A comprehensive experimental evaluation method for the migration, filling and plugging effects of underground cross-linked solidified plugging materials

Abstract

The present invention provides a comprehensive experimental evaluation method for the migration, filling and plugging effect of underground cross-linked solidified plugging materials, belonging to the technical field of drilling fluid plugging. The method of the present invention simplifies the evaluation steps of the filling state of underground cross-linked solidified plugging materials on cracks and the plugging effect of the plugging materials on cracks after solidification. According to the evaluation method of the present invention and the evaluation indicators of crack filling capacity and plugging capacity, the pressure-bearing plugging effect of underground cross-linked solidified plugging materials on target leaking layers can be effectively predicted, filling the gap of the current lack of pressure-bearing plugging evaluation methods for underground cross-linked solidified plugging materials.

Description

Technical Field

[0001] The invention relates to a comprehensive experimental evaluation method for the migration, filling and plugging effects of an underground cross-linked solidified plugging material, belonging to the technical field of drilling fluid plugging. Background Art

[0002] Well leakage refers to the phenomenon that a large amount of drilling fluid leaks into the formation during the drilling process. Well leakage not only consumes a large amount of drilling fluid and prolongs the drilling cycle, but improper handling may also cause complex situations such as well collapse, blowout, and drill bit sticking, and even lead to wellbore scrapping and major engineering accidents. As oil and gas exploration and development expands to deep, ultra-deep, unconventional, and low-grade resource areas, drilling projects face more stringent geological conditions and many technical bottlenecks. Malignant well leakage in fracture (fracture-hole) formations is one of the most common and most difficult to control complex drilling engineering accidents.

[0003] Underground cross-linked gel refers to the process of injecting polymers (or monomers), cross-linking agents, initiators, etc. into the target layer in the form of aqueous solution, and undergoing cross-linking reaction in the formation environment to generate a viscoelastic gel with a three-dimensional network. Underground cross-linked gels often have excellent gel strength, thus forming a good seal for formation pores and cracks. The gel types of underground cross-linked gel systems can be divided into two categories: strong gels and weak gels. Different types of gels have their own applicable conditions due to their unique properties. Strong gels have good strength and temperature resistance, and are suitable for profile control, water plugging, and plugging near wellbore areas; weak gel underground cross-linked gel systems have good deformation and migration properties, and are suitable for profile control, water plugging, oil recovery, and fracturing far from wells, and have achieved good application results on site.

[0004] Curable plugging materials refer to plugging materials with strong thixotropic and curing properties, which can quickly solidify and seal the leakage layer. Curable plugging materials are generally composed of a variety of materials such as curing agents, suspension stabilizers and retarders. Curable plugging materials can effectively stay in the leakage formation after entering the leakage formation for a period of time. Due to their strong thixotropic properties and large flow resistance in the leakage layer, they can quickly solidify and condense to form a solidified body with high strength, which can be bonded with the formation to seal the leakage channel and reduce the loss of mud and drilling fluid. Curable plugging materials have a wide source, low cost, high strength, simple preparation process, and high bonding strength after curing. However, they have high construction safety risks, poor resistance to high-mineralization formation water pollution and dilution ability, and are prone to problems such as stuck drill or being diluted and washed away by water in cracks or caves. In response to the above problems, Chinese patent documents CN116284607A and CN111961452A provide a water-soluble controllable curing resin plugging agent and a high-temperature resistant and high-strength thixotropic gel plugging agent. The controllable curing resin plugging agent can be used for plugging drilling fluid loss in malignant well leakage formations. It is an underground solidified or cross-linked continuous phase plugging material with easy injection, strong filling, strong retention, high temperature resistance and high strength. It is not limited by the fracture-hole leakage channel, and can meet the basic requirements of plugging under different fracture-hole combinations of fracture-hole carbonate rocks. It can achieve a high one-time plugging success rate and has broad application prospects. The high-temperature resistant and high-strength thixotropic gel plugging agent has the properties of "shear thinning and static thickening" in its plugging material solution, which is easy to pump into the wellbore and enter the formation leakage channel, and has strong adhesion after stopping the pump, and is easy to stay in the leakage channel to form a high-strength isolation layer. The above two plugging materials have optimized the crack sealing performance, but there is still no systematic description of the pressure plugging evaluation method of underground cross-linked curing plugging materials.

