Foamed fast-drying cementitious slurry, method of making and use thereof

Abstract

The present application relates to oil and gas field drilling cementing technical field, disclose a foamed fast drying cement slurry and its preparation method and application. The foamed fast drying cement slurry system is obtained by filling gas into fast drying cement slurry;The fast drying cement slurry includes: fast drying cement 100 parts by weight, thickening agent A 6-14 parts by weight, thickening agent B 0.1-1 parts by weight, toughening agent 0.1-0.4 parts by weight, fluid loss additive 2-8 parts by weight, retarder 1-10 parts by weight and water 35-60 parts by weight. The foamed fast drying cement slurry prepared by the present application not only significantly shortens the thickening time of the cement slurry, ensures that the cement stone with certain strength is formed in a short time, achieves the purpose of plugging, but also can have lower density, meets the residence of cement slurry in lost circulation well and the sealing of well wall rock, achieves the effect of well wall consolidation and prevents well wall collapse, and finally realizes the management of lost circulation well and well wall collapse in the superficial layer.

Description

Technical Field

[0001] This invention relates to the field of drilling and cementing technology in oil and gas fields, specifically to foamed quick-drying cement slurry, its preparation method and application, and particularly to the application of a foamed quick-drying cement slurry system in controlling shallow surface leakage. Background Technology

[0002] In oil and gas well engineering, conventional cementing operations use cementing fluid to effectively seal the annular space between the casing string and the formation or outer casing, preventing reservoir damage and ensuring safe and efficient oil and gas production. In the drilling and completion of complex oil and gas wells, cementing is also a crucial means of addressing complex downhole conditions.

[0003] In wells with drilling fluid loss, the loss of drilling fluid will cause adverse effects such as drilling fluid waste, wellbore instability, and reservoir damage. Common methods for plugging the loss include using plugging drilling fluid or pumping in conventional cement slurry to form a cement plug. This technique is effective for wells with low drilling fluid loss rates, but for wells with large losses and low formation pressure, this method requires very low density drilling fluid or cement slurry, which conventional cement slurry cannot meet. For the complex situation of wells with high loss rates, another method is to run expansion pipes or other tools into the well to plug the loss at the point of leakage. However, this method is costly, complex in construction, and the results are not ideal.

[0004] In shallow, high-loss wells, drilling fluid loss is significant, sometimes even leading to fluid backflow, causing wellbore instability and collapse. This severely impacts drilling safety and significantly increases well construction time. Furthermore, wells with high loss rates require a longer cement slurry thickening time. Prolonged thickening time results in cement slurry loss or erosion by formation fluids, preventing the formation of cement stone near the wellbore and the sealing of the lost circulation zone. The drilling fluid density is close to 1 g / cm³. 3 Significant leakage still exists, conventional sealing methods are not feasible, and expansion pipe sealing technology is costly. Therefore, there is an urgent need for a low-density, rapidly thickening cement slurry system and sealing method to address the complex situation of shallow surface leakage. Summary of the Invention

[0005] The purpose of this invention is to overcome the drilling problems of shallow drilling fluid loss and wellbore collapse in existing technologies, and to provide foamed quick-drying cement slurry, its preparation method, and its application. The foamed quick-drying cement slurry of this invention can rapidly thicken and seal lost circulation zones, and the resulting foamed quick-drying cement slurry system has a density lower than water, making it suitable for treating shallow leakage.

[0006] To achieve the above objectives, 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 inflating the quick-drying cement slurry with gas; 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 water loss reducing agent, 1-10 parts by weight of retarder and 35-60 parts by weight of water.

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

[0008] (1) Mix 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) Mix 2-8 parts by weight of water loss reducer, 1-10 parts by weight of retarder and 35-60 parts by weight of water to obtain slurry water;

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

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

[0012] The third aspect of this invention provides the application of the foam quick-drying cement slurry system described in the first aspect or the foam quick-drying cement slurry system prepared by the preparation method described in the second aspect in oilfield 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 and the foamed quick-drying cement slurry system prepared by the preparation method described in the second aspect are transported to the lost formation to displace the drilling fluid in the original well and return it to the well or descend into the lost formation to plug the leakage.

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

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

[0017] (2) The foam quick-drying cement slurry system of the present invention has a low density. For wells with shallow surface leakage reaching drilling fluid return, the density of the foam quick-drying cement slurry system is lower than that of water, which can reduce the bottom pressure of the well and prevent leakage. It can stay in the leakage layer and the well barrel 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 well barrel and prevent well wall collapse.

