Method for enhancing permeability of laumontite-containing reservoir and enhancing carbon dioxide sequestration

Abstract

The invention relates to the technical field of oil and gas reservoir permeation enhancement and carbon dioxide geological sequestration, and discloses a laumontite-containing reservoir permeation enhancement and carbon dioxide sequestration strengthening method. The method comprises the following steps: firstly, screening a reservoir with the laumontite content reaching the standard and meeting thermodynamic reaction conditions; injecting carbon dioxide into the target layer by adopting a two-stage pressure control strategy; and finally, the well closing duration is dynamically controlled by monitoring the bottom hole pressure in real time and calculating the change rate of the bottom hole pressure function, and when the change rate is continuously lower than a threshold value, it is indicated that stability tends to be achieved, and well closing is stopped. By utilizing the mineralization reaction of laumonite and carbon dioxide, the carbon dioxide is converted into calcium carbonate minerals for permanent storage while effective permeation enhancement of the reservoir is realized, and the method has the advantages of small reservoir damage, high storage safety and low cost, and meets the requirements of green and low-carbon development.

Description

Technical Field

[0001] This invention relates to the fields of oil and gas reservoir permeability enhancement technology and carbon dioxide geological storage technology, specifically to a method for enhancing permeability and carbon dioxide storage in turbid zeolite-containing reservoirs. Background Technology

[0002] Turbidite-bearing reservoirs are a core target stratum for global oil and gas exploration and development. They are extensively developed in large oil and gas basins such as Sichuan, Tarim, and Ordos in my country, as well as in continental clastic rocks and marine carbonate strata in major oil and gas-bearing regions worldwide, including the Rocky Mountains in North America and the Zagros in the Middle East. Statistics show that the associated oil and gas geological resources of this type of reservoir exceed one trillion tons of oil equivalent. In my country, proven oil and gas resources in onshore turbidite-bearing reservoirs account for more than 15% of the country's total proven reserves, making them a key potential area for ensuring increased oil and gas reserves and production. However, as an authigenic cementing mineral in reservoirs, turbidite crystallizes and strongly fills primary pores and throats, forming dense cemented zones. This results in reservoir porosity generally below 10%, with permeability mostly in the ultra-low to ultra-low permeability range of 0.1-10 mD, far below the economic extraction threshold. A large amount of proven oil and gas resources cannot be effectively utilized through conventional technologies, leading to resource idleness and hindering development efficiency and production capacity release.

[0003] Existing permeability enhancement technologies have significant shortcomings in addressing the low permeability problem of turbid zeolite reservoirs. Physical permeability enhancement technologies, represented by hydraulic fracturing, can create artificial fractures to improve conductivity, but formation stress can cause fracture closure, making it difficult to maintain the permeability enhancement effect in the long term. Chemical permeability enhancement technologies mainly employ acidizing treatment. While acid can improve seepage conditions by dissolving cementing minerals, the acid is prone to preferentially entering high-permeability channels and rapidly leaching away due to reservoir heterogeneity, resulting in uneven permeability enhancement. Furthermore, the pH value of the system rises after acidizing, and the resulting secondary precipitation can clog pore throats, causing irreversible reservoir damage.

[0004] With global carbon dioxide emissions continuing to rise and the greenhouse effect becoming increasingly serious, countries around the world have introduced carbon reduction policies. Geological carbon dioxide sequestration is a key approach to large-scale emission reduction, but traditional technologies require separate site selection and construction, and are generally limited by reservoir conditions, resulting in low sequestration efficiency—carbon dioxide exists mostly in a free or dissolved state, has poor long-term stability, and poses a risk of leakage.

[0005] It is evident that the technical objectives of enhanced permeability and carbon sequestration are disconnected, and their design schemes are isolated. Enhanced permeability technology fails to consider the long-term stability requirements of carbon sequestration on the reservoir structure, while carbon sequestration technology fails to utilize the favorable conditions created by the enhanced permeability process. This disconnect makes it difficult for the enhanced reservoir to adapt to efficient sequestration, and the carbon sequestration process cannot generate a sustained increase in permeability, thus limiting the overall benefits of development and emission reduction.

