Foam quick-drying cement paste as well as preparation method and application thereof

Abstract

The invention relates to the technical field of oil and gas field well drilling and cementing, and discloses foam quick-drying cement paste as well as a preparation method and application thereof. The foam quick-drying cement slurry system is obtained by filling gas into quick-drying cement slurry; the quick-drying cement paste comprises the following components in parts by weight: 100 parts of quick-drying cement, 6-14 parts of a thickening agent A, 0.1-1 part of a thickening agent B, 0.1-0.4 part of a toughening agent, 2-8 parts of a fluid loss agent, 1-10 parts of a retarder and 35-60 parts of water. According to the foam quick-drying cement paste prepared by the invention, the thickening time of the cement paste is remarkably shortened, set cement with certain strength is ensured to be formed within a short time, the purpose of leaking stoppage is achieved, and the foam quick-drying cement paste has low density, meets the requirements of retention of the cement paste in a leakage well and sealing of well wall rocks, and achieves well wall consolidation; and finally, the treatment of the well leakage of the shallow surface layer leakage well and the collapse of the well wall is realized.

Description

Technical Field

[0001] The invention relates to the technical field of oil and gas field drilling and cementing, in particular to foamed quick-drying cement slurry and a preparation method and application thereof, and in particular to application of a foamed quick-drying cement slurry system in treating shallow layer leakage. Background Art

[0002] In oil and gas well engineering, conventional cementing operations are to effectively seal the annular space between the casing string lowered into the well and the formation or outer casing through cementing working fluid to prevent reservoir damage and ensure safe and efficient production of oil and gas. In the process of drilling and completing complex oil and gas wells, cementing operations are also an important means to solve complex downhole working conditions.

[0003] In wells with drilling fluid leakage, the loss of drilling fluid will cause adverse effects such as drilling fluid waste, well wall instability, and reservoir damage. Usually, plugging drilling fluid is used to plug the leak, or conventional cementing cement slurry is pumped into the well to form a cement plug for plugging. This technology has a certain effect on the treatment of wells with low drilling fluid leakage rate, but for wells with large leakage and low formation pressure bearing capacity, this method requires a very low density of drilling fluid or cementing cement slurry, and conventional cementing cement slurry cannot meet the requirements. For the complex situation of high leakage wells, another method is to lower tools such as expansion pipes into the well and plug the leak at the leakage point through the expansion pipe, but this method is costly, the construction process is complicated, and the construction effect is not ideal.

[0004] In shallow wells with high leakage, the amount of drilling fluid loss is large, and there is even drilling fluid loss, which causes the wellbore to become unstable and collapse, seriously affecting drilling safety and seriously increasing the time required for single well construction. In addition, wells with high leakage rates have high requirements for cement slurry thickening time. If the thickening time is long, the cement slurry will leak or be washed away by the formation fluid, and it will be impossible to form cement stone near the wellbore and seal the leakage layer. The density of drilling fluid is close to 1g / cm 3 There is still a large amount of leakage, and conventional plugging methods cannot be implemented. The cost of expansion pipe plugging technology is high. Therefore, there is an urgent need for a low-density, fast-thickening cement slurry system and plugging method to solve the complex working conditions of shallow surface leakage. Summary of the invention

[0005] The purpose of the present invention is to overcome the drilling problems of shallow surface drilling fluid leakage and well wall collapse in the prior art, and to provide a foamed quick-drying cement slurry and its preparation method and application. The foamed quick-drying cement slurry of the present invention can quickly thicken and plug the leakage layer, and the foamed quick-drying cement slurry system formed has a density lower than that of water, and can be used to treat shallow surface leakage.

[0006] In order to achieve the above-mentioned object, the first aspect of the present invention provides a foamed quick-drying cement slurry, wherein the foamed quick-drying cement slurry system is obtained by filling gas into the quick-drying cement slurry; the quick-drying cement slurry comprises: 100 parts by weight of quick-drying cement, 6-14 parts by weight of thickener A, 0.1-1 parts by weight of thickener B, 0.1-0.4 parts by weight of toughening agent, 2-8 parts by weight of fluid loss reducer, 1-10 parts by weight of retarder and 35-60 parts by weight of water.