[0005] Therefore, it is necessary to invent a comprehensive experimental evaluation method for the migration, filling and plugging effect of underground cross-linked solidifying plugging materials to solve the lack of technology in this area. Summary of the invention

[0006] In view of the deficiencies of the prior art, the present invention provides a comprehensive experimental evaluation method for the migration, filling and plugging effects of underground cross-linked solidified plugging materials. The method of the present invention simplifies the evaluation steps of the filling state of underground cross-linked solidified plugging materials on cracks and the plugging effect of cracks after the plugging materials are solidified. According to the evaluation method of the present invention and the evaluation indicators of crack filling capacity and plugging capacity, the pressure-bearing plugging effect of underground cross-linked solidified plugging materials on the target leaking layer can be effectively predicted, filling the gap of the current lack of pressure-bearing plugging evaluation method for underground cross-linked solidified plugging materials.

[0007] The technical solution of the present invention is as follows:

[0008] A comprehensive experimental evaluation method for the migration, filling and plugging effect of underground cross-linked curing plugging materials includes the following steps:

[0009] (1) Invert the formation fracture scale according to the formation conditions to determine the simulated fracture core model;

[0010] (2) Use a large-scale fracture visualization simulation device to simulate the migration and filling state of underground cross-linked solidified plugging materials in fractures, and analyze the migration and filling effect of underground cross-linked solidified plugging materials on fractures;

[0011] (3) Use a high-temperature and high-pressure crack plugging simulation device to simulate the pressure-bearing plugging effect of underground cross-linked solidified plugging materials after solidification in cracks, and analyze the pressure-bearing plugging strength of underground cross-linked solidified plugging materials on cracks;

[0012] (4) Based on the pressure-bearing sealing strength of underground cross-linked solidified plugging materials on cracks, calculate the pressure-bearing capacity of underground cross-linked solidified plugging materials per unit length of cracks;

[0013] (5) The migration, filling and plugging effects of underground cross-linked and solidified plugging materials on cracks, pressure-bearing plugging strength and pressure-bearing capacity per unit length of cracks are used as the main parameters to predict and evaluate the migration, filling and plugging effects of underground cross-linked and solidified plugging materials on the target leaking layer.

[0014] According to the present invention, in step (1), the width of the fracture is calculated according to the existing technology based on the actual core of the formation, thereby determining the simulated fracture core model. The simulated fracture core model can be purchased commercially or prepared according to the existing technology.

[0015] Preferably, in step (2) of the present invention, the large-scale fracture visualization simulation device includes an injection pump, a pressure-resistant liquid storage tank a, a pressure-resistant liquid storage tank b, a gas cylinder, a flow meter, a large-scale fracture visualization physical model, a pressure and image acquisition device, and a fluid acquisition device. The injection pump is connected to the pressure-resistant liquid storage tank a and the pressure-resistant liquid storage tank b through a six-way valve a respectively; the pressure-resistant liquid storage tank a and the pressure-resistant liquid storage tank b are connected to the inlet of the large-scale fracture visualization physical model through a six-way valve c and a six-way valve d respectively; the gas cylinder is connected to the inlet of the large-scale fracture visualization physical model through a flow meter and a six-way valve c; a pressure sensor and a camera are provided inside the large-scale fracture visualization physical model, and are connected to an external pressure and image acquisition device; the outlet of the large-scale fracture visualization physical model is connected to the fluid acquisition device through a pipeline.

[0016] Preferably, in step (2) of the present invention, the method for testing the migration and filling effect of underground cross-linked curing plugging material on cracks is as follows: fill the crack model of the large-scale crack visualization simulation device with water to simulate the formation fluid; then inject the dyed underground cross-linked curing plugging material aqueous dispersion, and when the total injection amount is one crack volume, observe the distribution state of the dyed underground cross-linked curing plugging material aqueous dispersion in the crack space; divide the crack space into three parts of equal height, namely, upper, middle and lower parts, along the vertical direction, test the filling volume percentage of the dyed underground cross-linked curing plugging material aqueous dispersion in the upper, middle and lower parts of the crack space, and take the average value as the filling degree of the underground cross-linked curing plugging material aqueous dispersion in the crack.