[0006] Studies have shown that zeolite can undergo a spontaneous mineralization reaction with carbon dioxide. This reaction has dual technological value: firstly, the reduced total volume of solids after the reaction facilitates the formation of a well-connected secondary pore system within the reservoir, thereby effectively improving reservoir permeability; secondly, carbon dioxide can be solidified into stable calcium carbonate minerals through this reaction, significantly enhancing storage stability. This mechanism provides a new approach for reservoir permeability enhancement and carbon sequestration strengthening, but existing technologies have not designed specific solutions based on this mechanism, urgently requiring a gap to be filled. Summary of the Invention

[0007] This invention discloses a method for enhancing the permeability and carbon dioxide sequestration (CDS) of zeolite-containing reservoirs. Utilizing the spontaneous mineralization reaction characteristics of zeolite and carbon dioxide, a highly efficient permeation channel is formed within the reservoir, simultaneously enhancing CDS efficiency and stability. This method addresses the technical pain points of existing technologies, such as limited reservoir permeability enhancement, low CDS efficiency, and poor stability. It overcomes development bottlenecks, improves oil and gas utilization efficiency, and maximizes the reservoir's CDS potential, achieving both development and environmental benefits.

[0008] This method injects carbon dioxide into the target reservoir at ultra-fracture pressure, opening up the reservoir's tight channels and forming an artificial fracture network through high pressure. This provides ample contact space for zeolite and carbon dioxide, ensuring dissolution efficiency to achieve permeability enhancement, and also expands the diffusion range of carbon dioxide. Subsequently, a stable temperature and pressure environment is created by sealing the well, which promotes the full mineralization reaction between the two, ultimately achieving the dual goals of "permeability enhancement and storage enhancement".

[0009] To achieve the above objectives, the present invention provides the following technical solution: An integrated method for permeability enhancement and carbon dioxide storage in turbid zeolite reservoirs includes the following steps: (1) Screening turbid zeolite-containing reservoirs as target reservoirs; (2) Determine the appropriate carbon dioxide injection method and injection pressure based on reservoir characteristics and well spacing conditions, and inject carbon dioxide into the target reservoir; (3) The well is sealed to promote the full mineralization reaction between carbon dioxide and zeolite.

[0010] Preferably, turbid zeolite-containing reservoirs that meet preset conditions are selected as target reservoirs. The preset condition is that the Gibbs free energy change of the reaction between turbid zeolite and carbon dioxide is negative under reservoir conditions.

[0011] Preferably, the preset condition also includes a zeolite volume content of not less than 2%.

[0012] Preferably, the carbon dioxide injection method in step (2) is selected as continuous injection, slug injection or alternating injection according to the reservoir heterogeneity and the need for stimulation; the injection pressure is higher than the reservoir fracture pressure.

[0013] Preferably, the carbon dioxide injection adopts staged pressure control, including an initial injection stage and a subsequent injection stage; wherein, the initial injection pressure is 1.05 to 1.20 times the reservoir fracture pressure, and when the cumulative injection volume reaches 60% to 80% of the designed total and the wellhead pressure fluctuates within 15 minutes by less than ±5%, the subsequent injection stage is started, and the injection pressure is reduced to below the fracture pressure.

[0014] Preferably, the injection pressure in the subsequent injection stage is 0.75 to 0.85 times the rupture pressure.

