A method for preparing near-wellbore oil layer sand control fluid and its application
By injecting a sand-control fluid consisting of a mixture of paraffin wax and porous microparticles around the casing of the oil layer, the paraffin wax melts at the oil layer temperature to form new channels, thus solving the problem of sand particles falling off the bottom of the well and achieving effective sand control and efficient production of the oil layer.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- PETROCHINA CO LTD
- Filing Date
- 2022-09-16
- Publication Date
- 2026-06-30
AI Technical Summary
Existing sand control methods cannot effectively solve the problem of sand particles falling off and migrating near the bottom of the well in oil and gas extraction, leading to problems such as sand blockage and sand clogging in oil wells, and have a significant impact on the permeability of the oil layer or are costly.
A near-wellbore sand control fluid is prepared by injecting a mixture of paraffin wax and porous microparticles around the casing of the oil layer. The paraffin wax melts at the oil layer temperature to form a fluid, and after the cement slurry is discharged and solidifies, it forms a new oil layer channel, maintaining the connectivity and permeability of the oil layer.
It effectively prevents sand from entering the oil reservoir, avoids sand blockage and clogging problems, maintains the connectivity and permeability of the oil reservoir, reduces costs, and improves the production efficiency of oil wells.
Smart Images
Figure CN117757454B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of oil and gas field development technology, and more specifically, to a method for preparing a near-wellbore oil layer sand control fluid and its application. Background Technology
[0002] Loose sandstone oil reservoirs are widely distributed in my country. During the oil and gas extraction process, rock sand particles are often detached and transported out of the oil and gas layer by factors such as stress concentration, shear expansion, strength reduction, hydraulic impact, and solid phase migration near the bottom of the well. This is a very common problem, and the resulting problems such as sand blockage, sand burial, and sand plugging in oil wells are also very prominent. In actual treatment, technicians usually use the following methods.
[0003] Gravel packing method: Gravel is filled into the annular space between the screen pipe and the oil layer casing in the sand-producing section of the oil well to prevent oil layer sand from entering the pump barrel.
[0004] Mechanical sand control methods: Commonly used methods include wire-wound screens, slotted screens, metal powder pipes, and resin sand filter pipes. The basic principle is to install the above-mentioned mechanical pipes at the bottom of the oil well tubing to block the oil layer sand entering the oil well casing from the oil layer outside the tubing, thus preventing the oil layer sand from entering the pump barrel and causing sand jamming.
[0005] Chemical sand control: Injecting a chemical substance near the wellbore to increase its strength and prevent sand production. Resin sand control agents or coated sand control agents are commonly used.
[0006] Each of the above sand control methods has its shortcomings. Gravel packing and mechanical sand control only block sand in the oil reservoir and cannot fundamentally solve the sand production problem. Furthermore, due to their physical barrier effect, they significantly impact the oil reservoir's permeability and are ineffective against sand production in fine sand reservoirs. Chemical sand control ages rapidly under oil reservoir conditions, has a short effective period, and is costly. Summary of the Invention
[0007] The purpose of this invention is to provide a method for preparing a near-wellbore oil layer sand control fluid and its application, so as to improve the above-mentioned problems.
[0008] On one hand, the present invention provides a method for preparing a near-wellbore oil layer sand control fluid, comprising:
[0009] Obtain the pore size, pore throat size, and temperature of the sand oil layer;
[0010] Select paraffin wax with a melting point temperature lower than that of the sand-extracting oil layer;
[0011] Select porous microparticles that match the pore size and throat of the sand-producing oil layer, and drain the residual liquid or residue in the inner pores of the porous microparticles to obtain dry porous microparticles.
[0012] The paraffin wax and the dried porous microparticles are used to prepare near-wellbore oil layer sand control fluid filler. Water and cement are added to the near-wellbore oil layer sand control fluid filler to prepare a preliminary near-wellbore oil layer sand control fluid.
[0013] Add a retarder or a quick-setting agent to the initial near-wellbore oil layer sand control fluid to make the initial near-wellbore oil layer sand control fluid meet the set initial setting time, thus producing the near-wellbore oil layer sand control fluid.
[0014] Optionally, the melting point of the selected paraffin wax is 5-10°C lower than the temperature of the sand-extracting oil layer.
[0015] Optionally, the porous microparticles include at least one of porous activated carbon microparticles, porous calcined clay microparticles, porous fly ash microparticles, and porous artificial rock core microparticles.
