] Figure 28 Three-dimensional morphological image of KH-1861 after coating by atomic force microscopy;

[0060] Figure 29 Three-dimensional morphology of Al-822 after coating by atomic force microscopy;

[0061] Figure 30 Three-dimensional morphology of NXH-501 after coating by atomic force microscopy;

[0062] Figure 31 Three-dimensional morphology of the NXH-311w after coating is obtained by atomic force microscopy.

[0063] Figure 32 Comparison of rock surface roughness after coating with different coupling agents;

[0064] Figure 33 The acid-rock reaction rate at different NXH-311w concentrations;

[0065] Figure 34 The acid-rock reaction rate at different NXH-311w rotation speeds;

[0066] Figure 35 Comparison of acid-rock reaction rates between the original sample and the NXH-311w coated sample at different temperatures;

[0067] Figure 36 Comparison of acid-rock reaction rates between the original sample and the NXH-311w coated sample with different calcite contents;

[0068] Figure 37Comparison of acid-rock reaction rates between the original sample and the NXH-311w coated sample under different porosities;

[0069] Figure 38 Comparison of the effective action distance of different types of acid solutions at different temperatures; Detailed Implementation

[0070] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0071] This invention provides a method for screening carbonate rock acid fracturing coupling agents based on interfacial film formation to regulate acid-rock reactions, comprising the following steps:

[0072] Step 1: Preliminary screening and basic property characterization of coupling agents

[0073] Various types of coupling agent samples were selected, including but not limited to silane coupling agents (KH-550, KH-561, KH-563, KH-1861), aluminate coupling agents (Al-822), and titanate coupling agents (NXH-501, NXH-311w). The basic physical properties of the coupling agents were tested under simulated high-temperature formation conditions (160℃), including:

[0074] Apparent viscosity test: The apparent viscosity of the coupling agent was determined using a six-speed rotational viscometer to evaluate its flowability and diffusion capacity in rock pores.

[0075] Surface tension test: The surface tension of the coupling agent was measured using a liquid surface tension coefficient meter to evaluate its spreading ability on the rock surface.

[0076] Contact angle test: The contact angle of the coupling agent on the surface of carbonate rock samples was determined by the three-point method using an optical contact angle meter to evaluate its ability to regulate the wettability of the rock surface.

[0077] Based on the test results, a preliminary list of coupling agents with suitable viscosity, low surface tension, and good wetting control ability has been selected.

[0078] Step 2: Film-forming mechanism and interface structure characterization of coupling agents

[0079] The interfacial film-forming ability of the coupling agents obtained in step one was evaluated, and various microscopic characterization methods were used to reveal the adsorption and film-forming characteristics of the coupling agents on the carbonate rock surface:

[0080] Fourier transform infrared spectroscopy (FTIR) analysis: Analyze the changes in functional groups on the surface of carbonate rocks before and after modification with coupling agent, track the weakening of hydroxyl peaks and the appearance of characteristic peaks such as Si-OM (M=Ca, Mg), Al-O-Ca, Ti-O-Ca, etc., to determine the type of chemical bonding between the coupling agent and the rock surface and the degree of film formation reaction.

[0081] Scanning electron microscopy (SEM) observation: Observe the changes in the microstructure of the rock surface before and after the coupling agent modification, analyze the uniformity and density of the film coverage and the structural integrity before and after acid etching, and intuitively evaluate the acid etching resistance of the film.

[0082] Atomic force microscopy (AFM) measurement: Measure the three-dimensional morphology and roughness parameters of the rock surface before and after modification, including arithmetic mean roughness Ra and root mean square roughness Rq, to ​​quantitatively evaluate the smoothness, thickness distribution and adsorption uniformity of the film.

[0083] Through the above multi-scale characterization, the film-forming ability, chemical bonding structure and film stability of different coupling agents were clarified, and the target coupling agent with good film-forming performance was selected.