[0007] A second aspect of the present invention provides a method for preparing a foamed quick-drying cement slurry system, the preparation method comprising the following steps:

[0008] (1) mixing 100 parts by weight of quick-drying cement, 6-14 parts by weight of thickener A, 0.1-1 parts by weight of thickener B and 0.1-0.4 parts by weight of toughening agent to obtain a solid mixture;

[0009] (2) mixing 2-8 parts by weight of a fluid loss reducer, 1-10 parts by weight of a retarder, and 35-60 parts by weight of water to obtain slurry preparation water;

[0010] (3) mixing the solid mixture with the slurry preparation water to obtain a quick-drying cement slurry;

[0011] (4) The quick-drying cement slurry is mixed with 0.5-1 parts by weight of a foaming agent and 0.3-0.6 parts by weight of a foam stabilizer, and then aerated to obtain a foamed quick-drying cement slurry system.

[0012] The third aspect of the present invention provides the use of the foamed quick-drying cement slurry system described in the first aspect or the foamed quick-drying cement slurry system prepared by the preparation method described in the second aspect in oil field cementing.

[0013] A fourth aspect of the present invention provides a method for controlling shallow surface leakage in oil and gas wells, the method comprising:

[0014] The foamed quick-drying cement slurry system described in the first aspect or the foamed quick-drying cement slurry system prepared by the preparation method described in the second aspect is transported to the leaking formation to displace the drilling fluid in the original well and return it to the well or go down into the leaking formation to plug the leak.

[0015] Through the above technical solution, the beneficial technical effects achieved by the present invention are as follows:

[0016] (1) The quick-drying cement slurry of the present invention has a short thickening time and can be thickened to form cement stone with a certain strength during the cement slurry pumping process and the flow process in the leakage layer, thereby achieving the effect of plugging the leakage layer.

[0017] (2) The foamed quick-drying cement slurry system of the present invention has a low density. For wells with shallow surface leakage that results in drilling fluid loss, the foamed quick-drying cement slurry system has a density lower than that of water, which can reduce the bottom hole pressure and prevent leakage. It can stay in the leakage layer and the wellbore for a long time to form cement stone of a certain strength, which can not only seal the leakage layer, but also solidify the wellbore wall in the wellbore and control the collapse of the wellbore wall.

[0018] (3) The present invention combines the characteristics of foam cementing technology and proposes to use quick-drying cement slurry to shorten the cement thickening time, reduce the density of the cement slurry system by aeration, so as to seal the leakage layer and consolidate the unstable and collapsed wellbore wall, solve the complex problems of shallow drilling and completion, and construct a cementing method for shallow leakage well management, so as to provide technical support for reducing the drilling cycle and cost of shallow leakage wells.

[0019] (4) The strength of cement paste formed by the foamed quick-drying cement slurry system of the present invention is lower than that of cement paste formed by the conventional foamed cement slurry system, and it is easier to remove plugs. DETAILED DESCRIPTION

[0020] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0021] The first aspect of the present invention provides a foamed quick-drying cement slurry system, which is obtained by filling gas into quick-drying cement slurry; the quick-drying cement slurry comprises: 100 parts by weight of quick-drying cement, 6-14 parts by weight of thickener A, 0.1-1 parts by weight of thickener B, 0.1-0.4 parts by weight of toughener, 2-8 parts by weight of fluid loss reducer, 1-10 parts by weight of retarder and 35-60 parts by weight of water.

[0022] The invention combines quick-drying cement with components such as thickener A and thickener B to form quick-drying cement slurry, and then fills gas into the quick-drying cement slurry to obtain a foam quick-drying cement slurry system, so that the foam quick-drying cement slurry system has faster thickening and strength, and improves the plugging ability of the thickened cement.

[0023] The foamed quick-drying cement slurry of the present invention shortens the cement thickening time, solves the complex problems of shallow layer drilling and completion, constructs a cementing method for shallow layer leakage well management, and provides technical support for reducing the drilling cycle and cost of shallow layer leakage wells.

