Method and device for evaluating the effect of carbon dioxide huff and puff on the dissolution degree of a reservoir

Abstract

The present application belongs to the field of reservoir dissolution experiment detection, and particularly relates to a method and device for evaluating the influence of carbon dioxide huff and puff on the dissolution degree of a reservoir. The method comprises placing reservoir detritus with a mass of m, reservoir formation water with a volume of V and a calcium ion concentration of C into a reaction device; then injecting carbon dioxide and reacting; then displacing the solution in the reaction to a precipitation device; again measuring the mass of the reservoir detritus and the calcium ion concentration in the solution in the precipitation device; and calculating the degree of dissolution of the reservoir and the content of scale formed by carbon dioxide huff and puff through a formula. The experimental device comprises a booster pump, a reaction device and a precipitation device connected in sequence, and a glass slide is arranged in the precipitation device. The method can evaluate the influence of carbon dioxide huff and puff on the dissolution degree of a reservoir under high pressure conditions, and quantitatively analyze the content of scale formed by carbon dioxide huff and puff, thereby providing technical support for well drilling and single-well scale formation trend prediction.

Description

Technical Field

[0001] This invention belongs to the field of reservoir erosion test, specifically relating to a method and apparatus for evaluating the effect of carbon dioxide huff and puff on the degree of reservoir erosion. Background Technology

[0002] Gas injection (huff and puff) is the main focus of enhanced oil recovery in oilfields both domestically and internationally. To date, 3% of the world's crude oil production has been obtained through gas injection. However, carbon dioxide flooding (huff and puff) can cause severe corrosion and scaling problems in metal pipelines and equipment, resulting in huge economic losses. Therefore, studying the scaling mechanism and prediction model of calcium carbonate in produced water from carbon dioxide flooding (huff and puff) can provide theoretical and technical support for the application of carbon dioxide flooding (huff and puff) technology, and has important theoretical and practical significance.

[0003] Chinese invention patent applications CN103867193A "Simulation and Evaluation Device for Reservoir Damage from Injected Fluid", CN106525881A "A Method and Equipment for Determining the Degree of Reservoir Damage", and CN111101934A "A Method for Evaluating Reservoir Damage from Fracturing Stimulation" are experimental devices that allow real-time simulation of reservoir damage caused by injected fluids to wells with various complex structures based on similarity theory. However, they cannot quantitatively analyze the composition and content of scale formed after carbon dioxide inhalation and exhalation. Another Chinese invention patent application, "An Experimental Device and Method for Evaluating the Damage of Fracturing Fluid to Petroleum Reservoirs", uses microchannels in rock slabs to replace real rock cores, making it simple to use, with short measurement time, and capable of visual measurement. However, it cannot evaluate reservoir dissolution under high-pressure conditions.

[0004] Chinese invention patent application CN 106644871 A discloses a device and method for evaluating the impact of supercritical carbon dioxide fracturing fluid on oil and gas reservoir seepage. This device can only evaluate the permeability damage rate of carbon dioxide to the core under displacement conditions, but it cannot analyze the content and morphology of scale formed after carbon dioxide displacement / injection. It uses permeability to conduct research, but reservoirs also have phenomena such as rate sensitivity, which can also change permeability. It cannot be concluded that the change in permeability is caused by the formation of scale, and its measurement is not accurate.

[0005] Chinese invention patent application CN 112326484 A discloses a supercritical carbon dioxide dynamic rock dissolution test system and its working method. It employs a high-temperature, high-pressure reactor to apply high-temperature, high-pressure, and fluid flow conditions to the rock, achieving a realistic simulation of the reservoir environment during carbon dioxide extraction of hot dry rock. However, this invention can only analyze the dynamic dissolution phenomenon of supercritical carbon dioxide on rocks and cannot quantitatively analyze the composition and content of the scale formed after carbon dioxide displacement / injection.

