Efficient method for removing near-well reverse emulsion in offshore heavy oil thermal recovery well

Abstract

The application provides a high-efficiency removal method for a reverse emulsification zone near a thermal recovery well of offshore heavy oil, and belongs to the technical field of oilfield exploitation, and comprises the following steps: step 1, determining that a reverse emulsification zone exists near the thermal recovery well of offshore heavy oil; wherein the near-well emulsification zone of the oil reservoir under the condition is a hot huff and puff well, and the viscosity of the emulsion in the emulsification zone is increased by more than 3 times compared with the viscosity of the original crude oil; step 2, calculating the range of the reverse emulsification zone near the thermal recovery well of offshore heavy oil; step 3, forming a thought for removing the reverse emulsification zone near the thermal recovery well of offshore heavy oil; and step 4, forming a method for removing the reverse emulsification zone near the thermal recovery well of offshore heavy oil. The application can provide a high-efficiency removal method for the reverse emulsification zone of the thermal recovery well of offshore heavy oil, and guarantee the safe and efficient production of the thermal recovery well of offshore heavy oil.

Description

Technical Field

[0001] This invention belongs to the field of oilfield development technology, and in particular relates to an efficient method for removing near-wellbore reverse emulsion zones in offshore heavy oil thermal recovery wells. Background Technology

[0002] In recent years, during heavy oil extraction, it has been discovered that the viscosity of crude oil dehydrated and degassed at 50℃ in some heavy oil wells is not particularly high. However, after switching from pumping to extraction, the electric pump malfunctions, causing the well to fail to produce normally. Testing reveals that the viscosity of the produced fluid is 3 to 10 times higher than the actual viscosity. Specific research indicates that under the influence of multiple factors such as hot water heating, gas mixing, and hot water, the crude oil emulsion transforms from an o / w type emulsion to a w / o type emulsion, forming a reverse emulsification phenomenon. At this time, the viscosity of the crude oil emulsion increases significantly, leading to excessive friction during reservoir seepage or wellbore lifting, preventing normal production. If reverse emulsification occurs near the wellbore, forming an "emulsion zone," it will manifest as insufficient fluid supply during production, affecting oil-water treatment efficiency, causing the well to fail to produce normally, or even paralyzing the entire transportation process. For emulsion zones, existing technologies often use demulsifiers or viscosity reducers for treatment. However, using demulsifiers to unblock requires injecting a large amount of aqueous solution, which may exacerbate the complex underground conditions. In addition, considering the effective working temperature of demulsifiers, a platform heating device is required. Using viscosity reducers to unblock has a limited treatment radius and is more expensive. Summary of the Invention

[0003] In view of this, the present invention aims to propose an efficient method for removing the "reverse emulsion zone" near the wellbore of offshore heavy oil thermal recovery wells, based on the research on the "reverse emulsion zone" in the near-wellbore zone of heavy oil wells, so as to ensure the safe and efficient production of offshore heavy oil thermal recovery wells.

[0004] To achieve the above objectives, the technical solution of the present invention is as follows: a method for efficiently removing near-wellbore reverse emulsion zones in offshore heavy oil thermal recovery wells, comprising the following steps:

[0005] Step 1: Determine the presence of an inverse emulsion zone near the wellbore of offshore heavy oil thermal recovery wells; among them, injection wells with a near-wellbore emulsion zone where the viscosity of the emulsion is more than 3 times that of the original crude oil under reservoir conditions.

[0006] Step 2: Calculate the extent of the near-wellbore reverse emulsion zone in offshore heavy oil thermal recovery wells;

[0007] Step 3: Develop a strategy for resolving the near-wellbore reverse emulsion zone in offshore heavy oil thermal recovery wells;

[0008] Step 4: Method for removing the near-wellbore reverse emulsion zone in offshore heavy oil thermal recovery wells.

[0009] Furthermore, in step 1, it was determined that there was an anti-emulsification zone near the wellbore of the offshore heavy oil thermal recovery well. First, based on the analysis of the on-site production situation, the liquid volume decreased sharply, and the produced liquid had a serious impact on the original demulsification process, with significant changes in the viscosity and color of the produced liquid. Second, the results of viscosity tests of oil-water emulsions under different water content conditions in the laboratory were used for verification.

