SAGD (Steam Assisted Gravity Drainage) upwarp horizontal well thickened oil recovery system and method

Abstract

The invention discloses an SAGD upwarp horizontal well thickened oil recovery system, and relates to the field of thickened oil recovery, the SAGD upwarp horizontal well thickened oil recovery system comprises an upwarp horizontal well, the upwarp horizontal well comprises a vertical section, a deflecting section and an upwarp horizontal section which are connected in sequence, the vertical section, the deflecting section and the upwarp horizontal section are in a V shape, a steam injection tubular column and an oil pumping tubular column are arranged in the horizontal well, and the steam injection tubular column and the oil pumping tubular column are arranged in the horizontal well. An electric heating device is arranged at the position, located on the upwarp horizontal section, of the steam injection tubular column, the upwarp horizontal well is adopted, liquid gathering is easily formed at the heel position of the horizontal section, efficient operation of an oil well pump is better facilitated, the risk that steam enters the oil well pump can be reduced, and the use degree and yield of the horizontal section can be effectively improved; and meanwhile, an underground electric heating mode is adopted, so that heat loss of a shaft can be eliminated, and steam thermal recovery can be expanded to a deeper heavy oil reservoir.

Description

Technical Field

[0001] The invention relates to the field of heavy oil production, and in particular to a SAGD upturned horizontal well heavy oil production system and a production method. Background Art

[0002] Steam-assisted gravity drainage (SAGD) is the most effective technology for heavy oil production. Usually, in the process of heavy oil production, two parallel horizontal wells with a vertical distance of 5-7 meters are drilled in the oil layer, and steam is injected into the oil reservoir from a horizontal gas injection well located above. The heated crude oil and steam condensate are produced from the horizontal production well at the bottom of the oil reservoir. Although this development method can achieve higher heavy oil production and recovery rate, it is difficult and expensive to drill parallel double horizontal wells, and the minimum thickness of the oil layer is required to be greater than 10 meters, which limits the application scope of SAGD technology. In order to overcome this problem, a technology of using a single horizontal well to realize the SAGD production mechanism is proposed. Although the single horizontal well SAGD technology reduces the difficulty and cost of drilling wells, there are many unfavorable factors. The realization of steam injection and oil production processes in the same well greatly increases the difficulty of downhole operation control. First, the heat exchange between the injected high-temperature steam and the produced fluid can easily lead to an excessively high temperature of the produced fluid, causing part of the liquid to flash into gas, seriously interfering with the normal operation of the oil pump; on the other hand, it is difficult to maintain a stable gas-liquid interface in a horizontal well, and it is difficult to control the intrusion of steam into the production well section, making the operation difficult, resulting in a low gravity drainage rate, low horizontal section utilization efficiency and low final recovery rate. Summary of the invention

[0003] In view of the above problems, the present invention provides a SAGD upturned horizontal well heavy oil production system, which can improve the production efficiency and horizontal section utilization efficiency by establishing a higher liquid level near the heel of the horizontal section and saving energy consumption.

[0004] The technical solution of the present invention is:

[0005] A SAGD upturned horizontal well heavy oil production system comprises an upturned horizontal well, wherein the upturned horizontal well comprises a vertical section, a deflecting section and an upturned horizontal section connected in sequence, wherein the vertical section, the deflecting section and the upturned horizontal section are in a "√" shape, a steam injection string and an oil pumping string are arranged in the horizontal well, and an electric heating device is provided at the position of the steam injection string located in the upturned horizontal section.

[0006] The length of the upward-warped horizontal section of the horizontal well is 300-800 meters, and the upward-warping angle is 2-5°.

[0007] Mining includes the following steps:

[0008] S1. Complete drilling of the upturned horizontal well, run the production casing to the beginning of the horizontal section in the upturned horizontal well, and run the production screen in the horizontal section;

[0009] S2. Run a steam injection string and an oil pumping string into the production casing, install a high-temperature injection and production wellhead device at the wellhead of the horizontal well, extend the steam injection string to the toe of the upturned horizontal section of the horizontal well, extend the oil pumping string to the deflection section of the horizontal well, and install an oil pump at the end of the oil pumping string;

[0010] S3. Run a coiled tubing into the steam injection string, and install an electric heating device in the horizontal section of the coiled tubing;

[0011] S4, start the electric heating device, and inject cold water into the annulus of the gasoline injection pipe and the coiled oil pipe through the water injection device. The cold water is converted into steam through the electric heating device and enters the oil layer through the end of the gas injection string;

[0012] S5. The heated crude oil and steam condensate in the formation are lifted to the surface through the oil pump.

