A method for sand control in oil wells of high-muddy, loose sandstone reservoirs

Abstract

This invention relates to the field of sand control technology in oil and gas extraction, and particularly to a method for sand control in oil wells of high-muddy, loose sandstone reservoirs. The method includes: pulling out the original production tubing and sand control tubing; running a sand flushing tubing string for detection, and flushing sand after detection; performing well cleaning; scraping the tubing and performing forward circulation well washing; running a casing test tubing string for pressure testing; performing reservoir cleaning and acidizing pretreatment; purging the wellbore using nitrogen foam; using the tubing string in the wellbore to detect the sand surface and performing reverse circulation well washing; running an external sand control tubing string into the well; magnetic positioning; performing manifold pressure testing; setting and sealing the filling tool; filling with sand control; and backwashing the well. This invention eliminates near-wellbore blockage factors, inhibits the migration and blockage of fine sand and muddy particles in the far-wellbore area, establishes a high-conductivity channel artificial sand barrier near the wellbore, releases energy from high-muddy, loose sandstone reservoirs, improves oil well productivity, and achieves long-term, high-efficiency production in high-muddy, sand-producing oil wells.

Description

Technical Field

[0001] This invention relates to the field of sand control technology in oil and gas extraction, and particularly to a method for sand control in oil wells of high-muddy, loose sandstone reservoirs. Background Technology

[0002] Sand production is particularly common during the development of loose sandstone oil reservoirs. Sand production not only blocks fluid flow channels near the wellbore, reducing permeability, but also leads to sand burial of the producing layer due to the large amount of sand settling and accumulating in the wellbore, causing insufficient fluid supply and even pump jamming and production shutdowns. Therefore, oil wells in loose sandstone reservoirs need sand control treatment before they can operate normally. Currently, the most mature and widely used sand control technologies are chemical sand control and gravel-packed mechanical sand control, both of which have achieved some success in field applications.

[0003] However, as the exploration and development of oil fields continues to deepen, more and more high-muddy loose sandstone reservoirs are put into development and production. The existing sand control technology has become less adaptable to the process of such sand-producing formations. Sand control wells are low-yield and inefficient, the sand control cycle is short, the operating cost is high, and the sand control effect is not ideal.

[0004] High-clay-content, loosely cemented formations are characterized by high clay particle and silt content. These particles are small in size, have low initial flow velocity, and exhibit extremely high mobility and fluidity. Chemical sand control technology mainly utilizes the consolidation effect of resin on formation sand to achieve sand control. However, chemical sand control for these high-clay-content formations suffers from problems such as significant reservoir damage, large permeability loss, and low well productivity. Gravel packing sand control technology, during the filling process in high-clay-content reservoirs, presents the problem of mixed poor permeability zones formed by the mixing of filling sand with silt near the wellbore. In addition, under the influence of production pressure differential, a large number of highly mobile clay particles and silt in the formation near the wellbore migrate and block the gravel packing layer, hindering fluid flow channels. This results in insufficient fluid supply to the wellbore, poor sand control effect, difficulty in releasing reservoir energy, and underutilization of its production capacity, leading to poor reservoir development benefits.

[0005] Regarding high-muddy loose sandstone, the applicant previously researched a resin filter pipe, which is disclosed in utility model patent CN205955709U; and disclosed a vegetable oil asphalt cationic amide resin with dual functions of anti-swelling and sand control in Chinese patent application CN111100290A. The vegetable oil asphalt cationic amide resin has dual functions of anti-swelling and sand control and can be used as an anti-swelling and sand control agent, which can effectively solve the problem of rapid decline in oil well productivity in high-muddy loose sandstone reservoirs.

[0006] There are currently no reports on methods for sand control in oil wells of high-muddy, loose sandstone reservoirs. Summary of the Invention

[0007] The main objective of this invention is to provide a method for sand control in oil wells of high-muddy loose sandstone reservoirs. This method can eliminate near-wellbore blockage factors, inhibit the migration and blockage of fine sand and mud particles in the far-wellbore area, establish a high-conductivity channel artificial sand-blocking body near the wellbore, release the energy of high-muddy loose sandstone reservoirs, improve oil well productivity, achieve long-term high-efficiency production of high-muddy sand-producing oil wells, extend the sand control period, and improve reservoir development benefits.