[0024] In the present invention, the water used to prepare the foamed quick-drying cement slurry includes, but is not limited to: fresh water (eg, tap water, river or lake water, groundwater), sea water or mineralized water.

[0025] In order to improve the flow resistance of cement slurry in cracks and the performance of rapid thickening and plugging of leakage layers, in some preferred embodiments of the present invention, the quick-drying cement slurry comprises: 100 parts by weight of quick-drying cement, 8-11 parts by weight of thickener A, 0.4-0.6 parts by weight of thickener B, 0.2-0.33 parts by weight of toughener, 2-4 parts by weight of fluid loss reducer, 3-6 parts by weight of retarder and 35-60 parts by weight of water.

[0026] In some embodiments of the present invention, before filling the quick-drying cement slurry with gas, the process further includes: adding 0.5-1 parts by weight of a foaming agent and 0.3-0.6 parts by weight of a foam stabilizer to the quick-drying cement slurry; preferably, adding 0.6-0.9 parts by weight of a foaming agent and 0.4-0.5 parts by weight of a foam stabilizer to the quick-drying cement slurry.

[0027] In some embodiments of the present invention, the volume ratio of the gas to the quick-drying cement slurry is 30-80:1, preferably 45-65:1.

[0028] In some embodiments of the present invention, the gas is nitrogen or air.

[0029] In some embodiments of the present invention, when the ratio of the quick-drying cement to water is 100:44, the thickening time of the quick-drying cement slurry at 25-30° C. is 20 min-60 min.

[0030] The quick-drying cement slurry of the invention has a short thickening time and can be thickened to form cement stone with a certain strength during the cement slurry pumping process and the flow process in the leakage layer, so as to achieve the effect of plugging the leakage layer.

[0031] In some embodiments of the present invention, the quick-drying cement is sulphoaluminate cement, wherein the mass content of aluminium oxide is 30-40% based on the total mass of the sulphoaluminate cement.

[0032] In the present invention, when the ratio of the quick-drying cement to water is 100:44, the thickening time is 20 min to 60 min at 25-30°C.

[0033] In some embodiments of the present invention, the retarder is selected from one or more of hydroxyethylidene diphosphonic acid, citric acid, sodium citrate, sodium gluconate and tartaric acid.

[0034] The thickening time of the foam quick-drying cement slurry of the present invention can be adjusted by a retarder, and the thickening time is controllable, thereby ensuring safe construction.

[0035] In some embodiments of the present invention, the thickener A is selected from microsilica, wherein the content of SiO2 is 80-95wt%.

[0036] Preferably, the average particle size of the thickener A is 0.05-0.3 μm.

[0037] In some embodiments of the present invention, the thickener B is selected from xanthan gum or polyacrylamide polymer.

[0038] Preferably, the number average molecular weight of the polyacrylamide polymer is 4-8 million g / mol.

[0039] In some preferred embodiments of the present invention, the weight ratio of the thickener A to the thickener B is 5-30:1; further preferably, the weight ratio of the microsilica to the xanthan gum is 15-25:1.

[0040] In some embodiments of the present invention, the toughening agent is a fiber; preferably, the fiber is selected from one or more of glass fiber, silica fiber and chemical organic synthetic fiber.

[0041] In some preferred embodiments, the fiber has a diameter of 2-8 μm and a length of 2-5 mm.

[0042] The fiber is added to the foamed quick-drying cement slurry of the present invention, and when the foamed quick-drying cement slurry is thickened to form a cement stone of a certain strength, the fiber will increase the toughness of the cement stone. During the process of pumping the foamed quick-drying cement slurry, the dispersed cement particles formed by the thickening of the cement slurry will also be connected by the fiber to form a network of foamed cement stones, which have a super strong ability to plug the leakage layer.

[0043] In some embodiments of the present invention, the fluid loss additive is selected from one or more of 2-acrylamide-2-methylpropanesulfonic acid (AMPS) polymer, ketone-aldehyde condensation and polyvinyl alcohol (PVA) system.

[0044] Preferably, the amount of fluid loss reducer added is less than 3%-4%, and the performance of the cement slurry is more stable.