[0016] Optionally, the average particle size of the porous microparticles is smaller than the average particle size of the sand particles in the sand-oil layer.
[0017] Optionally, residual liquid or residue in the pores of the porous microparticles can be removed by high-temperature drying or calcination drying.
[0018] Optionally, near-wellbore oil-bearing sand control fluid filler is prepared using the paraffin wax and the dried porous microparticles. Water and cement are added to the near-wellbore oil-bearing sand control fluid filler to prepare a preliminary near-wellbore oil-bearing sand control fluid, comprising:
[0019] Heat the paraffin wax to a temperature 20°C or higher than its melting point to melt it;
[0020] After melting, add dry porous microparticles. The volume ratio between paraffin and dry porous microparticles is 1:1-3. After adding, heat and stir to mix evenly, and stabilize for more than 2 hours until the pores of the dry porous microparticles are filled with paraffin. Let it cool naturally to room temperature, and then grind it into powder using a grinding mill to obtain powdered porous microparticles. The particle size of the ground porous microparticles is smaller than the particle size of the sand produced by the sand-producing oil layer.
[0021] The cement and the powdered porous microparticles are mixed and stirred evenly to form a mixture, wherein the volume ratio between the cement and the powdered porous microparticles is 1:0.5-3.
[0022] Add water or formation water to the mixture and stir until it becomes a fluid to prepare a preliminary near-wellbore oil layer sand control fluid. The volume ratio of the water or formation water to the mixture is 1:1-3.
[0023] Optionally, the cement particle size is smaller than the average particle size of the sand particles produced by the sand-producing oil layer, and the cement meets the indicators in the national standard GB10238-2015 "Oil Well Cement".
[0024] On the other hand, the present invention provides an application of near-well oil layer sand control fluid, comprising: injecting the near-well oil layer sand control fluid into the sand-producing oil layer of the oil well.
[0025] Optionally, injecting the near-wellbore sand control fluid into the sand-producing oil layer of the production well includes:
[0026] Before injecting near-well oil layer sand control fluid, first inject 5-10 times the amount of near-freezing water to cool down the near-well sand and oil layer. Then, fill the tubing casing with near-freezing water to inject the near-well oil layer sand control fluid. Then, use a high-pressure pump truck to inject the prepared near-well oil layer sand control fluid into the oil layer through the tubing using a forward injection method. After calculation, determine the amount of displacement fluid to be injected to completely displace the near-well oil layer sand control fluid in the tubing string into the near-well sand and oil layer.
[0027] After the sand control fluid in the near-well oil layer has initially solidified, backwash the well with near-freezing water. Then, fill the wellbore with near-freezing water until the pressure formed is equivalent to the pressure of the sand-producing oil layer. After that, pull out the tubing string containing the sand control fluid in the near-well oil layer and shut in the well. Alternatively, backwash the well with near-freezing water for two wellbore volumes and then shut in the well directly, allowing it to solidify for 72 hours.
[0028] After 72 hours of waiting, the cement plug at the bottom of the well and the casing wall were cleaned of contamination from the near-well oil layer sand control fluid.
[0029] At the initial stage of well opening, clean water with a temperature higher than the melting point of paraffin is continuously circulated into the casing for 5-10 hours to accelerate the melting and discharge of paraffin in the near-wellbore sand control fluid after solidification in the sand-producing oil layer. After the paraffin is melted and discharged, normal oil production operations can be carried out.
[0030] Optionally, the amount of sand control fluid used in the near-wellbore oil layer can be calculated using formula (1), which is:
[0031] M = Kπ(r + D) 2 hφ (1)
[0032] In formula (1), M is the amount of sand control fluid used in the near-well oil layer, in cubic meters; K is the permeability coefficient of the sand control fluid, obtained experimentally, with a value range of 0.5-0.7; r is the wellbore radius, in meters; D is the radius of the sand control fluid in the near-well oil layer, in meters; h is the oil layer thickness, in meters; and φ is the oil layer porosity.
[0033] The beneficial effects of this invention are as follows:
[0034] 1. This invention injects a near-wellbore sand-control fluid into the sand-producing oil layer. After solidification, the paraffin melted into the porous microparticles melts at the oil layer temperature and is discharged from the solidified cement body under the oil layer pressure. This completes the transformation of the sand-producing oil layer, achieving the goal of preserving the connectivity and permeability of the sand-producing oil layer while establishing a new and solid oil layer skeleton, thus preventing sand production and enabling the oil well to produce normally.
