A method for step-by-step plugging of high water consumption thick strips in water injection wells

Abstract

This invention provides a method for stepwise plugging of high water-consuming thick strip formations in injection wells, comprising the following steps: preparing an inorganic plugging agent and forming the inorganic plugging agent into a particle system with different particle sizes; injecting the inorganic plugging agent from the injection well, and using a multi-round injection method, so that the inorganic plugging agent of different particle systems enters the different fracture levels of the high water-consuming thick strip formations, thereby stepwise plugging the fracture strips with different pore sizes; wherein, the plugging is performed stepwise from the fracture strips far from the injection well to the fracture strips close to the injection well, so as to plug the corresponding target locations of the high water-consuming thick strip formations.

Description

Technical Field

[0001] This invention belongs to the field of petroleum development and extraction technology, specifically relating to a method for step-by-step plugging of thick strips in high water consumption injection wells. Background Technology

[0002] Some injection wells possess thick, high-water-consumption zones, which are potential injection water advantage channels formed by a mixture of fractures, microfractures, and high-permeability layers. After long-term intensive injection and production in injection-production well groups, the injected water surges through these thick, high-water-consumption zones. As a result, the injected water always enters the production well along this advantage channel and is then extracted, exacerbating the ineffective circulation of injected water. This leads to a continuous increase in the water-to-oil ratio of the well group, increased water cut in the producing wells, and decreased oil production, resulting in increased development costs and reduced economic benefits. Studies have shown that the degree of reserve utilization varies greatly in such well groups, with the remaining oil in the wells mainly distributed within the range of 1 / 3 to 1 / 2 of the well spacing. Currently, implementing deep plugging and regulation measures in injection wells to change the direction of fluid flow in the deeper formations is an important technical means of tapping the potential of oil wells. However, deep plugging and regulation of thick, high-water-consumption zones requires suitable plugging and regulation agents.

[0003] Currently, most plugging and regulating agents limit their application scope. For example, cement-based plugging agents have high strength but poor injectability, cannot penetrate deep into the formation for plugging, have short plugging distances, and cause significant reservoir damage. Foam-type plugging agents have poor stability, short-lasting effects, require large injection doses, and have high operating costs, greatly limiting their field application. Organic plugging agents are widely used, but their low strength, high price, large formation adsorption capacity, and short shelf life restrict their widespread application. Summary of the Invention

[0004] To address the technical problems described above, this invention aims to propose a method for step-by-step plugging of high water-consuming thick strips in water injection wells. This method can effectively reduce the ineffective circulation of injected water, greatly improve the water injection effect, and is very beneficial for increasing oil production and oil extraction efficiency.

[0005] Therefore, according to the present invention, a method for stepwise plugging of high water-consuming thick strip formations in injection wells is provided, comprising the following steps: preparing an inorganic plugging agent and forming the inorganic plugging agent into a particle system with different particle sizes; injecting the inorganic plugging agent from the injection well and using a multi-round injection method, so that the inorganic plugging agent of different particle systems enters into different fracture levels of high water-consuming thick strip formations, thereby stepwise plugging fracture strips with different pore sizes; wherein, the plugging is performed stepwise from the fracture strips far from the injection well to the fracture strips close to the injection well, so as to plug the corresponding target positions of the high water-consuming thick strip formations.

[0006] In one embodiment, the inorganic plugging agent is prepared into a first-stage particle system, a second-stage particle system, and a third-stage particle system, wherein the particle size of the first-stage particle system is greater than 75 μm, the particle size of the second-stage particle system is 15~75 μm, and the particle size of the third-stage particle system is 5~15 μm.

[0007] In one embodiment, during multiple injections, the first-level particle system, the second-level particle system, and the third-level particle system are injected sequentially. The first-level particle system enters the fracture-level band, the second-level particle system enters the fracture-level band and the micro-fracture band, and the third-level particle system enters the fracture-level band, the micro-fracture band, and the high-permeability band.

[0008] In one embodiment, the inorganic blockage agent comprises, by mass content, 83-87% composite coagulant, 8-10% suspending agent, and 5-7% retarder.

[0009] In one embodiment, the composite coagulant is formed by mixing gypsum, calcium hydroxide, and ultrafine cement.

[0010] In one embodiment, the suspending agent is bentonite.

[0011] In one embodiment, the retarder is a compound of sodium gluconate.

