A hot melt bismuth agent alloy for oil and gas wellbore seal repair and methods of making and using the same

Abstract

The present application belongs to the technical field of oil and gas wellbore integrity plugging and repairing, and discloses a hot-melt bismuth agent alloy for sealing and repairing of oil and gas wellbore, and a preparation and use method thereof. The hot-melt bismuth agent alloy is composed of bismuth, tin, lead and silver in a certain proportion, and is prepared by mixing bismuth alloy powder into bismuth colloidal suspension with a particle size of 100-500 nm, mixing with silicate cement and other raw materials, and adding defoaming agent, chelating agent and pH regulator. The alloy has the advantages of high compressive strength, corrosion resistance, wide range of thermal expansion coefficient, etc. The use method is as follows: first, place the hot-melt bismuth agent alloy at the target position in the oil and gas well, melt it by using heating methods such as electric heating wire, then inject it into the damaged position of the wellbore and cool and solidify, so as to realize the repair and plugging of the wellbore.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of oil and gas wellbore integrity plugging and repairing, and particularly relates to a hot-melt bismuth agent alloy for oil and gas wellbore sealing and repairing, and a preparation and use method thereof. BACKGROUND

[0002] With large-scale exploitation of oil and gas resources, different forms of damage may occur in the wellbore during long-term production. According to statistics, about 2% to 5% of the wellbores need to be repaired every year. The wellbore damage mainly includes damage caused by corrosion, damage under dynamic load, operational damage and accident damage. Wellbore damage may cause oil and gas leakage and cross-layer pollution.

[0003] Among them, (1) the damage caused by corrosion is introduced as follows: the oil and gas wellbore is exposed to the formation environment for a long time, and the wellbore metal material is prone to various corrosion. According to the different corrosion conditions, it can be divided into uniform corrosion, pitting corrosion, stress corrosion cracking, hydrogen-induced cracking, and microbial influence corrosion. Among them, microbial corrosion can cause both uniform corrosion and local corrosion. The damage caused by oil and gas well corrosion is mainly manifested as wall thinning, pitting, and crevice corrosion, etc. (2) The damage under dynamic load is introduced as follows: the wellbore bears large axial tension, torsional torque, bending moment and external pressure load during production. Under the action of these complex dynamic loads, the wellbore may be damaged by fatigue fracture, plastic deformation, brittle fracture, etc. In a high humidity environment, fatigue fracture and stress corrosion cracking often coexist and promote each other, which seriously endangers the integrity of the wellbore. (3) The operational damage and accident damage are introduced as follows: improper operation or equipment accidents may also cause wellbore damage, such as drill bit accidents, fracturing operation accidents, and axial scratching damage caused by improper anchoring, etc. These damages are sudden and have a large damage area. Wellbore damage may cause oil and gas leakage and cross-layer pollution. In order to ensure the long-term operation integrity of the wellbore, repair measures must be taken to plug the damaged part in time.

[0004] In order to ensure the long-term operation integrity of the wellbore, it is necessary to take repair measures to block the damaged part in time. At present, the commonly used plugging repair technologies include water-based glue plugging technology, oil-based glue plugging technology, mechanical plugging technology, polymer gel plugging technology, cement plugging technology, fire plugging technology and the like. Specifically, (1) the water-based glue plugging technology is introduced as follows: the water-based glue is composed of water, polymer and filler and the like, and has certain strength, sealing property and compression resistance after solidification. However, the solidification time is long, the temperature is sensitive, the downhole environment is complex, the solidification is not easy to control, and the use effect is affected. Moreover, the strength and compression resistance are limited, and the wellbore repair of high pressure and large diameter cannot be adapted. (2) The oil-based glue plugging technology is introduced as follows: the oil-based glue has short solidification time and better mechanical properties than the water-based glue. However, the raw material cost is high, and the sealing and mechanical properties still cannot meet the repair requirements of the wellbore of high parameters. (3) The mechanical plugging technology is introduced as follows: the plugging device made of prefabricated rubber, metal or composite material is used to realize plugging by mechanical expansion force. This method is simple in operation and has high success rate, but is only suitable for plugging of local damage and cannot effectively repair long section and large area damage of the wellbore. (4) The polymer gel plugging technology is introduced as follows: two kinds of liquid monomer mixtures that react with each other are pumped into the downhole to realize plugging by rapid volume expansion of the gel. However, the gel strength is low and cannot adapt to the high pressure environment. (5) The cement plugging technology is introduced as follows: the cement slurry is pumped into the downhole to fill the damage gap and solidify to form cement stone to prevent oil and gas leakage. This technology is mature and reliable, and is convenient to use. However, the compression strength of the cement is limited, and the solidification time is long, so that the repair effect of the wellbore damage of high parameters and long section is not good. (6) The fire plugging technology is introduced as follows: the high-temperature molten substance is generated by combustion reaction to realize high-pressure plugging. This method has good sealing effect, but needs a combustion device, and the operation is complex, so that it is only suitable for downhole plugging and cannot be used for long section damage. However, the above plugging repair technologies have certain limitations and cannot meet the high-quality repair requirements of the long section, large area and high parameter damage of the oil and gas wellbore. SUMMARY

[0005] In view of the problems in the above background art and the limitations of the existing experimental device, the purpose of the present application is to provide a hot-melt bismuth agent alloy for sealing and repairing the oil and gas wellbore, and a preparation and use method thereof. The present application can meet the high-quality repair requirements of the long section, large area and high parameter damage of the oil and gas wellbore.