[0035] 2. This invention prevents sand production in a sand-producing oil layer during oilfield development by preventing sand from being produced in that layer. This prevents sand from being buried, stuck, or blocked in the oil well, which would lead to production stoppages and eventually cause problems such as collapse around the bottom of the oil well, casing deformation, and even the abandonment of the oil well.
[0036] 3. This invention involves adding paraffin wax, whose melting point is lower than that of the oil layer, to porous microparticles, then mixing it with cement to create a near-wellbore sand-control fluid. This fluid is then injected into the sand-producing oil layer, where it solidifies in the near-wellbore zone. As the oil layer temperature gradually recovers, the paraffin wax in the porous filler microparticles melts and flows out under oil layer pressure, forming a new channel from the oil layer to the wellbore, thus completing the modification of the sand-producing oil layer. This method is simple to operate, safe, reliable, and low in cost. It solves the sand production problem, improves the production rate of oil wells, and further enhances the oilfield development effect.
[0037] Other features and advantages of the invention will be set forth in the following description, and will be apparent in part from the description, or may be learned by practicing embodiments of the invention. The objects and other advantages of the invention may be realized and obtained by means of the structures particularly pointed out in the written description, claims, and drawings. Attached Figure Description
[0038] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.
[0039] Figure 1 This is a schematic diagram of the sand control process in the near-wellbore oil layer in an embodiment of the present invention;
[0040] The markings in the diagram are: 1- Sand-producing oil layer; 2- Oil production well; 3- Oil layer casing; 4- Activated carbon particles melted into paraffin; 5- Bridge plug; 6- Cement injection tubing string; 7- Cement slurry particles. Detailed Implementation
[0041] On the one hand, the present invention provides a method for preparing a near-wellbore oil layer sand control fluid:
[0042] Step S10: Obtain the pore size, throat size, and temperature of the sand oil layer;
[0043] Step S20: Select paraffin wax with a melting point temperature lower than that of the sand-extracting oil layer;
[0044] Step S30: Select porous microparticles that match the pore size and throat of the sand-exposed oil layer, and drain the residual liquid or residue in the inner pores of the porous microparticles to obtain dry porous microparticles.
[0045] Step S40: Prepare near-wellbore oil layer sand control fluid filler using the paraffin wax and the dried porous microparticles; add water and cement to the near-wellbore oil layer sand control fluid filler to prepare a preliminary near-wellbore oil layer sand control fluid.
[0046] Step S50: Add a retarder or a quick-setting agent to the initial near-wellbore oil layer sand control fluid to make the initial near-wellbore oil layer sand control fluid meet the set initial setting time, thus producing the near-wellbore oil layer sand control fluid.
[0047] Furthermore, in step S10, one method for determining the pore size and throat size of the sand-producing oil layer can be as follows: First, select a specific producing sand-producing oil layer from a particular oil well. Then, analyze the flowing sand in the produced fluid (including oil and formation water) to determine its color, hardness, shape, particle size, sand content, and composition. Combine this with geological research findings to infer the microstructure, pore size, and throat size of the sand-producing oil layer. Alternatively, during sand flushing operations at the oil well, collect a portion of the sand flushed from the bottom of the well for compositional analysis.
[0048] Another method is to analyze the core of the sand-producing oil layer in a certain oil well, or the core of the oil layer in the same sand body of an adjacent well, and then obtain the pore size and pore throat size of the sand-producing oil layer in a certain well.
[0049] Furthermore, in step S20, the temperature of the sand-producing oil layer can be obtained by checking the fluid temperature in the same oil sand body of an adjacent well, or by conducting a temperature test on the oil layer of the well, so as to select paraffin wax with a melting point that matches the oil layer temperature. Generally, paraffin wax with a melting point temperature 5-10℃ lower than the oil layer temperature is selected.
[0050] Furthermore, in step S30, porous microparticles with good pore connectivity that match the pore size and throat of the sand-producing oil layer are selected as fillers. The fillers can be porous activated carbon microparticles, porous calcined clay microparticles, porous fly ash microparticles, or porous artificial rock core microparticles, or one or a combination of these. The average particle size of the fillers should be smaller than the average particle size of the sand particles in the sand-producing oil layer.
[0051] The filler treatment can be carried out by high-temperature drying or calcination drying to remove residual liquid or residue in the microparticle pores, thereby maximizing the effectiveness and connectivity of the micropores and facilitating the melting of paraffin.