[0006] Therefore, there is an urgent need to establish an experimental device and method for the dissolution-transfer-precipitation of reservoirs by carbon dioxide huff and puff. This device and method can not only evaluate the degree of reservoir dissolution by carbon dioxide huff and puff under high temperature and high pressure conditions, but also quantitatively analyze the content of scale formed by carbon dioxide huff and puff, providing technical support for well development and prediction of scaling trends in single wells. Summary of the Invention

[0007] To address the shortcomings of existing technologies, this invention provides a method for evaluating the impact of carbon dioxide huff and puff on reservoir dissolution under high-pressure conditions, while also quantitatively analyzing the content of scale formed by carbon dioxide huff and puff and observing the morphology of simulated scale.

[0008] To achieve the objectives of this invention, the following technical solution is adopted:

[0009] A method for evaluating the impact of carbon dioxide huff and puff on reservoir dissolution includes the following steps:

[0010] (1) Place reservoir rock cuttings with mass m and reservoir formation water with volume V and calcium ion concentration C into the reaction apparatus;

[0011] (2) Inject carbon dioxide into the reaction apparatus and react;

[0012] (3) Displace the reacted solution into a precipitation apparatus;

[0013] (4) The mass of reservoir rock cuttings was measured again as m1, and the concentration of calcium ions in the solution in the precipitation device was measured as C1;

[0014] (5) Apply formula a to calculate the degree of reservoir dissolution caused by carbon dioxide huff and puff, and apply formula b to calculate the amount of scale formed, M:

[0015] Reservoir dissolution degree η=100 (m-m1) / m……………………a;

[0016] Scale content M=2.4419 (0.4) (m-m1) / V+C-C1) V………b.

[0017] In the above formula, 0.4 is the ratio of the molar mass of calcium ions (40 g / mol) to the molar mass of calcium carbonate.

[0018] In basic chemistry, it is believed that carbonate ions (from excess carbon dioxide injection) react completely with calcium ions to produce calcium carbonate precipitate. However, in actual production processes, trace amounts of calcium carbonate can dissolve in water, and small amounts of both calcium ions and carbonate ions can coexist in oilfield water. Based on this, by introducing excess carbon dioxide into simulated water containing calcium chloride, a correlation was established between the mass of calcium ion loss and the amount of calcium carbonate precipitate formed. The mass of calcium carbonate precipitate formed was then calculated based on the amount of calcium ion loss, as detailed below:

[0019] Prepare calcium chloride aqueous solutions with calcium ion concentrations of 10000 mg / L, 5000 mg / L, 1000 mg / L, 500 mg / L, and 100 mg / L, respectively. Transfer 100 mL of each of these calcium chloride aqueous solutions to five 250 mL Erlenmeyer flasks, and bubble excess carbon dioxide through them until the precipitate has completely settled and the solution is clear. Filter the precipitate through filter paper and dry it in an oven at 50-60℃ to constant weight. Establish a linear relationship between the amount of calcium ion loss and the mass of calcium carbonate precipitate: y = 2.4419x, R. 2 =0.9992, see the linear relationship graph. Figure 1 Therefore, the coefficient in the formula for calculating scale content is 2.4419.

[0020] Preferably, a glass slide is also placed in the precipitation device. After the experiment is completed, the glass slide is removed and the morphology of the scale on the glass slide is observed using energy dispersive spectroscopy or a microscope.

[0021] Preferably, the pressure of carbon dioxide in step (2) simulates the pressure of the reservoir, with a pressure of 0-70 MPa.

[0022] Preferably, the temperature of the reaction in step (2) is 20-200℃, and the reaction time is 70-75h.

[0023] Preferably, the pressure of carbon dioxide injected in step (2) is 7.5-50 MPa, and the temperature of the reaction is 35-150 °C.

[0024] Preferably, constant temperature and pressure conditions are used during displacement in step (3).

[0025] Preferably, in step (4), the pressure of the reaction device and the precipitation device is released before the re-measurement, and then the reservoir rock fragments in the reaction device, the glass slide and the solution in the precipitation device are taken out for measurement.

[0026] Preferably, the reservoir rock cuttings in step (4) are dried at 50-60℃ for 22-26 hours before being measured.