[0045] In some embodiments of the present invention, the foaming agent is a protein foaming agent or a compound of a protein foaming agent and an ionic surfactant; preferably, the ionic surfactant is selected from one or more of sodium fatty alcohol polyoxyethylene ether sulfate, cocamidopropyl betaine and sodium α-olefin sulfonate.

[0046] In some embodiments of the present invention, the foam stabilizer is selected from one or more of carboxymethyl cellulose, polyanionic cellulose, hydroxypropyl methyl cellulose, hydroxyethyl cellulose and hydroxyethyl methyl cellulose.

[0047] In some embodiments of the present invention, the foamed quick-drying cement slurry system has a density of 0.7-1.2 g / cm at 25-60°C and 7-12 MPa.3 , fluidity greater than 14cm, water separation less than 1%, upper and lower density difference less than 0.03g / cm 3 .

[0048] A second aspect of the present invention provides a method for preparing a foamed quick-drying cement slurry, the method comprising the following steps:

[0049] (1) mixing 100 parts by weight of quick-drying cement, 6-14 parts by weight of thickener A, 0.1-1 parts by weight of thickener B and 0.1-0.4 parts by weight of toughening agent to obtain a solid mixture;

[0050] (2) mixing 2-8 parts by weight of a fluid loss reducer, 1-10 parts by weight of a retarder, and 35-60 parts by weight of water to obtain slurry preparation water;

[0051] (3) mixing the solid mixture with the slurry preparation water to obtain a quick-drying cement slurry;

[0052] (4) The quick-drying cement slurry is mixed with 0.5-1 parts by weight of a foaming agent and 0.3-0.6 parts by weight of a foam stabilizer, and then aerated to obtain a foamed quick-drying cement slurry system.

[0053] The selection of each component in the present invention is the same as that in the first aspect mentioned above. Please refer to the description of the first aspect mentioned above and will not be repeated here.

[0054] In the present invention, the quick-drying cement slurry obtained in step (3) is pumped through a foam cement slurry mixing skid, and a foaming agent and a foam stabilizer are added to the mixing skid; then, a normal temperature high-pressure gas (such as nitrogen) is continuously injected at the outlet end of the mixing skid to form a foam quick-drying cement slurry system.

[0055] The present invention combines the technical characteristics of foam cementing and proposes to use a foam quick-drying cement slurry system to shorten the cement thickening time and reduce the density of cement slurry to seal the leakage layer and consolidate the unstable and collapsed wellbore wall, solve the complex problems of shallow drilling and completion, and construct a cementing method for shallow leakage well management, providing technical support for reducing the drilling cycle and cost of shallow leakage wells.

[0056] The strength of cement paste formed by the foam quick-drying cement slurry system of the present invention is lower than that of cement paste formed by the conventional foam cement slurry system, and it is easier to remove plugs.

[0057] In some embodiments of the present invention, the inflation step specifically comprises: inflation under stirring conditions at a gas pressure of 1-25 MPa, preferably 3-12 MPa.

[0058] In some embodiments of the present invention, the volume ratio of the gas to the quick-drying cement slurry is 30-80:1, preferably 45-65:1.

[0059] In some embodiments of the present invention, the gas is nitrogen or air.

[0060] In this step, the nitrogen is nitrogen at room temperature and pressure formed by gasification of liquid nitrogen, and the content of the nitrogen can be adjusted according to the density requirement of the foam quick-drying cement slurry system.

[0061] In some embodiments of the present invention, the foamed quick-drying cement slurry system has a density of 0.7-1.2 g / cm at 25-60°C and 7-12 MPa. 3 , fluidity greater than 14cm, water separation less than 1%, upper and lower density difference less than 0.03g / cm 3 .

[0062] The third aspect of the present invention provides a foamed quick-drying cement slurry system, which is prepared by the foamed quick-drying cement slurry system described in the first aspect or the preparation method described in the second aspect and is used in oilfield cementing.

[0063] In some embodiments of the present invention, the foamed quick-drying cement slurry system is used in shallow surface leakage of oil and gas wells.