[0013] The electric energy source used by the electric heating device is solar energy, wind energy or other energy sources.

[0014] The method further comprises an injection string and an electric power controller, wherein the injection string is used to inject cold water into the well, and the electric power controller is used to control the well electric heating device and the oil pump.

[0015] The horizontal section of the horizontal well is completed using a screen pipe.

[0016] The downhole steam generation rate and the input power of the electric heating device have the following relationship:

[0017]

[0018] Where: q s is the steam generation rate, m 3 / d; P is the electric power, kW; η is the thermal conversion power coefficient of the electric heater; ρ w is the water density at reference temperature, kg / m 3 ;H l is the liquid phase enthalpy of saturated steam at a given pressure, kj / kg; H v is the vapor phase enthalpy of saturated steam at a given pressure, kj / kg; f is the steam dryness, fraction; C w is the specific heat capacity of water, kj / (kg.℃); T i is the initial temperature of the injected water before it enters the electric heater, °C; T r The reference temperature of the injected water.

[0019] The beneficial effects of the present invention are:

[0020] 1. The upward-warped horizontal well is used, which is easy to form liquid accumulation at the heel of the horizontal section, which is more conducive to maintaining a higher gas-liquid interface and ensuring the efficient operation of the oil well pump;

[0021] 2. The liquid thickness at the heel of the horizontal section is greater than that at other sections, which can reduce the risk of steam entering the oil pump, improve the downhole controllability of the horizontal well, and increase the utilization degree of the horizontal section and crude oil production;

[0022] 3. Upward horizontal wells can be reasonably arranged along the structural height variation law at the bottom of the oil layer, which is conducive to improving the efficiency of oil layer reserve production;

[0023] 4. Using downhole electric heating devices to generate steam can eliminate wellbore heat loss, which is conducive to expanding steam thermal recovery to deeper heavy oil reservoirs;

[0024] 5. Injecting cold water from the ground into the underground heating device and utilizing reverse flow heat exchange can provide a cooling process for the produced liquid, which is beneficial to lowering the temperature of the produced liquid underground, reducing flash evaporation of the produced liquid and steam intrusion, and making underground control more stable;

[0025] 6. Injecting cold water to exchange heat with the produced fluid can increase the water temperature at the inlet of the underground electric heating device, which is beneficial to reduce the energy consumption required to generate steam underground, save electricity and reduce carbon emissions;

[0026] 7. The steam generation method downhole can control the pressure and temperature of steam entering the formation very accurately. For shallow heavy oil reservoirs with unstable cap layers and poor sealing, this process can be used to control the lower steam chamber pressure to improve the thermal efficiency of the oil layer, and at the same time prevent steam from escaping to the surface at a higher pressure to cause environmental pollution;

[0027] 8. The electric heating device is installed in the coiled tubing. The heat energy generated by the electric heater is quickly taken away by the water medium flowing in the annulus, which can ensure the working environment temperature of the electric heating device, thereby ensuring the service life and safety of the electric heating device;

[0028] 9. The single horizontal well arrangement saves half of the drilling cost compared to the double horizontal well SAGD. At the same time, the electric heating device can also save the circulation preheating production link, which is more energy-saving and environmentally friendly. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a schematic diagram of the overall structure of a heavy oil production system with an upturned horizontal well and downhole electric heating according to an embodiment of the present invention;

[0030] Figure 2 It is a schematic diagram of the arrangement of electric heating devices of a heavy oil production system with upturned horizontal wells and downhole electric heating according to an embodiment of the invention. DETAILED DESCRIPTION

[0031] The embodiments of the present invention will be further described below in conjunction with the accompanying drawings.

[0032] Example:

[0033] like Figure 1 - Figure 2 As shown, a SAGD upturned horizontal well heavy oil production system includes an upturned horizontal well, wherein the upturned horizontal well includes a vertical section, a deflecting section and an upturned horizontal section connected in sequence, wherein the vertical section, the deflecting section and the upturned horizontal section are in a "√" shape, and a steam injection string and an oil pumping string are arranged in the horizontal well, wherein an electric heating device is installed in the steam injection string at the position of the upturned horizontal section, and an oil pump is installed in the oil pumping string.