[0018] (3) Combining the characteristics of foam cementing technology, this invention proposes to use fast-drying cement slurry to shorten the cement thickening time and reduce the density of the cement slurry system by aeration in order to seal the lost circulation zone and the well wall of the well that has collapsed due to consolidation instability, solve the complex problems of shallow drilling and completion, construct a cementing method for the treatment of shallow lost circulation wells, and provide technical support for reducing the drilling cycle and cost of shallow lost circulation wells.

[0019] (4) The cement stone formed by the foam quick-drying cement slurry system of the present invention has lower strength than that of conventional foam cement slurry system, making it easier to clear blockages. Detailed Implementation

[0020] The endpoints and any values ​​of the ranges disclosed herein 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 the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0021] The first aspect of the present invention provides a foamed quick-drying cement slurry system, wherein the foamed quick-drying cement slurry system is obtained by filling quick-drying cement slurry with gas; 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 water loss reducing agent, 1-10 parts by weight of retarder and 35-60 parts by weight of water.

[0022] This invention combines fast-drying cement with thickeners A and B to form a fast-drying cement slurry, and then fills the fast-drying cement slurry with gas to obtain a foamed fast-drying cement slurry system. This foamed fast-drying cement slurry system has a faster thickening and strength, and improves the sealing ability of the thickened cement.

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

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

[0025] To improve the flow resistance of cement slurry within cracks and its performance in rapidly thickening and sealing leaking layers, in some preferred embodiments of the present invention, the fast-drying cement slurry comprises: 100 parts by weight of fast-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 toughening agent, 2-4 parts by weight of water loss reducing agent, 3-6 parts by weight of retarder, and 35-60 parts by weight of water.

[0026] In some embodiments of the present invention, before introducing gas into the quick-drying cement slurry, the method further includes adding 0.5-1 parts by weight of foaming agent and 0.3-0.6 parts by weight of foam stabilizer to the quick-drying cement slurry; preferably, adding 0.6-0.9 parts by weight of foaming agent and 0.4-0.5 parts by weight of 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 quick-drying cement to water is 100:44, the thickening time of the quick-drying cement slurry at 25-30°C is 20-60 minutes.

[0030] The fast-drying cement slurry of this invention has a short thickening time, and can thicken into cement stone with a certain strength during the cement slurry pumping process and during the flow within the leakage layer, thereby achieving the effect of sealing the leakage layer.

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

[0032] In this invention, when the ratio of quick-drying cement to water is 100:44, the thickening time is 20-60 minutes 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 foamed quick-drying cement slurry of this invention can be adjusted by a retarder, making the thickening time controllable and ensuring safe construction.

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

[0036] Preferably, the thickener A has an average particle size of 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 million to 8 million g / mol.

[0039] In some preferred embodiments of the present invention, the weight ratio of thickener A to thickener B is 5-30:1; more preferably, the weight ratio of microsilica to 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 chemically synthesized organic fiber.

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

[0042] The present invention incorporates fibers into the foamed quick-drying cement slurry. As the foamed quick-drying cement slurry thickens to form a cement stone of a certain strength, the fibers increase the toughness of the cement stone. During the pumping process of the foamed quick-drying cement slurry, the dispersed cement particles formed by the thickening of the slurry are also connected by fibers to form a network of foamed cement stone, which has a superior ability to seal leaking layers.

[0043] In some embodiments of the present invention, the water loss reducing agent is selected from one or more of 2-acrylamide-2-methylpropanesulfonic acid (AMPS) polymers, ketaldehyde condensates, and polyvinyl alcohol (PVA) systems.

[0044] Preferably, the amount of water loss reducing agent added is less than 3%-4%, resulting in more stable cement slurry performance.

[0045] In some embodiments of the present invention, the foaming agent is a protein-based foaming agent or a mixture of a protein-based 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-alkenyl 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 / cm³ under conditions of 25-60°C and 7-12 MPa.3 The fluidity is greater than 14 cm, the water separation is less than 1%, and the density difference between the upper and lower parts is less than 0.03 g / cm³. 3 .

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

[0049] (1) Mix 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) Mix 2-8 parts by weight of water loss reducer, 1-10 parts by weight of retarder and 35-60 parts by weight of water to obtain slurry water;

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

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

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

[0054] In this invention, the quick-drying cement slurry obtained in step (3) is pumped through a foamed cement slurry mixing skid, and a foaming agent and a foam stabilizer are added inside the mixing skid; then, room temperature high-pressure gas (e.g., nitrogen) is injected into the outlet end of the mixing skid to form a foamed quick-drying cement slurry system.