[0064] In the present invention, the above application scheme is as follows:

[0065] 1) After the drill pipe is lowered to the bottom of the well, the drilling fluid is circulated to meet the cementing requirements;

[0066] 2) Pumping conventional low-density foamed cement slurry from the drill pipe according to the designed cement slurry volume and cement slurry density; the conventional low-density foamed cement slurry is a foamed cement slurry formed by adding a foaming agent and a foam stabilizer to conventional cement slurry and then filling it with nitrogen;

[0067] 3) After the conventional low-density foam cement slurry is pumped, the drilling fluid is used to replace the slurry. After the slurry is replaced, the wellhead drill pipe pump valve is closed;

[0068] 4) Slowly pump the foamed quick-drying cement slurry or the foamed quick-drying cement slurry system from the annulus pipeline according to the designed density and displacement, observe the wellhead pumping pressure, and stop pumping the cement slurry after the pumping pressure increases by 2-5MPa;

[0069] 5) Guan Jing and Hou Ning.

[0070] In step 4), the on-site preparation method of the foamed quick-drying cement slurry or the foamed quick-drying cement slurry system specifically comprises the following steps:

[0071] 41) Mix quick-drying cement, thickener A, thickener B and toughening agent in a ash mixing tank to obtain a solid mixture, and transport the solid mixture to an on-site ash tank for standby use;

[0072] 42) The on-site water tank stores an appropriate amount of on-site water, and mixes the water and other additives, including fluid loss reducer and retarder, into slurry preparation water;

[0073] 43) The solid mixture and the slurry preparation water are pumped into a cementing vehicle for mixing and stirring to obtain a quick-drying cement slurry;

[0074] 44) The quick-drying cement slurry in the cementing vehicle is pumped into the foam cement slurry mixing skid, and a foaming agent and a foam stabilizer are added to the agent filling port in the mixing skid to form a foam quick-drying cement slurry;

[0075] Optionally, 45) after the foaming agent and the foam stabilizer in the foam cement slurry mixing skid are added to the quick-drying cement slurry, high-pressure nitrogen at room temperature is injected at the nitrogen injection port to form a foam quick-drying cement slurry system.

[0076] The foamed quick-drying cement slurry system of the present invention has a low density. For wells with shallow surface leakage reaching the point of drilling fluid loss, the foamed quick-drying cement slurry system has a density lower than water, which can reduce the bottom hole pressure and prevent leakage. It stays in the leakage layer and the wellbore for a long time to form cement stone of a certain strength, which can not only seal the leakage layer, but also solidify the well wall in the wellbore and control the collapse of the well wall.

[0077] A fourth aspect of the present invention provides a method for controlling shallow surface leakage in oil and gas wells, the method comprising:

[0078] The foamed quick-drying cement slurry system described in the first aspect or the foamed quick-drying cement slurry system prepared by the preparation method described in the second aspect is transported to the leaking formation to displace the drilling fluid in the original well and return it to the well or go down into the leaking formation to plug the leak.

[0079] In some embodiments of the present invention, the foamed quick-drying cement slurry system is cured to solidify.

[0080] The present invention determines the pressure and temperature according to the well depth. The curing pressure of a well with a depth of 500-1500m is 5-15MPa, and the curing temperature is 35-70°C.

[0081] In some preferred embodiments of the present invention, the curing temperature is 35-70°C, the pressure is 5-15 MPa, and the time is 24-72 hours.

[0082] The technical solutions in the present invention are described clearly and completely by way of embodiments below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0083] In the following examples and comparative examples, if no specific conditions are specified, the experiments were carried out under conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used, if no manufacturer is specified, are all conventional products that can be obtained through commercial channels.

[0084] In the following examples,

[0085] Cement was quick-drying cement purchased from Sichuan Jiahua Cement Factory.

[0086] The model of the fluid loss reducer is DZJ-Y, the model of the retarder is DZH-2, the model of the foaming agent is DZF, and the model of the foam stabilizer is DZW, all of which are from Texas Continental Shelf Petroleum Engineering Technology Co., Ltd.

[0087] Thickener A is microsilica with a particle size of 0.1-0.3 μm.