[0010] Furthermore, step 2 specifically involves performing a simulation using CMG software. The key parameters and specific simulation steps are as follows:

[0011] Based on the formation hot water injection rate and backflow rate parameters, the amount of water remaining in the formation is calculated. A numerical simulation model of the target well is established in the commercial reservoir numerical simulation software CMG. The emulsification reaction formula is set. Through historical fitting and production prediction, the amount of emulsified heavy oil in the formation of the target well is calculated. After removing the radius of the near-well water zone, the range of the near-well reverse emulsion zone of the offshore heavy oil thermal recovery well can be obtained.

[0012] Furthermore, step 3 includes injecting a composite "thin oil + chemical agent" solution to relieve emulsification blockage by reducing viscosity and resistance.

[0013] Furthermore, step 4 specifically involves using hot thin oil to reduce viscosity, and using a combination of reverse demulsifier and nano viscosity reducer to reduce drag.

[0014] Furthermore, after the hot thin oil comes into contact with the reverse emulsion belt, it has a dissolving and viscosity-reducing effect, which is used to significantly reduce the viscosity of the oil-water mixture in the emulsion belt; after the solvent of the reverse demulsifier and nano viscosity reducer comes into contact with the reverse emulsion belt, the reverse demulsifier has a demulsifying and viscosity-reducing effect, and the nano viscosity reducer has a nano effect. The combined action of the reverse demulsifier and the nano viscosity reducer can prevent the multiple emulsification behavior caused by the emulsification effect of the asphalt-based natural emulsifier; the purpose of reducing viscosity is achieved by using hot thin oil, and the purpose of reducing drag is achieved by using the combination of reverse demulsifier and nano viscosity reducer, forming a "thin oil + chemical agent" composite feeding method.

[0015] Compared with existing technologies, the efficient method for removing near-wellbore reverse emulsion zones in offshore heavy oil thermal recovery wells described in this invention has the following advantages:

[0016] (1) The method described in this invention can effectively remove the reverse emulsion zone near the wellbore of offshore heavy oil thermal recovery wells, thereby ensuring the safe and efficient production of offshore heavy oil thermal recovery wells;

[0017] (2) The method described in this invention can effectively utilize the platform's light oil resources, has a large processing radius, and extracts the light oil after it is injected into the formation and mixed with the emulsified heavy oil, which greatly reduces the cost of measures and effectively and economically removes the emulsion blockage.

[0018] (3) The method described in this invention can effectively exert the synergistic effect of "viscosity reduction" and "drag reduction". The thin oil can significantly reduce the viscosity of crude oil. At the same time, as a carrier of chemical agents (reverse demulsifier and nano viscosity reducer), the chemical agents weaken the liquid resistance effect and effectively prevent the formation from emulsification problems from recurring.

[0019] (4) The method described in this invention proposes and designs the process flow for heating and reinjecting light oil on offshore platforms for the first time, and guides the completion of the first field test of the "light oil + chemical agent" composite huff and puff technology in offshore heavy oil fields. Detailed Implementation

[0020] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0021] This example provides an efficient method for removing near-wellbore emulsion zones in offshore heavy oil thermal recovery wells. The method consists of four steps: determining the formation of the near-wellbore reverse emulsion zone, calculating the extent of the near-wellbore emulsion zone, determining the removal strategy for the near-wellbore reverse emulsion zone, and formulating an efficient method for removing near-wellbore emulsion zones in offshore heavy oil thermal recovery wells. Ultimately, this method removes the near-wellbore emulsion zone in offshore heavy oil thermal recovery wells, achieving successful resumption of production. The proposed "light oil + chemical agent" composite huff and puff method effectively utilizes the platform's light oil resources, has a large processing radius, low cost, and can effectively remove emulsion blockages. Specifically, it includes the following steps:

[0022] Step 1: Determine the presence of an inverse emulsion zone near the wellbore of offshore heavy oil thermal recovery wells; among them, injection wells with a near-wellbore emulsion zone where the viscosity of the emulsion is more than 3 times that of the original crude oil under reservoir conditions.

[0023] The presence of a reverse emulsion zone near the wellbore in offshore heavy oil thermal recovery wells was determined through two methods: first, analysis of the on-site production conditions showed a sharp decrease in fluid volume, which severely impacted the original demulsification process, resulting in significant changes in the viscosity, color, and other properties of the produced fluid; second, the results of viscosity tests on oil-water emulsions under different water content conditions in the laboratory were used for verification.