[0015] Preferably, the well shut-in time in step (3) needs to be dynamically adjusted based on real-time monitoring data, specifically: continuously monitoring the bottom hole pressure P wf (t), use formula (1) to calculate the bottom hole pressure function value F(t), use formula (2) to calculate the rate of change η of the bottom hole pressure function value; when η is less than 3% for 3 consecutive cycles, it indicates that the mineralization reaction tends to be stable, and the well is shut down. Each cycle Δt is 1 day; (1) In equation (1), F(t) is the dimensionless bottom hole pressure function value at time t, which is dimensionless; P wf (t) represents the bottom hole pressure monitored at time t, in MPa; P ref For reference pressure, the initial bottom hole pressure at the start of the wellbore operation is taken, in MPa; Z(P) wf (t) represents the pressure P of carbon dioxide at the bottom of the well. wf (t) and the compressibility factor at reservoir temperature, dimensionless; (2) In equation (2), η is the rate of change of the bottom hole pressure function value, which is dimensionless; F(t+Δt) is the pressure function value calculated from the bottom hole pressure at time t+Δt, which is dimensionless; Δt is the monitoring time interval, d.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. Achieving Synergistic Progress in Permeability Enhancement and Carbon Sequestration. This invention achieves the dual objectives of reservoir permeability enhancement and carbon sequestration enhancement simultaneously through a single process, overcoming the limitations of traditional technologies that promote these two aspects independently. This process relies on the mineralization reaction between zeolite and carbon dioxide, achieving both selective dissolution of the zeolite cement, significantly improving reservoir permeability, and solidifying carbon dioxide into calcium carbonate minerals for stable sequestration.

[0017] 2. Ensuring reservoir structural stability. This invention relies on spontaneous mineralization reactions to enhance reservoir permeability, fundamentally avoiding the risks of acid fingering, uneven permeability enhancement, and secondary precipitation blockage caused by traditional acidizing. It effectively protects the integrity of the reservoir's pore structure, providing a solid foundation for long-term reservoir permeability enhancement and stable carbon dioxide sequestration.

[0018] 3. Significantly reduces the overall cost of oil and gas development and carbon sequestration, achieving efficient utilization of reservoir space. This invention uses turbid zeolite reservoirs as both permeability enhancement targets and carbon sequestration space, eliminating the need for separate site selection and construction for sequestration. This achieves space reuse, significantly saving upfront investment and operating costs for carbon sequestration, demonstrating high technical and economic feasibility.

[0019] 4. Enhanced carbon sequestration stability and environmental friendliness. This invention converts carbon dioxide into calcium carbonate through mineral-based sequestration, which significantly improves sequestration stability compared to free-state sequestration, aligning with the requirements of green and low-carbon development. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the implementation process of a method for enhancing the permeability and carbon dioxide sequestration of turbid zeolite reservoirs.

[0021] Figure 2 The graph shows the rate of change η of the bottom hole pressure function value as a function of the well stagnation time in Example 1.

[0022] Figure 3 This is a bar chart comparing the porosity of core samples before and after the experiment in Example 1.

[0023] Figure 4 This is a bar chart comparing the permeability of core samples before and after the experiment in Example 1.

[0024] Figure 5 This is a graph showing the rate of change η of the bottom hole pressure function value as a function of the well slumping time in Example 2.

[0025] Figure 6 This is a bar chart comparing the porosity of core samples before and after the experiment in Example 2.

[0026] Figure 7 This is a bar chart comparing the permeability of core samples before and after the experiment in Example 2.

[0027] Figure 8 This is a scanning electron microscope image of newly formed carbonate minerals on the core surface after the experiment in Example 2. Detailed Implementation

[0028] To make the technical solution, innovative points, and beneficial effects of the present invention clearer, a detailed description will be provided below in conjunction with specific embodiments. It should be noted that the embodiments listed herein are merely illustrative of the core principles and typical applications of the present invention and are not intended to exhaustively limit the scope of protection of the present invention. Other technical solutions that can be obtained by those skilled in the art through logical reasoning, experimentation, or conventional technical means based on an understanding of the concept and technical solution of the present invention should all be considered within the scope of protection claimed by the present invention.