[0017] Preferably, the dye used in the dyed underground cross-linked curing plugging material aqueous dispersion is Sudan III, and the mass concentration of the dyeing reagent is 0.05-0.1%.

[0018] Preferably, the injection rate of the dyed underground cross-linked curing plugging material aqueous dispersion is determined as follows: the migration time of the underground cross-linked curing plugging material aqueous dispersion in the actual formation fractures is determined according to the existing method based on the total volume of pumped liquid and the pumping rate at the oil field site, and then the total volume of pumped liquid is divided by the above migration time to obtain the injection rate.

[0019] Preferably, in step (3), the high-temperature and high-pressure fracture plugging simulation device comprises an injection pump, a pressure-resistant liquid storage tank a, a pressure-resistant liquid storage tank b, a gas cylinder, a flow meter, a fracture core model, a pressure collection device, a fluid collection device, and a heating box. The injection pump is connected to the pressure-resistant liquid storage tank a and the pressure-resistant liquid storage tank b through a six-way valve a; the pressure-resistant liquid storage tank a and the pressure-resistant liquid storage tank b are connected to the inlet of the fracture core model through a six-way valve c and a six-way valve d respectively; the gas cylinder is connected to the inlet of the fracture core model through a flow meter and a six-way valve c; a pressure sensor is provided inside the fracture core model and is connected to an external pressure collection device; the outlet of the fracture core model is connected to the fluid collection device through a pipeline; the fracture core model and the fluid collection device are provided in the heating box.

[0020] Preferably, in step (3) of the present invention, the test method of the pressure-bearing plugging strength of the underground cross-linked solidifying plugging material on the crack is as follows: injecting the aqueous dispersion of the underground cross-linked solidifying plugging material into the crack core model in the high-temperature and high-pressure crack plugging simulation device to fill the crack space; then raising the temperature to completely solidify the underground cross-linked solidifying plugging material; slowly increasing the displacement pressure until a large amount of leakage suddenly occurs. The corresponding pressure is the pressure-bearing plugging strength.

[0021] Preferably, according to the present invention, in step (5), when the filling degree of the underground cross-linked solidifying plugging material to the crack is 100%, the pressure bearing capacity per unit length of the crack is ≥5MPa / m, and the pressure bearing plugging strength is ≥7MPa, the underground cross-linked solidifying plugging material has an excellent effect on the migration, filling and plugging of the target leaking layer.

[0022] The technical features and beneficial effects of the present invention are as follows:

[0023] 1. The present invention obtains the fracture scale and the migration rate of the plugging material solution by inverting the similarity criterion of the underground fracture scale and the field injection rate according to the existing method, so as to obtain accurate experimental parameters and improve the reliability of the evaluation results.

[0024] 2. The present invention builds a large-scale fracture visualization simulation device to more clearly evaluate the migration and filling conditions of underground cross-linked curing plugging materials in fractures, providing a basis for subsequent evaluation of plugging effects and migration and filling effects.

[0025] 3. The present invention uses a high-temperature and high-pressure crack plugging simulation device to analyze the plugging performance of underground cross-linked solidified plugging materials in simulated formation cracks, thereby improving the application efficiency of plugging materials in actual operations. The present invention calculates the pressure-bearing capacity of underground cross-linked solidified plugging materials per unit length of cracks based on the pressure-bearing plugging strength of underground cross-linked solidified plugging materials on cracks, which can better characterize the plugging effect of plugging materials.

