A method for testing the plugging property of a nanometer-micrometer plugging agent artificial filter cake

Abstract

The application discloses a kind of nanometer micro-particle plugging agent artificial filter cake plugging test method, it is related to drilling engineering technical field, its steps include: the filter cake base paste of stirring uniform is poured into the drilling fluid cup of high temperature high pressure filter loss instrument, under the condition of room temperature and 3.45Mpa pressure, after filtration, water loss is passed through two hours, obtain initial filter cake;Determine the filtration loss L1 of 30min room temperature and 3.45Mpa pressure condition, after adding nanometer micro-particle plugging agent, again determine the filtration loss L3 of 30min room temperature and 3.45Mpa pressure condition;Through the permeability filtration loss reduction rate P, evaluate the plugging performance of nanometer micro-particle plugging agent to artificial filter cake.The application can simply, conveniently and effectively evaluate the plugging performance of nanometer micro-particle plugging agent to artificial filter cake, realizes the organic combination of intuitive and quantitative research.

Description

Technical Field

[0001] This invention relates to the field of drilling engineering technology, and in particular to a method for testing the plugging performance of artificial filter cakes containing nano- or micro-sized plugging agents. Background Technology

[0002] In drilling operations, wellbore instability is highly likely to occur due to the development of microfractures and pores in shale formations. Excellent plugging properties of drilling fluids are crucial for resolving wellbore instability. Nanomaterials, with their small particle size, can penetrate micro- and nano-scale fractures and pores to effectively plug them, thereby stabilizing the wellbore.

[0003] There is no unified standard for evaluating nano- and micro-sized plugging agents. Currently, the main methods for evaluating the plugging effect of nano- and micro-sized plugging agents and drilling fluid systems are as follows: Yue Qiansheng et al. used low-permeability artificial rock cores, sliced ​​metal rock cores, and oil-based drilling fluid filter cake permeability to characterize the plugging ability of single agents and drilling fluid systems on micro-fractures in order to simulate micro-fractures in hard and brittle shale. Chen Liang, based on the characteristics of micro-fractured formations, used a self-made metal fracture plate in conjunction with a high-temperature and high-pressure fluid loss meter. By adjusting the ruler and screws, the iron block can simulate micro-fractures of 20-100μm with a depth of 5mm. The internal surface of the fracture is rough, and the interior of the fracture can be observed after completion. It is simple, practical, and accurately simulates micro-fractures. Yang Juesuan et al. used dry drilling to obtain standard rock core columns, fractured the rock core columns, and simulated micro-fractures (micron-level) of different widths by using tin foil of different thicknesses on the fracture surface of the rock core. Yan Jing used natural rock cores and cast microfractures with metal foils of varying thicknesses and cementing materials to simulate real pore throats and microfractures, evaluating the sealing performance of plugging agents. The simulated cores showed a minimum fracture width of 3.33 μm and a stroke of 5-10 cm, with high repeatability. These methods directly simulate rock fractures and provide some guidance for evaluating the sealing effects of nano- and micro-sized plugging agents and drilling fluids. However, they suffer from poor repeatability and the inability to deeply analyze the mechanism of action of plugging agents from a microscopic perspective.

[0004] Based on the above analysis, the problems and shortcomings of the existing technology are as follows:

[0005] There is currently no standard method for evaluating the plugging performance of sealing agents. Due to the low permeability and small pore size of shale formations, there is no dedicated medium to simulate them. Therefore, the objectivity and accuracy of the sealing performance data obtained by existing technologies are relatively poor. Summary of the Invention

[0006] The purpose of this invention is to provide a method for testing the plugging performance of artificial filter cakes containing nano- or micro-sized plugging agents, to conduct research on the evaluation methods and mechanisms of action of nano- or micro-sized plugging agents, to optimize and determine the evaluation methods for nano- or micro-sized plugging agents, to systematically evaluate nano- or micro-sized plugging agents based on these methods, and to clarify the mechanism of action of nano- or micro-sized plugging agents by combining instrumental testing and theoretical analysis.

[0007] The technical solution adopted by this invention to achieve its objective is to provide a method for testing the plugging performance of artificial filter cakes containing nano- or micro-sized plugging agents, the steps of which are as follows:

[0008] S1. Pour a well-stirred filter cake base slurry into the drilling fluid cup of the high-temperature and high-pressure filtration instrument. After two hours of filtration and water loss at room temperature and 3.45 MPa pressure, the initial filter cake is obtained.

