By using the combustion principle of the internal combustion engine, the intermittent combustion of the engine is changed into continuous combustion, coupled with an automatic control system and other auxiliary equipment to generate and directly inject a mixture of high-temperature nitrogen, carbon dioxide and water vapor into the oil well. Can replace the current steam injection boiler steam thermal recovery, carbon dioxide injection and nitrogen injection and other measures to increase oil production; Well washing device can replace the current thermal carrier well washing equipment.
How the device works:
Based on the combustion theory and engineering technology of internal combustion engine, a "high temperature gas injection device" for thermal recovery of petroleum is developed. The principle is that oxygen in air is used as oxidant, nitrogen in air is used as nitrogen source, fuel oil is used as combustion agent. High-temperature gas (about 2500 ℃) is produced by combustion at high pressure, and then mixed with water for heat exchange, so that water can absorb heat and vaporize, so that the gas can be cooled by exothermic heat. Finally, a high-temperature mixture gas suitable for thermal recovery or well washing is formed.
High temperature gas composition:
Thermal gas injection device: (gas temperature 300 ℃) steam (dry) 40%, nitrogen (N2) 45%, carbon dioxide (CO2) 15%.
Gas temperature 120 ℃, steam 50%, nitrogen (N2) 40%, carbon dioxide (CO2) 10%.
Device structure:
The device consists of a central controller and the following subsystems:
1, air compression subsystem,
2, fuel injection subsystem
3, gas generator subsystem
4, ignition system
5, vaporized water injection subsystem
6, cooling subsystem
7, security subsystem
Internal _ combustion _ type _ thermal _ recovery _ gas _ injection _ device
Internal _ combustion _ type _ well _ washing _ dewaxing _ device
Device structure
Characteristics of high-temperature gas mixtures:
1. Energy consumption is small, the energy consumption of every ton of gas produced is only 43% of that of steam boiler;
2. All the mixed gases are injected into the strata and the environment is not polluted;
3. The outlet temperature and dry degree are high, the temperature can be more than 350 ℃;
4. Because it is a non-condensing gas, CO2,N2 has the function of miscibility and viscosity reduction, which can greatly improve oil recovery.
5. The operating cost is only 30% of the conventional boiler, and the equipment cost is only 1/4 of the 9T/h portable boiler.
6. The volume of non-condensing gas injected into oil layer is more than three times that of steam.
7. The mixed gas can not only reduce the viscosity of crude oil, but also have a large amount of N2 gas around the injection well to form a gas ring, thus providing gas drive power, can rapidly increase the formation energy (pressure, temperature);
8. The equipment is small in size, light in weight, flexible and convenient, especially suitable for use on offshore platforms.
Device main index parameter
The main parameters of the thermal gas injection device are as follows:
Gas generation at high temperature: G = 900kg/h
Fuel consumption: Gr = 40 kg/h
Vaporized water consumption: GH2O = 260 kg/h
Maximum power consumption: 180 kW (average 80 kW)
Dry degree of high temperature mixture gas: 1
High temperature mixed gas pressure (automatically adjusted with well pressure): 1~35MPa
High temperature mixture gas temperature (set according to oil recovery process) 200 ℃ 360 ℃
The advantages and disadvantages of the two methods in comparison with the thermal recovery of water injection steam
At present, according to reservoir conditions, heavy oil recovery methods are mainly steam huff-puff and steam drive. However, there are many shortcomings, notably:
1. Steam boiler comprehensive thermal efficiency is low, heat loss is large, heat utilization rate is only about 70%.
2. The steam dryness is only 80%, which greatly reduces the heat brought into the well, thus reducing the recovery factor. Due to the heat dissipation along the way, the steam dryness will be less than 0.5 when it reaches the downhole reservoir, that is, half of the steam will become water.
3. Boiler steam production cost is high, resulting in high oil production costs.
4. Pollute the environment. Every ton of fuel is burned to produce a large amount of nitrogen and carbon dioxide. They were all discharged into the atmosphere and caused Greenhouse Effect.
5. Effective gas composition is wasted. The main components of the flue gas discharged from the boiler are N _ 2 and CO _ 2, but they are very useful for improving the recovery of crude oil.
6. The fixed assets investment is large, the operation cost is high. It takes 30 million yuan to build a gas supply station for a 23-ton boiler, a 9-ton boiler costs about 9 million yuan, and a mobile 9-ton boiler on board has a price of more than 10 million yuan.