[0008] To achieve the above objectives, the present invention adopts the following technical solution:

[0009] This invention provides a method for sand control in oil wells of high-muddy, loose sandstone reservoirs, comprising the following steps: retrieving the original production tubing and sand control tubing; running a sand flushing tubing into the production well for detection, and flushing sand after detecting the sand surface; running a well cleaning tubing for well cleaning; running a scraper tubing for scraping and performing positive circulation well cleaning; running a casing pressure testing tubing for pressure testing; running a tubing string with a sand flushing pen tip into the well casing for pre-treatment of the oil layer cleaning and acidizing; purging the wellbore using nitrogen foam; using the tubing string in the wellbore to detect the sand surface and performing reverse circulation well cleaning; running an external sand control tubing into the well; magnetically positioning the production wire screen tube so that the lower end is 1.5-2m below the lower boundary of the production oil layer and the upper end is 2.5-3m above the upper boundary of the production oil layer; performing a manifold pressure test, setting and sealing the filling tool, filling with sand control, and backwashing the well, thus obtaining the desired result.

[0010] Furthermore, the sand flushing string includes tubing and a sand flushing pen tip. The sand flushing string connects the sand flushing pen tip to the tubing from bottom to top to the wellhead. After the sand surface is detected, sand flushing fluid is pumped into the annular space formed by the sand flushing string and casing to flush the sand. The sand flushing ends when the sand reaches the bottom of the artificial well or the cement plug surface.

[0011] Furthermore, the sand flushing discharge rate is 500-600 L / min.

[0012] Furthermore, the scraper string includes an oil pipe, an oil pipe coupling, and a scraper, with the lower end of the oil pipe connected to the oil pipe coupling and the lower end of the oil pipe coupling connected to the scraper.

[0013] Furthermore, the scraper runs at a speed of 35-40 tubes per hour, scraping the tubes to the top boundary of the oil layer perforation.

[0014] Furthermore, the well-washing fluid is pumped into the tubing and returned from the annulus. The discharge rate of the well-washing fluid is not less than 500L / min. The well-washing is stopped after the inlet and outlet water quality is consistent, and the scraper string is pulled out.

[0015] Furthermore, the casing pressure test string includes a packer and a tubing connected in sequence from bottom to top. When the packer is lowered to a position 4 - 6 meters above the top boundary of the perforated interval of the oil layer, the string is lowered while being rotated to set the packer, effectively sealing the annular space between the oil pipe and the casing. Then, a well flushing fluid is pumped into the annular space between the tubing and the casing. When the injection pressure reaches 70 - 75% of the internal pressure resistance strength of the casing steel grade, the pump is stopped and the pressure is held for 5 - 7 minutes. If the pressure remains stable without dropping, it is considered qualified.

[0016] Furthermore, the pre - treatment of oil layer cleaning and acidification includes the following steps: filling the wellbore with a well flushing fluid, and successively squeezing in a cleaning agent, a displacing fluid, an acid fluid, and a displacing fluid.

[0017] Furthermore, the cleaning agent includes the following components and their weight parts: 10 - 20 parts of an organic solvent, 0.5 - 2 parts of an alcohol - ether amphiphilic surfactant, and 80 - 90 parts of water.

[0018] Furthermore, the acid fluid includes the following components and their weight parts: 6 - 15 parts of hydrochloric acid, 2 - 9 parts of boric acid, 5 - 13 parts of hydrofluoric acid, 1.5 - 5 parts of a corrosion inhibitor, 0.5 - 3 parts of an iron ion stabilizer, 1 - 2.5 parts of a助排剂 (oil displacement aid), 3 - 5 parts of ammonium chloride, and 50 - 80 parts of water; the oil displacement aid includes one or several of high - carbon fatty alcohol polyoxyethylene ether, methanol, ethylene glycol, and glycerol pentaerythritol.

[0019] Through the physical and chemical actions of the cleaning agent, the crude oil, especially the aged oil formed by the deposition of resin, asphaltene, and wax, attached to the surface of the perforations and formation rock sand grains is softened, peeled off, and dissolved, improving the fluidity of the crude oil. At the same time, the surface of the perforations and the rock sand grains in the near - wellbore area, which serve as the oil flow channels, are fully exposed.