[0084] Step 3: Compatibility evaluation of fracturing fluid system

[0085] The compatibility evaluation of the selected coupling agents in step two with fracturing fluid systems was conducted. The coupling agents were added to different types of fracturing fluid systems, including slickwater fracturing fluid, low-viscosity fracturing fluid, and guar gum fracturing fluid. Stability experiments were performed under simulated high-temperature formation conditions (160℃). Phase separation time, turbidity changes, precipitation formation, and viscosity changes were observed and recorded to evaluate the compatibility performance of the coupling agents with different fracturing fluid systems. The coupling agent-fracturing fluid combination with good compatibility with the field working fluid was selected.

[0086] Step 4: Optimization experiment of coating process parameters

[0087] For the coupling agent selected in step three that exhibits good compatibility, optimization experiments were conducted on the coating process parameters to determine the optimal concentration and injection rate.

[0088] Coupling agent concentration optimization: Different coupling agent concentration gradients (0%, 2%, 4%, 6%, 8%, 10%) were set, and the core samples were coated under the same rotation speed. The changes in acid rock reaction rate, porosity, and permeability were measured, and a "concentration-effect" curve was plotted. The optimal coating concentration that maximizes the reduction in reaction rate was selected.

[0089] Injection rate optimization: Different stirring speed gradients (0, 100, 200, 300, 400, 500 r / min) were set to simulate shear and mass transfer conditions under different injection rates. The core was coated under the optimal concentration conditions, and the changes in acid rock reaction rate, porosity and permeability were measured. The optimal injection rate that maximizes the reduction in reaction rate was selected.

[0090] Step 5: Establishment of evaluation indicators for the rate control of acid-rock reactions

[0091] An evaluation index for the rate control of acid-rock reaction was established to quantitatively evaluate the acid-rock reaction rate under different coupling agent conditions. Using the acid-rock reaction rate of untreated rock samples as a blank control, the rate reduction under different coupling agent treatments was calculated. A quantitative evaluation index with the rate reduction as the core was established, and the optimal rate control conditions were determined by combining experimental data from different concentrations and rotation speeds.

[0092] Step 6: Comprehensive evaluation of reservoir adaptability

[0093] Adaptability experiments were conducted under different reservoir conditions to comprehensively evaluate the film-forming ability, compatibility, and rate-controlling effect of the coupling agent:

[0094] Temperature adaptability evaluation: Set different temperature conditions (160℃, 170℃, 180℃, 190℃, 200℃), compare the acid-rock reaction rate of untreated rock samples and rock samples treated with the best process, calculate the slow rate, and clarify the effective temperature window and optimal temperature point of the coupling agent.

[0095] Mineral composition adaptability evaluation: Natural cores with different calcite contents (2.4%, 12.5%, 20.1%, 29.7%, 35.6%) were selected and acid-rock reaction experiments were conducted after treatment under the optimal process to analyze the influence of rock mineral composition on the coating effect and retardation performance of coupling agent.

[0096] Porosity adaptability evaluation: Natural rock cores with different porosities (1.27%, 2.93%, 3.55%, 5.26%, 6.93%) were selected and acid-rock reaction experiments were conducted after treatment under the optimal process to analyze the influence of rock properties on the coating effect and retardation performance of coupling agent.

[0097] Acid system adaptability evaluation: The selected coupling agent is combined with different acid systems (gelling acid, redirecting acid, thickening acid, etc.) to evaluate the comprehensive performance of the composite system and calculate reaction kinetic parameters (reaction order, activation energy, etc.).

[0098] Through the above multi-dimensional adaptability evaluation, coupling agents suitable for the target reservoir conditions were comprehensively screened.

[0099] Example 1: Preliminary screening and film-forming mechanism analysis of coupling agents

[0100] 1. Sample preparation: Seven types of coupling agents were selected, including silane coupling agents (KH-550, KH-561, KH-563, KH-1861), aluminate coupling agents (Al-822), and titanate coupling agents (NXH-501, NXH-311w), and prepared into a 10% (w / w) aqueous solution.