[0026] 4. Through the evaluation method of the present invention, the fracture scale is multiplied according to the formation conditions, and the migration rate of the plugging material solution is obtained according to the similarity criterion of the on-site injection rate. The two key aspects of migration and filling effect and plugging effect are comprehensively considered. The performance of the plugging material, especially the migration and filling effect in the fracture and the performance related to fracture plugging, can be comprehensively evaluated, and the plugging effect in the target leaking layer can be more accurately predicted and evaluated, providing reference and guidance for practical engineering applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a structural schematic diagram of a large-scale fracture visualization simulation device of the present invention;

[0028] Figure 2 This is a schematic structural diagram of a high-temperature and high-pressure crack plugging simulation device of the present invention;

[0029] Among them, 1 is an injection pump, 2 is a pressure-resistant liquid storage tank a, 3 is a pressure-resistant liquid storage tank b, 4 is a gas cylinder, 5 is a flow meter, 6 is a large-scale fracture visualization physical model, 7 is a pressure and image acquisition device, 8 is a fluid acquisition device, 9 is a six-way valve a, 10 is a six-way valve c, 11 is a six-way valve d, 12 is a fracture core model, 13 is a pressure acquisition device, and 14 is a heating box;

[0030] Figure 3 This is a diagram showing the filling state of the underground cross-linked curing plugging material aqueous dispersion in the crack space when 0.5 PV is injected;

[0031] Figure 4 This is a graph showing the pressure-bearing plugging strength of the highly thixotropic underground cross-linked curing plugging material aqueous dispersion in Example 1 for 5 mm parallel cracks.

[0032] Figure 5 This is a graph showing the pressure-bearing and sealing strength of the strongly thixotropic underground cross-linked curing plugging material aqueous dispersion in Example 1 on a wedge-shaped crack with an inlet of 7 mm and an outlet of 5 mm.

[0033] Figure 6 This is a graph showing the pressure-bearing plugging strength of the strongly thixotropic underground cross-linked curing plugging material aqueous dispersion in Example 2 for 3 mm parallel cracks. DETAILED DESCRIPTION

[0034] The present invention is further described below with reference to specific examples, but is not limited thereto. The raw materials used in the examples are all conventional raw materials and can be obtained commercially; the methods described are all conventional methods and prior art unless otherwise specified.

[0035] The weak thixotropic underground cross-linked curing plugging material aqueous dispersion, the medium thixotropic underground cross-linked curing plugging material aqueous dispersion, and the strong thixotropic underground cross-linked curing plugging material aqueous dispersion used in the examples are prepared by the following methods:

[0036] An underground cross-linked curing plugging material aqueous dispersion comprises the following raw materials in percentage by mass: 10% acrylamide monomer, 0.8% N-hydroxymethyl acrylamide, 0-2.0% lithium bentonite, 0.02% tert-butyl hydroperoxide, and the balance is water.

[0037] The method for preparing the underground cross-linked curing plugging material aqueous dispersion comprises the following steps:

[0038] (1) adding acrylamide monomer and N-hydroxymethyl acrylamide into water in sequence, and stirring at 300 rpm until completely dissolved to obtain a mixed solution A;

[0039] (2) Add tert-butyl hydroperoxide to the mixed solution A, and stir at 550 rpm until it becomes viscous to obtain a mixed solution I1, which is a weak thixotropic underground cross-linking curing plugging material aqueous dispersion I1, for later use.

[0040] By adding 1.0% and 2.0% lithium-based bentonite to the weak thixotropic underground cross-linked curing plugging material aqueous dispersion I1, respectively, a medium thixotropic underground cross-linked curing plugging material aqueous dispersion I2 and a strong thixotropic underground cross-linked curing plugging material aqueous dispersion I3 can be obtained.

[0041] Example 1

[0042] A comprehensive experimental evaluation method for the migration, filling and plugging effect of underground cross-linked curing plugging materials, comprising the following steps:

[0043] (1) Determine the simulated fracture core model

[0044] According to the actual core of the formation and the fracture simulation of common technology, the underground fracture scale (fracture width is 5mm) is inverted and the fracture model is designed and processed. Therefore, a large fracture visualization physical model with a fracture length of 20cm, a fracture width of 5mm and a fracture height of 10cm is used, and a parallel steel column pressure-resistant fracture with a fracture length of 30cm, a fracture height of 2.5cm and a fracture width of 5mm is used as the core model for the pressure-bearing and plugging strength test, or a wedge-shaped steel column pressure-resistant fracture with an inlet of 7mm, an outlet of 5mm and a fracture length of 30cm is used as the core model for the pressure-bearing and plugging strength test.

