Patent Application
20190249532
Present invention is applicable to oil and gas reservoirs with edge and bottom water, such as heavy oil reservoirs and high pour-point oil reservoirs, which can be thermally recovered in oil industry. It is mainly proposed to solve the problems of high viscosity or wax content of crude oil, low thermal recovery efficiency of steam stimulation or steam flooding, short stable production time, high decline rate and low recovery degree.
Huff and puff or steam stimulation, steam flooding, hot-water flooding and in-situ combustion are all efficient technical methods in thermal recovery. However, with gradually in-depth development, more and more problems have been exposed in production. Especially for middle-deep to super-deep reservoirs (depth of 600˜2300 m), the contradiction in production is more prominent: 1) As pipeline and wellbore heat loss in steam huff and puff, steam drive, hot water drive is serious, thermal efficiency is low, water production rate of production wells is high, production rate is low, decline rate is high, the ultimate recovery degree of reservoir is affected; 2) although in-situ combustion is effective to production test of some common-heavy oil fault blocks and can satisfy the requirement of industry production, it cannot be applied to most of the super-heavy oil reservoirs, in addition, the method is destructive to the reservoir. Once the reservoir is destroyed, any advanced thermal recovery method invented in the future will be impossible for operation; 3) at present, electric heating method is confined to the sucker rod and wellbore heating method. Its purpose is to improve the oil and gas lifting ability capacity of the production wells, and to reduce oil viscosity and wax deposition of crude oil around the production wells; 4) horizontal well hydraulic fracturing and electric heating oil shale in-situ thermal recovery method is difficult to implement in heavy oil reservoirs, high cost and serious environmental pollution; 5) at present, all thermal recovery methods belong to a method of local heating oil layers. Oil layers are heated unevenly, the thermal holding time is short, the efficiency is low, and the remaining oil has high oil saturation, which is mainly concentrated in the areas with low thermal energy and low thermal efficiency.
Trap is a place where oil and gas can continue to migrate and gather in it. The trap consists of three parts: reservoir, cap rock and barrier which prevents oil and gas from migrating and causes oil and gas accumulation. It can be the bending deformation of cap rock itself, such as anticline, or other barrier, such as fault, lithological change, etc. In a word, traps are effective space for capturing dispersed hydrocarbons to form hydrocarbon accumulation, and have the ability to store oil and gas, but there are not always oil and gas in traps. Once a sufficient amount of oil and gas enters the trap, fills the trap or occupies a part of the trap, oil and gas reservoirs can be formed. Any oil and gas reservoir with edge and bottom water can be treated as a whole unit sealed by cap rock and barriers including anticline structure, fault, lithological change, edge and bottom water, etc.
In accordance with the invention, there is provided a method of centralized thermal recovery based on an oil reservoir comprising the steps of: treating the whole oil reservoir with edge and bottom water as a integrated unit sealed by cap rock, barrier including edge and bottom water, etc.; providing at least one or more horizontal wells extending into edge and bottom water layers at a depth below the oil-water interface, near the oil layers, with an electric heating system configured to be positioned in each horizontal well; continuously centralized electric heating the edge and bottom water with electric heating system and thermal energy gradually accumulates in the oil reservoir until temperature of the whole oil reservoir rises to the state of the crude oil in place becoming mobile and flowing; centralized excavating the crude oil with at least one or more production wells; after the completion of primary oil recovery, the residual oil and water in reservoir can be separated by gravity and the formation water can be re-heated for secondary oil recovery.
In another embodiments, a concentrated thermal recovery method based on an oil reservoir comprising treating the whole oil reservoir with edge and bottom water as a integrated unit sealed by cap rock, barrier including edge and bottom water, etc. comprising the direction of heat transfer is mainly upward and the heat conduction velocity of reservoir is higher than that of surrounding rocks and the thermal insulation effect of surrounding rock is high therefore the heat can be continuously transferred upward and accumulated gradually in the oil reservoir.
In another embodiments, a concentrated thermal recovery method based on an oil reservoir comprising treating the whole oil reservoir with edge and bottom water as a integrated unit sealed by cap rock, barrier including edge and bottom water, etc. comprising most of the reservoirs develop edge and bottom water and contain adequate formation water resources which make it possible that horizontal wells continuously electric heat edge and bottom water for a long time and supply substantial thermal energy to the oil reservoir.
In further embodiments, a concentrated thermal recovery method based on an oil reservoir comprising providing at least one or more horizontal wells extending into edge and bottom water layers at a depth below the oil-water interface, near the oil layers comprising horizontal wells can be sidetracking horizontal wells of original production wells, or they can be horizontal wells that meet water layers alone.
In further embodiments, a concentrated thermal recovery method based on an oil reservoir comprising providing at least one or more horizontal wells extending into edge and bottom water layers at a depth below the oil-water interface, near the oil layers comprising horizontal wells can be independent horizontal wells or multi-branch horizontal wells.
In further embodiments, a concentrated thermal recovery method based on an oil reservoir comprising providing at least one or more horizontal wells extending into edge and bottom water layers at a depth below the oil-water interface, near the oil layers comprising horizontal wells are equably arranged on a horizontal plane in the edge and bottom water layer.