[0101] 2. Basic physical property analysis: Tests were conducted using a six-speed rotational viscometer, surface tension meter, and contact angle meter. The apparent viscosity results are as follows: Figure 2 As shown, silane coupling agents have the lowest viscosity (KH-550: 2.8 mPa·s), exhibiting good flowability and diffusion capabilities; titanate coupling agent NXH-501 has the highest viscosity (94.1 mPa·s), which is beneficial for forming a thick film. Surface tension measurement results are as follows... Figure 3 As shown, the surface tension of solutions from different types of coupling agents was significantly lower than that of pure water (72 mN / m), demonstrating good interfacial activity. Different types of coupling agents exhibited variations in surface tension, but the overall variation was not significant. Contact angle measurement results are shown below. Figure 4 As shown, the contact angle of the rock surface increased and the hydrophobicity was enhanced after treatment with all coupling agents.

[0102] 3. FTIR Analysis: To clarify the chemical bonding mechanism and film-forming reaction characteristics between the coupling agent and the carbonate rock surface, Fourier transform infrared spectroscopy was used to test carbonate rock samples before and after modification with silane, aluminate, and titanate coupling agents. The peak shape changes of hydroxyl (-OH) groups and characteristic film-forming chemical bonds were closely monitored. The results are shown below. Figure 5 , Figure 6 , Figure 7 As shown. Infrared spectrum of the silane coupling agent after modification ( Figure 5 The results showed that, compared with unmodified rock samples, all samples treated with silane coupling agents showed improved performance at 3440 cm⁻¹. -1 The stretching vibration peaks of hydroxyl (-OH) groups in the vicinity were all significantly weakened, with the hydroxyl peak at KH-550 showing the most significant attenuation, indicating that more hydroxyl groups on the rock surface were involved in the coupling reaction; meanwhile, at 1100 cm⁻¹... -1 A characteristic Si-O-Si peak appears at 950 cm⁻¹. -1 The detection of Si-O-Ca characteristic peaks at the surface confirms that silane coupling agents interact with Ca on the carbonate rock surface. 2+ Stable film formation is achieved through the formation of Si-O-Ca chemical bonds, and the characteristic peak intensity of KH-1861 is the highest, indicating superior film density. Infrared analysis results of Al-822 modification with aluminate coupling agent ( Figure 6 This indicates that the modified rock sample at 3440 cm⁻¹... -1The hydroxyl peak at 655 cm⁻¹ was actually enhanced, presumably due to the formation of hydrogen bonds between the coupling agent molecules and the rock surface or an increase in the number of active hydroxyl groups; -1 and 755 cm -1 Clear characteristic absorption peaks of Al-O-Ca and Al-O were observed at the respective locations, with significantly increased peak intensities compared to the original sample. This demonstrates that aluminate molecules formed a stable film with an Al-O framework through a complexation reaction with the calcium carbonate surface, thus achieving interface modification. Infrared spectrum of the titanate-based coupling agent modification (… Figure 7 The rock samples treated with NXH-501 and NXH-311w exhibit typical bonding characteristics, with a hydroxyl peak at 3440 cm⁻¹. -1 All values ​​showed a significant decrease, with the hydroxyl peak of NXH-311w showing a more significant decrease, indicating a more complete coupling reaction with hydroxyl groups on the rock surface; and NXH-311w showed a significant decrease at 565 cm⁻¹. -1 A clear Ti-O-Ca characteristic peak appears at this location, which is due to the interaction between the Ti-OR functional groups in the titanate coupling agent and the Ca in the carbonate rock. 2+ Direct evidence of directional coordination reactions was obtained, and the weaker Ti-O-Ca characteristic peak of NXH-501 indicated that NXH-311w had a better degree of chemical bonding and stronger film stability. The FTIR experimental results, shown in Table 1, confirmed that KH-550 possessed the highest surface reactivity, NXH-311w performed best in Ti-O-Ca bond formation and film compactness, while Al-822 showed the best performance in Al-O / Al-O-Ca coordination absorption and surface coverage. Therefore, KH-550, NXH-311w, and Al-822 were ultimately selected from the infrared spectroscopy experiments, corresponding to the three key properties of high reactivity, high film-forming properties, and high stability, respectively.