[0012] In one embodiment, the solidification time of the inorganic plugging agent is 8 to 240 hours.

[0013] In one embodiment, the viscosity of the inorganic plugging agent is less than 30 mPa·s.

[0014] In one embodiment, the injection pressure of the inorganic plugging agent is less than the well fracturing pressure.

[0015] Compared with the prior art, the advantages of this application are:

[0016] The inorganic plugging agent prepared according to the present invention, using the stepwise plugging method for high water-consuming thick strips in water injection wells, has a solidification time of 8–240 hours, which is highly beneficial for ensuring safe construction. The inorganic plugging agent has good fluidity, is suitable for deep plugging of high water-consuming thick strips, is very easy to inject, and has a viscosity of less than 30 mPa·s. The system has high strength after solidification, can bond with rock, and provides a long-lasting plugging effect. This stepwise plugging method for high water-consuming thick strips in water injection wells can accurately locate and permanently plug high water-consuming thick strips, redirecting the fluid flow to medium-low permeability potential layers, expanding the swept volume, and ultimately reducing ineffective circulation of injected water, greatly improving the water injection effect. Furthermore, this method is highly practical. Utilizing the advantages of the good fluidity and spreadability of the inorganic plugging agent, it achieves stepwise deep plugging and modification, realizing small-dose, high-intensity, deep multi-round plugging and modification, greatly improving the profile modification effect, significantly increasing the oil production and oil production efficiency of oil wells, increasing the water injection pressure of water injection wells, and with low plugging and modification operation costs. Attached Figure Description

[0017] The invention will now be described with reference to the accompanying drawings.

[0018] Figure 1 The schematic diagram illustrates the principle of the high water consumption thick strip step-by-step plugging method for injection wells according to the present invention.

[0019] In this application, all drawings are schematic and are used only to illustrate the principles of the invention, and are not drawn to scale. Detailed Implementation

[0020] The present invention will now be described with reference to the accompanying drawings. It should be noted that these descriptions are provided merely to illustrate the principles of the invention and do not limit the scope of the invention.

[0021] In this application, it should be noted that the directional terms or qualifiers such as "up" and "down" used in this application are all specific to the referenced appendix. Figure 1 The references to this invention are merely for the purpose of facilitating description and simplification, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, be constructed or operated in a specific orientation, and therefore should not be construed as limiting the invention.

[0022] Figure 1 A schematic diagram illustrating the principle of the high water consumption thick strip step-by-step plugging method for injection wells according to the present invention is shown. Figure 1As shown, in the formation, the high water-consuming thick strip formation 3 is located between the injection well 1 and the production well 2. From bottom to top, the high water-consuming thick strip formation 3 consists of fracture-level strips 31, micro-fracture strips 32, high-permeability strips 33, and medium-low permeability strips 34. The fracture porosity decreases from fracture-level strips 31, micro-fracture strips 32, high-permeability strips 33, to medium-low permeability strips 34. The sealing targets of the step-by-step plugging method for the high water-consuming thick strip formation in the injection well of this invention are fracture-level strips 31, micro-fracture strips 32, and high-permeability strips 33. This step-by-step plugging method for the high water-consuming thick strip formation in the injection well includes the following steps:

[0023] First, an inorganic blockage modifier is prepared. The inorganic blockage modifier is made from an inorganic composite coagulant, suspending agent, and retarder. The inorganic blockage modifier comprises, by mass content, 83-87% composite coagulant, 8-10% suspending agent, and 5-7% retarder. For example, in a preferred embodiment, the inorganic blockage modifier may include, by mass content, a composite coagulant: suspending agent: retarder = 85:9:6.

[0024] Composite coagulants are potential coagulants. In one embodiment, the composite coagulant is formed by mixing gypsum, calcium hydroxide, and ultrafine cement. Preferably, the mass ratio of gypsum, calcium hydroxide, and ultrafine cement can be 1:2:2. This can significantly improve the coagulation effect of the composite coagulant.

[0025] In one embodiment, the suspending agent is bentonite. The suspending agent serves to stabilize and suspend the material.

[0026] In one embodiment, the retarder is a compound of sodium gluconate.