[0006] To achieve the above purpose, the technical scheme adopted by the present application is as follows:

[0007] A preparation method of a hot-melt bismuth agent alloy for sealing and repairing the oil and gas wellbore, comprising the following processes:

[0008] The bismuth agent alloy mixed powder is configured into a suspension with deionized water;

[0009] The suspension is prepared into a bismuth colloidal suspension;

[0010] Mix the bismuth colloidal suspension with ordinary Portland cement, then add defoaming agent and mix evenly, then add chelating agent and pH regulator and mix evenly to obtain the hot-melt bismuth agent alloy for sealing repair of oil and gas wellbore.

[0011] Preferably, the bismuth agent alloy mixed powder is an alloy powder of Bi, Sn, Pb and Ag, and the alloy powder contains Bi 45-55%, Sn 15-35%, Pb 10-25% and Ag 5-10% by mass.

[0012] Preferably, the solid mass percentage concentration in the suspension is 10-15%.

[0013] Preferably, the bismuth colloidal suspension has a particle size of 100-500 nm and a mass concentration of 10-15%.

[0014] Preferably, the ordinary Portland cement is P.O 42.5 ordinary Portland cement.

[0015] The defoaming agent is an alkane defoaming agent, and the alkane defoaming agent is one or more of polyethylene wax, polypropylene wax, polypropylene wax, hydrogenated wax, microcrystalline wax and silicone oil.

[0016] The chelating agent is an organic chelating agent, and the organic chelating agent is one or more of EDTA, NTA, DTPA, EGTA and GLDA.

[0017] The pH regulator is sodium carbonate or an organic acid, and the organic acid is tartaric acid or citric acid.

[0018] Preferably, 50 g of ordinary Portland cement, 0.3-0.5% by volume of defoaming agent, 0.2-0.3% by volume of chelating agent and 0.15-0.2% by volume of pH regulator are added to 50 ml of bismuth colloidal suspension.

[0019] Preferably, the bismuth colloidal suspension is stirred with ordinary Portland cement for 2-3 min, the defoaming agent is added and stirred for 3-5 min, and the chelating agent and pH regulator are added and stirred for 10-15 min. The stirring rate of the suspension is 100-200 r / min.

[0020] The application also provides a hot-melt bismuth agent alloy for sealing repair of oil and gas wellbore, which is prepared by the preparation method of the application.

[0021] The method for using the hot-melt bismuth agent alloy for sealing and repairing oil and gas wellbore as described above comprises the following processes:

[0022] The hot-melt bismuth agent alloy is lowered to the target position of the oil and gas wellbore, and then the hot-melt bismuth agent alloy is heated to melt and fill the target position, and after the hot-melt bismuth agent alloy is cooled and solidified, the target position of the gas wellbore is repaired or plugged.

[0023] Preferably, the process for plugging the target position of the oil and gas wellbore comprises:

[0024] The target position of the oil and gas wellbore is isolated by the packer, the hot-melt bismuth agent alloy is transported to the target position by the bismuth alloy filling bin, and then the hot-melt bismuth agent alloy in the bismuth alloy filling bin is heated and melted into a liquid state by the heating module, and then the liquid hot-melt bismuth agent alloy in the bismuth alloy filling bin is filled on the upper side of the packer, and after the hot-melt bismuth agent alloy is cooled and solidified, the target position of the oil and gas wellbore is plugged.

[0025] The present application has the following beneficial effects:

[0026] 1) The bismuth agent plugging plug prepared by the present application has good air tightness and high compressive strength. The solidified compressive strength is as high as 30 MPa or more, fully meeting the plugging and repairing needs of high-pressure wellbores, and the sealing and repairing effect is remarkable; 2) The bismuth agent plugging plug is corrosion-resistant. The bismuth metal itself has good acid and alkali resistance in the composition of the bismuth agent plugging plug, and can withstand the corrosion of various chemicals. Therefore, the bismuth agent plugging plug has good corrosion resistance in various chemical media and can be used in various corrosive environments; 3) The hot-melt bismuth agent alloy of the present application can completely penetrate into the damaged space of the wellbore in a molten state, the repair wound length is short, and the construction cost is greatly reduced; 4) The hot-melt bismuth agent alloy has a low melting point and a large thermal expansion coefficient, which can reach 16x10 -6 ~ 22x10 -6 / ℃, which can generate sufficient solidification pressure during solidification; 5) Bismuth and its alloys have certain micro-toxicity, which can inhibit or kill the growth and reproduction of bacteria, prevent secondary pollution and corrosion damage of microorganisms to the bismuth agent alloy, and improve the long-term sealing effect; 6) The construction is simple and convenient, and can be applied to land or offshore oil and gas wells to achieve remote and fixed-point plugging in the well. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 The bismuth agent preparation and plugging flowchart in the embodiments of the present application;