[0027] Another objective of this invention is to provide an experimental apparatus for evaluating the effects of carbon dioxide huff and puff on reservoir dissolution-transfer-precipitation, for implementing the above-mentioned experimental method, comprising a gas pressurization system I, a reaction device, and a precipitation device connected in sequence; the reaction device is provided with a core cuttings slot for placing the reservoir cuttings to be tested, and the precipitation device is provided with a slide slot for placing a glass slide.

[0028] Preferably, the core cuttings slot is provided with small holes on the top and side, and the small holes on the top and side are connected to each other to allow reservoir formation water to flow in the device.

[0029] Preferably, the slide slot has a groove, the lower part of the groove is the same width as the slot, the upper part of the groove is the middle position of the slot, and the upper width of the groove is smaller than the lower width of the groove. The groove is convex in cross-sectional direction.

[0030] Preferably, a back pressure valve I and a six-way valve II are connected in sequence between the reaction device and the precipitation device, and the other end of the precipitation device is connected to a back pressure valve II and a liquid recovery device.

[0031] Preferably, both the reaction device and the precipitation device are equipped with piston valves.

[0032] Preferably, the experimental apparatus further includes a six-way valve I, a pressure gauge, a simulated water intermediate container, and an injection pump I; one end of the upper part of the six-way valve I is connected to the pressure gauge, and the other end of the upper part of the six-way valve I is sequentially connected to the simulated water intermediate container and the injection pump I.

[0033] Preferably, a pressure gauge is provided on one side of the six-way valve I, and the other side is connected in sequence to a pressure stabilizing valve and a pressure monitoring system; a balance is also connected below the simulated water intermediate container; the injection pump I is connected to the reaction device, the injection pump II is connected to the sedimentation device, and the sedimentation device is also connected in sequence to the gas pressurization system II and the N2 gas cylinder.

[0034] Another objective of this invention is to provide the application of the above-mentioned method or experimental apparatus in the quantitative analysis of the degree of reservoir dissolution and the content of scale formed after carbon dioxide huff and puff.

[0035] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0036] This invention establishes an experimental apparatus and method for evaluating the effects of carbon dioxide huff and puff on reservoir dissolution-transfer-precipitation. It can not only evaluate the degree of reservoir dissolution caused by carbon dioxide huff and puff, but also quantitatively analyze the content of scale formed by carbon dioxide huff and puff, providing technical support for well development and single-well scaling trend prediction in oil reservoirs. Attached Figure Description

[0037] Figure 1 The graph shows the linear relationship between calcium ion loss and the mass of calcium carbonate precipitate.

[0038] Figure 2 A diagram of the experimental setup used to evaluate the effects of carbon dioxide huff and puff on reservoir dissolution-transfer-precipitation.

[0039] The attached figures are labeled as follows:

[0040] 1-CO2 cylinder, 2-Gas pressurization system I, 3-Six-way valve I, 4-Pressure gauge, 5-Pressure stabilizing valve, 6-Pressure monitoring system, 7-Balance, 8-Simulated water intermediate container, 9-Injection pump I, 10-Reaction device, 11-Piston I, 12-Core and rock cuttings slot, 13-Injection pump III, 14-Back pressure valve I, 15-Pressure gauge, 16-Six-way valve II, 17-CO2 recovery device, 18-Sedimentation device, 19-Piston II, 20-Slide slot, 21-Injection pump II, 22-Back pressure valve II, 23-Balance, 24-Liquid recovery device, 25-CO2 recovery device, 26-Gas pressurization system II, 27-N2 cylinder, 28-Temperature control system;

[0041] Figure 3 This is a top view of the core and cuttings slot 12; the black part is a solid made of 316L steel plate, and the white part is a small hole for liquid flow.

[0042] Figure 4 This is a side view of core and cuttings slot 12; the black part is a solid made of 316L steel plate, and the white part is a small hole for liquid flow.

[0043] Figure 5 This is a top view of the slide slot 20; the black part is the solid material made of 316L steel plate, and the white part is the groove.

[0044] Figure 6 This is a side view of the slide slot 20; the black part is the solid material made of 316L steel plate, and the white part is the groove.