[0020] Through the chemical action of the acid fluid, especially by utilizing the chemical properties of fluoboric acid generated in the system, the clay mineral particles and a small part of free fine sand particles that are extremely easy to migrate and cause blockage in the highly muddy formation rock exposed after cleaning in the near - bottom well area are fused into inert particles, melted and cemented in place to inhibit the secondary migration of particles. On the other hand, due to the dissolution of the ash and mud minerals in the cementing material between the sand grains by the acid fluid, a large number of weakly cemented fine sand particles in the formation will be released and dissolved and decomposed by the effective component hydrofluoric acid in the acid fluid, reducing the content of fine sand in the near - wellbore area.

[0021] Furthermore, in the step of using nitrogen foam to empty the wellbore:

[0022] Connect the outlet of the air - nitrogen making truck and the outlet of the cement pump truck to the inlet end of the three - way device of the foam generator through a pipe manifold, and then connect the outlet end of the foam generator to the casing gate of the wellhead device with a rigid pipeline; connect the tubing gate of the wellhead device to a rigid pipeline and enter the emptying pool.

[0023] Note: In ID=9, "助排剂" is directly translated as "oil displacement aid" as there is no specific English term provided in the original for this component. It can be further adjusted according to the actual common English expression in relevant fields.The cement pump truck pumps foaming liquid into the foam generator at a rate of 100-150 L / min, while the air nitrogen generator truck pumps it at a rate of 1000-1200 m / min. 3 Nitrogen gas is injected into the foam generator at a discharge rate of / h; the foaming liquid is an aqueous solution of sodium dodecyl sulfate with a mass concentration of 1%-2%;

[0024] When foam liquid is seen returning from the drain tank, the cement pump truck stops working, and the air nitrogen generator continues construction until no more foam liquid flows out of the drain tank outlet. Keep the casing outlet and oil pipe outlet continuously spraying into the drain tank without obstruction for 8-10 hours.

[0025] By using nitrogen foam to purge the air, under the strong negative pressure at the bottom of the well, the mud particles, fine sand, and residual acid formed after acidizing that are prone to starting and migrating and causing later blockage damage in the near-wellbore area will be forcibly displaced and flowed back into the wellbore. This fundamentally eliminates the potential adverse factors that may induce formation blockage, cleans the production zone environment, and further expands the seepage space.

[0026] Furthermore, the sand surface is detected using the tubing string in the wellbore, and sand flushing fluid is pumped into the annular space formed by the tubing and casing. At the same time, the tubing string is lowered, and when the sand is flushed to 30m below the production oil layer, reverse circulation well washing is performed. Well washing is stopped when clear water is seen at the outlet and there are no sand particles, and all sand flushing tubing strings in the well are pulled out.

[0027] Furthermore, the external sand control tubing string is connected in sequence from bottom to top to include a plug, tubing, centralizer, production wire-wound screen, tubing short section, centralizer, tubing, signal wire-wound screen, and tubing; a flushing string is inserted into the external sand control tubing; a suspension packer is connected to the upper end of the flushing string and the upper end of the external sand control tubing string, and the upper end of the packer is connected to the tubing string to the wellhead.

[0028] Furthermore, during sand control filling, pre-filled fluid and guar gum fluid are sequentially injected into the tubing. After the injection pressure stabilizes, sand-carrying fluids with different sand-to-fluid ratios are continuously injected sequentially. When the pump pressure rises to 6-8 MPa, the injection of sand-carrying fluid is stopped. After replacing 2-3 cubic meters of guar gum fluid exceeding the tubing volume in the well, the pump is stopped. When the tubing pressure drops to zero MPa, the casing gate valve is opened, and then sand-carrying fluid with a sand-to-fluid mass ratio of 5-6% is pumped into the tubing in a positive circulation manner at a rate of 500-550 L / min. When the pressure rises to 3-4 MPa, the addition of sand-carrying fluid is stopped, and circulation and well washing continue. When the pressure rises to 12-14 MPa, the pump is stopped, and the annulus between the screen and casing is saturated.

[0029] Furthermore, the sand-carrying liquid with different sand-liquid ratios is continuously and sequentially injected into the sand-carrying liquid step, and the sand-liquid ratio of the injected sand-carrying liquid gradually increases.

[0030] Furthermore, the pre-polymerized liquid is composed of dimethyl diallyl ammonium chloride, ammonium chloride, and water in a mass ratio of 0.5-1:2-3:100; the guar gum solution is an aqueous solution of hydroxypropyl guar gum thickener with a mass percentage concentration of 0.3-0.6%.