[0052] At the same time, the size and connectivity of porous microparticles can be observed using an electron microscope as needed, which can then be used to adjust the permeability of the oil layer after sand control.
[0053] Further, in step S40, firstly, a certain amount of paraffin wax with a certain melting point is placed in a container and heated to a temperature 20°C or higher than the melting point of the paraffin wax to melt it. Then, dried porous microparticles are added, with a volume ratio of paraffin wax to dried porous microparticles of 1:1-3. The mixture is heated, stirred, and stirred until homogeneous, and stabilized for more than 2 hours until the pores of the porous microparticles are filled with paraffin wax. The mixture is then allowed to cool naturally to room temperature and then ground into powder using a grinding mill. After grinding, the porous microparticles must be filled with paraffin wax, and the particle size of the ground porous microparticles must be smaller than the particle size of the sand produced by the sand-producing oil layer.
[0054] The cement and powdered porous microparticles are mixed and stirred evenly to form a mixture. The volume ratio between cement and powdered porous microparticles is 1:0.5-3. The cement particle size is smaller than the average particle size of the sand particles produced in the sand-producing oil layer, and the cement meets the indicators in the national standard GB10238-2015 "Oil Well Cement".
[0055] The porosity of the sand-producing oil layer can be adjusted by changing the ratio of cement to powdered porous microparticles. During the preparation process, an appropriate amount of quartz sand (silica powder) smaller than the sand particle size of the sand-producing oil layer can be added to the cement to adjust its hardness and wear resistance. An appropriate amount of resin can also be added to the cement to adjust its toughness.
[0056] Add water or formation water to the mixture and stir until it becomes a fluid to prepare a preliminary near-wellbore oil layer sand control fluid. The volume ratio of water or formation water to the mixture is 1:1-3.
[0057] Furthermore, in step S50, the initial setting time of the preliminary near-wellbore oil layer sand control fluid is first determined; then it is determined whether the initial setting time of the preliminary near-wellbore oil layer sand control fluid meets the set time. If the initial setting time of the preliminary near-wellbore oil layer sand control fluid does not meet the set time, a retarder or accelerator is added to the preliminary near-wellbore oil layer sand control fluid to make the preliminary near-wellbore oil layer sand control fluid meet the set initial setting time, thus producing the near-wellbore oil layer sand control fluid; wherein, the retarder includes: phosphate or borax; the accelerator includes: calcium chloride or sodium silicate;
[0058] On the other hand, the present invention provides an application of near-wellbore oil layer sand control fluid, that is, using near-wellbore oil layer sand control fluid for near-wellbore oil layer sand control treatment, that is, sand control is performed in the annular zone of the oil layer near the oil layer casing around the oil layer casing, with the purpose of preventing oil layer sand from entering the wellbore, including the following steps:
[0059] First, calculate the amount of sand control fluid needed for the near-wellbore oil layer using formula (1), which is:
[0060] M = Kπ(r + D) 2 hφ (1)
[0061] In formula (1), M is the amount of sand control fluid used in the near-well oil layer, in cubic meters; K is the permeability coefficient of the sand control fluid, obtained experimentally, with a value range of 0.5-0.7; r is the wellbore radius, in meters; D is the radius of the sand control fluid in the near-well oil layer, in meters; h is the oil layer thickness, in meters; and φ is the oil layer porosity.
[0062] Before injecting near-well oil layer sand control fluid, inject 5-10 times the amount of near-well oil layer sand control fluid with near-freezing point water to cool the sand-producing oil layer. Then, fill the tubing and casing with near-freezing point water to inject the near-well oil layer sand control fluid. Next, use a high-pressure pump truck to inject the prepared near-well oil layer sand control fluid into the sand-producing oil layer through the tubing using a forward injection method. The amount of displacement fluid to be injected is determined by calculation to completely displace the near-well oil layer sand control fluid in the tubing string into the sand-producing oil layer. The temperature of the near-freezing point water can be 5℃, 6℃, 7℃, etc.