[0055] This invention combines the characteristics of foam cementing technology and proposes to use a foam quick-drying cement slurry system to shorten the cement thickening time and reduce the cement slurry density to seal lost circulation zones and consolidate unstable and collapsed well walls, solving the complex problems of shallow drilling and completion, and constructing a cementing method for the treatment of shallow lost circulation wells, providing technical support for reducing the drilling cycle and cost of shallow lost circulation wells.

[0056] The cement stone formed by the foam quick-drying cement slurry system of this invention has lower strength than that of conventional foam cement slurry system, making it easier to clear blockages.

[0057] In some embodiments of the present invention, the inflation step specifically includes: inflation under agitation 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 gas is liquid nitrogen vaporized to form room temperature and pressure nitrogen gas. The nitrogen content can be adjusted according to the density requirements 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 / cm³ under conditions of 25-60°C and 7-12 MPa. 3 The fluidity is greater than 14 cm, the water separation is less than 1%, and the density difference between the upper and lower parts is less than 0.03 g / cm³. 3 .

[0062] The third aspect of the present invention provides a foamed quick-drying cement slurry system, wherein the foamed quick-drying cement slurry system prepared by the foamed quick-drying cement slurry system described in the first aspect or the preparation method described in the second aspect 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 this 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 until the cementing requirements are met;

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

[0067] 3) After the conventional low-density foamed cement slurry pumping is completed, drilling fluid is used to replace the slurry. After the slurry replacement is in place, the wellhead drill pipe pumping port valve is closed.

[0068] 4) Slowly pump foam quick-drying cement slurry or foam quick-drying cement slurry system from the annulus pipeline according to the design density and flow rate, observe the pumping pressure at the wellhead, and stop pumping cement slurry after the pumping pressure rises by 2-5 MPa.

[0069] 5) Guan Jinghou Ning.

[0070] Step 4) specifically includes the following steps in the on-site preparation method of foamed quick-drying cement slurry or foamed quick-drying cement slurry system:

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

[0072] 42) Store an appropriate amount of on-site water in the on-site water tank, and mix the water with other additives, including water loss reducers and retarders, to form slurry water;

[0073] 43) The solid mixture and the slurry preparation water are mixed and stirred in the cementing truck to obtain quick-drying cement slurry;

[0074] 44) The quick-drying cement slurry in the cementing truck is pumped into the foam cement slurry mixing skid. Foaming agent and foam stabilizer are added at the agent injection port in the mixing skid to form foam quick-drying cement slurry.

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

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

[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 and the foamed quick-drying cement slurry system prepared by the preparation method described in the second aspect are transported to the lost formation to displace the drilling fluid in the original well and return it to the well or descend into the lost formation to plug the leakage.

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

[0080] This invention determines the pressure and temperature based on the well depth. The maintenance pressure for wells with a depth of 500-1500m is 5-15MPa, and the maintenance temperature is 35-70℃.

[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 h.

[0082] The technical solutions of the present invention will be clearly and completely described below through embodiments. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0083] Unless otherwise specified in the following examples and comparative examples, all conditions were performed under standard conditions or conditions recommended by the manufacturer. Reagents or instruments used, unless otherwise specified, are all commercially available products.

[0084] In the following embodiments,

[0085] The cement was purchased from Sichuan Jiahua Cement Plant as fast-drying cement.

[0086] The water loss reducer is model DZJ-Y, the retarder is model DZH-2, the foaming agent is model DZF, and the foam stabilizer is model DZW, all from Dezhou 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 SCW-H.

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

[0090] The indoor experiment used a foamed quick-drying cement slurry system formed by high-speed rotation of a slurry cup, while the on-site engineering application used pure nitrogen, which was high-pressure room-temperature nitrogen formed by heating and vaporizing liquid nitrogen.

[0091] Density: Measured according to GB / T 19139-2012 Oil Well Cement Test Method.

[0092] Thickening time: Measured according to GB / T 19139-2012 Oil Well Cement Test Method.

[0093] Compressive strength: Measured according to GB / T 19139-2012 Oil Well Cement Test Method.

[0094] Time to initial strength: Measured according to GB / T 19139-2012 Test Method for Cement in Oil Wells.