[0031] After the pre-fluid enters the formation, due to the numerous cationic groups on the polydimethyldiallylammonium chloride molecular chain, it is strongly adsorbed on the exchange points of the clay in a network form. Through intermolecular forces and hydrogen bonding, it is firmly adsorbed on the surface of negatively charged clay particles and formation sand, connecting the particles to the formation surface, preventing the hydration, expansion, dispersion, and migration of clay particles, inhibiting sand flow, and playing a role in stabilizing the formation sand.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] This invention, through processes such as formation cleaning, acidizing, and nitrogen foam venting, not only effectively clears the fluid flow channels near the wellbore bottom but also removes a large number of mobile, highly mobile clay particles and fine sand inherent in high-muddy formations near the wellbore. In the far-well zone, the functional groups on the molecular chains of polydimethyldiallyl ammonium chloride with high-density positive charges are mutually adsorbed with reservoir particles through hydrogen bonds and electrostatic interactions, achieving in-situ fixation of formation fine sand and clay particles. This fundamentally eliminates potential adverse factors that could cause blockage damage near the wellbore, improving sand control efficiency, extending the effective period of sand control, and ensuring long-term high-efficiency oil well production.

[0034] The method of this invention removes the original fine sand and clay particles in the formation near the wellbore before carrying out high sand ratio gravel filling. This not only effectively utilizes the ceramsite to saturate and fill the volume deficit zone of the formation near the wellbore, but also reduces the risk of ceramsite mixing with formation sand during the filling process. It realizes the construction of a high-strength artificial ceramsite sand retainer with high conductivity channels in the near-bottom zone, which is conducive to the release of reservoir energy and greatly improves the oil well productivity. Detailed Implementation

[0035] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0036] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments of the present invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, and / or combinations thereof.

[0037] To enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below with reference to specific embodiments.

[0038] Example 1

[0039] A method for sand control in oil wells of porous sandstone reservoirs with high clay content includes the following steps:

[0040] Step 1: Retrieve the original well production tubing.

[0041] Retrieve the existing production tubing and sand control tubing from the wellbore. The production tubing includes tubing, a pump, and sucker rod; the sand control tubing includes a drop packer, tubing, a centralizer, a sand control screen, and plugs.

[0042] Step 2. Lower the sand-testing tubing.

[0043] A sand-flushing string with a sand-flushing pen tip is lowered into the well casing. The sand-flushing string includes tubing and a sand-flushing pen tip. From bottom to top, the pen tip connects to the tubing to the wellhead, and the tubing and the sand-flushing pen tip are connected by threads. After the sand surface is detected, sand-flushing fluid is pumped into the annular space formed by the sand-flushing string and casing to flush the sand. The sand is flushed to the bottom of the artificial well or the cement plug surface. The sand-flushing fluid is a mixture of oilfield de-oiled wastewater and 1.5-2.0% KCl by weight. The sand-flushing discharge rate is...

[0044] Step 3. Well cleaning

[0045] A wellbore string equipped with a well gauge is lowered into the well. The wellbore string includes tubing, a tubing adapter, and a well gauge. From bottom to top, the wellbore string consists of the well gauge, the tubing adapter, and the tubing. The lower end of the tubing connects to the tubing adapter, and the lower end of the tubing adapter connects to the well gauge. The tubing, tubing adapter, and well gauge are threaded together. The wellbore string is lowered at a rate of 35-40 strings per hour. The wellbore is purged to the bottom of the perforation in the oil layer, and then the wellbore string is retrieved.

[0046] Step 4. Scraping the pipe

[0047] A scraper string with a casing scraper is lowered into the well. The scraper string includes tubing, a tubing adapter, and a scraper. From bottom to top, the scraper string consists of the scraper, the tubing adapter, and the tubing. The lower end of the tubing is connected to the tubing adapter, and the lower end of the tubing adapter is connected to the scraper. The tubing, the tubing adapter, and the scraper are connected by threads.

[0048] The scraping and pipe-laying speed is 35 - 40 pipes per hour. Scrape the pipe until the top boundary of the oil layer perforation; then conduct normal circulation well flushing. Pump the well flushing fluid into the well through the tubing, and the well flushing fluid returns from the annulus between the tubing and the casing. The displacement of the well flushing fluid is not less than 500 L / min. Stop well flushing after the water quality at the inlet and outlet is consistent; the well flushing fluid is the deoiled sewage from this oilfield area with 1.5 - 2.0% KCl added by weight. Pull out the scraping pipe string.