[0063] After the near-well oil layer sand control fluid has initially solidified, the well is backwashed with near-freezing water. Then, the wellbore is filled with near-freezing water until the pressure formed is equivalent to the pressure of the sand-producing oil layer. Alternatively, the wellbore is filled with near-freezing water and the wellhead tubing gate valve is closed to prevent the fluid level in the tubing string from dropping. After 72 hours of solidification, the tubing string containing the near-well oil layer sand control fluid is pulled out to ensure that the melted paraffin remains in the filler of the sand control fluid after initial solidification. At this time, because the oil layer temperature is higher than the melting point of the paraffin in the filler, the paraffin in the filler will gradually melt to form a fluid and form two incompatible systems with the cement stone formed after the cement slurry solidifies.
[0064] After the cement slurry in the near-well oil layer sand control fluid solidifies, under the condition of pressure difference in the oil layer, the molten liquid paraffin will flow from the oil layer into the wellbore. When the lift pump is installed in the wellbore for production, the oil can be extracted to the surface through the molten paraffin channel. Since the paraffin channel is smaller than the sand particle size of the sand-producing oil layer, the oil layer channel can be guaranteed and the sand control purpose can be achieved.
[0065] After 72 hours of waiting, drilling, scraping and other processes are required to remove the cement plug at the bottom of the well and the casing wall from the sand control fluid in the near-well oil layer.
[0066] At the initial stage of well opening, clean water with a temperature higher than the melting point of paraffin is continuously added to the casing and circulated for 5-10 hours to accelerate the melting and discharge of paraffin in the near-wellbore sand control fluid after the cement slurry in the sand-producing oil layer has solidified. After the paraffin is melted and discharged, normal oil production operations can be carried out.
[0067] This sand control method can be applied not only to sand-producing oil layers in oil production wells, but also to sand control work in sand-producing oil layers in injection wells.
[0068] The following examples illustrate this in detail:
[0069] Example 1
[0070] A method for preparing a near-wellbore oil-bearing sand control fluid includes:
[0071] like Figure 1 As shown, firstly, an oil well 2 was selected, and sand control operations were required for the sand-producing oil layer 1 at a depth of 1500m. During the operation, a sand-flushing string was used to flush sand from the bottom of the oil well. A portion of the sand particles flushed from the bottom of the well was collected from the sand-flushing tank at the well site for analysis. The average particle size (150μm) and uniformity of the sand particles were measured using an electron microscope, thereby determining the pore size and throat size of the sand-producing oil layer 1. After removing the sand-flushing string, the temperature of the sand-producing oil layer inside the casing 3 was measured to be 70℃ and the pressure to be 11MPa.
[0072] Based on the tested temperature of 70℃ for the sand-producing oil layer 1, the melting point of paraffin wax (65℃) was selected. According to the measurement results, the pore size and throat of the sand-producing oil layer 1 are 150μm, so activated carbon microparticles with a particle size less than 150μm and good porous connectivity, dried at 130℃, were selected as the filler. Oil well cement (GB10238-2015) with an average particle size less than 150μm was selected as the curing agent.
[0073] Then, place 300 ml of paraffin wax with a melting point of 65°C in a container and heat it to a temperature 20°C above the melting point of the paraffin wax to melt it. Then add 300 ml of dried activated carbon microparticles with a particle size of less than 150 μm and good porous connectivity as filler. The ratio (volume ratio) is paraffin wax: porous activated carbon microparticles = 1:1. Heat and stir to mix evenly and stabilize for more than 2 hours until the pores of the porous activated carbon microparticles are filled with paraffin wax, forming activated carbon microparticles 4 with paraffin wax infused. Let it cool naturally to room temperature, and then grind it into powder using a pulverizer. Take a sample and use an electron microscope to observe whether its interior is filled with paraffin wax and whether the particle size of the activated carbon microparticles 4 with paraffin wax infused after grinding is smaller than the particle size of the sand-exposed oil layer. After passing the test, proceed to the next step.
[0074] A mixture is prepared by mixing oil well cement (national standard GB10238-2015) with activated carbon particles 4 that have been melted into paraffin and ground into powder with a particle size of less than 150μm. The ratio (volume ratio) of cement to activated carbon particles melted into paraffin is 1:1. The above mixture is then mixed with water to form a fluid and prepared as a near-wellbore oil layer sand control fluid. The ratio (volume ratio) of water added is 1:2.
[0075] Next, test the initial setting time of the above formula based on the oil layer temperature and pressure. If the initial setting time of 2 hours is not reached, it can be adjusted to the set initial setting time of 2 hours by adding a retarder or accelerator.