[0024] Step 2: Calculate the extent of the near-wellbore reverse emulsion zone in offshore heavy oil thermal recovery wells; specifically, use CMG software for simulation, and the key parameters and specific simulation steps are as follows:

[0025] Based on parameters such as formation hot water injection volume and backflow rate, the amount of water remaining in the formation is calculated. A numerical simulation model of the target well is established in the commercial reservoir numerical simulation software CMG. The emulsification reaction formula is set. Through historical fitting and production prediction, the amount of emulsified heavy oil in the formation of the target well is calculated. After removing the radius of the near-well water zone, the range of the near-well reverse emulsification zone of the offshore heavy oil thermal recovery well can be obtained.

[0026] Step 3: Develop a strategy for removing the near-wellbore reverse emulsion zone in offshore heavy oil thermal recovery wells; preferably use a combined injection of "light oil + chemical agent" to remove emulsion blockage by reducing viscosity and drag.

[0027] Step 4: Develop a method to remove the near-wellbore reverse emulsion zone in offshore heavy oil thermal recovery wells; specifically, use hot thin oil to achieve viscosity reduction, and use a combination of reverse demulsifier and nano viscosity reducer to achieve drag reduction.

[0028] When hot thin oil comes into contact with the reverse emulsion zone, it fully utilizes its dissolving and viscosity-reducing effects, significantly lowering the viscosity of the oil-water mixture in the emulsion zone. When the solvent, a mixture of reverse demulsifier and nano-viscosity reducer, comes into contact with the reverse emulsion zone, it fully utilizes the demulsifying and viscosity-reducing effects of the reverse demulsifier, while the nano-effect of the nano-viscosity reducer alters the aggregation morphology of the asphaltenes in the reverse emulsion, preventing multiple emulsification behaviors caused by the natural emulsification of asphaltenes. This combined approach of "thin oil + chemical agent" ensures the system effectively reduces viscosity and drag, relieving emulsion blockage.

[0029] Take a heavy oil thermal recovery well in an offshore oil field as an example.

[0030] Step 1: Determine the presence of an inverse emulsion zone near the wellbore of offshore heavy oil thermal recovery wells;

[0031] To address the issues of insufficient formation energy and high crude oil viscosity in a target well at an offshore oil field, a multi-element hot fluid injection system was implemented, with a cumulative hot water injection volume of approximately 3,000 tons. After starting production with the electric pump, the initial daily fluid production was 66 cubic meters per second. 3 After four days of production, the fluid volume and flowing pressure decreased, and the annular fluid replenishment effect was poor, leading to pump shutdown. The multi-component thermal fluid injection system had a short production time, initially providing heating and viscosity reduction, but the flowing pressure and temperature dropped rapidly, resulting in insufficient formation fluid supply. Crude oil sample analysis showed a viscosity of 4845 mPa·s (50℃), four times that of the initial production period. Combined with the low fluid production and reduced flowing pressure from the increased frequency of the ESP, and the condition of the produced oil samples, it was determined that a reverse emulsion zone existed near the target offshore heavy oil well, causing formation blockage.

[0032] Step 2: Calculate the extent of the near-wellbore reverse emulsion zone in offshore heavy oil thermal recovery wells;

[0033] The target well has low formation pressure, high viscosity of heavy oil near the wellbore, and severe reverse emulsification after the injection of low-temperature multi-component thermal fluid. During the multi-component thermal fluid operation, approximately 3000 tons of hot water were injected, with only 476 tons flowed back, a flowback rate of about 16%. A large amount of injected water remained in the formation. A numerical simulation model of the target well was established using the commercial reservoir numerical simulation software CMG, and an emulsification reaction formula was set. Through historical data fitting and production prediction, the amount of emulsified heavy oil in the target well exceeded 3000 m³. 3 After removing the 2m radius of the near-wellwater zone, the radius of the near-well reverse emulsion zone of the target well is predicted to be 4m.

[0034] Step 3: Develop a strategy for resolving the near-wellbore reverse emulsion zone in offshore heavy oil thermal recovery wells;

[0035] To address the near-wellbore reverse emulsion zone issue in the target well, an analysis was conducted considering factors such as the degree of emulsification, emulsion radius, and available light oil resources. Given the large formation emulsion area, injecting aqueous slugs is not recommended as it would further complicate the underground emulsion situation. Furthermore, conventional oil-soluble viscosity reducers are costly. The platform possesses abundant light oil resources, which are similar in properties to oil-soluble viscosity reducers. Viscosity reduction can be achieved through the principle of "like dissolves like," and the platform has the capability for combined light oil injection and unblocking. Therefore, a combined "light oil + chemical agent" injection and unblocking method with a larger processing radius and lower cost is proposed. Using light oil and a highly efficient viscosity reducer as the medium, the injected light oil dilutes the underground heavy oil, while the chemical agent reduces drag and enhances efficiency, thereby resolving the emulsion blockage through viscosity and drag reduction.