[0028] Figure 2 The heating module and the hot-melt bismuth alloy combination structure schematic diagram in the embodiments of the present application;

[0029] Figure 3A schematic diagram of simulating a wellbore structure in an embodiment of the present application;

[0030] Figure 4 A schematic diagram of simulating a plugging test of an underground gas storage in an embodiment of the present application;

[0031] Figure 5 A schematic diagram of implementing plugging of an oil and gas well in an embodiment of the present application.

[0032] In the figure: 1, heating module, 2, hot-melt bismuth agent alloy sleeve, 3, pulley, 4, ignition device cable, 5, annulus, 6, packer, 7, bismuth agent alloy filling cartridge, 8, injection module, 9, detection module, 10, thermocouple, 11, wellbore. DETAILED DESCRIPTION

[0033] The present application will be further described in detail below in conjunction with the accompanying drawings and embodiments.

[0034] In the description of the present application, it should be noted that the terms "upper", "lower", "inner", "outer", "top / bottom end" and the like indicate the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation,

[0035] Reference Figure 1 In the first exemplary embodiment of the present application, the preparation method of the hot-melt bismuth agent alloy for sealing and repairing of an oil and gas wellbore mainly comprises the following steps:

[0036] Step 1, selecting an appropriate bismuth agent alloy, preferably a Bi, Sn, Pb, Ag four-element alloy; the composition of the bismuth agent alloy ranges from 45% to 70% Bi, 15% to 35% Sn, 10% to 25% Pb, and 5% to 10% Ag by mass percentage.

[0037] Step 2, mix the selected bismuth agent alloy powder with deionized water to prepare a mixed solution with a solid mass percentage concentration of 10% to 15%, and place the mixed solution in an ultrasonic cleaner for ultrasonic treatment for 30 minutes to prepare a uniform bismuth agent alloy powder suspension;

[0038] Step 3, place the bismuth agent alloy powder suspension in a high-speed homogenizer for 2 hours to obtain a bismuth colloid suspension with a particle size of 100 to 500 nm and a concentration of 10% to 15%; the suspension does not settle significantly after 24 hours, indicating good stability;

[0039] Step 4: Take 50 ml of the above bismuth colloidal suspension and mix it with 50 g of ordinary silicate cement (P.O42.5) for 2-3 min. Add 0.3%-0.5% volume percentage of defoamer and mix for 3-5 min. Then add 0.2%-0.3% volume percentage of chelating agent and 0.15%-0.2% volume percentage of pH adjuster and continue mixing for 10-15 min to prepare a uniform and pumpable hot-melt bismuth alloy.

[0040] In the above-described scheme of the present invention, the defoamer is an alkane-based defoamer, which is one or more of polyethylene wax, polypropylene wax, hydrogenated wax, microcrystalline wax and silicone oil; the chelating agent is an organic chelating agent (one or more of EDTA, NTA, DTPA, EGTA and GLDA); and the pH adjuster is sodium carbonate and organic acid (tartaric acid, citric acid).

[0041] like Figure 2 As shown, the hot-melt bismuth alloy sleeve 2 prepared by the above-described scheme of the present invention is connected to the detachable steel heating module 1 via pulley 3 and cable 4 and inserted into the gas storage tank model, as shown. Figure 3 As shown, the model consists of two casings. The outer diameter of the inner casing 13 is Φ100mm and the inner diameter is Φ80mm. The width of the gap (i.e., the annulus 5) around the casing 13 is 10mm and the length is 500mm.

[0042] After the hot-melt bismuth alloy was injected into annulus 5, it was cured at room temperature for 24 hours. Upon removal of the sample, it was observed that the hot-melt bismuth alloy was uniformly distributed within annulus 5 and expanded towards the annular wall.

[0043] The airtightness of the sample was tested using a helium detector, and the results showed that the sample was completely airtight and met the sealing requirements.

[0044] The above examples demonstrate that the method of the present invention can obtain a uniformly distributed hot-melt bismuth alloy and achieve complete sealing. This method requires no on-site mixing, is simple to operate, and can be implemented using existing cementing equipment, thus overcoming the operational difficulties encountered in related patents. By adjusting the preparation process of the bismuth suspension, hot-melt bismuth alloys with different volume fractions and particle sizes can be obtained, optimizing the expansion effect and operability.