[0034] The working principle of the above technical solution is as follows:

[0035] The steam generated downhole enters the formation through the screen from the end of the injection string, and the heated crude oil and condensed water flow back into the screen, forming a steam cavity in the formation. Since the horizontal well is in the form of a "√", a thicker liquid can be formed at the heel, which is lifted to the ground by the oil pump installed above the heel of the horizontal section. By establishing a higher liquid level near the heel of the horizontal section and improving the drainage efficiency of the oil pump, the production efficiency and the horizontal section utilization efficiency can be improved, the difficulty of single horizontal well SAGD operation can be reduced, and energy consumption can be saved. At the same time, the use of downhole electric heating can eliminate the heat loss of the wellbore, which is conducive to expanding steam thermal recovery to deeper heavy oil reservoirs.

[0036] The length of the upturned horizontal section of the horizontal well is 300-800 meters, and the upturned angle is 2-5°.

[0037] Mining includes the following steps:

[0038] S1. Complete the drilling of the upturned horizontal well, run the production casing to the beginning of the horizontal section (the heel of the horizontal section), and run the production screen in the horizontal section;

[0039] S2. Run a steam injection string and an oil pumping string into the production casing, install a high-temperature injection and production wellhead device at the wellhead of the horizontal well, extend the steam injection string to the toe of the upturned horizontal section of the horizontal well, extend the oil pumping string to the deflection section of the horizontal well, and install an oil pump at the end of the oil pumping string;

[0040] S3. Run a coiled tubing into the steam injection string, and install an electric heating device in the horizontal section of the coiled tubing;

[0041] S4, start the electric heating device, and at the same time inject cold water into the annulus of the gasoline injection pipe and the coiled oil pipe through the water injection device, the cold water is converted into steam through the electric heating device, and enters the oil layer through the end of the steam injection pipe string;

[0042] S5. The heated crude oil and steam condensate in the formation are lifted to the surface through the oil pump.

[0043] The horizontal section of the horizontal well is completed with a screen pipe to ensure sufficient drainage area during the production process.

[0044] Cold water on the ground is injected through the annulus of the coiled oil pipe and the steam injection string. After heat exchange with the electric heating device installed in the horizontal section, the water temperature is continuously increased and finally becomes saturated steam, flows to the end of the horizontal section, and enters the oil layer through the oil layer screen, heats the crude oil, and forms a steam cavity in the oil layer.

[0045] The oil pump can be a rod pump or a rodless pump such as an electric submersible pump, depending on the well conditions. The crude oil and condensate heated in the steam chamber enter the horizontal well section through the screen pipe and form a certain amount of liquid accumulation on the upper part of the horizontal production well. Due to the use of the upturned well structure, the liquid height at the heel of the horizontal section is the largest, which is beneficial to the drainage and efficiency of the oil pump. The fluid leaking from the formation to the wellbore is continuously lifted to the ground through the oil pump.

[0046] The electric heating device is installed in the coiled tubing to ensure the reliability of heating.

[0047] The electric energy source of the electric heating device is solar energy, and can also be clean energy such as wind power, which has a good environmental protection effect.

[0048] The method also includes a controller, which is used to control the operation of the electric heating device, the oil pump and the water injection device, so as to realize automated operation and improve operation efficiency and reliability.

[0049] The relationship between the underground steam generation rate and the input power required by the electric heating device is as follows:

[0050]

[0051] Where: q s is the steam generation rate, m 3 / d; P is the electric power, kW; η is the thermal conversion power coefficient of the electric heater; ρ w is the water density at reference temperature, kg / m 3 ;H l is the liquid phase enthalpy of saturated steam at a given pressure, kj / kg; H v is the vapor phase enthalpy of saturated steam at a given pressure, kj / kg; f is the steam dryness, fraction; C w is the specific heat capacity of water, kj / (kg.℃); T i is the initial temperature of the injected water before it enters the electric heater, °C; T r The reference temperature of the injected water.

[0052] By controlling the cold water injection rate into the steam injection string and the heating power of the electric heating device, the amount of steam generated in the well can be well controlled. By controlling the initial temperature, flow rate, downhole pressure and input electric power of the injected water, the downhole steam dryness can be regulated; the amount of produced fluid can be controlled by the operating parameters of the downhole pump, so as to achieve the coordinated work of steam injection and oil production in the same horizontal well. The downhole temperature and pressure will be regulated according to the control rules of the downhole steam-assisted gravity drainage requirements to ensure that the downhole fluid temperature at the heel is 10-30℃ lower than the saturated steam temperature at the corresponding pressure, so as to achieve the production method of simultaneous steam injection and oil production in the entire horizontal section of the same well.