[0103] Table 1 FTIR Experimental Results

[0104]

[0105] 4. SEM Analysis: The microstructure of carbonate rock surfaces before and after acid etching was observed using scanning electron microscopy (SEM) with different coupling agents (as shown in Figure 8-23). ​​Although silane coupling agents KH-550, KH-561, and KH-563 could form a coating layer on the rock surface, with blurred grain outlines and uniform coating before acid etching, the coating characteristics basically disappeared after acid etching, with only KH-1861 retaining a small amount of coating traces. The aluminate coupling agent Al-822 had an insignificant coating effect, and obvious dissolution pits and mineral erosion appeared on the rock surface after acid etching. Among the titanate coupling agents, NXH-501 still retained some film structure after acid etching, while NXH-311w had uniform surface particles and strong coating before acid etching, and the crystal structure remained intact after acid etching, with no obvious dissolution pits or peeling. Its film density and acid etching resistance were the best among the three types of coupling agents, showing the best interface protection performance.

[0106] 5. AFM Analysis: The three-dimensional morphology and roughness of carbonate rock surfaces coated with different coupling agents were characterized using atomic force microscopy (AFM). Figure 24-31 and Figure 32 As shown in the figure, among silane coupling agents, KH-550 and KH-561 have uniformly distributed micro-protrusions, obvious layered structure, moderate roughness, and the best film uniformity; KH-563 and KH-1861 have problems with loose film layers and uneven adsorption; the aluminate coupling agent Al-822 has island-like distribution on the surface, uneven particle size, strong film dispersion, and unstable structure; among titanate coupling agents, NXH-311w performs best, with a highly regular layered structure on its surface, orderly particle arrangement, and significantly higher roughness (Ra and Rq) than other coupling agents, forming a continuous, dense, and sufficiently thick film, while NXH-501, although dense in particles, has slightly inferior uniformity; overall, NXH-311w has the best film integrity, adsorption uniformity, and structural stability, making it the coupling agent with the best film-forming performance.

[0107] 6. Preliminary conclusions: Based on comprehensive analysis of physical properties, bonding and microstructure, the titanate coupling agent NXH-311w can form a chemically bonded dense film on the surface of carbonate rocks, exhibiting the best acid corrosion resistance. It is preliminarily determined to be the preferred coupling agent.

[0108] Example 2: Compatibility and Application Parameter Optimization

[0109] 1. Compatibility Test: Seven coupling agents were mixed with slickwater, low-viscosity liquid, and guar gum crosslinking liquid, respectively, and observed after standing at 160℃ for 2 hours. The results showed that most coupling agents exhibited obvious stratification, turbidity, or gelation in slickwater and low-viscosity liquid, while NXH-311w remained homogeneous and stable in the guar gum system, indicating that it had the best compatibility with the guar gum system.

[0110] 2. Concentration Optimization: Guarnica gum was used as the carrier fluid to prepare NXH-311w treatment solutions with a concentration gradient of 0%-10%. The core samples were treated at 100 r / min, followed by acid-rock reaction experiments. The results are as follows: Figure 33 As shown, the reaction rate first decreases and then increases with increasing concentration, with the largest decrease occurring at a concentration of 2%, which is determined to be the optimal concentration for use.

[0111] 3. Discharge Optimization: With a fixed concentration of 2%, core samples were treated at different rotation speeds (0-500 r / min). Results are as follows... Figure 34 As shown, the reaction rate first decreases and then increases with increasing rotational speed, with the best effect observed at 100 r / min. Too low a rotational speed results in insufficient mass transfer and uneven coating; too high a rotational speed leads to excessive shear force, which may damage the membrane.