[0045] A second exemplary embodiment of the present invention provides a method for plugging oil and gas wellbores using a hot-melt bismuth alloy material. The plugging method can be implemented using the hot-melt bismuth alloy material described in the first exemplary embodiment above, and the plugging method mainly includes the following steps:

[0046] Step 1, when drilling into the reservoir, determine the lithology by mud logging; after entering the reservoir, determine the in-situ pressure and temperature gradient by pressure and temperature measurement, which provides reference data for later gas storage. The geothermal gradient of salt rock layer is relatively high, and the temperature is generally 80-120℃. The pressure gradient is usually higher than the normal pressure gradient of oil and gas due to the influence of salt brine pressure.

[0047] Step 2, according to the downhole temperature conditions, select the hot-melt bismuth agent alloy material with matching melting point. When the downhole temperature is 80-100℃, select Bi-Sn bismuth tin alloy with a melting point of 138℃; when the temperature exceeds 150℃, select Bi-Ag bismuth silver alloy with a melting point of 221℃. The alloy material has been fully tested and verified to meet the requirements of various temperature working environments downhole.

[0048] Step 3, according to the melting point of bismuth alloy, calculate the formula of designed hot-melt agent. Configure the hot-melt agent that can make the reaction temperature reach 30-50℃ above the melting point of bismuth alloy, for example, Bi-Sn bismuth tin low-temperature hot-melt bismuth agent alloy with a melting point of 138℃, the reaction temperature is controlled at 180-200℃. Optimize the configuration of hot-melt agent to prevent burning through the heating module 1, which can adopt a detachable steel heating module.

[0049] Step 4, refer to Figure 4 and Figure 5 , connect the end of the bismuth alloy filling chamber 7 with the packer 6 through the ignition device cable 4, and slowly put it into the downhole together with the heating module 1, injection module 8 and other equipment, monitor the cable tension to keep it at 10-15kN, and put it into the preset downhole target layer. Monitor and record operating parameters such as tension, displacement, rotation speed and other data.

[0050] Step 5, after reaching the preset downhole target layer, open the packer 6, and the packer 6 is opened to realize interlayer isolation. The heating wire in the heating module 1 is powered on through the ignition device cable 4 to ignite the hot-melt agent, and the hot-melt agent reaction fully releases heat to melt the bismuth alloy in the bismuth alloy filling chamber 7 into liquid state.

[0051] Step 6, after the bismuth alloy is melted into liquid state, open the injection module connected to the top of the bismuth agent filling chamber 7, and the bottom of the bismuth agent filling chamber 7 is provided with a pressure outlet. The high-pressure gas pump or booster equipment in the injection module injects the liquid bismuth alloy solution in the bismuth agent filling chamber 7 from the pressure outlet of the bismuth agent filling chamber 7 into the wellbore above the packer 6.

[0052] Step 7, after injecting the liquid bismuth alloy into the wellbore, quickly extract the heating module 1 and bismuth agent filling chamber 7 and other equipment within a preset time, at which time the temperature of the liquid bismuth alloy is still relatively high, and the residual heat can keep the liquid bismuth alloy in a flowing and diffusing state. At the same time, the power supply is turned off and no longer heated. The extraction time is accurately controlled within 2-5min.

[0053] Step 8, install a radio frequency transceiver downhole, monitor the solidification and cooling process of the bismuth alloy through the downhole radio frequency transceiver, and transmit information to the ground to record the real-time temperature change curve. The solidification time of liquid bismuth alloy is affected by the downhole temperature, generally 2-4 hours. Strictly control the solidification time to avoid early pressure test.

[0054] Step 9, after the solidification temperature stabilizes for 6 hours, the solidified bismuth alloy body is subjected to pressure test. The pressure is gradually increased along the pressure gradient, and when it reaches 1.25 times the design pressure and remains stable for 4 hours without pressure drop, the test is completed. The pressure curve change is continuously monitored and recorded during the test.

[0055] Step 10, subsequent multiple pressure tests are carried out in the reservoir to detect pressure recovery. Good pressure recovery indicates that there is no obvious damage or leakage channel in the reservoir. After the pressure test confirms that the gas storage system is complete and reliable, start from the upper guide well to fill high-pressure natural gas in layers and steps, and carry out underground gas storage. The bismuth alloy body provides a stable long-term wellbore barrier.

[0056] In the above-mentioned second exemplary embodiment of the present application, the temperature of the hot melt agent is required to reach 30-50℃ above the melting point temperature of the hot melt bismuth alloy to fully melt the bismuth alloy. For example, if the melting point of the bismuth alloy is 138℃, the reaction temperature should be controlled at 168-188℃. The ratio of oxidizer to fuel can be adjusted to control the reaction heat effect and optimize the reaction temperature. Generally, the mass ratio of oxidizer to fuel is designed to be 1:0.5-1.5.

[0057] Catalysts, stabilizers and other auxiliary additives can also be added to the hot melt agent to help complete the reaction and control the reaction rate. Common catalysts include CuO, MnO2, etc.; stabilizers include borax, etc. A typical formula can be: potassium permanganate, formic acid, ammonium nitrate, CuO, borax, with a mass ratio of 2:1:1:0.1:0.2. The burning temperature of this formula is 180℃ after testing.