[0045] Figure 7 Original image of a dirt sample on a glass slide observed under a microscope;

[0046] Figure 8 A partial image of the dirt sample on a glass slide observed under a microscope;

[0047] Figure 9 Scanning image of a dirt sample on a glass slide for microscopic observation;

[0048] Figure 10 The slide was labeled "spectrum". Figure 2 Energy dispersive spectroscopy (EDS) analysis diagram of the composition of calcium salt scale on the surface. Detailed Implementation

[0049] The present invention will be further described below with reference to specific embodiments. The following embodiments are all described in conjunction with the accompanying drawings. Figure 2The device was tested.

[0050] Example 1

[0051] This invention adopts Figure 2 The device is used to quantitatively analyze the degree of reservoir dissolution after carbon dioxide injection. The structure of the device includes a CO2 cylinder 1, a gas pressurization system I 2, a six-way valve I 3, a reaction device 10, a back pressure valve I 14, a six-way valve II 16, a precipitation device 18, a gas pressurization system II 26, and an N2 cylinder 27 connected in sequence.

[0052] Among them, the upper end of the six-way valve I3 is connected to the pressure gauge 4, the other end is connected to the simulated water intermediate container 8 and the injection pump I9, and the lower part is connected to the pressure monitoring system 6 through the pressure stabilizing valve 5;

[0053] A pressure gauge 15 is connected to one end of the upper part of the six-way valve II 16, and a CO2 recovery device 17 is connected to the other end.

[0054] The upper part of the sedimentation device 18 is sequentially connected to the back pressure valve II 22, the liquid recovery device 24 and the CO2 recovery device 25; wherein the liquid recovery device 24 is placed on a balance.

[0055] In addition, the reaction device 10 is equipped with piston I 11 and core cuttings slot 12, which is used to hold the reservoir cuttings to be tested. The sedimentation device 18 is equipped with piston II 19 and slide slot 20, which is used to hold glass slides. The core cuttings slot 12 has small holes on its top and side, which are connected to each other to allow reservoir formation water to flow within the device. Figure 3-4 As shown; the slide holder has a groove, the lower part of which is the same width as the holder, and the upper part of which is the middle position of the holder. The upper width of the groove is smaller than the lower width of the groove. The groove is convex in cross-section, as shown. Figure 5-6 As shown.

[0056] The lower parts of the reaction apparatus 10 and the precipitation apparatus 18 are respectively connected to injection pump Ⅲ13 and injection pump Ⅱ21.

[0057] The working principle of this device is as follows:

[0058] Calcium carbonate from reservoir rock fragments and reservoir formation water are added to reaction device 10 via injection pump I9 and simulated water intermediate container 8. Carbon dioxide is injected into reaction device 10 via gas pressurization system I2, and the reaction proceeds. After the reaction is completed, back pressure valve I14 and six-way valve II16 are opened to displace the reaction solution into precipitation device 18. After the system stabilizes, the pressure is released, and calcium carbonate in reaction device 10 is removed, dried at 50°C for 24 hours, and weighed. The slide and solution in precipitation device 18 are removed, and the morphology of the scale on the slide is observed under a microscope. The concentration of calcium ions in the solution is determined, and the degree of carbon dioxide ionization on the calcium carbonate reservoir is calculated.

[0059] Example 2

[0060] Place the cleaned and dried glass slide into slide holder 20 for later use. Weigh 10.1g of reservoir rock fragment calcium carbonate and 100mL of reservoir formation water (calcium ion concentration 550.5ppm), and place them into reaction apparatus 10. Inject carbon dioxide at 8MPa through gas pressurization system I2. After reacting at 150℃ for 72h, displace the solution in reaction apparatus 10 to precipitation apparatus 18 under constant pressure. After depressurization, remove the calcium carbonate from reaction apparatus 10, dry it at 50℃ for 24h, and weigh it to be 9.87g. Remove the glass slide and solution (calcium ion concentration 550.5ppm) from precipitation apparatus 18 and apply the formula:

[0061] Reservoir dissolution degree η=100 (m-m1) / m……………………a;

[0062] Scale content M=2.4419 (0.4) (m-m1) / V+C-C1) V………b.