[0009] S2. Add 100 mL of distilled water to the drilling fluid cup containing the initial filter cake using a glass rod, and measure the filtration loss L1 under the conditions of room temperature and 3.45 MPa pressure for 30 min. Then pour out the remaining distilled water.

[0010] S3. Weigh 20g of nano-micro plugging agent sample and add it to a beaker containing 180mL of distilled water or white oil. Disperse the sample in an ultrasonic disperser for 15min to obtain a sample solution. Then, use a glass rod to guide the sample solution into a drilling fluid cup containing the initial filter cake to obtain a filter cake with added nano-micro plugging agent. Measure its filtration loss L2 under 30min conditions at room temperature and 3.45MPa pressure. If L2≥L1, discard the filter cake with added nano-micro plugging agent and repeat step S1. If L2<L1, pour out the remaining sample solution first, and then proceed to step S4.

[0011] S4. Add 100 mL of distilled water to the drilling fluid cup containing the filter cake with added nano-micro plugging agent using a glass rod, and measure the filtration loss L3 under the conditions of room temperature and 3.45 MPa pressure for 30 min.

[0012] S5. The sealing performance of nano-micro plugging agents on artificial filter cake is evaluated by the permeability loss reduction rate P. The formula for calculating the permeability loss reduction rate P is as follows:

[0013]

[0014] In the formula:

[0015] L1 represents the water permeability loss of the initial filter cake, in mL; L3 represents the water permeability loss of the filter cake with added nano-micron blocking agent, in mL.

[0016] Furthermore, in step S1, after obtaining the initial filter cake, it is necessary to remove the initial filter cake from the drilling fluid cup, blow it with a hot air blower for 20 seconds, measure its thickness l, and then put it back into the drilling fluid cup; in step S5, the sealing performance of the initial filter cake needs to be evaluated by the average permeability K, where the average permeability K (unit: 10) 2 The formula for calculating mD is:

[0017]

[0018] In the formula:

[0019] q represents the volume of distilled water lost per unit time, in cm³. 3 / s; l is the filter cake thickness in cm; μ is the viscosity of distilled water at room temperature in mPa·s; A is the filter cake area in cm². 2 ; △p is the experimental pressure difference, in MPa;

[0020] Wherein: μ is the viscosity of distilled water at 25℃, which is 0.8937 mPa·s; the experimental pressure difference Δp is 3.45 MPa.

[0021] Furthermore, the filter cake base slurry in step S1 is a uniform suspension formed by adding ordinary barite and nano-barite to a solution of polyacrylamide and sodium polyacrylate and dispersing them.

[0022] Furthermore, the specific preparation method of the filter cake base slurry is as follows: First, add polyacrylamide and sodium polyacrylate to water according to the set mass ratio and stir for one hour to completely dissolve them; then, add composite barite made of ordinary barite and nano barite while stirring, and stir for 30 minutes to mix them evenly.

[0023] Furthermore, the mass ratio of each raw material in the filter cake base slurry is as follows: ordinary barite: nano barite: water: polyacrylamide: sodium polyacrylate = 250:100:1000:3:9.

[0024] Furthermore, the median grain size of the ordinary barite is 200 μm, and the median grain size of the nano-barite is 0.89 μm.

[0025] Furthermore, the nano-micro plugging agent is ultrafine calcium carbonate, or emulsified modified rubber MORLF, or ULIA nano pressure-bearing plugging agent.

[0026] Furthermore, the thickness l of the filter cake is measured using a needle thickness gauge.

[0027] The beneficial effects of this invention are:

[0028] This invention uses an artificial filter cake simulating microfractures in shale formations as the filtration medium and evaluates the performance of nano- and micro-sized plugging agents by the reduction rate of permeability loss. This evaluation method uses a compound of barite and polymers to prepare the filter cake, simulating formation microfractures, and selectively chooses nano- and micro-sized plugging agents that match the formation, achieving an organic combination of intuitive and quantitative research.

[0029] This invention evaluates the plugging performance of three plugging agents with significant differences in particle size (ultrafine CaCO3, emulsion-modified rubber MORLF, and ULIA nano pressure-bearing plugging agent), verifies the accuracy of the evaluation method, and provides a simple analysis of their plugging mechanisms.

[0030] The thickness of the artificial filter cake in this invention is stable at around 3 mm, and the permeability is stable at 10. -3 ~10 -4 Within the mD range, the evaluation methods are parallel and accurate, and can serve as a guiding method for evaluating nano- and micro-sized plugging agents.