[0058] In the above-mentioned second exemplary embodiment of the present application, the well is flattened and leveled before the running of the packer 6 to position, and the pressure parameters are recorded for subsequent comparison and reference. The pressure control accuracy is high, and the leveling time is not more than 2h. The top end of the packer 6 is connected to the bottom end of the bismuth alloy filling bin 7, which is a circular container storing hot melt bismuth alloy for melting and plugging. The bismuth alloy filling bin 7 and the heating module 1 inside the bismuth alloy filling bin 7 are both circular in shape, so that they can be closely fitted to ensure effective diffusion of temperature and sufficient heating of the bismuth alloy.

[0059] The heating module 1 is placed in the pre-prepared hot melt agent, so that the heat released by the hot melt agent can melt the bismuth alloy in the bismuth alloy filling bin 7. The top end of the heating module 1 is connected with the ignition device cable 4, and the ignition device cable 4 can heat the heating wire in the heating module 1 after being electrified, so as to ignite the hot melt agent in the heating module 1. The bottom end of the injection module 8 is connected with the top end of the bismuth alloy filling bin 7. When the hot melt agent in the heating module 1 fully releases heat to melt the bismuth alloy in the bismuth alloy filling bin 7, the liquid alloy in the bismuth alloy filling bin 7 can be injected into the wellbore above the packer 6 by using a high-pressure gas pump or a pressure boosting device. The bottom end of the detection module 9 is connected with the top end of the injection module 8, and the detection module 9 monitors and records operating parameters such as tension, displacement, and rotation speed.

[0060] In order to better understand the above-mentioned exemplary embodiments of the present application, the following further illustrates them in combination with specific application examples.

[0061] Embodiment 1

[0062] The preparation method and plugging method of the hot melt bismuth agent alloy for sealing the oil and gas wellbore in this embodiment mainly include the following steps:

[0063] Step 1, the components of the bismuth agent alloy in this embodiment include Bi 55%, Sn 15%, Pb 25%, and Ag 5% by mass percentage.

[0064] Step 2, the selected bismuth agent alloy powder is mixed with deionized water to prepare a mixed solution with a solid mass percentage of 10%, and the mixed solution is placed in an ultrasonic cleaner for ultrasonic treatment for 30 min to prepare a uniform bismuth agent alloy mixed powder suspension. The bismuth agent alloy mixed powder suspension is placed in a high-speed homogenizer for 2 h to obtain a bismuth colloid suspension with a particle size of 100-500 nm and a concentration of 10%; the suspension does not obviously settle after being placed for 24 h, indicating good stability.

[0065] Step 3, 50 ml of the above bismuth colloid suspension is mixed with 50 g of ordinary Portland cement (P.O 42.5) for 3 min, 0.5% volume percentage of polyethylene wax defoaming agent is added, mixed for 5 min, then 0.3% volume percentage of EDTA chelating agent and 0.2% volume percentage of sodium carbonate pH adjuster are added, and the mixing is continued for 15 min to prepare a uniform pumpable hot melt bismuth agent alloy.

[0066] Step 4, the prepared hot melt bismuth agent alloy sample is placed in the heater of a melting point instrument, heated to completely melt the sample, and the melting point of the prepared hot melt bismuth agent alloy is recorded as 125℃.

[0067] Step 5, according to the melting point of bismuth alloy, calculate the equipped hot melt agent. The formula used can be: potassium permanganate, formic acid, ammonium nitrate, CuO, borax ratio of 2:1:1:0.1:0.2. The formula tested combustion temperature is 180℃. The reaction temperature is higher than the melting point of the prepared bismuth agent alloy by 55℃, which is sufficient to completely melt the bismuth alloy.

[0068] Step 6, by igniting the device cable 4, connecting the packer 6 to the end of the bismuth alloy filling bin 7, together with the heating module 1, injection module 8 and other equipment slowly put into the well, monitor the cable tension to keep at 10-15kN, put into the preset downhole target layer. Monitor and record operating parameters such as tension, displacement, speed and other data. After reaching the preset downhole target layer, open the packer 6, and the packer 6 is opened to achieve interlayer isolation. The heating wire in the heating module 1 is energized by the ignition device cable 4 to ignite the hot melt agent, and the hot melt agent reaction fully releases heat to melt the bismuth alloy in the bismuth alloy filling bin 7 into liquid state.

[0069] Step 7, after the bismuth alloy is melted into liquid state, open the injection module 8 connected to the top of the bismuth agent filling bin 7, and set a pressure outlet at the bottom end of the bismuth agent filling bin 7. The high-pressure gas pump or booster in the injection module 8 injects the liquid bismuth alloy solution in the bismuth agent filling bin 7 from the pressure outlet into the wellbore above the packer 6. After injecting the liquid bismuth alloy into the wellbore, the heating module 1 and the bismuth agent filling bin 7 and other equipment are quickly extracted within a predetermined time. At this time, the temperature of the liquid bismuth alloy is still high, and the residual heat can keep the liquid bismuth alloy in a flowing and diffusing state. At the same time, the power supply is turned off and no longer heated. The extraction time is accurately controlled within 4 minutes.