[0053] Compared with traditional SAGD, due to the heat exchange of the produced liquid by the injected cold water, the produced liquid can form a higher degree of supercooling, which is beneficial to improving the injection and production stability and thermal efficiency of the oil well. Specific embodiment 1:

[0055] The target oil layer is buried at a depth of about 200 meters, with an inclination of 3-5 degrees, a thickness of about 15 meters, an oil saturation of 50%-70%, a porosity of 30%, a permeability of 500-2000mD, and a degassed crude oil viscosity of about 100000mPa.s at 50°C. According to the structural morphology of the oil layer, an upturned horizontal well is completed at the bottom of the oil layer. The horizontal section is about 400 meters long and the upturn angle is 2-5°. Steam is generated by downhole electric heating, and enters the oil layer from the end of the horizontal section through the injection string. The mixture of heated crude oil and steam condensate enters the upturned horizontal well section, flows back to the root of the well under the action of gravity, and is lifted to the ground by a pump. The steam chamber pressure can be controlled by generating steam pressure at the bottom of the well to ensure that the temperature of the produced fluid at the heel of the horizontal section (the lowest point in the well) is 10-30°C lower than the steam saturation temperature under this pressure. The steam will not enter the pump, so that the oil layer above the upturned horizontal section can be fully utilized. The injection temperature from the ground is about 20°C, and the rate is 50m 3 / d of cold water, under the condition of underground input power of 1000KW and operating pressure of about 1.5MPa, the underground electric heating device will produce steam with temperature of 198℃ and dryness of about 50%. Based on the SAGD mining mechanism, the oil pump lifts liquid at a rate of about 50~60m 3 / d.

[0056] The above-mentioned embodiments only express the specific implementation of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the present invention. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention.

Claims

1. A SAGD upturned horizontal well heavy oil production system, characterized in that: It includes an upturned horizontal well, which includes a vertical section, a deflecting section and an upturned horizontal section connected in sequence, and the vertical section, the deflecting section and the upturned horizontal section are in a "√" shape. A steam injection string and an oil pumping string are arranged in the horizontal well, and an electric heating device is provided at the position of the steam injection string located in the upturned horizontal section.

2. A SAGD upturned horizontal well heavy oil production system according to claim 1, characterized in that: The length of the upward-warped horizontal section of the horizontal well is 300-800 meters, and the upward-warping angle is 2-5°.

3. A SAGD upturned horizontal well heavy oil production system according to claim 1, characterized in that: Mining includes the following steps: S1. Complete drilling of the upturned horizontal well, run the production casing to the beginning of the horizontal section in the upturned horizontal well, and run the production screen in the horizontal section; S2. Run a steam injection string and an oil pumping string into the production casing, install a high-temperature injection and production wellhead device at the wellhead of the horizontal well, extend the steam injection string to the toe of the upturned horizontal section of the horizontal well, extend the oil pumping string to the deflection section of the horizontal well, and install an oil pump at the end of the oil pumping string; S3. Run a coiled tubing into the steam injection string, and install an electric heating device in the horizontal section of the coiled tubing; S4, start the electric heating device, and inject cold water into the annulus of the gasoline injection pipe and the coiled oil pipe through the water injection device. The cold water is converted into steam through the electric heating device and enters the oil layer through the end of the gas injection string; S5. The heated crude oil and steam condensate in the formation are lifted to the surface through the oil pump.

4. A SAGD upturned horizontal well heavy oil production system according to claim 1 or 3, characterized in that: The electric energy source used by the electric heating device is solar energy, wind energy or other sources.

5. A SAGD upturned horizontal well heavy oil production system according to claim 1, characterized in that: The method also includes an injection string, a downhole pump and an electric controller.

6. A SAGD upturned horizontal well heavy oil production system according to claim 1, characterized in that: The horizontal section of the horizontal well is completed using a screen pipe.

7. A SAGD upturned horizontal well heavy oil production system according to claim 1, characterized in that: The downhole steam generation rate and the input power of the electric heating device have the following relationship: Where: q s is the steam generation rate, m 3 / d; P is the electric power, kW; η is the thermal conversion power coefficient of the electric heater; ρ w is the water density at reference temperature, kg / m 3 ;H l is the liquid phase enthalpy of saturated steam at a given pressure, kj / kg; H v is the vapor phase enthalpy of saturated steam at a given pressure, kj / kg; f is the steam dryness, fraction; C w is the specific heat capacity of water, kj / (kg.℃); T i is the initial temperature of the injected water before it enters the electric heater, °C; T r The reference temperature of the injected water.

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