[0031] The technical solution of this invention solves the long-standing technical problem in the petroleum industry that plugging materials for oil-based drilling fluids cannot be evaluated simply, conveniently, and effectively. Attached Figure Description

[0032] Figure 1 This is a graph showing the reduction rate of filter cake permeability loss after adding different nano-micro plugging agents in the embodiments of the present invention;

[0033] Figure 2 This is an initial filter cake diagram of an embodiment of the present invention;

[0034] Figure 3 This is a filter cake image after adding ultrafine calcium carbonate blocking agent in Example 1 of the present invention;

[0035] Figure 4 This is a filter cake image after adding the emulsified modified rubber MORLF plugging agent in Example 2 of the present invention;

[0036] Figure 5 This is a filter cake image after adding ULIA nano pressure-bearing plugging agent in Example 3 of the present invention. Detailed Implementation

[0037] To better understand the above-mentioned objectives, features, and advantages of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0038] Example 1

[0039] The first specific embodiment of the present invention is a method for testing the plugging performance of artificial filter cakes using nano-micro plugging agents, comprising the following steps:

[0040] S1. Pour a well-stirred filter cake base slurry into the drilling fluid cup of the high-temperature and high-pressure filtration analyzer. After filtration and water loss for two hours at room temperature and 3.45 MPa pressure, the initial filter cake is obtained. Take out the initial filter cake from the drilling fluid cup, blow the filter cake with a hot air blower for 20 seconds, measure its thickness l with a needle thickness gauge, and then put it back into the drilling fluid cup.

[0041] S2. Add 100 mL of distilled water to the drilling fluid cup containing the initial filter cake using a glass rod, and measure the filtration loss L1 under the conditions of room temperature and 3.45 MPa pressure for 30 min. Then pour out the remaining distilled water.

[0042] S3. Weigh 20g of nano-micro plugging agent sample and add it to a beaker containing 180mL of distilled water or white oil. Disperse the sample in an ultrasonic disperser for 15min to obtain a sample solution. Then, use a glass rod to guide the sample solution into a drilling fluid cup containing the initial filter cake to obtain a filter cake with added nano-micro plugging agent. Measure its filtration loss L2 under 30min conditions at room temperature and 3.45MPa pressure. If L2≥L1, discard the filter cake with added nano-micro plugging agent and repeat step S1. If L2<L1, pour out the remaining sample solution first, and then proceed to step S4.

[0043] S4. Add 100 mL of distilled water to the drilling fluid cup containing the filter cake with added nano-micro plugging agent using a glass rod, and measure the filtration loss L3 under the conditions of room temperature and 3.45 MPa pressure for 30 min.

[0044] S5. The sealing performance of nano-micro plugging agents on artificial filter cake is evaluated by the permeability loss reduction rate P. The formula for calculating the permeability loss reduction rate P is as follows:

[0045]

[0046] In the formula:

[0047] L1 represents the water permeability loss of the initial filter cake, in mL; L3 represents the water permeability loss of the filter cake with added nano-micron blocking agent, in mL.

[0048] The plugging performance of the initial filter cake also needs to be evaluated using the average permeability K, where the average permeability K (in units of 10) is... 2 The formula for calculating mD is:

[0049]

[0050] In the formula:

[0051] q represents the volume of distilled water lost per unit time, in cm³. 3 / s; l is the filter cake thickness in cm; μ is the viscosity of distilled water at room temperature in mPa·s; A is the filter cake area in cm². 2 ; △p is the experimental pressure difference, in MPa;

[0052] Wherein: μ is the viscosity of distilled water at 25℃, which is 0.8937 mPa·s; the experimental pressure difference Δp is 3.45 MPa.

[0053] In this embodiment, the filter cake base slurry is a uniform suspension formed by adding ordinary barite and nano-barite to a solution of polyacrylamide and sodium polyacrylate and dispersing them.

[0054] The specific preparation method of filter cake base slurry is as follows: First, add polyacrylamide and sodium polyacrylate to water according to the set mass ratio and stir for one hour to completely dissolve them; then add composite barite made of ordinary barite and nano barite while stirring, and stir for 30 minutes to mix them evenly.

[0055] The mass ratio of each raw material in the filter cake base slurry is as follows: ordinary barite: nano barite: water: polyacrylamide: sodium polyacrylate = 250:100:1000:3:9.

[0056] The median grain size of the ordinary barite is 200 μm, and the median grain size of the nano-barite is 0.89 μm.

[0057] In this embodiment, the nano-micro plugging agent is ultrafine calcium carbonate with a median particle size of 38150 nm.