[0070] Step 8, install a radio frequency transceiver downhole, monitor the solidification and cooling process of the bismuth agent alloy through the downhole radio frequency transceiver, and transmit information to the ground to record the real-time temperature change curve. The solidification time of the liquid bismuth alloy is affected by the downhole temperature, and the solidification time of this embodiment is 3 hours.

[0071] Step 9, after the solidification temperature is stable for 6 hours, the interlayer pressure integrity test is performed on the bismuth alloy body. Hydraulic oil or gas is used as the medium. The test pressure is not less than 1.25 times the expected use pressure, and the pressure is gradually increased along the pressure gradient for 5 hours. After confirming that there is no leakage and no pressure drop, the test is completed. The pressure curve change is continuously monitored and recorded during the test.

[0072] Step 10, subsequent multiple pressure tests are performed in the reservoir to detect pressure recovery. Good pressure recovery indicates that there is no obvious damage or leakage channel in the reservoir range. After confirming that the gas storage system is complete and reliable through the pressure test, start from the upper guide well to fill high-pressure natural gas in layers and steps to store gas underground. The bismuth agent alloy body provides a stable long-term wellbore barrier.

[0073] Step 11, after curing, the compressive strength is as high as 30 MPa or more, fully meeting the plugging and repairing needs of high-pressure wellbore. Using a thermal expansion coefficient tester, the linear expansion amount of the bismuth alloy prepared above is calculated according to the expansion amount during the process of increasing the temperature of the bismuth alloy from 20℃ to the melting point of the bismuth alloy, 180℃, at an ambient temperature of 20℃. The test results show that the thermal expansion coefficient of the hot-melt bismuth alloy prepared in this embodiment is 16x10 -6 / ℃. The produced fluid is obtained from the well bottom, and the produced fluid is divided into multiple groups for design control experiments, and different concentrations of bismuth are added to each group to test the bacteriostatic rate of the hot-melt bismuth alloy on common oilfield microorganisms. The results can show that as the content of bismuth increases, the inhibition of bacterial growth is enhanced. This indicates that bismuth elements can play a certain bactericidal function, which is conducive to improving the long-term plugging effect of the hot-melt bismuth alloy and preventing secondary pollution and corrosion damage of microorganisms to the bismuth alloy.

[0074] Embodiment 2

[0075] The preparation method and plugging method of the hot-melt bismuth alloy for sealing oil and gas wellbore in this embodiment mainly include the following steps:

[0076] Step 1, the components of the bismuth alloy in this embodiment include Bi 45%, Sn 35%, Pb 12%, and Ag 8% by mass percentage.

[0077] Step 2, the selected bismuth alloy mixed powder is mixed with deionized water to prepare a mixed solution with a solid mass percentage concentration of 10%, and the mixed solution is placed in an ultrasonic cleaner for ultrasonic treatment for 30 min to prepare a uniform bismuth alloy mixed powder suspension. The bismuth alloy mixed powder suspension is placed in a high-speed homogenizer for 2 h to obtain a bismuth colloid suspension with a particle size of 100-500 nm and a concentration of 10%; the suspension has no obvious sedimentation after being placed for 24 h, indicating good stability;

[0078] Step 3, 50 ml of the above bismuth colloid suspension is mixed with 50 g of ordinary Portland cement (P.O 42.5) for 3 min, 0.5% volume percentage concentration of polypropylene wax defoaming agent is added, mixed for 5 min, then 0.3% volume percentage concentration of NTA chelating agent and 0.2% volume percentage concentration of tartaric acid pH adjuster are added, and the mixing is continued for 15 min to prepare a uniform and pumpable hot-melt bismuth alloy.

[0079] Step 4, the hot-melt bismuth alloy sample prepared above is placed in the heater of the melting point instrument, heated to complete melting of the sample, and the melting point of the hot-melt bismuth alloy prepared above is recorded as 135℃.

[0080] Step 5, according to the melting point of bismuth alloy, calculate the amount of hot melt agent. The formula used can be: potassium permanganate, formic acid, ammonium nitrate, CuO, borax with a mass ratio of 2:1:1:0.1:0.2. The formula tested combustion temperature is 180℃. Make the reaction temperature higher than the melting point of the prepared bismuth agent alloy by 45℃, which is enough to completely melt the bismuth alloy.

[0081] Step 6, the packer 6, bismuth agent filling bin 7 and other equipment are transported to the downhole through the ignition device cable 4 to carry out plugging operation on the oil and gas wellbore, and the operation steps are the same as those described in example 1.

[0082] Step 7, install a radio frequency transceiver downhole, monitor the solidification and cooling process of the bismuth alloy through the downhole radio frequency transceiver, and transmit the information to the ground to record the real-time temperature change curve. The solidification time of liquid bismuth alloy is affected by the downhole temperature, and the solidification time of this example is 3 hours.