[0045] (2) Determine the injection rate

[0046] According to the total volume of pumped liquid and the pumping rate at the oil field site, the migration time of the underground cross-linked curing plugging material water dispersion in the actual formation fracture is determined according to the existing method. Then the total volume of pumped liquid is divided by the above migration time to obtain the injection rate, which is 1.5 mL min -1 .

[0047] (3) Build a large-scale crack visualization simulation device, such as Figure 1 As shown, it includes an injection pump 1, a pressure-resistant liquid storage tank a2, a pressure-resistant liquid storage tank b3, a gas cylinder 4, a flow meter 5, a large-scale fracture visualization physical model 6, a pressure and image acquisition device 7, and a fluid acquisition device 8. The injection pump 1 is connected to the pressure-resistant liquid storage tank a2 and the pressure-resistant liquid storage tank b3 through a six-way valve a9; the pressure-resistant liquid storage tank a2 and the pressure-resistant liquid storage tank b3 are connected to the inlet of the large-scale fracture visualization physical model 6 through a six-way valve c10 and a six-way valve d11 respectively; the gas cylinder 4 is connected to the inlet of the large-scale fracture visualization physical model 6 through a flow meter 5 and a six-way valve c10; a pressure sensor and a camera are arranged inside the large-scale fracture visualization physical model 6, and are connected to the external pressure and image acquisition device 7; the outlet of the large-scale fracture visualization physical model 6 is connected to the fluid acquisition device 8 through a pipeline. The inclination angle of the seam plate of the large-scale fracture visualization physical model 6 is 90° to simulate a vertical fracture.

[0048] The migration and filling performance of the prepared weak thixotropic underground cross-linked curing plugging material aqueous dispersion I1, medium thixotropic underground cross-linked curing plugging material aqueous dispersion I2, and strong thixotropic underground cross-linked curing plugging material aqueous dispersion I3 on ​​the vertical fracture space were tested by using a large-scale fracture visualization simulation device. The steps are as follows: the dyed underground cross-linked curing plugging material aqueous dispersion (the dye is Sudan III, and the mass concentration of the dyeing reagent is 0.1%) is loaded into a pressure-resistant liquid storage tank a2, and water is loaded into a pressure-resistant liquid storage tank b3; the six-way valve a9 and the injection pump 1 are adjusted to fill the large-scale fracture visualization physical model 6 of the large-scale fracture visualization simulation device with water to simulate the formation fluid; then the six-way valve a9 and the injection pump 1 are adjusted to allow the dyed underground cross-linked curing plugging material aqueous dispersion to be injected at a rate of 1.5 mL min -1 Injection into a large fracture visualization physical model 6; During the injection process, observe the distribution state of the dyed underground cross-linked curing plugging material water dispersion in the fracture space; When the total injection volume is one fracture volume, divide the fracture space into three parts of upper, middle and lower heights in the vertical direction, test the filling volume percentage of the underground cross-linked curing plugging material water dispersion in the upper, middle and lower parts of the fracture space, and take the average value as the filling degree of the underground cross-linked curing plugging material water dispersion in the fracture. The closer the filling degree is to 100%, the more uniform the distribution of the plugging material in the vertical fracture and the better the filling effect, which is used to evaluate its migration effect in the fracture.

[0049] The filling state of the crack space when the injection volume of weak thixotropic underground cross-linking curing plugging material aqueous dispersion I1, medium thixotropic underground cross-linking curing plugging material aqueous dispersion I2 and strong thixotropic underground cross-linking curing plugging material aqueous dispersion I3 is 0.5PV is shown as follows Figure 3 The filling volume percentage for a 5 mm crack is shown in Table 1.

[0050] Table 1 Filling effect of different thixotropic plugging material solutions on different parts of the same crack size

[0051]

[0052] According to the above filling volume percentage, the average value is the filling degree of the underground cross-linking curing plugging material aqueous dispersion in the crack, as shown in Table 2.