[0058] Filter cake base slurry formulation selection:

[0059] To obtain a reproducible "artificial core" that can simulate the nano- and nano-micron pores of the formation, multiple experimental studies determined that ordinary barite (200μm) and nano-barite (0.89μm) should be mixed and added to a polymer solution to disperse it into a uniform suspension. Under high pressure differential, it should be compacted into a filter cake of a fixed size. This filter cake can simulate the nano- and nano-micron pores of the formation and can serve as a reproducible simulated "artificial core".

[0060] The mass ratio of each raw material in Experiment 1# is as follows: ordinary barite: nano barite: water: polyacrylamide: sodium polyacrylate = 1000: 100: 1000: 3: 9.

[0061] The mass ratio of each raw material in Experiment 2# is as follows: ordinary barite: nano barite: water: polyacrylamide: sodium polyacrylate = 500: 100: 1000: 3: 9.

[0062] The mass ratio of each raw material in Experiment 3# is as follows: ordinary barite: nano barite: water: polyacrylamide: sodium polyacrylate = 333:100:1000:3:9.

[0063] The mass ratio of each raw material in Experiment 4# is: ordinary barite: nano barite: water: polyacrylamide: sodium polyacrylate = 250:100:1000:3:9.

[0064] Table 1 Initial filter cake performance under different barite blends

[0065]

[0066] Based on the experimental results, the filter cake was determined to use the formula of Experiment 4# for simulating artificial rock cores, with a permeability of 10. -3 ~10 -4 mD.

[0067] Quasi-parallelism analysis of test methods:

[0068] Parallel experiments were conducted on the permeability and thickness of the artificial filter cake. The results are shown in Table 2. The results were stable after 10 repeated experiments. The water loss in the clean water test remained consistently between 2 and 2.5 mL, the thickness of the artificial filter cake was approximately 3 mm, and the permeability remained at 10. -3 ~10 -4 Within the mD range, it can be seen that the fluctuations of each group of data are very small, proving that the artificial filter cake prepared by this experimental method has good parallelism and stability.

[0069] Table 2. Filter cake performance in parallel experiments

[0070]

[0071] Evaluation of the plugging performance of nano- and micro-sized plugging agents on artificial filter cakes:

[0072] like Figure 1 As shown, in this embodiment, after adding ultrafine calcium carbonate plugging agent, the permeability loss reduction rate P is 41.7% to 45.5%.

[0073] Example 2

[0074] The second specific embodiment of the present invention is basically the same as that in Example 1, except that the nano-micro plugging agent is an emulsion-modified rubber MORLF with a median particle size of 584 nm.

[0075] Evaluation of the plugging performance of nano- and micro-sized plugging agents on artificial filter cakes:

[0076] like Figure 1 As shown in this embodiment, after adding the emulsified modified rubber MORLF plugging agent, the permeability loss reduction rate P is 50% to 55.6%.

[0077] Example 3

[0078] The third specific embodiment of the present invention has the same steps as that in Example 1, except that the nano-micro plugging agent is ULIA nano pressure-bearing plugging agent with a median particle size of 2442 nm.

[0079] Evaluation of the plugging performance of nano- and micro-sized plugging agents on artificial filter cakes:

[0080] like Figure 1 As shown in this embodiment, after adding ULIA nano pressure-bearing sealant, the permeability loss reduction rate P is 40% to 42.9%.

[0081] Analysis and summary of three examples:

[0082] like Figure 1 As shown, the emulsified modified rubber MORLF, with the smallest average particle size, exhibits the highest reduction rate in permeability loss and the best sealing performance compared to the other two plugging agents.

[0083] like Figures 2-5 As shown, the filter cake after plugging with the emulsified modified rubber MORLF was significantly more uniform than the other two, forming a black waxy plugging layer on the filter cake surface. In contrast, the macroscopic changes on the filter cake surface before and after plugging with ultrafine calcium carbonate and ULIA nano-pressure-bearing plugging agent were minimal. This indicates that this experimental method can accurately evaluate the performance of nano- and micro-sized plugging agents.

[0084] Furthermore, through multiple experiments, it was found that single-type barite has a limited and narrow particle size distribution, resulting in poor filter cake quality. The more concentrated the particle size distribution, the worse the filter cake quality. In contrast, compounded barite has a wider particle size distribution, with smaller particles providing a more significant filling effect, resulting in filter cake quality far superior to that of single-type barite. Among the various compounded barite combinations, the highest bulk density and best filter cake quality were obtained when ordinary barite and nano-barite were combined in a 250:100 ratio. Using this ratio of compounded barite to prepare the artificial filter cake as the filtration medium, the artificial filter cake thickness remained stable at 3 mm, and the permeability remained stable at 10. -3 ~10 -4 Within the mD range, the test results show good parallelism.