[0049] Step 5. Casing pressure test

[0050] Lower a casing pressure test pipe string with a Y221 packer into the well. The pipe string includes a tubing and a packer. The pipe string from bottom to top is respectively the packer head and the tubing, and the tubing is threadedly connected to the packer. The pipe-laying speed is 35 - 40 pipes per hour. When the packer reaches 4 - 6 meters below the top boundary of the oil layer perforation interval, lower and rotate the pipe string simultaneously to set the packer. The setting load is 7 - 8 tons to effectively seal the annulus between the oil and casing. The setting position is required to avoid the casing collar; then pump the well flushing fluid into the annulus formed by the tubing and the casing. When the injection pressure reaches 70% of the internal pressure resistance strength of the casing steel grade, stop the pump and hold the pressure for 5 minutes. If the pressure remains stable without dropping, it is qualified. The well flushing fluid is a mixed liquid of deoiled sewage from this oilfield area with 1.5 - 2.0% KCl added by weight.

[0051] Step 6. Oil layer cleaning and acidification pretreatment

[0052] Lower a pipe string with a sand washing tip into the wellbore casing. The pipe string includes a tubing and a sand washing tip. The pipe string from bottom to top is the tip connected to the tubing to the wellhead, and the tubing and the sand washing tip are threadedly connected; lower the sand washing tip to 150 m - 200 m below the upper boundary of the oil layer, install the wellhead device; connect the pump truck to the wellhead device through the surface pipe manifold, displace and fill the wellbore with deoiled sewage from this oilfield area with 2% KCl by mass concentration added through the tubing, then squeeze the oil layer cleaning agent into the tubing, and then squeeze the displacement fluid to fully inject the cleaning agent into the production oil layer. Then continuously squeeze the acid fluid and the displacement fluid into the tubing in sequence to fully inject the acid fluid into the oil layer, avoiding excessive acid fluid staying in the casing, and then shut in the well for reaction for hours.

[0053] The usage amount of the cleaning agent is 4 - 8 cubic meters per meter of the oil layer; the cleaning agent consists of the following components and their weight parts: 3 parts of xylene, 9 parts of acetone, 6 parts of diesel, 0.5 part of diethylene glycol monobutyl ether, 1.5 parts of alkylphenol polyoxyethylene ether, and 80 parts of water.

[0054] The displacement fluid is deoiled sewage from this oilfield area with 2% KCl added by mass percentage.

[0055] The acid solution is composed of the following components and their weight parts: 10 parts hydrochloric acid, 4 parts boric acid, 13 parts hydrofluoric acid, 1.5 parts corrosion inhibitor, 1 part citric acid, 1.5 parts high carbon fatty alcohol polyoxyethylene ether, 2 parts ammonium chloride, and 67 parts domestic water.

[0056] Step 7. Nitrogen foam venting of the wellbore

[0057] The outlets of the air nitrogen generator truck and the cement pump truck are connected to the inlet of the foam generator's tee device via manifolds. The outlet of the foam generator is then connected to the casing gate of the wellhead device via a rigid pipeline. The tubing gate of the wellhead device is connected to the venting pool via a rigid pipeline. All connections are unibody connections.

[0058] After the surface pipeline pressure test is passed, the cement pump truck pumps foaming liquid into the foam generator at a rate of 100-150 L / min. Simultaneously, the air-nitrogen generator injects nitrogen gas into the foam generator at a rate of 1000-1200 cubic meters / h. The foaming liquid is a 1%-2% sodium dodecyl sulfate aqueous solution. When foam liquid is seen returning from the drain tank, the cement pump truck stops operating, while the air-nitrogen generator continues operation until no more foam liquid flows out of the drain tank outlet. At this point, it indicates that the wellbore fluid column above the sandblasting tip has been emptied. Then, the casing outlet and tubing outlet are continuously vented into the drain tank without obstruction for 8 hours.

[0059] Step 8. Probe the sand.

[0060] Using the tubing string in the wellbore to detect the sand surface, while pumping flushing fluid into the annular space formed by the tubing and casing, the tubing string is lowered. The flushing fluid returns from the tubing to the surface, with a flushing fluid discharge rate of not less than 400 L / min. When the sand is flushed to 30m below the lower boundary of the production oil layer, reverse circulation well washing is implemented, with the well washing discharge rate controlled at 500-600 L / min. Well washing is stopped when clear water is seen at the outlet and there are no sand particles, thus removing the sand column from the wellbore and cleaning the wellbore environment. All flushing tubing strings in the well are then retrieved.