[0029] Example 1 Based on the method of this invention, the following is a specific implementation example of the Triassic Xujiahe Formation sandstone reservoir in the Sichuan Basin: (1) Reservoir Screening and Evaluation. Typical representative core samples were taken from the field. The lithology was lithic sandstone strongly cemented by zeolite. Quantitative mineral analysis was performed using X-ray diffraction (XRD), and the volume content of zeolite was found to be 8.1%. Experimental conditions were set to simulate the reservoir environment of this formation: temperature 110℃ and pore pressure 38MPa. Using PHREEQC thermodynamic simulation software, the formation water chemical composition (mineralization approximately 12000 mg / L) was input, and the Gibbs free energy change (ΔG) of the reaction between zeolite and carbon dioxide under these conditions was calculated to be -18.5 kJ / mol, indicating that the reaction can proceed spontaneously. Pre-experimental core physical property measurements showed that its gas permeability was 0.08 mD and its porosity was 6.5%.

[0030] (2) Injection Parameter Design. Rock mechanics tests determined the fracture pressure of the core sample under simulated formation confining pressure to be 58 MPa. Based on this, the injection parameters were designed as follows: the initial injection stage pressure was set to 1.12 times the fracture pressure, i.e., 65.0 MPa, to effectively fracturing the reservoir; the subsequent injection stage pressure was reduced to 46 MPa (approximately 0.79 times the fracture pressure) to promote diffusion and reaction. Given the strong heterogeneity of the reservoir, slug injection was adopted (12 hours of injection, 6 hours of rest, repeated twice).

[0031] (3) Carbon dioxide injection and wellbore monitoring. The core was loaded into a high-temperature, high-pressure core displacement device. First, the initial injection stage was performed: carbon dioxide was injected at a pressure of 65.0 MPa. During this process, the cumulative injection volume and wellhead injection pressure were monitored in real time. When the cumulative injection volume reached 70% of the designed total injection volume (1.4 times the core pore volume PV) (i.e., 0.98 times PV), and the fluctuation range of the wellhead injection pressure within 15 consecutive minutes was less than ±5% of its average value, the initial injection stage target was determined to be completed. Subsequently, the subsequent injection stage was started: the injection pressure was reduced to 46 MPa, and the remaining carbon dioxide (0.42 times PV) was injected until the cumulative injection volume reached 1.4 times PV. After the injection was completed, the outlet and inlet ends were immediately closed, and the inlet pressure P was continuously monitored.wf (t). Take the initial pressure P of the well. ref =41.5MPa.

[0032] (4) Reaction process assessment and well closure termination. The monitoring data is analyzed and processed. Based on the daily P... wf Given t and temperature (110℃), the carbon dioxide compressibility factor Z (P) is calculated using the equation of state (1). wf (t)).

[0033] (1) Where Z is the compressibility factor, dimensionless; P is the absolute pressure of the gas, MPa; V is the molar volume of the gas, m³ / mol; R is the universal gas constant, usually taken as 8.314462618 J / (mol·K) or 0.008314462618 MPa·m³ / (mol·K); and T is the absolute temperature of the gas, K.

[0034] Calculate the pressure function value and its rate of change using equations (2) and (3): (2) Where F(t) is the dimensionless bottom hole pressure function value at time t, and is dimensionless; P wf (t) represents the bottom hole pressure monitored at time t, in MPa; P ref For reference pressure, the initial bottom hole pressure at the start of the wellbore operation is taken, in MPa; Z(P) wf (t) represents the pressure P of carbon dioxide at the bottom of the well. wf (t) and the compressibility factor at reservoir temperature, dimensionless; (3) In equation (2), η is the rate of change of the bottom hole pressure function value, which is dimensionless; F(t+Δt) is the pressure function value calculated from the bottom hole pressure at time t+Δt, which is dimensionless; Δt is the monitoring time interval, d. In this embodiment, the monitoring time interval Δt is 1 day.