[0085] The above embodiments are only used to illustrate the present invention and are not intended to limit the technical solutions described in the present invention. Although the present invention has been described in detail with reference to the above embodiments, the present invention is not limited to the specific embodiments described above. Therefore, any modifications or equivalent substitutions to the present invention without departing from the spirit and scope of the invention are all covered within the scope of the claims of the present invention.

Claims

1. A method for testing the plugging property of a nanometer-micrometer plugging agent artificial filter cake, characterized in that, The method comprises the following steps: S1, the common barite, nanobarite, water, polyacrylamide and sodium polyacrylate are prepared into filter cake base slurry according to the mass ratio of 250:100:1000:3:9, specifically, the polyacrylamide and sodium polyacrylate are first added into water and stirred for one hour to make them completely dissolved, then the composite barite compounded by the common barite and nanobarite is added under stirring condition, and stirred for 30 min to make them uniformly mixed, to obtain the uniformly stirred filter cake base slurry; one part of the uniformly stirred filter cake base slurry is poured into the drilling fluid cup of the high temperature and high pressure filtration instrument, and after filtration and water loss for two hours under the condition of room temperature and 3.45 Mpa pressure, the initial filter cake is obtained, the thickness of the initial filter cake is stabilized at about 3 mm, and the permeability is stabilized in the range of 10 -3 ~10 -4 mD; S2, 100 mL of distilled water is added to the drilling fluid cup containing the initial filter cake by glass rod, and the fluid loss L1 of the initial filter cake under the condition of 30 min room temperature and 3.45 MPa pressure is measured, and then the remaining distilled water is poured out; S3, 20 g of nanometer and micrometer plugging agent sample is weighed and added into a beaker containing 180 mL of distilled water or white oil, and is placed in an ultrasonic dispersing instrument for dispersion for 15 min to obtain a sample solution, and then the sample solution is added to the drilling fluid cup containing the initial filter cake by glass rod to obtain a filter cake added with nanometer and micrometer plugging agent, and the fluid loss L2 of the filter cake under the condition of 30 min room temperature and 3.45 MPa pressure is measured; if L2≥L1, the filter cake added with nanometer and micrometer plugging agent is discarded, and step S1 is repeated, and if L2 S4, 100 mL of distilled water is added to the drilling fluid cup containing the filter cake added with nanometer and micrometer plugging agent by glass rod, and the fluid loss L3 of the filter cake under the condition of 30 min room temperature and 3.45 MPa pressure is measured. S5, evaluate the plugging performance of the nanometer plugging agent to the artificial filter cake by the permeability filtration loss reduction rate P, the permeability filtration loss reduction rate The calculation formula is: In the formula, L1 is the water permeability fluid loss of the initial filter cake, and the unit is mL; L3 is the water permeability fluid loss of the filter cake added with nanometer and micrometer plugging agent, and the unit is mL.

2. The method according to claim 1, wherein the method is characterized by, After the initial filter cake is obtained in the step S1, the initial filter cake in the drilling fluid cup is taken out, and the filter cake is blown by a hot air blower for 20s to measure the thickness thereof , and then the filter cake is returned to the drilling fluid cup; in the step S5, the average permeability of the initial filter cake is calculated , and the sealing performance of the initial filter cake is evaluated 2 , wherein the average permeability (unit: 10 2 mD) is calculated according to the following formula: In the formula, V is the volume of distilled water filtration loss per unit time, in cm 3 / s; H is the thickness of the filter cake, in cm; η is the viscosity of distilled water at room temperature, in mPa·s; A is the area of the filter cake, in cm 2 ; P is the experimental pressure difference, in Mpa; wherein: μ The viscosity of the distilled water was 0.8937 mPa-s at 25°C; the experimental pressure difference ΔP p was 3.45 MPa.

3. The method according to claim 1, wherein the method is characterized by, The median particle size of the ordinary barite is 200 μm, and the median particle size of the millimicro barite is 0.89 μm.

4. The method according to claim 1 or 2, wherein the method is characterized by, The nanometer and micrometer plugging agent is superfine calcium carbonate, or emulsified modified rubber MORLF, or ULIA nanometer pressure-bearing plugging agent.

5. The method of claim 2, wherein the method is characterized by: The filter cake thickness Measured with a needle gage.

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