7. After multiple cycles of water injection steam huff and puff operation, too much water collection in the reservoir leads to a great increase of water cut during recovery, which is more than 80%. It is not economical to reduce oil production.
8. Compared with the boiler steam, it has less heat into the ground, which may reduce the thermal recovery effect of the super heavy oil.
Characteristics of Wax cleaning device for well washing
Do not affect normal production and other operations of oil wells.
It has little influence on sensitive oil layer and no harm to oil layer, which is beneficial to improve oil recovery.
All the gas directly injected into the well does not pollute the atmospheric environment.
Energy saving, low operating cost. Can be mounted on board or pry, mobile and flexible, convenient and practical.
It can be used in combination with chemical dewaxing and anti-wax technology.
Can burn associated natural gas, fuel sources are convenient. It has a good application prospect in wax cleaning and scale cleaning of oil wells.
Simulation and experiment abroad
After long-term waterflooding, the MAUREEN oil field in the North Sea UK has produced 53 percent of its oil reserves. Through the simulation of gas injection and the evaluation of feasibility test, the ideal gas composition is 34% steam and 16% CO2,50% N 2.
Theoretical and Experimental Research at Home and abroad
Theoretical research on thermal recovery of mixed gas injection at home and abroad shows that high-temperature mixture gas has the following complex effects in crude oil reservoirs:
1. Physical and chemical action
CO2 is conducive to reducing viscosity of crude oil, which can generally reduce the viscosity of crude oil to 1 × 10. 5%.
2. Aerodynamic action
The gas N2 is helpful to increase the oil layer pressure and form a quite large gas region around the production well, which increases the gas-liquid drive power, makes the heat and gas redistribute in the reservoir, and increases the recovery factor due to the pressure-driven action of N2 gas.
3. Heat action
The heat exchange between the heat carrier and the reservoir increases the reservoir temperature, decreases the viscosity, and increases the fluidity of crude oil.
4. Many experimental studies have proved that CO2 is an effective agent for improving crude oil recovery. When CO2 is dissolved in crude oil at a certain pressure, its effect is as follows:
(1) increased volume and mobility of crude oil
(2) the oil film can be washed off the surface of rock particles.
(3) reduce the interfacial tension of oil-water and enhance the wettability of water to porous media.
(4) improving capillary dialysis to increase the sweep efficiency of oil-water movement evenly.
5 because the viscosity of crude oil is reduced and the fluidity is enhanced, the consumption of heat carrier is reduced.
At present, relevant departments at home and abroad have theoretically established the mathematical model of high-temperature mixture gas flowing in the wellbore and the mathematical model of productivity prediction of high-temperature mixture gas injection production.
According to the laboratory experiment of Shengli Oilfield Oil recovery Research Institute, it is proved that the CO _ 2 mixture can increase the oil recovery by up to 20% compared with the single injection of steam with the addition of N _ 2.
Popularization and Application and Economic benefit
1. It can be used in huff and puff oil recovery
Injection of mixed gas can increase the formation pressure, there is a large amount of gas in the formation, the energy increases, especially in the middle and late stages of oil wells, the effect is remarkable, therefore, it can be used for gas injection service in the throughput well.
2. It can be used in gas drive oil recovery.
Injection of mixed gas can increase sweep coefficient, increase dryness, raise formation pressure and temperature, and provide effective equipment for oil field to be fully transferred to gas drive.
3. Can be used for well washing, wax removal and tubing viscosity reduction, wax removal.
4. It can be used to increase production of gas injection in oil field at the end of water injection production.
5 can be used for gas injection thermal recovery in low and middle permeability reservoirs.
6. It can be used in conjunction with chemical exploitation to increase the driving power of chemical raw materials.
The high temperature mixture gas injection device has the value of application and popularization.
1. Less investment
1 the purchase cost of steam boiler is relatively high, it needs to invest 1000-30 million yuan to build a steam injection station of steam boiler, and the price of a set of mixed gas injection device is 280-4 million yuan.
2the steam boiler is installed on the ground, and the heat-insulated gas transmission pipeline should be laid between the separate wellheads. The installation cost of the pipeline is about 1 million yuan / km.. The high temperature mixture gas injection device directly injects the gas into the wellhead, but the vehicle can be installed and moved without the need to lay the gas transmission pipeline, thus saving a large amount of expenses.
2. The operation cost is low.
The operating cost of a mixed gas injection unit is only 1 / 4 / 1 / 3 of the steam charge of the boiler for a one-time huff and puff operation.
3. High recovery rate
Injection of high-temperature mixture can further improve oil recovery than injecting boiler steam.