[0095] Example 1

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

[0097] (1) Mix 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) to obtain a solid mixture;

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

[0099] (3) The solid mixture is mixed and stirred with the slurry water to obtain quick-drying cement slurry;

[0100] (4) Pump the quick-drying cement slurry obtained in step (3) through the foam cement slurry mixing skid, add 1 part by weight of foaming agent (DZF) and 0.6 parts by weight of foam stabilizer (DZW) into the mixing skid; then inject nitrogen gas at 25°C and 10MPa 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 chamber and cured at 50℃ and 10MPa for 48 hours. The results of its density, thickening time, compressive strength after solidification, and other properties are shown in Table 1.

[0102] Example 2

[0103] The foamed quick-drying cement slurry system was prepared according to the method in 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, while 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 in 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, while 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 in Example 1, except that the amount of foaming agent (DZF) added was 0.5 parts by weight and the amount of foam stabilizer (DZW) was 0.3 parts by weight, while the other components and steps remained the same. The results are shown in Table 1.

[0108] Comparative Example 1

[0109] The cement slurry system was prepared according to steps (1)-(3) of Example 1, except that the foaming agent, foam stabilizer and aeration steps (4) were not performed. The results are shown in Table 1.

[0110] The cement slurry system in Comparative Example 1 is not a foamed quick-drying cement slurry system and does not meet the density requirements of this invention for foamed quick-drying cement slurry systems; therefore, it was not used. It was only used to evaluate the basic properties of foamed quick-drying cement slurry.

[0111] Comparative Example 2

[0112] The cement slurry system was prepared according to the method in Example 1, except that thickener A was not added; that is, the amount of thickener A added was 0 parts by weight. 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 in Example 1, except that thickener B was not added; that is, the amount of thickener B added was 0 parts by weight, while 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 in Example 1, except that the quick-drying cement was replaced with conventional oil well cement (Jiahua G grade), while the other components and steps remained the same. The results are shown in Table 1.

[0117] Table 1

[0118]

[0119] As shown in Table 1, compared with the cement slurries of Comparative Examples 1, 2, and 3, the density of the foamed quick-drying cement slurries in Examples 1-4 is significantly reduced. This indicates a significant reduction in leakage of the plugging cement slurry in the lost circulation zone, improving the efficiency and success rate of sealing the lost circulation zone during well cementing operations, and the compressive strength meets the requirements for downhole plugging. Compared with Comparative Example 4, the foamed quick-drying cement slurry system in Examples 1-4 has a shorter strength development time, meets the requirements for construction and well leakage prevention, and is more conducive to achieving cement slurry plugging and consolidation of the well wall within the well, thus achieving the treatment of shallow lost circulation wells.

[0120] Application examples

[0121] The foamed quick-drying cement slurry systems of Examples 1-4 and the cement slurry systems of Comparative Examples 1-4 were respectively applied in the field to treat shallow surface leakage. The specific implementation process included:

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

[0123] (2) Pump the foamed quick-drying cement slurry system formed in Examples 1-4 or the cement slurry system formed in Comparative Examples 1-4 into the drill pipe according to the designed cement slurry volume and density, with a discharge rate of 0.8 m³ / s. 3 / min, pumping rate 63m 3 ;

[0124] (3) After the cement slurry system is pumped out, drilling fluid is used to replace the slurry. After the slurry is replaced, the wellhead drill pipe pump injection port valve is closed.

[0125] (4) Inject cement slurry into the well through the pipeline. Before the cement slurry reaches the lost circulation zone, the pumping rate in the pipeline is 0.8 m³. 3 After the cement slurry reaches the leakage layer at a rate of 0.4 m / min, adjust the pump discharge rate to 0.4 m. 3 / min.

[0126] (5) Observe the changes in pipeline pumping pressure. When the pump pressure slowly rises and the increase reaches 2MPa, stop pumping cement grout. The total pumping volume should reach 35m³. 3 Pump 1m 3 The pipeline was flushed with clean water, and the well was closed to allow the water to condense.

[0127] (6) After shutting in the well and allowing it to solidify for 24 hours, the well was opened and the plug was removed. After the drill bit penetrated the cement plug at the location of the lost circulation zone, the drilling fluid returned to the surface, and the cement slurry treatment of the shallow layer loss was completed. The results are shown in Table 2.

[0128] Table 2

[0129]

[0130] As can be seen from the results in Table 2, the foamed quick-drying cement slurry system of Examples 1-4 of this invention has a significant sealing effect, achieving the sealing of shallow wells with large leakage in a relatively short time. The cement slurry system of Comparative Examples 1-4 has a poor sealing effect or cannot meet the requirements of field application.