[0061] Step 9. Lower the sand control pipe column

[0062] The external sand control tubing string is assembled from bottom to top as follows: threaded plug, tubing, centralizer, production wire-wound screen, tubing short section, centralizer, tubing, signal wire-wound screen, and tubing; then a flushing string is inserted into the external sand control tubing string, the length of which is 0.5-1m shorter than the length of the external sand control tubing string; the upper end of the flushing string and the upper end of the external sand control tubing string are simultaneously connected to a suspended packer, and the upper end of the packer is connected to the tubing string to the wellhead.

[0063] Step 10. Magnetic positioning

[0064] Magnetic positioning and depth adjustment are used to ensure that the lower end of the production wire-winding screen tube is 1.5-2m below the lower boundary of the production oil layer, and the upper end of the production wire-winding screen tube is 2.5-3m above the upper boundary of the production oil layer.

[0065] Step 11. Sand control construction

[0066] The specific steps are as follows:

[0067] (1) Manifold pressure test: Connect the pump truck outlet to the upper end of the wellhead oil pipe gate valve using the ground pipeline, run the pump to test the pressure to 35MPa, and it is qualified if there is no puncture or leakage after 5 minutes.

[0068] (2) Setting and filling tools: Use a pump truck to fill the tubing with water. After filling, pressurize in stages at 4MPa, 6MPa, 8MPa, 10MPa and 12MPa and stabilize the pressure for 3 minutes each. Continue to increase the pressure to about 20MPa. When the pressure suddenly drops to 0MPa, open the filling channel and continue the positive circulation well washing until the wellhead casing gate outlet is effluent.

[0069] (3) Sand control: Close the wellhead casing gate valve, and the pump truck moves at a speed of 1.5-2.5m. 3At a flow rate of / min, 20-30 cubic meters of pre-fluid and 25-30 cubic meters of guar gum solution are sequentially injected into the tubing. After the injection pressure stabilizes, the first sand-carrying fluid is continuously injected sequentially at a rate of 15-20 cubic meters. The first sand-carrying fluid is a mixture of guar gum solution and 20-40 mesh ceramsite, with a volume ratio of ceramsite to guar gum solution of 0.5:10, i.e., 0.5 cubic meters of ceramsite added to every 10 cubic meters of guar gum solution. Then, the second sand-carrying fluid is injected at a rate of 15-18 cubic meters, and the second sand-carrying fluid is a mixture of guar gum solution and 20-40 mesh ceramsite. The mixture is composed of guar gum solution and 20-40 mesh ceramsite, with a volume ratio of ceramsite to guar gum solution of 1:10, meaning 1 cubic meter of ceramsite is added to every 10 cubic meters of guar gum solution. The third sand-carrying solution is then injected at a rate of 15-20 cubic meters. This third sand-carrying solution is a mixture of guar gum solution and 20-40 mesh ceramsite, with a volume ratio of ceramsite to guar gum solution of 1.5:10, meaning 1.5 cubic meters of ceramsite is added to every 10 cubic meters of guar gum solution. The sand-addition intensity at this stage is 2-4 cubic meters of ceramsite per meter of oil layer. Finally, the fourth sand-carrying solution is injected at a rate of 20-30 cubic meters, consisting of guar gum solution and 20-40 mesh ceramsite. The first stage involves mixing ceramsite with guar gum solution at a volume ratio of 2:10 (2 cubic meters of ceramsite added to every 10 cubic meters of guar gum solution). The sand-addition intensity at this stage is 3-6 cubic meters of ceramsite per meter of oil layer. The second stage involves injecting a fifth sand-carrying solution at a volume of 12-15 cubic meters, composed of guar gum solution and 20-40 mesh ceramsite, with a volume ratio of 3:10 (3 cubic meters of ceramsite added to every 10 cubic meters of guar gum solution). The sand-addition intensity at this stage is 2-4 cubic meters of ceramsite per meter of oil layer. The third stage involves injecting a sixth sand-carrying solution at a volume of 10- The first stage involves injecting 15 cubic meters of guar gum solution, which is a mixture of guar gum solution and 20-40 mesh ceramsite. The volume ratio of ceramsite to guar gum solution is 4:10, meaning 4 cubic meters of ceramsite are added to every 10 cubic meters of guar gum solution. The sand-addition intensity at this stage is 1-3 cubic meters of ceramsite per meter of oil layer. The second stage involves injecting the seventh sand-carrying solution, which is a mixture of guar gum solution and 20-40 mesh ceramsite. The volume ratio of ceramsite to guar gum solution is 5:10, meaning 5 cubic meters of ceramsite are added to every 10 cubic meters of guar gum solution. The sand-addition intensity at this stage is 0.5-2 cubic meters of ceramsite per meter of oil layer.