[0076] Example 2
[0077] This embodiment provides the field application of the near-wellbore oil-bearing sand control fluid prepared in Embodiment 1 above, including:
[0078] Given that the thickness of the sand-producing oil layer 1 in the oil well to be implemented is h = 3m, the porosity of the oil layer is φ = 38%, the wellbore radius is r = 62.9mm, the radius of the near-wellbore sand control fluid is D = 1.5m, and the permeability coefficient of the sand control fluid is K = 0.6, then according to the injection volume calculation formula M = Kπ(r + D) 2 From hφ, we can obtain M = 5.25m 3 Then prepare 5.25m 3 Near-well oil layer sand control fluid;
[0079] First, design the wellbore of oil well 2: including bottom sand filling and the lower bridge plug 5 above the sand-producing oil layer 1. Then, run the ash injection string 6, insert the insertion tube at the bottom of the ash injection string 6 into the bridge plug 5, and then use a high-pressure pump truck to inject the prepared near-well oil layer sand control fluid into the sand-producing oil layer 1 from the wellhead of oil well 2.
[0080] During the implementation process, when injecting near-well oil layer sand control fluid, first inject 40 cubic meters of near-freezing point clean water (temperature 5℃) to cool down the sand-producing oil layer 1 at an injection rate of 10 cubic meters / hour. Then, fill the casing 3 outside the injection string 6 with near-freezing point clean water. Then, use a high-pressure pump truck to inject the prepared near-well oil layer sand control fluid into the sand-producing oil layer 1 from the injection string 6 using a forward injection method. After calculation, determine the amount of replacement fluid to be injected, so that all the near-well oil layer sand control fluid in the injection string 6 can be replaced into the sand-producing oil layer 1. However, the sand surface inside the oil layer casing should be retained to the top of the sand-producing oil layer by 0.5-1m.
[0081] After two hours of initial setting, backwash the well with near-freezing water. Then, fill the casing 3 of well 2 with near-freezing water until the pressure is equivalent to that of the sand-producing oil layer 1. After that, pull out the injection string 6 containing the near-well oil layer sand control fluid and shut in the well, or backwash the well with near-freezing water for two wellbore volumes and then shut in the well directly. This ensures that the melted paraffin remains in the mixture of the sand control fluid after initial setting. After 72 hours of setting, as the temperature of the sand-producing oil layer 1 gradually recovers and exceeds the melting point of the paraffin in the mixture, the paraffin in the mixture will gradually melt to form a fluid and form two incompatible systems with the cement slurry particles 7.
[0082] At this time, after the process of retrieving bridge plug 5, drilling plug, scraping and other processes, the oil pump is lowered into the oil well 2, and the pumping unit is started under load to suck up the well fluid. The fluid level in the well is lowered and a pressure difference is formed with the oil layer. The liquid paraffin in the activated carbon particles 4 melted into the paraffin will flow from the oil layer into the well under the presence of the pressure difference, thereby forming a new oil layer channel. Since the paraffin channel is smaller than the sand particles in the sand-producing oil layer 1, it can both ensure the oil layer channel and achieve the purpose of sand prevention.
[0083] At the initial stage of well 2, clean water at a temperature 30-40°C higher than the melting point of paraffin can be continuously circulated into casing 3 for 8 hours to accelerate the melting and discharge of paraffin in the near-wellbore sand control fluid after solidification in the sand-producing oil layer. After the paraffin is melted and discharged, normal oil production operations can be carried out.
[0084] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.
Claims
1. A method for preparing a near-wellbore oil-bearing sand control fluid, characterized in that, include: Obtain the pore size, pore throat size, and temperature of the sand oil layer; Select paraffin wax with a melting point temperature lower than that of the sand-extracting oil layer; Select porous microparticles that match the pore size and throat of the sand-producing oil layer, and drain the residual liquid or residue in the inner pores of the porous microparticles to obtain dry porous microparticles. The paraffin wax and the dried porous microparticles are used to prepare near-wellbore oil layer sand control fluid filler. Water and cement are added to the near-wellbore oil layer sand control fluid filler to prepare a preliminary near-wellbore oil layer sand control fluid. Add a retarder or a quick-setting agent to the initial near-wellbore oil layer sand control fluid to make the initial near-wellbore oil layer sand control fluid meet the set initial setting time, thus producing a near-wellbore oil layer sand control fluid. A near-wellbore oil-bearing layer sand control fluid filler is prepared using the paraffin wax and the dried porous microparticles. Water and cement are added to the near-wellbore oil-bearing layer sand control fluid filler to prepare a preliminary near-wellbore oil-bearing layer sand control fluid, comprising: Heat the paraffin wax to a temperature 20°C or higher than its melting point to melt it; After melting, add dry porous microparticles. The volume ratio between paraffin and dry porous microparticles is 1:1-3. After adding, heat and stir to mix evenly, and stabilize for more than 2 hours until the pores of the dry porous microparticles are filled with paraffin. Let it cool naturally to room temperature, and then grind it into powder using a grinding mill to obtain powdered porous microparticles. The particle size of the ground porous microparticles is smaller than the particle size of the sand produced by the sand-producing oil layer. The cement and the powdered porous microparticles are mixed and stirred evenly to form a mixture, wherein the volume ratio between the cement and the powdered porous microparticles is 1:0.5-3. Add water or formation water to the mixture and stir until it becomes a fluid to prepare a preliminary near-wellbore oil layer sand control fluid. The volume ratio of the water or formation water to the mixture is 1:1-3.