[0112] Example 3: Reservoir Adaptability Evaluation

[0113] 1. Temperature adaptability: Acid-rock reaction experiments were conducted at 160-200℃. Results are as follows... Figure 35 As shown, the reaction rates of core samples treated with the optimal 2% NXH-311w process were significantly lower than those of the original samples at all temperatures, with an average reduction of 65.48%. The slowing effect was most significant at 180℃, with a reaction rate reduction of up to 73.03%, confirming the effectiveness of this technology in ultra-high temperature environments.

[0114] 2. Calcite Content Adaptability: Core samples with calcite content ranging from 2.4% to 35.6% were selected for experiments. Results are as follows... Figure 36 As shown, after treatment with NXH-311w, the reaction rates of all rock samples decreased significantly, with an average reduction of 51.78%. The lower the calcite content, the better the retardation effect, with the highest reduction of 52.04% at 2.4%.

[0115] 3. Porosity adaptability: Core samples with porosities ranging from 1.27% to 6.93% were selected for experiments. The results are as follows... Figure 37 As shown, after treatment with NXH-311w, the reaction rates of all rock samples decreased significantly, with an average reduction of 49.81%. The lower the porosity, the better the retardation effect, with the highest reduction of 52.01% at 1.27%.

[0116] Example 4: Effective Distance Simulation and Prediction

[0117] Based on the principles of acid-rock reaction kinetics, a predictive model for the effective interaction distance of acid fluids was constructed, taking into account filtration loss from natural fractures and formation temperature. Combining experimentally obtained kinetic parameters, the effective interaction distances of crosslinked acid, redirecting acid, thickened acid, and the "gelling acid + NXH-311w" composite system were simulated and calculated under conditions of 160-200℃.

[0118] Simulation results are as follows Figure 38As shown, within the temperature range of 160-200℃, the average effective working distance of the "gelling acid + NXH-311w" system is 24.44 m, which is 72.01% higher than that of the redirecting acid, 102.27% higher than that of the thickened acid, and 11.43% higher than that of the crosslinking acid. Furthermore, this system exhibits the smallest decrease in effective working distance with increasing temperature (a decrease of 22.01% for every 10℃ increase), indicating its optimal high-temperature adaptability.

[0119] In summary, the method described in this invention successfully screened the titanate coupling agent NXH-311w as the target reagent, clarified its optimal application conditions (2% concentration, compatible with guar gum system, 100 r / min injection rate), verified its excellent slowing performance under high temperature (180℃) conditions, and confirmed its ability to significantly improve the effective action distance of acid liquid through numerical simulation, providing a new technical path for efficient acid fracturing stimulation of deep carbonate reservoirs.

Claims

1. A method for screening carbonate rock acidizing coupling agents based on interface film formation regulating acid rock reaction, characterized in that, Includes the following steps: S1: Test the basic physical properties of the coupling agent, including apparent viscosity, surface tension, and contact angle on the carbonate rock surface. Evaluate the wettability and spreading ability of the coupling agent on the rock surface based on the test results to complete the preliminary screening of the coupling agent. S2: Evaluate the interfacial film-forming ability of the coupling agent obtained in step S1, including: analyzing the chemical bond structure between the coupling agent and carbonate rock minerals, observing the microscopic morphological changes on the rock surface, measuring the three-dimensional morphology and roughness of the rock surface, thereby determining the adsorption and film-forming characteristics of the coupling agent on the rock surface. S3: Conduct compatibility evaluation of the coupling agent obtained in step S2 on the fracturing fluid system. Add the coupling agent to different types of fracturing fluid systems and conduct stability tests under set temperature conditions to evaluate the compatibility performance between the coupling agent and the fracturing fluid system. S4: Conduct acid-rock reaction experiments in an acid-rock reaction experimental apparatus. Analyze the effect of coupling agent on the acid-rock reaction rate by measuring the reaction rate between acid and carbonate rock samples and by changing the concentration of coupling agent and stirring speed. S5: Establish an evaluation index for the rate control of acid-rock reaction and quantitatively evaluate the acid-rock reaction rate under different coupling agent conditions; S6: Conduct adaptability experiments under different reservoir conditions, including temperature, mineral composition and rock porosity, and comprehensively evaluate the film-forming ability, compatibility and rate control effect of the coupling agent, so as to screen out the target coupling agent suitable for acid fracturing construction in carbonate reservoirs.