[0088] Thickener B is xanthan gum, model number is SCW-H.

[0089] The toughening agent is a fiber with a diameter of 1-5 μm and a length of 2-5 μm.

[0090] Indoor experiments use a foamed quick-drying cement slurry system formed by high-speed rotation of the slurry cup, and on-site engineering applications use pure nitrogen, which is high-pressure, room-temperature nitrogen formed by heating and gasifying liquid nitrogen.

[0091] Density: Measured by GB / T 19139-2012 oil well cement test method.

[0092] Thickening time: measured by GB / T 19139-2012 oil well cement test method.

[0093] Compressive Strength: Measured by GB / T 19139-2012 Oil Well Cement Test Method.

[0094] Strength development time: measured by GB / T 19139-2012 oil well cement test method.

[0095] Example 1

[0096] A method for preparing a foamed quick-drying cement slurry system comprises the following steps:

[0097] (1) 100 parts by weight of quick-drying cement, 10 parts by weight of thickener A (microsilica), 0.5 parts by weight of thickener B (SCW-H) and 0.33 parts by weight of toughening agent (fiber) were mixed to obtain a solid mixture;

[0098] (2) 4 parts by weight of fluid loss reducer (DZJ-Y), 1 part by weight of retarder (DZH-2) and 58 parts by weight of water were mixed and stirred to prepare slurry water;

[0099] (3) mixing and stirring the solid mixture with the slurry preparation water to obtain a quick-drying cement slurry;

[0100] (4) The quick-drying cement slurry obtained in step (3) is pumped through a foam cement slurry mixing skid, and 1 part by weight of a foaming agent (DZF) and 0.6 part by weight of a foam stabilizer (DZW) are added to the mixing skid; then nitrogen at 25° C. and 10 MPa is injected into the outlet end of the mixing skid to form a foam quick-drying cement slurry system.

[0101] The foamed quick-drying cement slurry system was placed in a curing box and cured at 50°C and 10 MPa for 48 h. The performance results such as density, thickening time, and compressive strength after solidification are shown in Table 1.

[0102] Example 2

[0103] The foamed quick-drying cement slurry system was prepared according to the method of Example 1, except that the amount of thickener A added was 6 parts by weight and the amount of thickener B added was 1 part by weight, and the other components and steps remained unchanged. The results are shown in Table 1.

[0104] Example 3

[0105] The foamed quick-drying cement slurry system was prepared according to the method of Example 1, except that the amount of thickener A added was 14 parts by weight and the amount of thickener B added was 0.1 parts by weight, and the other components and steps remained unchanged. The results are shown in Table 1.

[0106] Example 4

[0107] The foamed quick-drying cement slurry system was prepared according to the method of Example 1, except that the amount of the foaming agent (DZF) added was 0.5 parts by weight and the amount of the foam stabilizer (DZW) added was 0.3 parts by weight, and the other components and steps remained unchanged. The results are shown in Table 1.

[0108] Comparative Example 1

[0109] The cement slurry system was prepared according to the method of steps (1) to (3) of Example 1, except that step (4) of adding a foaming agent, a foam stabilizer and aeration was omitted. The results are shown in Table 1.

[0110] The cement slurry system of Comparative Example 1 is not a foamed quick-drying cement slurry system, does not meet the density requirements of the present invention for the foamed quick-drying cement slurry system, and is not used. It is only used to evaluate the basic performance of the foamed quick-drying cement slurry.

[0111] Comparative Example 2

[0112] The cement slurry system was prepared according to the method of Example 1, except that no thickener A was added, that is, the amount of thickener A added was 0 parts by weight, and the other components and steps remained unchanged. The results are shown in Table 1.

[0113] Comparative Example 3

[0114] The cement slurry system was prepared according to the method of Example 1, except that no thickener B was added, that is, the amount of thickener B added was 0 parts by weight, and the other components and steps remained unchanged. The results are shown in Table 1.

[0115] Comparative Example 4

[0116] The cement slurry system was prepared according to the method of Example 1, except that the quick-drying cement was replaced with conventional oil well cement (Jiahua G grade), and the other components and steps remained unchanged. The results are shown in Table 1.