[0070] When the pump pressure rises to 6-8 MPa, stop adding sand and replace 2-3 cubic meters of guar gum fluid exceeding the tubing volume in the well. Then stop the pump and wait until the tubing pressure drops to zero MPa before opening the casing gate valve. Subsequently, pump sand-carrying fluid into the tubing in a positive circulation manner at a sand ratio of 5-6% and a flow rate of 500 L / min. When the pressure rises to 3-4 MPa, stop adding sand and continue circulating the well. When the pressure rises to 12 MPa, stop the pump and saturate the annulus between the screen and the casing.

[0071] The pretreatment solution is composed of polydimethyldiallylammonium chloride, ammonium chloride and water in a mass ratio of 0.5-1:2-3:100;

[0072] The guar gum solution is an aqueous solution of hydroxypropyl guar gum thickener with a mass percentage concentration of 0.3-0.6%.

[0073] (4) Backwashing well: Connect the pump truck outlet to the wellhead casing gate valve using the pipeline, open the tubing gate valve, use the local formation water with an added 2% potassium chloride as the well washing working fluid, backwash the well to wash out the excess ceramsite sand in the tubing, and the outlet enters the emptying pool until the inlet and outlet water quality is consistent.

[0074] (5) Release: Raise the sand control pipe column to the original suspended load, then rotate the pipe column forward 25-27 times and release the release, and remove all the pipe column above the release.

[0075] Production can begin after the sand control construction is completed and the pump is put into operation.