[0063] Calculations show that carbon dioxide injection causes 2.28% dissolution of calcium carbonate, resulting in 224.65 mg of calcium scale.

[0064] Example 3

[0065] Place the cleaned and dried glass slide into slide holder 20 for later use. Weigh 10.36g of reservoir rock fragments calcium carbonate and 100mL of reservoir formation water (calcium ion concentration 550.5ppm), and place them into reaction apparatus 10. Inject carbon dioxide at 50MPa through gas pressurization system I2. After reacting at 85℃ for 72h, displace the solution in reaction apparatus 10 to precipitation apparatus 18 under constant pressure. After depressurization, remove the calcium carbonate from reaction apparatus 10, dry it at 60℃ for 22h, and weigh it to be 9.99g. Remove the glass slide and solution (calcium ion concentration 263.3ppm) from precipitation apparatus 18. Apply the formula:

[0066] Reservoir dissolution degree η=100 (m-m1) / m……………………a;

[0067] Scale content M=2.4419 (0.4) (m-m1) / V+C-C1) V………b.

[0068] Calculations show that carbon dioxide inhalation and exhalation causes 3.57% dissolution of calcium carbonate, resulting in 431.53 mg of calcium scale.

[0069] Example 4

[0070] Place the cleaned and dried glass slide into slide holder 20 for later use. Weigh 10.04g of reservoir rock fragments calcium carbonate and 100mL of reservoir formation water (calcium ion concentration 550.5ppm), and place them into reaction apparatus 10. Inject carbon dioxide at 11MPa through gas pressurization system I2. After reacting at 35℃ for 75h, displace the solution in reaction apparatus 10 to precipitation apparatus 18 under constant pressure. After depressurization, remove the calcium carbonate from reaction apparatus 10, dry it at 50℃ for 24h, and weigh it to 9.5g. Remove the glass slide and solution (calcium ion concentration 311.2ppm) from precipitation apparatus 18. Apply the formula:

[0071] Reservoir dissolution degree η=100 (m-m1) / m……………………a;

[0072] Scale content M=2.4419 (0.4) (m-m1) / V+C-C1) V………b.

[0073] Calculations show that carbon dioxide injection causes 5.38% dissolution of calcium carbonate, resulting in 585.89 mg of calcium scale.

[0074] Example 5

[0075] Place the cleaned and dried glass slide into slide holder 20 for later use. Weigh 10.09g of reservoir rock fragments calcium carbonate and 100mL of reservoir formation water (calcium ion concentration 550.5ppm), and place them into reaction apparatus 10. Inject carbon dioxide at 15MPa through gas pressurization system I2. After reacting at 85℃ for 72h, displace the solution in reaction apparatus 3 to precipitation apparatus 18 under constant pressure. After depressurization, remove the calcium carbonate from reaction apparatus 10, dry it at 50℃ for 24h, and weigh it to be 929g. Remove the glass slide and solution (calcium ion concentration 851.7ppm) from precipitation apparatus 18. Apply the formula:

[0076] Reservoir dissolution degree η=100 (m-m1) / m……………………a;

[0077] Scale content M=2.4419 (0.4) (m-m1) / V+C-C1) V………b.

[0078] Calculations show that carbon dioxide injection causes 7.93% dissolution of calcium carbonate, resulting in 707.86 mg of calcium scale.

[0079] Microscopic observation and energy dispersive spectroscopy analysis were performed on the scale sample on the glass slide in Example 2. The results are shown in the figure. Figure 7-10 See Table 1.

[0080] Table 1. Energy dispersive spectroscopy (EDS) analysis results of dirt samples from glass slides.

[0081] weight% atom% C 32.48 52.92 O 17.37 21.24 Cl 30.19 16.66 Ca 14.89 7.27 Cr 5.07 1.91 Total 100.00 -

[0082] The above detailed description is a specific description of one of the feasible embodiments of the present invention. This embodiment is not intended to limit the patent scope of the present invention. All equivalent implementations or modifications that do not depart from the present invention should be included within the scope of the technical solution of the present invention.