[0053] Table 2 Filling degree

[0054]

[0055] From the above comparison, it can be seen that the filling degree of weak thixotropic underground cross-linked curing plugging materials and medium thixotropic underground cross-linked curing plugging materials is poor, that is, their migration and filling effects are poor, and they are not suitable for plugging the target leaking layer; the strong thixotropic underground cross-linked curing plugging material has an excellent filling effect, that is, an excellent migration and filling effect, and the following pressure-bearing plugging strength test is carried out.

[0056] (4) Build a high-temperature and high-pressure crack plugging simulation device, such as Figure 2 As shown, it includes an injection pump 1, a pressure-resistant liquid storage tank a2, a pressure-resistant liquid storage tank b3, a gas cylinder 4, a flow meter 5, a fracture core model 12, a pressure collection device 13, a fluid collection device 8, and a heating box 14. The injection pump 1 is connected to the pressure-resistant liquid storage tank a2 and the pressure-resistant liquid storage tank b3 through a six-way valve a9; the pressure-resistant liquid storage tank a2 and the pressure-resistant liquid storage tank b3 are connected to the inlet of the fracture core model 12 through a six-way valve c10 and a six-way valve d11 respectively; the gas cylinder 4 is connected to the inlet of the fracture core model 12 through a flow meter 5 and a six-way valve c10; a pressure sensor is arranged inside the fracture core model 12, and is connected to the external pressure collection device 13; the outlet of the fracture core model 12 is connected to the fluid collection device 8 through a pipeline; the fracture core model 12 and the fluid collection device 8 are arranged in the heating box 14.

[0057] The sealing strength of the underground cross-linked solidifying plugging material aqueous dispersion I3 on ​​the cracks is tested in the following steps: the underground cross-linked solidifying plugging material aqueous dispersion is added into the pressure-resistant liquid storage tank a2 of the high-temperature and high-pressure crack plugging simulation device, and the injection pump 1 and the six-way valve a9 are adjusted to inject the underground cross-linked solidifying plugging material aqueous dispersion into the crack core model 12 and fill the crack space; then the temperature of the heating box 14 is increased to 140°C until it is completely solidified; the nitrogen in the gas cylinder 4 is introduced into the crack core model 12 through the flowmeter 5 to slowly increase the displacement pressure of the plugging instrument until a large amount of leakage occurs suddenly. The corresponding pressure is the pressure-bearing sealing strength.

[0058] The pressure-bearing plugging strength of the strongly thixotropic underground cross-linked curing plugging material aqueous dispersion I3 on ​​5mm parallel cracks and wedge-shaped cracks with an inlet of 7mm and an outlet of 5mm are as follows: Figure 4 and 5 shown.

[0059] (5) Based on the pressure-bearing plugging strength of the underground cross-linked solidifying plugging material with strong thixotropy on cracks, the pressure-bearing capacity of the underground cross-linked solidifying plugging material per unit length of cracks is calculated, as shown in Table 3.

[0060] Table 3 Pressure-bearing plugging effect of underground cross-linked curing plugging materials

[0061]

[0062] (6) The migration, filling and plugging effects of the highly thixotropic underground cross-linked curing plugging material on cracks, the pressure-bearing plugging strength and the pressure-bearing capacity per unit length of cracks were used as the main parameters to evaluate its migration, filling and plugging effects on the target leaking layer.

[0063] The filling degree of the target cracks by the strong thixotropic underground cross-linking curing plugging material used is 100%, the pressure bearing capacity per unit length of the crack is ≥5MPa / m, and the pressure bearing plugging strength is <7MPa. Therefore, the plugging effect of the target leaking layer by the strong thixotropic underground cross-linking curing plugging material used does not meet the requirements.