2. The method for preparing near-wellbore oil layer sand control fluid according to claim 1, characterized in that, The selected paraffin wax has a melting point temperature that is 5-10°C lower than that of the sand-extracting oil layer.
3. The method for preparing near-wellbore oil layer sand control fluid according to claim 1, characterized in that, The porous microparticles include at least one of porous activated carbon microparticles, porous calcined clay microparticles, porous fly ash microparticles, and porous artificial rock core microparticles.
4. The method for preparing near-wellbore oil layer sand control fluid according to claim 1, characterized in that, The average particle size of the porous microparticles is smaller than the average particle size of the sand particles in the sand-oil layer.
5. The method for preparing near-wellbore oil layer sand control fluid according to claim 1, characterized in that, The residual liquid or residue in the pores of the porous microparticles is removed by high-temperature drying or calcination drying.
6. The method for preparing near-wellbore oil layer sand control fluid according to claim 1, characterized in that, The cement particle size is smaller than the average particle size of the sand particles produced by the sand-oil layer, and the cement meets the indicators in the national standard GB10238-2015.
7. The application of the near-wellbore oil-bearing sand control fluid prepared by the method according to any one of claims 1-6, characterized in that, include: The near-well oil layer sand control fluid is injected into the sand-producing oil layer of the oil well.
8. The application of the near-wellbore oil-bearing sand control fluid prepared by the method described in claim 7, characterized in that, Injecting the near-wellbore sand control fluid into the sand-producing oil layer of the production well includes: Before injecting near-well oil layer sand control fluid, first inject near-freezing water to cool the near-well sand and oil layer. Then, fill the tubing casing with near-freezing water to inject the near-well oil layer sand control fluid. Then, use a high-pressure pump truck to inject the prepared near-well oil layer sand control fluid into the oil layer through the tubing using a forward injection method. After calculation, determine the amount of displacement fluid to be injected to completely displace the near-well oil layer sand control fluid in the tubing string to the near-well sand and oil layer. After the sand control fluid in the near-well oil layer has initially solidified, backwash the well with near-freezing water. Then, fill the wellbore with near-freezing water until the pressure formed is equivalent to the pressure of the sand-producing oil layer. After that, pull out the tubing string containing the sand control fluid in the near-well oil layer and shut in the well. Alternatively, backwash the well with near-freezing water for two wellbore volumes and then shut in the well directly, allowing it to solidify for 72 hours. After 72 hours of waiting, the cement plug at the bottom of the well and the casing wall were cleaned of contamination from the near-well oil layer sand control fluid. At the initial stage of well opening, clean water with a temperature higher than the melting point of paraffin is continuously circulated into the casing for 5-10 hours to accelerate the melting and discharge of paraffin in the near-wellbore sand control fluid after solidification in the sand-producing oil layer. After the paraffin is melted and discharged, normal oil production operations can be carried out.
9. The application of the near-wellbore oil-bearing sand control fluid prepared by the method described in claim 8, characterized in that, The dosage of sand control fluid for near-wellbore oil layers is calculated using formula (1), which is: M=Kπ(r+D) 2 hφ(1) In formula (1), M is the amount of sand control fluid used in the near-well oil layer, in cubic meters; K is the permeability coefficient of the sand control fluid, obtained experimentally, with a value range of 0.5-0.7; r is the wellbore radius, in meters; D is the radius of the sand control fluid in the near-well oil layer, in meters; h is the oil layer thickness, in meters; and φ is the oil layer porosity.