[0076] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A method for sand control in oil wells of high-muddy, loose sandstone reservoirs, characterized in that, It includes the following steps: Pull out the original production string and sand control string from the well; Lower a sand washing string into the production well for detection. After detecting the sand surface, conduct sand washing; Lower a hole cleaning string to conduct hole cleaning; Lower a pipe scraping string to scrape the pipe and conduct normal circulation well flushing; Lower a casing pressure testing string to conduct pressure testing; Lower a string with a sand washing nib into the casing of the wellbore to conduct pre-treatment of oil layer cleaning and acidification; Use nitrogen foam to evacuate the wellbore; Use the string in the wellbore to detect the sand surface and conduct reverse circulation well flushing; Lower an external sand control string into the well; Magnetic positioning is carried out to make the lower end of the production wire-wrapped screen pipe 1.5 - 2 m lower than the lower boundary of the production oil layer, and the upper end of the production wire-wrapped screen pipe 2.5 - 3 m higher than the upper boundary of the production oil layer; Conduct pipe manifold pressure testing, set and pack the packing tool, pack sand for sand control, and conduct reverse well flushing to obtain the result; The sand washing string includes a tubing and a sand washing nib. The sand washing string is connected from the bottom up with the sand washing nib connecting the tubing to the wellhead; After detecting the sand surface, pump sand washing fluid into the annular space formed by the sand washing string and the casing for sand washing; Stop sand washing when reaching the artificial bottom or the cement plug surface; The sand washing displacement is from 500 to 600 L / min; The pipe scraping string includes a tubing, a tubing reducer joint and a pipe scraper. The lower end of the tubing is connected to the tubing reducer joint, and the lower end of the tubing reducer joint is connected to the pipe scraper; The pipe scraping speed for lowering the pipe is 35 - 40 stands per hour, and scrape the pipe to the top boundary of the oil layer perforation; Pump well flushing fluid from the tubing, and the well flushing fluid returns from the annulus between the tubing and the casing. The displacement of the well flushing fluid is not less than 500 L / min. Stop well flushing after the water quality at the inlet and outlet is consistent, and pull out the pipe scraping string; The casing pressure testing string includes a packer and a tubing connected in sequence from bottom to top; When the packer is lowered to 4 - 6 m from the top boundary of the oil layer perforation interval, lower and rotate the string simultaneously to make the packer set and effectively seal the annular space between the oil pipe and the casing; Then pump well flushing fluid from the annular space between the tubing and the casing. When the injection pressure reaches 70 - 75% of the internal pressure resistance strength of the casing steel grade, stop pumping and hold the pressure for 5 - 7 min. If the pressure is stable without dropping, it is qualified; In the pre-treatment of oil layer cleaning and acidification, it includes the following steps: Fill the wellbore with well flushing fluid, and squeeze in the cleaning agent, displacement fluid, acid fluid, and displacement fluid in sequence; The cleaning agent includes the following components and their weight parts: 10 - 20 parts of organic solvent, 0.5 - 2 parts of alcohol ether amphiphilic surfactant, and 80 - 90 parts of water; The acid fluid includes the following components and their weight parts: 6 - 15 parts of hydrochloric acid, 2 - 9 parts of boric acid, 5 - 13 parts of hydrofluoric acid, 1.5 - 5 parts of corrosion inhibitor, 0.5 - 3 parts of iron ion stabilizer, 1 - 2.5 parts of助排剂 (oil displacement agent), 3 - 5 parts of ammonium chloride, and 50 - 80 parts of water; The oil displacement agent includes one or several of high-carbon fatty alcohol polyoxyethylene ether, methanol, ethylene glycol, and glycerol pentaerythritol; In the step of using nitrogen foam to evacuate the wellbore: Connect the outlet of the air nitrogen making vehicle and the outlet of the cement pump vehicle to the inlet end of the three-way device of the foam generator through a pipe manifold, and then connect the outlet end of the foam generator to the casing gate of the wellhead device with a hard pipeline; Connect the tubing gate of the wellhead device to a hard pipeline and enter the evacuation pool; A cement pump truck pumps foaming liquid into a foam generator at a displacement of 100-150 L / min, while an air nitrogen generator injects nitrogen gas into the foam generator at a displacement of 1000-1200 cubic meters / h; the foaming liquid is a sodium dodecyl sulfate aqueous solution with a mass concentration of 1%-2%. When foam liquid is seen returning from the drain tank, the cement pump truck stops working, and the air nitrogen generator continues construction until no more foam liquid flows out of the drain tank outlet. Keep the casing outlet and oil pipe outlet continuously spraying into the drain tank without obstruction for 8-10 hours. Using the tubing string in the wellbore to detect the sand surface, pumping sand flushing fluid into the annular space formed by the tubing and casing, and simultaneously lowering the tubing string. When the sand is flushed to 30m below the production oil layer, reverse circulation well washing is performed. When clear water is seen at the outlet and there are no sand particles, well washing is stopped and all sand flushing tubing strings in the well are pulled out. The external sand control tubing string is connected from bottom to top in the following order: plug, tubing, centralizer, production wire-wound screen, tubing short section, centralizer, tubing, signal wire-wound screen, and tubing; a flushing string is inserted into the external sand control tubing; a suspension packer is connected to the upper end of the flushing string and the upper end of the external sand control tubing string, and the upper end of the packer is connected to the tubing string to the wellhead; During sand control filling, pre-fluid and guar gum are sequentially injected into the tubing. After the injection pressure stabilizes, sand-carrying fluids with different sand-to-liquid ratios are continuously injected sequentially. When the pump pressure rises to 6-8 MPa, the injection of sand-carrying fluid is stopped, and guar gum fluid exceeding the tubing volume by 2-3 cubic meters is injected. The pump is then stopped until the tubing pressure drops to zero MPa. At this point, the casing gate valve is opened, and sand-carrying fluid with a sand-to-liquid mass ratio of 5-6% is pumped into the tubing in a positive circulation manner at a rate of 500-550 L / min. When the pressure rises to 3-4 MPa... When the pressure reaches 12-14 MPa, stop adding the sand-carrying fluid and continue circulating the well. When the pressure rises to 12-14 MPa, stop the pump and fill the annulus between the screen and casing to saturation. In the step of continuously and sequentially injecting sand-carrying fluids with different sand-to-fluid ratios, the sand-to-fluid ratio of the injected sand-carrying fluid gradually increases. The pre-polymer is composed of dimethyl diallyl ammonium chloride, ammonium chloride, and water in a mass ratio of 0.5-1:2-3:

100. The guar gum solution is an aqueous solution of hydroxypropyl guar gum thickener with a mass percentage concentration of 0.3-0.6%.

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