2. The screening method according to claim 1, characterized in that, The basic physical property parameter tests mentioned in step S1 specifically include: measuring the apparent viscosity of the coupling agent using a six-speed rotational viscometer, measuring the liquid surface tension coefficient of the coupling agent using a surface tension meter, and measuring the contact angle of the coupling agent on the surface of the carbonate rock sample using a contact angle meter through the three-point method, thereby evaluating the wettability and spreading ability of the coupling agent on the rock surface.

3. The screening method according to claim 1, characterized in that, The evaluation of interfacial film-forming ability in step S2 specifically includes: Fourier transform infrared spectroscopy was used to analyze the changes in functional groups on the surface of carbonate rocks before and after modification with coupling agents. The weakening of the hydroxyl peak and the appearance of characteristic peaks of Si-OM, Al-O-Ca and Ti-O-Ca were tracked to determine the type of chemical bonding between the coupling agent and the rock surface. The microscopic morphological changes of the rock surface before and after modification with coupling agent were observed using scanning electron microscopy, and the uniformity, density and structural integrity of the film before and after acid etching were analyzed. Atomic force microscopy was used to measure the three-dimensional morphology and roughness parameters of the rock surface before and after modification, including the arithmetic mean roughness Ra and the root mean square roughness Rq, to ​​quantitatively evaluate the smoothness and structural stability of the film.

4. The screening method according to claim 1, characterized in that, The compatibility evaluation of the fracturing fluid system described in step S3 specifically includes: adding the coupling agent to slickwater fracturing fluid, low-viscosity fracturing fluid, and guar gum fracturing fluid respectively, observing them under set temperature conditions, and recording the phase separation time, turbidity changes, precipitation formation, and viscosity changes, thereby evaluating the compatibility performance between the coupling agent and different fracturing fluid systems.

5. The screening method according to claim 1, characterized in that, The experiment on the regulation effect of acid-rock reaction described in step S4 specifically includes: setting a coupling agent concentration gradient and a stirring speed gradient in the acid-rock reaction experimental device, measuring the reaction rate between acid and carbonate rock samples under different conditions, recording the changes in porosity and permeability of the core before and after the reaction and the morphological characteristics of the core end face, and analyzing the regulation effect of the coupling agent on the acid-rock reaction rate.

6. The screening method according to claim 5, characterized in that, The concentration gradient of the coupling agent is 0%-10%; the stirring speed gradient is 0 r / min-500 r / min.

7. The screening method according to claim 1, characterized in that, The establishment of the acid-rock reaction rate control evaluation index in step S5 specifically includes: using the acid-rock reaction rate of the untreated rock sample as a blank control, calculating the rate reduction under different coupling agent treatment conditions, plotting the concentration-reaction rate relationship curve and the rotation speed-reaction rate relationship curve, determining the optimal rate control concentration and the optimal rate control rotation speed, and establishing a quantitative evaluation index with the rate reduction as the core.

8. The screening method according to claim 1, characterized in that, The reservoir adaptability experiment described in step S6 specifically includes: conducting acid-rock reaction experiments on carbonate rock samples treated with coupling agents under different temperature conditions, different calcite contents, and different rock porosities, measuring the change in reaction rate, and comprehensively screening out coupling agents suitable for the target reservoir conditions by combining the film-forming ability evaluation results of step S2, the compatibility evaluation results of step S3, and the rate control effect evaluation results of steps S4-S5.

9. The screening method according to claim 8, characterized in that, The temperature range is 160℃-200℃; the calcite content includes low, medium and high content gradients; the rock porosity includes low porosity, medium porosity and high porosity gradients.

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