[0035] The calculation results show that the η value was higher than 3% in the initial stage of well closure (days 2 to 4), reaching a maximum of 3.85%, indicating that the reaction was in an active adjustment period. Thereafter, the η value continued to decrease. From day 5 to day 7, the value was lower than 3% for three consecutive days (day 5: 2.64%, day 6: 1.54%, day 7: 0.97%), indicating that the reaction had stabilized. Therefore, well closure was terminated on day 8.

[0036] Post-experiment evaluation: The permeability of the core sample increased to 1.5 mD after the experiment, a significant increase. Scanning electron microscopy (SEM) confirmed the dissolution of zeolite and the formation of new rhombic calcium carbonate minerals. Ion chromatography analysis of the displaced water sample, combined with calculations based on the carbon mass balance before and after the reaction, showed that the carbon dioxide mineralization and sequestration efficiency of this experiment was approximately 91%.

[0037] Example 2 Based on the method of this invention, the following specific implementation case of the Triassic Leikoupo Formation carbonate reservoir in the Sichuan Basin is given: (1) Reservoir Screening and Evaluation. Typical representative core samples were taken from the field. The lithology was microcrystalline limestone, and the fractures were filled with zeolite. Quantitative mineral analysis was performed using X-ray diffraction (XRD), and the volume content of zeolite was found to be 3.0%. Experimental conditions were set to simulate the reservoir environment of this formation: temperature 102℃ and pore pressure 32MPa. Using PHREEQC thermodynamic simulation software, the chemical composition of formation water (mineralization approximately 7000mg / L) was input, and the Gibbs free energy change (ΔG) of the reaction between zeolite and carbon dioxide under these conditions was calculated to be -14.0kJ / mol, indicating that the reaction can proceed spontaneously. Pre-experimental core physical property measurements showed that its gas permeability was 0.25mD and its porosity was 5.9%.

[0038] (2) The fracture pressure of the core under simulated formation confining pressure was determined to be 47 MPa through rock mechanics tests. Based on this, the injection parameters were designed as follows: the initial injection stage pressure was set to 1.07 times the fracture pressure, i.e., 50.3 MPa, to effectively fracture; the subsequent injection stage pressure was reduced to 40 MPa (approximately 0.85 times the fracture pressure) to promote diffusion and reaction. Continuous injection was adopted.

[0039] (3) Carbon dioxide injection and wellbore monitoring. The core was loaded into a high-temperature, high-pressure core displacement device. First, the initial injection stage was performed: carbon dioxide was injected at a pressure of 50.3 MPa. During this process, the cumulative injection volume and wellhead injection pressure were monitored in real time. When the cumulative injection volume reached 70% of the designed total injection volume (1.0 times PV) (i.e., 0.7 times PV), and the fluctuation range of the wellhead injection pressure within 15 consecutive minutes was less than ±5% of its average value, the initial injection stage target was determined to be completed. Subsequently, the subsequent injection stage was started: the injection pressure was reduced to 40 MPa, and the remaining carbon dioxide (0.3 times PV) was injected until the cumulative injection volume reached 1.0 times PV. After the injection was completed, the outlet and inlet ends were immediately closed, and the inlet pressure P was continuously monitored. wf (t). Take the initial pressure P of the well. ref =35.2MPa.

[0040] (4) Reaction process assessment and well closure termination. Based on daily P... wfGiven t and temperature (102℃), the carbon dioxide compressibility factor Z (P) is calculated using the equation of state (1). wf (t), and use equations (2) and (3) to calculate the pressure function value and its rate of change (Δt=1 day).

[0041] The calculation results show that in the initial stage of well closure (days 1 to 3), the η value is higher than or equal to 3%, reaching a maximum of 4.37%; from day 4 onwards, the η value drops to below 3% and remains below this threshold for three consecutive days (day 4: 2.25%, day 5: 1.32%, day 6: 0.78%), indicating that the reaction has stabilized, so well closure was terminated on day 6.