[0064] Example 2

[0065] A comprehensive experimental evaluation method for the migration, filling and plugging effect of underground cross-linked curing plugging materials, comprising the following steps:

[0066] (1) Determine the simulated fracture core model

[0067] According to the actual core of the formation and the fracture simulation of common technology, the underground fracture scale (fracture width is 3mm) is inverted and the fracture model is designed and processed. Therefore, a large fracture visualization physical model with a fracture length of 20cm, a fracture width of 3mm and a fracture height of 10cm is used, and a parallel steel column pressure-resistant fracture with a fracture length of 30cm, a fracture height of 2.5cm and a fracture width of 3mm is used as the core model for the pressure-bearing plugging strength test.

[0068] (2) Determine the injection rate

[0069] According to the total volume of pumped liquid and the pumping rate at the oil field site, the migration time of the underground cross-linked curing plugging material water dispersion in the actual formation fracture is determined according to the existing method. Then the total volume of pumped liquid is divided by the above migration time to obtain the injection rate, which is 1mL·min -1 .

[0070] (3) The construction method of the large-scale crack visualization simulation device is the same as that of Example 1.

[0071] The migration and filling performance of the prepared strong thixotropic underground cross-linked curing plugging material aqueous dispersion I3 on ​​the vertical fracture space was tested using a large-scale fracture visualization simulation device. The test method was the same as in Example 1, except that the dyed underground cross-linked curing plugging material aqueous dispersion was injected at a speed of 1 mL min -1 .

[0072] The filling effect of the strong thixotropic underground cross-linking curing plugging material aqueous dispersion I3 on ​​different parts of the 3mm crack is shown in Table 4.

[0073] Table 4 Filling effect

[0074]

[0075] According to the above filling volume percentage, the average value is the filling degree of the strong thixotropic underground cross-linking curing plugging material aqueous dispersion in the crack, which is 100%.

[0076] (4) The construction of the high-temperature and high-pressure crack plugging simulation device is the same as that in Example 1.

[0077] The sealing strength of the strong thixotropic underground cross-linked curing plugging material aqueous dispersion I3 on ​​cracks was tested using the same method as in Example 1.

[0078] The pressure-bearing sealing strength of the strong thixotropic underground cross-linked curing plugging material aqueous dispersion I3 on ​​cracks is as follows Figure 6 As shown, it is 7.3MPa.

[0079] (5) Based on the pressure-bearing sealing strength of the underground cross-linked solidifying plugging material with strong thixotropy on cracks, the pressure-bearing capacity of the underground cross-linked solidifying plugging material per unit length of cracks is calculated to be 24.3 MPa / m.

[0080] (6) The migration, filling and plugging effects of the highly thixotropic underground cross-linked curing plugging material on cracks, the pressure-bearing plugging strength and the pressure-bearing capacity per unit length of cracks were used as the main parameters to evaluate its migration, filling and plugging effects on the target leaking layer.

[0081] The strong thixotropic underground cross-linked curing plugging material has a filling degree of 100% for cracks, a pressure bearing capacity per unit length of cracks ≥5MPa / m, and a pressure bearing and plugging strength ≥7MPa. Therefore, the strong thixotropic underground cross-linked curing plugging material has excellent migration, filling and plugging effects on the target leaking layer.