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

[0132] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within 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 quick-drying cement slurry with gas; 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 water loss reducing agent, 1-10 parts by weight of retarder and 35-60 parts by weight of water; The quick-drying cement is sulfoaluminate cement, wherein the mass content of aluminum oxide is 30-40% based on the total mass of the sulfoaluminate cement. The thickener A is microsilicon, wherein the SiO2 content is 80-95 wt%; the average particle size of the microsilicon is 0.05-0.3 μm; The thickener B is selected from xanthan gum or polyacrylamide polymer; The toughening agent is fiber; The aforementioned foamed quick-drying cement slurry system has a density of 0.7-1.2 g / cm³ under conditions of 25-60℃ and 7-12 MPa. 3 The fluidity is greater than 14 cm, the water separation is less than 1%, and the density difference between the upper and lower parts is less than 0.03 g / cm³. 3 ; Before introducing gas into the quick-drying cement slurry, the method further includes adding 0.5-1 parts by weight of foaming agent and 0.3-0.6 parts by weight of foam stabilizer to the quick-drying cement slurry.

2. The foamed quick-drying cement slurry system according to claim 1, wherein, The volume ratio of the gas to the quick-drying cement slurry is 30-80:1; And / or, the gas is nitrogen or air.

3. The foamed quick-drying cement slurry system according to claim 2, wherein, The volume ratio of the gas to the quick-drying cement slurry is 45-65:

1.

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

5. The foamed quick-drying cement slurry system according to claim 1 or 2, wherein, The retarder is selected from one or more of hydroxyethylidene diphosphonic acid, citric acid, sodium citrate, sodium gluconate, and tartaric acid.

6. The foamed quick-drying cement slurry system according to claim 1 or 2, wherein, The number-average molecular weight of the polyacrylamide polymer is 4 million to 8 million g / mol.

7. The foamed quick-drying cement slurry system according to claim 1 or 2, wherein, The fiber has a diameter of 2-8 μm and a length of 2-5 mm; And / or, the water loss reducing agent is selected from one or more of 2-acrylamide-2-methylpropanesulfonic acid polymers, ketaldehyde condensates, and polyvinyl alcohol systems; And / or, the foaming agent is a protein-based foaming agent or a mixture of a protein-based foaming agent and an ionic surfactant; 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.

8. The foamed quick-drying cement slurry system according to claim 7, wherein, The ionic surfactant is selected from one or more of sodium fatty alcohol polyoxyethylene ether sulfate, cocamidopropyl betaine, and sodium α-alkenyl sulfonate.

9. A method for preparing the foamed quick-drying cement slurry system according to any one of claims 1-8, characterized in that, The preparation method includes the following steps: (1) Mix 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) Mix 2-8 parts by weight of water loss reducer, 1-10 parts by weight of retarder and 35-60 parts by weight of water to obtain slurry water; (3) The solid mixture is mixed with the slurry water to obtain quick-drying cement slurry; (4) Mix the quick-drying cement slurry with 0.5-1 parts by weight of foaming agent and 0.3-0.6 parts by weight of foam stabilizer, and then inflate to obtain a foam quick-drying cement slurry system.

10. The preparation method according to claim 9, wherein, The inflation step specifically includes: inflation under agitation conditions and a gas pressure of 1-25 MPa.

11. The preparation method according to claim 10, wherein, The inflation step specifically includes: inflation under agitation conditions and a gas pressure of 3-12 MPa.

12. The application of the foam quick-drying cement slurry system as described in any one of claims 1-8 in oilfield cementing; during the pumping process of the foam quick-drying cement slurry system, the dispersed cement particles formed by the thickening of the foam quick-drying cement slurry system are connected by the fibers to form a network of foam cement stone.

13. The application according to claim 12, wherein, Application of the foamed quick-drying cement slurry system in shallow surface leakage of oil and gas wells.

14. A method for controlling shallow surface leakage in oil and gas wells, characterized in that, The method includes: The foam quick-drying cement slurry system according to any one of claims 1-8 is delivered to the lost formation to displace the drilling fluid in the original well and return it to the well or descend into the lost formation for plugging; wherein, during the pumping of the foam quick-drying cement slurry system, the dispersed cement particles formed by the thickening of the foam quick-drying cement slurry system are connected by the fibers to form a network of foam cement stone.

15. The method according to claim 14, wherein, The foamed quick-drying cement slurry system is cured to allow it to solidify.

16. The method according to claim 15, wherein, The curing temperature is 35-70℃, the pressure is 5-15MPa, and the time is 24-72h.

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