[0117] Table 1

[0118]

[0119] From the results in Table 1, it can be seen that compared with the cement slurries of Comparative Examples 1, 2 and 3, the density of the foamed quick-drying cement slurries of Examples 1-4 is greatly reduced, indicating that the loss of the plugging cement slurry in the leakage layer is significantly reduced, the efficiency and success rate of plugging the leakage layer during the cementing construction process are improved, and the compressive strength meets the requirements for downhole plugging. Compared with Comparative Example 4, the foamed quick-drying cement slurry system of Examples 1-4 has a short strength-building time, and the compressive strength meets the requirements for construction and in-well leakage prevention, and is more conducive to plugging the cement slurry and staying in the well to consolidate the well wall, and realizing the treatment of shallow surface leakage wells.

[0120] Application Examples

[0121] The foamed quick-drying cement slurry system of Examples 1-4 and the cement slurry system of Comparative Examples 1-4 were respectively applied on-site in the treatment of shallow surface leakage. The specific implementation process includes:

[0122] (1) After the drill pipe is lowered to the bottom of the well, the drilling fluid is circulated to meet the cementing requirements;

[0123] (2) According to the designed cement slurry volume and cement slurry density, the foamed quick-drying cement slurry system formed in Examples 1-4 or the cement slurry system formed in Comparative Examples 1-4 were pumped into the drill pipe, with a displacement of 0.8 m 3 / min, pumping volume 63m 3 ;

[0124] (3) After the cement slurry system is pumped, use drilling fluid to replace the slurry. After the slurry is replaced, close the wellhead drill pipe pump valve;

[0125] (4) Inject cement slurry into the well through the pipeline. Before the cement slurry reaches the leakage zone, the pumping rate in the pipeline is 0.8m 3 / min, after the cement slurry reaches the leakage layer, adjust the pumping rate to 0.4m 3 / min.

[0126] (5) Observe the changes in the pumping pressure of the pipeline. When the pumping pressure rises slowly and the increase reaches 2MPa, stop pumping cement slurry. When the total amount of pumping reaches 35m 3 . Pump 1m 3 Flush the pipeline with clean water and shut down the well for freezing.

[0127] (6) After the well was shut down for 24 hours, the well was opened to clean the plug. After the drill bit drilled through the cement plug at the leakage layer, the drilling fluid returned to the surface, and the cement slurry treatment of shallow surface leakage was completed. The results are shown in Table 2.

[0128] Table 2

[0129]

[0130] It can be seen from the results in Table 2 that the foamed quick-drying cement slurry systems of Examples 1-4 of the present invention have obvious plugging effects and achieve plugging of shallow surface large leakage wells in a relatively short period of time. The cement slurry systems of Comparative Examples 1-4 have poor plugging effects or cannot meet the requirements of field applications.

[0131] In summary, the foamed quick-drying cement slurry or the foamed quick-drying cement slurry system of the present invention has a significantly better plugging effect in shallow surface high-loss wells.

[0132] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A foamed quick-drying cement slurry system, characterized in that: The foamed quick-drying cement slurry system is obtained by filling gas into quick-drying cement slurry; the quick-drying cement slurry comprises: 100 parts by weight of quick-drying cement, 6-14 parts by weight of thickener A, 0.1-1 parts by weight of thickener B, 0.1-0.4 parts by weight of toughener, 2-8 parts by weight of fluid loss reducer, 1-10 parts by weight of retarder and 35-60 parts by weight of water.

2. The foamed quick-drying cement slurry system according to claim 1, wherein: Before the gas is charged into the quick-drying cement slurry, the method further comprises: adding 0.5-1 parts by weight of a foaming agent and 0.3-0.6 parts by weight of a foam stabilizer into the quick-drying cement slurry; and / or, the volume ratio of the gas to the quick-drying cement slurry is 30-80:1, preferably 45-65:1; And / or, the gas is nitrogen or air.

3. The foamed quick-drying cement slurry system according to claim 1 or 2, wherein: When the ratio of the quick-drying cement to water is 100:44, the thickening time of the quick-drying cement slurry at 25-30° C. is 20 min-60 min.