[0082] The preferred experimental evaluation method of the present invention is described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A comprehensive experimental evaluation method for the migration, filling and plugging effect of underground cross-linked curing plugging materials, comprising the following steps: (1) Invert the formation fracture scale according to the formation conditions to determine the simulated fracture core model; (2) Use a large-scale fracture visualization simulation device to simulate the migration and filling state of underground cross-linked solidified plugging materials in fractures, and analyze the migration and filling effect of underground cross-linked solidified plugging materials on fractures; The large-scale fracture visualization simulation device includes an injection pump, a pressure-resistant liquid storage tank a, a pressure-resistant liquid storage tank b, a gas cylinder, a flow meter, a large-scale fracture visualization physical model, a pressure and image acquisition device, and a fluid acquisition device; The injection pump is connected to the pressure-resistant liquid storage tank a and the pressure-resistant liquid storage tank b through the six-way valve a respectively; the pressure-resistant liquid storage tank a and the pressure-resistant liquid storage tank b are connected to the inlet of the large-scale fracture visualization physical model through the six-way valve c and the six-way valve d respectively; the gas cylinder is connected to the inlet of the large-scale fracture visualization physical model through the flow meter and the six-way valve c; the large-scale fracture visualization physical model is provided with a pressure sensor and a camera inside, and is connected to the external pressure and image acquisition device; the outlet of the large-scale fracture visualization physical model is connected to the fluid acquisition device through a pipeline; The test method of the migration and filling effect of underground cross-linked curing plugging materials on cracks is as follows: fill the crack model of the large-scale crack visualization simulation device with water to simulate the formation fluid; then inject the dyed underground cross-linked curing plugging material water dispersion, and when the total injection amount is one crack volume, observe the distribution state of the dyed underground cross-linked curing plugging material water dispersion in the crack space; divide the crack space into three parts of upper, middle and lower heights in the vertical direction, test the filling volume percentage of the dyed underground cross-linked curing plugging material water dispersion in the upper, middle and lower parts of the crack space, and take the average value as the filling degree of the underground cross-linked curing plugging material water dispersion in the crack; The injection rate of the dyed underground cross-linked curing plugging material aqueous dispersion is determined as follows: the migration time of the underground cross-linked curing plugging material aqueous dispersion in the actual formation fracture is determined according to the total volume of the pumped liquid and the pumping rate at the oil field site, and then the total volume of the pumped liquid is divided by the above migration time to obtain the injection rate; (3) Use a high-temperature and high-pressure crack plugging simulation device to simulate the pressure-bearing plugging effect of underground cross-linked solidified plugging materials after solidification in cracks, and analyze the pressure-bearing plugging strength of underground cross-linked solidified plugging materials on cracks; The high-temperature and high-pressure fracture plugging simulation device includes an injection pump, a pressure-resistant liquid storage tank a, a pressure-resistant liquid storage tank b, a gas cylinder, a flow meter, a fracture core model, a pressure collection device, a fluid collection device, and a heating box; The injection pump is connected to the pressure-resistant liquid storage tank a and the pressure-resistant liquid storage tank b through the six-way valve a respectively; the pressure-resistant liquid storage tank a and the pressure-resistant liquid storage tank b are connected to the inlet of the fracture core model through the six-way valve c and the six-way valve d respectively; the gas cylinder is connected to the inlet of the fracture core model through the flow meter and the six-way valve c; a pressure sensor is arranged inside the fracture core model and is connected to an external pressure acquisition device; The outlet of the fracture core model is connected to the fluid collection device through a pipeline; the fracture core model and the fluid collection device are arranged in a heating box; The test method of the pressure-bearing plugging strength of underground cross-linked solidified plugging materials on cracks is as follows: inject the water dispersion of underground cross-linked solidified plugging materials into the crack core model in the high-temperature and high-pressure crack plugging simulation device to fill the crack space; then increase the temperature to completely solidify the underground cross-linked solidified plugging materials; slowly increase the displacement pressure until a large amount of leakage occurs suddenly, and the corresponding pressure is the pressure-bearing plugging strength; (4) Based on the pressure-bearing sealing strength of underground cross-linked solidified plugging materials on cracks, calculate the pressure-bearing capacity of underground cross-linked solidified plugging materials per unit length of cracks; (5) Using the migration and filling effect of underground cross-linked solidified plugging materials on cracks, pressure-bearing plugging strength and pressure-bearing capacity per unit length of cracks as the main parameters, predict and evaluate the migration, filling and plugging effect of underground cross-linked solidified plugging materials on the target leaking layer; When the underground cross-linked solidifying plugging material fills the cracks to a degree of 100%, the pressure bearing capacity per unit length of the cracks is ≥5MPa / m, and the pressure bearing plugging strength is ≥7MPa, the underground cross-linked solidifying plugging material has an excellent effect on the migration, filling and plugging of the target leaking layer.

2. The comprehensive experimental evaluation method for the migration, filling and plugging effect of underground cross-linked curing plugging material according to claim 1, characterized in that: The dye used in the dyed underground cross-linked curing plugging material water dispersion is Sudan III, and the mass concentration of the dyeing reagent is 0.05-0.1%.

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