[0027] According to the present invention, in preparing the inorganic plugging agent, the inorganic plugging agent is prepared into a particulate system with different particle sizes. The composite coagulant, suspending agent, and retarder have various combinations with particle sizes greater than 5 μm, and can be configured into different micron-sized particle systems as needed. For example, the inorganic plugging agent can be prepared into a first-level particulate system, a second-level particulate system, and a third-level particulate system, wherein, depending on the actual geological conditions, the particle size of the first-level particulate system is greater than 75 μm, the particle size of the second-level particulate system is 15~75 μm, and the particle size of the third-level particulate system is 5~15 μm. During plugging operations, the first-level particulate system enters the fracture-level bands, the second-level particulate system enters the fracture-level bands and micro-fracture bands, and the third-level particulate system enters the fracture-level bands, micro-fracture bands, and high-permeability bands. This allows for the step-by-step plugging of different fracture-level bands.

[0028] After the inorganic plugging and conditioning agent is prepared, it is injected into the injection well.

[0029] According to the present invention, the inorganic plugging agent is injected from the injection well in multiple rounds, and the inorganic plugging agents of different particle systems are injected into different fracture levels of the high water-consuming thick strip formation, thereby sealing the fracture levels of different strips step by step.

[0030] In one embodiment, the inorganic plugging agent is injected in three rounds. Preferably, the inorganic plugging agent is injected in stages from the fracture strips farther from the injection well 1 to the fracture strips closer to the injection well 1 to seal the corresponding target locations in the high water-consuming thick strip formations. That is, as... Figure 1 As shown, from right to left, the fracture-level strip at the first target location 4, the fracture-level strip and micro-fracture strip at the second target location 5, and the fracture-level strip, micro-fracture strip and high-permeability strip at the third target location 6 are sealed in sequence.

[0031] According to the present invention, during the multi-round injection of inorganic plugging agent, the particle size of the injected inorganic plugging agent decreases sequentially, that is, the first-level particle system, the second-level particle system, and the third-level particle system are injected sequentially. The number of injection rounds of inorganic plugging agent is determined according to geological conditions, and different particle systems correspond to entering different level bands. Specifically, the first-level particle system injected in the first round enters the fracture level band at the first target location 4, thereby sealing the fracture level band at the first target location 4. The second-level particle system injected in the second round enters the fracture level band and microfracture band at the second target location 5, thereby sealing the fracture level band and microfracture band at the second target location 5. The third-level particle system injected in the third round enters the fracture level band, microfracture band, and high-permeability band at the third target location 6, thereby sealing the fracture level band, microfracture band, and high-permeability band at the third target location 5. Thus, through stepwise deep regulation and control, small-dose, high-intensity, deep multi-round plugging and control is achieved. The step-by-step sealing process greatly improves the profile adjustment effect.

[0032] During the actual injection operation, the next stage is injected continuously after the previous stage has completely solidified, until the injection of each stage system is completed. The injection volume of each stage is simulated and calculated according to the plugging target design, and the injection pressure is ensured to be lower than the well fracturing pressure. In addition, the specific number of injection cycles and the ramp-up pressure are implemented according to the geological design of the well.

[0033] According to the present invention, the setting time of the inorganic plugging agent is 8–240 hours, which ensures safe construction and gives the inorganic plugging agent system good fluidity, which is very beneficial for easy injection. The viscosity of the inorganic plugging agent is less than 30 mPa·s, which allows the inorganic plugging agent to bond with the rock and provide a long-lasting sealing effect.

[0034] The following detailed embodiments illustrate the method for step-by-step plugging of high water-consuming thick strips in injection wells according to the present invention.

[0035] Example 1

[0036] An inorganic blockage modifier is prepared, comprising, by mass percentage: 85% composite coagulant, 9% suspending agent, and 6% retarder. The inorganic blockage modifier is prepared into three particle systems: a first-stage particle system, a second-stage particle system, and a third-stage particle system. The particle size of the first-stage particle system is greater than 75 μm, the particle size of the second-stage particle system is 15–75 μm, and the particle size of the third-stage particle system is 5–15 μm.

[0037] Inorganic plugging agents are injected from the injection well. A three-round injection method is used to sequentially inject inorganic plugging agents of different particle sizes from the injection well. Furthermore, the plugging is performed sequentially from the farthest point from the injection well 1 to the first target location 4, the second target location 5, and the third target location 6. In the first round, the inorganic plugging agent of the first-level particle size system is injected into the corresponding fracture-level band at the first target location 4 to plug the fracture-level band at that location. In the second round, the inorganic plugging agent of the second-level particle size system is injected into the corresponding fracture-level band and microfracture band at the second target location 5 to plug the fracture-level band and microfracture band at that location. In the third round, the inorganic plugging agent of the third-level particle size system is injected into the corresponding fracture-level band, microfracture band, and high-permeability band at the third target location 5 to plug the fracture-level band, microfracture band, and high-permeability band at that location.