[0083] Step 8, after the solidification temperature is stable for 6 hours, the interlayer pressure integrity test is carried out on the bismuth alloy body. Hydraulic oil or gas is used as the medium. The test pressure is not less than 1.25 times the expected use pressure, and the pressure is gradually increased along the pressure gradient for 5 hours, and the test is completed after confirming that there is no leakage and no pressure drop. The pressure curve change is continuously monitored and recorded during the test. Subsequently, multiple pressure tests are carried out in the reservoir to detect the pressure recovery. Good pressure recovery indicates that there is no obvious damage or leakage channel in the reservoir range. After confirming that the gas storage system is complete and reliable, start from the upper guide well to fill high-pressure natural gas in layers and steps to carry out underground gas storage. The bismuth alloy body provides a stable long-term wellbore barrier.

[0084] Step 9, after testing, the solidified compressive strength is as high as more than 30MPa, which fully meets the plugging and repair needs of high-pressure wellbore. The thermal expansion coefficient tester is used to test the hot melt bismuth alloy prepared in this example, and the operation steps are the same as those in example 1. The test results show that the thermal expansion coefficient of the hot melt bismuth alloy prepared in this example is 22×10 -6 / ℃. The produced fluid is obtained from the bottom of the well, and the produced fluid is divided into multiple groups for design control experiments, and different concentrations of bismuth are added to each group to test the bacteriostatic rate of the hot melt bismuth alloy on common oilfield microorganisms. The results can show that as the content of bismuth increases, the inhibition of bacterial growth increases. This indicates that bismuth can play a certain bactericidal function, which is beneficial to improve the long-term plugging effect of the hot melt bismuth alloy and prevent secondary pollution and corrosion damage of microorganisms to the bismuth alloy.

[0085] Example 3

[0086] The preparation method and plugging method of the hot melt bismuth alloy for sealing the oil and gas wellbore in this example mainly include the following steps:

[0087] Step 1, the composition of the bismuth agent alloy in this embodiment includes Bi 50%, Sn 30%, Pb 10%, and Ag 10% by mass percentage.

[0088] Step 2, the selected bismuth agent alloy mixed powder is mixed with deionized water to prepare a mixed solution with a solid mass percentage of 10%, and the mixed solution is placed in an ultrasonic cleaner for ultrasonic treatment for 30 min to prepare a uniform bismuth agent alloy mixed powder suspension. The bismuth agent alloy mixed powder suspension is placed in a high-speed homogenizer for 2 h to obtain a bismuth colloid suspension with a particle size of 100-500 nm and a concentration of 10%; the suspension is placed for 24 h without obvious sedimentation, indicating good stability;

[0089] Step 3, 50 ml of the above bismuth colloid suspension is mixed with 50 g of ordinary Portland cement (P.O 42.5) for 3 min, 0.5% of a hydrogenated wax defoaming agent by volume percentage is added, mixed for 5 min, then 0.3% of a DTPA chelating agent by volume percentage and 0.2% of a citric acid pH adjuster by volume percentage are added, and the mixing is continued for 15 min to prepare a uniform and pumpable hot-melt bismuth agent alloy.

[0090] Step 4, the hot-melt bismuth agent alloy sample prepared above is placed in the heater of a melting point instrument, heated until the sample is completely melted, and the melting point of the hot-melt bismuth agent alloy prepared above is recorded as 130℃.

[0091] Step 5, according to the melting point of the bismuth alloy, the hot-melt agent is calculated. The formula used can be: potassium permanganate, formic acid, ammonium nitrate, CuO, borax with a mass ratio of 2:1:1:0.1:0.2. The formula is tested to have a burning temperature of 180℃. The reaction temperature is higher than the melting point of the prepared bismuth agent alloy by 50℃, which is sufficient to completely melt the bismuth alloy.

[0092] Step 6, the packer 6, bismuth agent filling bin 7 and other equipment are transported to the downhole through the ignition device cable 4 to carry out plugging operations on the oil and gas wellbore, and the operation steps are the same as those described in embodiment 1.

[0093] Step 7, a radio frequency transceiver is installed downhole, the solidification and cooling process of the bismuth agent alloy is monitored through the downhole radio frequency transceiver, and the information is transmitted to the ground to record the real-time temperature change curve. The solidification time of the liquid bismuth alloy is affected by the downhole temperature, and the solidification time in this embodiment is 3 hours.

[0094] Step 8, after 6 hours of stabilization at the curing temperature, the bismuth alloy body is subjected to an interlaminar pressure integrity test. Hydraulic oil or gas is used as the medium. The test pressure is not less than 1.25 times the expected service pressure, and is increased stepwise along the pressure gradient for 5 hours, and the test is completed after confirming that there is no leakage and no pressure drop. The pressure curve is continuously monitored and recorded during the test. Subsequent multiple pressure tests are performed in the reservoir to detect pressure recovery. Good pressure recovery indicates that there are no obvious damage or leakage channels in the reservoir range. After the gas storage system is confirmed to be complete and reliable by the pressure test, the high-pressure natural gas is injected into the reservoir in layers and steps from the upper guide well, and the gas is stored underground. The bismuth agent alloy body provides a stable long-term wellbore barrier.