[0036] Step 4: Method for removing the near-wellbore reverse emulsion zone in offshore heavy oil thermal recovery wells.

[0037] The key to removing the reverse emulsion zone in the target well lies in reducing crude oil viscosity and mitigating the liquid resistance effect. Field sampling of emulsified crude oil and usable light oil resources from the target well was conducted, and viscosity reduction experiments were performed using diluents. The viscosity reduction effect was greater than 90% under different diluent ratios. Adding different viscosity-reducing systems, under experimental conditions, could convert the emulsion from W / O to O / W, achieving resistance reduction on the basis of viscosity reduction. The composite viscosity-reducing system formed by combining reverse demulsifier and nano-viscosity reducer showed a significantly higher viscosity-reducing effect than ordinary viscosity reducers. The droplets formed after emulsification and dispersion were significantly smaller, and the liquid resistance effect was weakened. Using the actual reservoir geological model of the target well, numerical simulations of a "light oil + chemical agent" composite huff and puff reservoir were carried out under different injection and production parameters. Reasonable injection and production parameters for the "light oil + chemical agent" composite huff and puff of the offshore heavy oil target well are given, with specific types shown in Table 1. The predicted net oil production of the scheme reaches 2500 m³. 3 .

[0038] Table 1. Parameters for Combined Huff and Puff Injection of "Light Oil + Chemical Agent"

[0039]

[0040]

[0041] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. 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 efficiently removing near-wellbore reverse emulsion zones in offshore heavy oil thermal recovery wells, characterized in that, Includes the following steps: Step 1: Determine the presence of an inverse emulsion zone near the wellbore of offshore heavy oil thermal recovery wells; among them, injection wells with a near-wellbore emulsion zone where the viscosity of the emulsion is more than 3 times that of the original crude oil under reservoir conditions. The presence of an inverse emulsion zone near the wellbore in offshore heavy oil thermal recovery wells was determined through two main methods: first, analysis of the on-site production conditions revealed a sharp decrease in fluid volume, which severely impacted the original demulsification process, resulting in significant changes in the viscosity and color of the produced fluid; second, the results of viscosity tests on oil-water emulsions under different water content conditions in the laboratory were used for verification. Step 2: Calculate the extent of the near-wellbore reverse emulsion zone in offshore heavy oil thermal recovery wells; specifically, use CMG software for simulation, with key parameters and specific simulation steps as follows: Based on the parameters of formation hot water injection and backflow rate, the amount of water remaining in the formation is calculated. A numerical simulation model of the target well is established in the commercial reservoir numerical simulation software CMG. The emulsification reaction formula is set. Through historical fitting and production prediction, the amount of emulsified heavy oil in the formation of the target well is calculated. After removing the radius of the near-well water zone, the range of the near-well reverse emulsification zone of the offshore heavy oil thermal recovery well can be obtained. Step 3: Develop a strategy for removing the near-wellbore reverse emulsion zone in offshore heavy oil thermal recovery wells; this includes a combined injection and chemical agent huff-and-puff method to remove emulsion blockage by reducing viscosity and drag; Step 4: Method for removing the near-wellbore reverse emulsion zone in offshore heavy oil thermal recovery wells.

2. The method for efficiently removing near-wellbore reverse emulsion zone in offshore heavy oil thermal recovery wells according to claim 1, characterized in that: Step 4 specifically involves using hot thin oil to reduce viscosity, and using a combination of reverse demulsifier and nano viscosity reducer to reduce drag.

3. The method for efficiently removing near-wellbore reverse emulsion zone in offshore heavy oil thermal recovery wells according to claim 2, characterized in that: When hot thin oil comes into contact with the reverse emulsion belt, it has the effect of dissolving and reducing viscosity, and is used to significantly reduce the viscosity of the oil-water mixture in the emulsion belt; When the solvent containing the inverse demulsifier and the nano viscosity reducer comes into contact with the inverse emulsion, the inverse demulsifier has the effect of demulsifying and reducing viscosity, while the nano viscosity reducer has the effect of nanotechnology. The combined action of the inverse demulsifier and the nano viscosity reducer can prevent the multiple emulsification behavior caused by the emulsification effect of the natural emulsifier of asphaltene. The purpose of reducing viscosity is achieved by using hot thin oil, and the purpose of reducing drag is achieved by using the combination of the inverse demulsifier and the nano viscosity reducer. This combination forms a composite feeding and discharging method of thin oil and chemical agents.

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