[0038] Example 2

[0039] An inorganic blockage modifier is prepared, comprising, by mass percentage: 83% composite coagulant, 10% suspending agent, and 7% retarder. The inorganic blockage modifier is prepared into three particle systems: a first-stage particle system, a second-stage particle system, and a third-stage particle system. The particle size of the first-stage particle system is greater than 75 μm, the particle size of the second-stage particle system is 15–75 μm, and the particle size of the third-stage particle system is 5–15 μm.

[0040] Inorganic plugging agents are injected from the injection well. Different particle sizes of inorganic plugging agents are injected sequentially from the injection well using a three-stage injection method. Furthermore, the plugging is carried out sequentially at the first target location 4, the second target location 5, and the third target location 6, from the furthest point from the injection well 1.

[0041] In the first round, inorganic plugging agents from the third-stage particle system are injected into the corresponding fracture-level, micro-fracture, and high-permeability bands at the third target location 5 to seal these bands. In the second round, inorganic plugging agents from the second-stage particle system are injected into the corresponding fracture-level and micro-fracture bands at the second target location 5 to seal these bands. In the third round, inorganic plugging agents from the first-stage particle system are injected into the corresponding fracture-level bands at the first target location 4 to seal these bands.

[0042] Example 3

[0043] An inorganic blockage modifier is prepared, comprising, by mass percentage: 87% composite coagulant, 8% suspending agent, and 5% retarder. The inorganic blockage modifier is prepared into three particle systems: a first-stage particle system, a second-stage particle system, and a third-stage particle system. The particle size of the first-stage particle system is greater than 75 μm, the particle size of the second-stage particle system is 15–75 μm, and the particle size of the third-stage particle system is 5–15 μm.

[0044] Inorganic plugging agents are injected into the injection well. Inorganic plugging agents of different particle sizes are mixed and injected into the injection well in a single injection. Furthermore, the plugging is carried out sequentially from the farthest point from the injection well (first target position 4, second target position 5, and third target position 6).

[0045] Among them, the inorganic plugging and conditioning agent of the first-level particle system can enter the fracture-level strip, the inorganic plugging and conditioning agent of the second-level particle system can enter the fracture-level strip and micro-fracture strip, and the inorganic plugging and conditioning agent of the third-level particle system can enter the fracture-level strip, micro-fracture strip and high-permeability strip, so as to seal the different fracture-level strips at the corresponding target locations of the high water-consuming thick strip formation.

[0046] Example 4

[0047] Comparison of profile control performance of water injection wells:

[0048] Using the high water consumption thick strip step-by-step plugging method of water injection wells in Examples 1 to 3, the changes in oil production performance of the corresponding injection and production well groups after adopting the methods in each example are statistically analyzed. The results are shown in Table 1.

[0049] Table 1

[0050] Example Example 1 Example 2 Example 3 Average increase in oil consumption +28% +10% +17% Average water content of oil wells -32% -16% -20% Water injection pressure in water injection wells +5MPa +2MPa +3MPa Average blockage cost -30% -20% -20%

[0051] The plugging system formed by the high water consumption, thick strip, step-by-step plugging method for injection wells according to the present invention can meet the requirements of achieving deep plugging through a small-dose, multi-round process. The plugging system can bond with the rock, thereby achieving permanent plugging, and the high water consumption, thick strip, step-by-step profile control process is highly practical. Furthermore, as shown in the table above, the plugging method of Example 1 significantly increases oil production, significantly reduces water content, effectively increases water injection pressure, and significantly reduces plugging and control costs.

[0052] After on-site operations, the results of the nine water injection wells implemented showed a 100% effectiveness rate and a cost reduction of at least 30%. This method effectively modulates the profile of water injection wells, increasing the average water injection pressure by 20% and correspondingly increasing the oil production of oil wells by an average of 28%.