4. The foamed quick-drying cement slurry system according to any one of claims 1 to 5, wherein: The quick-drying cement is sulphoaluminate cement, wherein the mass content of aluminium oxide is 30-40% based on the total mass of the sulphoaluminate cement; And / or, the retarder is selected from one or more of hydroxyethylidene diphosphonic acid, citric acid, sodium citrate, sodium gluconate and tartaric acid.

5. The foamed quick-drying cement slurry system according to any one of claims 1 to 4, wherein: The thickener A is microsilicon, wherein the content of SiO2 is 80-95wt%; preferably, the average particle size of the microsilicon is 0.05-0.3μm; And / or, the thickener B is selected from xanthan gum or polyacrylamide polymer, preferably, the number average molecular weight of the polyacrylamide polymer is 4-8 million g / mol.

6. The foamed quick-drying cement slurry system according to any one of claims 1 to 5, wherein: The toughening agent is a fiber; preferably, the fiber has a diameter of 2-8 μm and a length of 2-5 mm; And / or, the fluid loss agent is selected from one or more of 2-acrylamide-2-methylpropanesulfonic acid polymer, ketone-aldehyde condensation and polyvinyl alcohol system; And / or, the foaming agent is a protein foaming agent or a compound of a protein foaming agent and an ionic surfactant; preferably, the ionic surfactant is selected from one or more of sodium fatty alcohol polyoxyethylene ether sulfate, cocamidopropyl betaine and sodium α-olefin sulfonate; And / or, the foam stabilizer is selected from one or more of carboxymethyl cellulose, polyanionic cellulose, hydroxypropyl methyl cellulose, hydroxyethyl cellulose and hydroxyethyl methyl cellulose.

7. The foamed quick-drying cement slurry system according to any one of claims 1 to 6, wherein: The foamed quick-drying cement slurry system has a density of 0.7-1.2 g / cm at 25-60°C and 7-12 MPa. 3 , fluidity greater than 14cm, water separation less than 1%, upper and lower density difference less than 0.03g / cm 3 .

8. A method for preparing a foamed quick-drying cement slurry system, characterized in that: The preparation method comprises the following steps: (1) mixing 100 parts by weight of quick-drying cement, 6-14 parts by weight of thickener A, 0.1-1 parts by weight of thickener B and 0.1-0.4 parts by weight of toughening agent to obtain a solid mixture; (2) mixing 2-8 parts by weight of a fluid loss reducer, 1-10 parts by weight of a retarder, and 35-60 parts by weight of water to obtain slurry preparation water; (3) mixing the solid mixture with the slurry preparation water to obtain a quick-drying cement slurry; (4) The quick-drying cement slurry is mixed with 0.5-1 parts by weight of a foaming agent and 0.3-0.6 parts by weight of a foam stabilizer, and then aerated to obtain a foamed quick-drying cement slurry system.

9. The preparation method according to claim 8, wherein: The aeration step specifically comprises: aeration under stirring conditions at a gas pressure of 1-25 MPa, preferably 3-12 MPa; Preferably, the volume ratio of the gas to the quick-drying cement slurry is 30-80:1, preferably 45-65:1; Preferably, the gas is nitrogen or air.

10. Use of the foamed quick-drying cement slurry system according to any one of claims 1 to 7 or the foamed quick-drying cement slurry system prepared by the preparation method according to claim 8 or 9 in oil field cementing.

11. The use according to claim 10, wherein: The foam quick-drying cement slurry system is used in shallow surface leakage of oil and gas wells.

12. A method for treating shallow surface leakage in oil and gas wells, characterized in that: The method includes: The foamed quick-drying cement slurry system according to any one of claims 1 to 7 or the foamed quick-drying cement slurry system prepared by the preparation method according to claim 8 or 9 is transported to the leaking formation to displace the drilling fluid in the original well and return it to the well or go down into the leaking formation to plug the leak.

13. The method according to claim 12, wherein: Curing the foamed quick-drying cement slurry system to solidify it; Preferably, the curing temperature is 35-70°C, the pressure is 5-15MPa, and the time is 24-72h.

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