[0042] Post-experimental evaluation: The core permeability was measured to increase to 2.0 mD after the experiment, a significant increase. Scanning electron microscopy (SEM) confirmed that the zeolite filling the fractures was effectively dissolved, and newly formed, regularly shaped secondary carbonate minerals were observed adhering to the surface (see...). Figure 8 The displaced water sample was analyzed by ion chromatography, and the carbon mass balance before and after the reaction was calculated. The carbon dioxide mineralization and sequestration efficiency of this experiment was approximately 87%.

[0043] The present invention has been described in detail above through specific embodiments, the purpose of which is to help understand the technical content and implementation process of the present invention, and not to limit the scope of implementation of the present invention in any way. For those skilled in the art, any adaptive modifications, equivalent substitutions, or partial adjustments made to the method steps, process parameters, or material selections involved in the foregoing embodiments without departing from the core technical principles and essential spirit disclosed in the present invention should be considered as reasonable extensions and changes based on the technical solution of the present invention, and should also fall within the legal protection scope defined by the claims of the present invention.

Claims

1. A method for integrating permeability enhancement and carbon dioxide storage in turbid zeolite reservoirs, characterized in that, Includes the following steps: (1) Screening turbid zeolite-containing reservoirs as target reservoirs; (2) Determine the appropriate carbon dioxide injection method and injection pressure based on reservoir characteristics and well spacing conditions, and inject carbon dioxide into the target reservoir; (3) The well is sealed to promote the full mineralization reaction between carbon dioxide and zeolite.

2. The method according to claim 1, characterized in that, Turbid zeolite reservoirs that meet the preset conditions are selected as target reservoirs. The preset condition is that the Gibbs free energy of the reaction between turbid zeolite and carbon dioxide becomes negative under the reservoir conditions.

3. The method according to claim 2, characterized in that, The preset conditions also include a zeolite volume content of not less than 2%.

4. The method according to claim 1, characterized in that, The carbon dioxide injection method in step (2) is selected as continuous injection, slug injection or alternating injection according to the reservoir heterogeneity and the need for stimulation; the injection pressure is higher than the reservoir fracture pressure.

5. The method according to claim 4, characterized in that, For reservoirs with good homogeneity, continuous injection is used; for reservoirs with strong heterogeneity that require balanced stimulation, slug injection or injection of other fluids is used.

6. The method according to claim 1, characterized in that, The carbon dioxide injection adopts staged pressure control, including an initial injection stage and a subsequent injection stage. The initial injection pressure is 1.05 to 1.20 times the reservoir fracture pressure. When the cumulative injection volume reaches 60% to 80% of the designed total and the wellhead pressure fluctuates within 15 minutes by less than ±5%, the subsequent injection stage begins, and the injection pressure is reduced to below the fracture pressure.

7. The method according to claim 6, characterized in that, The injection pressure in the subsequent injection stage is 0.75 to 0.85 times the rupture pressure.

8. The method according to claim 1, characterized in that, In step (3), the well shut-in time needs to be dynamically adjusted based on real-time monitoring data. Specifically, the bottom-hole pressure P is continuously monitored. wf (t), use formula (1) to calculate the bottom hole pressure function value F(t), use formula (2) to calculate the rate of change η of the bottom hole pressure function value; when η is less than 3% for 3 consecutive cycles, it indicates that the mineralization reaction tends to be stable, and the well is shut down. Each cycle Δt is 1 day; （1） In equation (1), F(t) is the dimensionless bottom hole pressure function value at time t, which is dimensionless; P wf (t) represents the bottom hole pressure monitored at time t, in MPa; P ref For reference pressure, the initial bottom hole pressure at the start of the wellbore operation is taken, in MPa; Z(P) wf (t) represents the pressure P of carbon dioxide at the bottom of the well. wf (t) and the compressibility factor at reservoir temperature, dimensionless; （2） In equation (2), η is the rate of change of the bottom hole pressure function value, which is dimensionless; F(t+Δt) is the pressure function value calculated from the bottom hole pressure at time t+Δt, which is dimensionless; Δt is the monitoring time interval, d.

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