[0053] Example 5

[0054] The high water-consuming thick strip step-by-step plugging method for injection wells according to the present invention was applied to the YS-212 well group in the Eastern Oilfield. This group consists of one injection well and four production wells, characterized by long-term strong injection and production. Water surges along the dominant planar channel, forming a high water-consuming strip, resulting in ineffective circulation of injected water. The average well depth is 1240 meters. The average porosity is 14.1%, the average oil layer thickness is 15.4 meters, and the average permeability is 22 md (with significant variations, ranging from a minimum of 8 md to a maximum of 105 md). Construction began in November 2019, involving three rounds of plugging the high water-consuming thick strip in the injection wells. The total amount of profile control fluid used was 150 cubic meters, and the average plugging cost decreased by 30%. Results: By the end of 2020, statistics showed that three wells in the group significantly increased oil production, the injection pressure of the injection wells increased by 5 MPa, the average water cut of the oil wells decreased by 32%, and the average oil production increased by 32%.

[0055] The inorganic plugging agent prepared according to the present invention, using the stepwise plugging method for high water-consuming thick strips in water injection wells, has a solidification time of 8–240 hours, which is highly beneficial for ensuring safe construction. The inorganic plugging agent has good fluidity, is suitable for deep plugging of high water-consuming thick strips, is very easy to inject, and has a viscosity of less than 30 mPa·s. The system has high strength after solidification, can bond with rock, and provides a long-lasting plugging effect. This stepwise plugging method for high water-consuming thick strips in water injection wells can accurately locate and permanently plug high water-consuming thick strips, redirecting the fluid flow to medium-low permeability potential layers, expanding the swept volume, and ultimately reducing ineffective circulation of injected water, greatly improving the water injection effect. Furthermore, this method is highly practical. Utilizing the advantages of the good fluidity and spreadability of the inorganic plugging agent, it achieves stepwise deep plugging and modification, realizing small-dose, high-intensity, deep multi-round plugging and modification, greatly improving the profile modification effect, significantly increasing the oil production and oil production efficiency of oil wells, increasing the water injection pressure of water injection wells, and with low plugging and modification operation costs.

[0056] It should be noted that, in Figure 1In the diagram, the downward arrow indicates the injection direction into injection well 1, while the upward arrow indicates the oil production direction of the oil well.

[0057] Finally, it should be noted that the above description is merely a preferred embodiment of the present invention and does not constitute any limitation on the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for step-by-step plugging of a high water consumption thick strip in a water injection well, comprising the following steps: Preparation of an inorganic plugging agent, and preparation of a particle system with different particle sizes from the inorganic plugging agent; Injecting the inorganic plugging agent from the water injection well, and using multiple injection rounds to make the inorganic plugging agent with different particle sizes enter different fracture level strips of the high water consumption thick strip formation, thereby step-by-step plugging of different pore fracture strips; Wherein, the particle system includes a first level particle system, a second level particle system and a third level particle system with decreasing particle size, Step-by-step plugging from the fracture strip far from the water injection well to the fracture strip close to the water injection well to plug the corresponding target position of the high water consumption thick strip formation, In multiple injection rounds, the first level particle system, the second level particle system and the third level particle system are injected step-by-step, The first level particle system enters the fracture level strip, the second level particle system enters the fracture level strip and the micro-fracture strip, and the third level particle system enters the fracture level strip, the micro-fracture strip and the high permeability strip. 2.The method for step-by-step plugging of a high water consumption thick strip in a water injection well according to claim 1, wherein, The particle size of the first level particle system is greater than 75 μm, the particle size of the second level particle system is greater than 15 μm and less than 75 μm, and the particle size of the third level particle system is greater than 5 μm and less than 15 μm.

3. The method according to claim 1 or 2, characterized in that, The inorganic plugging agent includes a composite coagulant 83-87%, a suspending agent 8-10%, and a retarder 5-7% by mass content.

4. The method according to claim 3, wherein the method is characterized by, The composite coagulant is formed by mixing gypsum, calcium hydroxide and ultra-fine cement.

5. The method according to claim 3, wherein the method is characterized by, The suspending agent is bentonite.

6. The method according to claim 3, wherein the method is characterized by, The retarder is a compound of sodium gluconate.

7. The method according to claim 3, wherein the method is characterized by, The coagulation time of the inorganic plugging agent is 8-240 hours.

8. The method according to claim 3, wherein the method is characterized by, The viscosity of the inorganic plugging agent is less than 30 mPa.s.

9. The method according to claim 1, wherein the method is characterized by, The injection pressure of the inorganic plugging agent is less than the fracture pressure of the oil well.

Images