[0095] Step 9, after testing, the compressive strength after curing is as high as 30 MPa or more, fully meeting the plugging and repair requirements of high-pressure wellbores. The thermal expansion coefficient tester is used to test the hot-melt bismuth agent alloy prepared in this embodiment, and the operation steps are the same as in Example 1. The test results show that the thermal expansion coefficient of the hot-melt bismuth agent alloy prepared in this embodiment is 19 x 10 -6 / ℃. The produced fluid is obtained from the bottom of the well, and the produced fluid is divided into multiple groups for design control experiments, and different concentrations of bismuth are added to each group to test the bacteriostatic rate of the hot-melt bismuth agent alloy on common oilfield microorganisms. The results show that as the content of bismuth increases, the inhibition of bacterial growth increases. This indicates that bismuth can play a certain bactericidal function, which is beneficial to improve the long-term plugging effect of the hot-melt bismuth agent alloy and prevent secondary pollution and corrosion damage of microorganisms to the bismuth agent alloy.

Claims

1. A method for the preparation of a hot-melt bismuthing alloy for oil and gas wellbore seal repair, characterized by, The process comprises the following steps: a bismuth agent alloy mixed powder is configured into a suspension with deionized water; the suspension is made into a bismuth colloidal suspension; specifically, the bismuth agent alloy mixed powder suspension is processed in a high-speed homogenizer to obtain a bismuth colloidal suspension with a particle size of 100-500 nm and a concentration of 10%-15%; the bismuth colloidal suspension is uniformly mixed with ordinary Portland cement, then a defoaming agent is added and uniformly mixed, then a chelating agent and a pH regulator are added and uniformly mixed to obtain the hot-melt bismuth agent alloy for oil and gas wellbore sealing repair; the bismuth agent alloy mixed powder is an alloy powder of Bi, Sn, Pb and Ag, and the alloy powder comprises, in mass percentage, Bi 45%-55%, Sn 15%-35%, Pb 10%-25% and Ag 5%-10%; the solid mass percentage concentration in the suspension is 10%-15%.

2. A method of preparing a hot-melt bismuth agent alloy for sealing and repairing oil and gas wellbore according to claim 1, characterized in that, the ordinary Portland cement is P.O 42.5 ordinary Portland cement; the defoaming agent is an alkane defoaming agent, which is one or more of polyethylene wax, polypropylene wax, hydrogenated wax, microcrystalline wax and silicone oil; the chelating agent is an organic chelating agent, which is one or more of EDTA, NTA, DTPA, EGTA and GLDA; the pH regulator is sodium carbonate or an organic acid, which is tartaric acid or citric acid.

3. A method of preparing a hot-melt bismuth alloy for sealing and repairing oil and gas wellbore according to claim 2, characterized in that, 50 g of ordinary Portland cement, 0.3%-0.5% of the defoaming agent in volume percentage, 0.2%-0.3% of the chelating agent in volume percentage and 0.15%-0.2% of the pH regulator in volume percentage are added to every 50 ml of the bismuth colloidal suspension.

4. A method of preparing a hot-melt bismuth agent alloy for sealing and repairing oil and gas wellbore according to claim 3, characterized in that, The bismuth colloidal suspension is stirred and mixed with the ordinary Portland cement for 2-3 min, the defoaming agent is added and mixed for 3-5 min, and the chelating agent and the pH regulator are added and mixed for 10-15 min, and the stirring rate of the suspension is 100-200 r / min.

5. A hot melt bismuth agent alloy for oil and gas wellbore seal repair, characterized by, The hot-melt bismuth agent alloy for oil and gas wellbore sealing repair is prepared by the preparation method of any one of claims 1-4.

6. The method of using a hot-melt bismuth alloy for oil and gas wellbore seal repair of claim 5, wherein, The process comprises the following steps: the hot-melt bismuth agent alloy is lowered to a target position in an oil and gas wellbore, then the hot-melt bismuth agent alloy is heated to melt and fill the hot-melt bismuth agent alloy in the target position, and after the hot-melt bismuth agent alloy is cooled and solidified, the target position in the oil and gas wellbore is repaired or plugged.

7. The method of using a hot-melt bismuth alloy for oil and gas wellbore seal repair of claim 6, wherein, The process of plugging the target position in the oil and gas wellbore comprises the following steps: the target position in the oil and gas wellbore is isolated by an annular packer (6), the hot-melt bismuth agent alloy is delivered to the target position by a bismuth alloy filling chamber (7), then the hot-melt bismuth agent alloy in the bismuth alloy filling chamber (7) is heated and melted into a liquid state by a heating module (1), then the liquid hot-melt bismuth agent alloy in the bismuth alloy filling chamber (7) is filled above the annular packer (6), and after the hot-melt bismuth agent alloy is cooled and solidified, the target position in the oil and gas wellbore is plugged.

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