Claims

1. A method for evaluating the impact of carbon dioxide huff and puff on the degree of reservoir dissolution, characterized in that, Includes the following steps: (1) Place reservoir rock cuttings with mass m and reservoir formation water with volume V and calcium ion concentration C into the reaction apparatus; (2) Inject carbon dioxide into the reaction apparatus and react; (3) Displace the reacted solution into a precipitation apparatus; (4) The mass of reservoir rock cuttings was measured again as m1, and the concentration of calcium ions in the solution in the precipitation device was measured as C1; (5) Apply formula a to calculate the degree of reservoir dissolution caused by carbon dioxide huff and puff, and apply formula b to calculate the amount of scale formed, M: Reservoir dissolution degree η=100 (m-m1) / m……………………a; Scale content M=2.4419 (0.4) (m-m1) / V+C-C1) V………b.

2. The method according to claim 1, characterized in that, In steps (1) and (2), a glass slide is also placed in the precipitation device. After the experiment is completed, the glass slide is taken out and the morphology of the scale on the glass slide is observed by energy dispersive spectroscopy or microscopy.

3. The method according to claim 1, characterized in that, The pressure of carbon dioxide injected in step (2) is 0-70 MPa, the temperature of the reaction is 20-200℃, and the reaction time is 70-75 h.

4. The method according to claim 1, characterized in that, In step (2), the pressure of carbon dioxide injected is 7.5-50 MPa, and the temperature of the reaction is 35-150 °C.

5. The method according to claim 1, characterized in that, In step (3), constant temperature and pressure conditions are used for displacement.

6. The method according to any one of claims 1-5, characterized in that, Step (4) Before the retest, depressurize the reaction device and the precipitation device, and then take out the reservoir rock fragments in the reaction device, the glass slide and the solution in the precipitation device for testing.

7. The method according to claim 1, characterized in that, Before the re-measurement described in step (4), the reservoir rock cuttings should be dried at 50-60℃ for 22-26 hours.

8. An experimental apparatus for evaluating the effects of carbon dioxide huff and puff on reservoir dissolution-transfer-precipitation, characterized in that, The experimental apparatus is used to implement the method described in any one of claims 1-7, comprising a gas pressurization system I, a reaction device, and a precipitation device connected in sequence; the reaction device is provided with a core cuttings slot for placing the reservoir cuttings to be tested, and the precipitation device is provided with a slide slot for placing a slide.

9. The experimental apparatus according to claim 8, characterized in that, The core cuttings slot has small holes on its top and sides, and these holes are connected to each other, allowing reservoir formation water to flow within the device.

10. The experimental apparatus according to claim 8, characterized in that, The slide slot has a groove, the lower part of which is the same width as the slot, the upper part of which is located in the middle of the slot, and the upper part of which is narrower than the lower part. The groove is convex in cross-sectional direction.

11. The experimental apparatus according to claim 8, characterized in that, The reaction device and the precipitation device are connected in sequence by a back pressure valve I and a six-way valve II, and the other end of the precipitation device is connected to a back pressure valve II and a liquid recovery device.

12. The experimental apparatus according to claim 8, characterized in that, Both the reaction device and the precipitation device are equipped with piston valves.

13. The experimental apparatus according to claim 8, characterized in that, The experimental setup also includes a six-way valve I, a pressure gauge, a simulated water intermediate container, and an injection pump I; one end of the upper part of the six-way valve I is connected to the pressure gauge, and the other end of the upper part of the six-way valve I is connected in sequence to the simulated water intermediate container and the injection pump I.

14. The experimental apparatus according to claim 13, characterized in that, A pressure gauge is provided on one side of the six-way valve I, and the other side is connected in sequence to a pressure stabilizing valve and a pressure monitoring system; an injection pump III is connected above the simulated water intermediate container, and a balance is also connected below it; the injection pump I is connected to the reaction device, the injection pump II is connected to the sedimentation device, and the sedimentation device is also connected in sequence to the gas pressurization system II and an N2 gas cylinder.

15. The application of the method according to any one of claims 1-7 or the experimental apparatus according to any one of claims 8-14 in the quantitative analysis of the degree of reservoir dissolution and the content of scale formed after carbon dioxide huff and puff.

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