In further embodiments, a concentrated thermal recovery method based on an oil reservoir comprising providing at least one or more horizontal wells extending into edge and bottom water layers at a depth below the oil-water interface, near the oil layers comprising the depth determination depends on reservoir volume. The larger the volume, the deeper the depth.
In another embodiments, a concentrated thermal recovery method based on an oil reservoir comprising an electric heating system comprising: an inner liner positioned in the horizontal well comprising the upper half of the inner liner slotted and the lower half of the inner liner vacuum-sealed; a heat insulation board set at a horizontal diameter of the inner liner, several ferrite permanent magnet rods fixed on the inner wall of the upper half inner liner; a waterproof spiral electric immersion heater connected in series provided on the heat insulation board in the middle of the upper liner; wherein the lower liner is vacuum-sealed by a sealing board in cooperation with the heat insulation board.
In another embodiments, a concentrated thermal recovery method based on an oil reservoir comprising an electric heating system comprising
In accordance with the invention, a method of centralized thermal recovery based on an oil reservoir comprising continuously centralized electric heating the edge and bottom water with electric heating system until the temperature of the whole oil reservoir increases to the state that all of in-place oil becomes mobile and flows comprising edge and bottom water playing prominent roles during the process of concentrated electric heating and concentrated oil production:
In another embodiment, a method of centralized thermal recovery based on an oil reservoir comprising continuously centralized electric heating the edge and bottom water with electric heating system until the temperature of the whole oil reservoir increases to the state that all of in-place oil becomes mobile and flows comprising the electric heating system preferably includes a thermocouple operatively connected to the surface power unit for monitoring heating time and heating temperature, accordingly, further to control the pressure of the oil reservoir according to the congruent relationship between boiling point and pressure of water.
In further embodiment, a method of centralized thermal recovery based on an oil reservoir comprising continuously centralized electric heating the edge and bottom water with electric heating system until the temperature of the whole oil reservoir increases to the state that all of in-place oil becomes mobile and flows comprising the gradually accumulated reservoir pressure and temperature can be released with some production wells to prevent cracking in closed reservoirs.
In some embodiment, a method of centralized thermal recovery based on an oil reservoir comprising continuously centralized electric heating the edge and bottom water with electric heating system until the temperature of the whole oil reservoir increases to the state that all of in-place oil becomes mobile and flows comprising thermal energy coming from resistance heat generated by immersion electric heater and electromagnetic induction beat generated by upward moving formation water passing through electromagnetic field.
In another embodiment, a method of centralized thermal recovery based on an oil reservoir comprising providing at least one or more horizontal wells extending into at least one or more edge and bottom water layers at a depth below the oil-water interface with an electric heating system configured to be positioned in each horizontal well comprising high-power electric heating formation water to the boiling point temperature under initial formation pressure, and then lowering power continuous electric heating formation water at low-temperature.
In some embodiment, a method of centralized thermal recovery based on an oil reservoir comprising with electric heating system until the temperature of the whole oil reservoir increases to the state that all of in-place oil becomes mobile and flows comprising the temperature of the top oil reservoir rising up at least to the range of 80° C.˜150° C.
In another embodiment, a method of centralized thermal recovery based on an oil reservoir comprising continuously electric heating the edge and bottom water at a pressure lower than the reservoir fracture pressure.
In further embodiment, a method of centralized thermal recovery based on an oil reservoir comprising under a certain pressure lower than the reservoir fracture pressure comprising under certain pressure conditions, when water is heated, the water temperature will gradually rise until the boiling point temperature, and then continue to heat, the temperature will not rise along with substantial steam generated until the pressure continues to increase.
In another embodiment, a method of centralized thermal recovery based on an oil reservoir comprising continuously centralized electric heating the edge and bottom water at a temperature of the edge and bottom water around the immersion heater lower than 450° C.
In some embodiment, a method of centralized thermal recovery based on an oil reservoir comprising characteristics of temperature variation inside the oil reservoir during centralized electric heating and centralized oil production comprising during continuously electric heating the edge and bottom water layers, as heat transfers upwards, the temperature of the bottom oil reservoir is higher than that of the top oil reservoir, and the cross section temperature of electric heating horizontal well is higher than that between wells, the upper temperature of the former is equal to the middle and lower temperature of the latter. When electric heating stopped, over time, heat gradually diffuses and homogenizes in the reservoir until the end of centralized oil production.
In accordance with another embodiment, a method of centralized thermal recovery based on an oil reservoir comprising an electric heating system comprising: a connector system for connecting the electric immersion heater to an electrical cable, and, a surface power unit for delivering electrical power to the electrical heater through the electrical cable.
In further embodiments, a concentrated thermal recovery method based on an oil reservoir comprising providing at least one or more horizontal wells extending into at least one or more edge and bottom water layers at a depth below the oil-water interface with an electric heating system configured to be positioned in each horizontal well comprising a waterproof spiral electric immersion heater connected in series, when immersion heater is immersed in water, thermal energy mainly comes from resistance heat of the waterproof spiral electric heater and electromagnetic induction heat of formation water flowing up and down in the magnetic field because water itself is an electric conductor, and the water can be heated quickly. Simultaneously, the electric wire will not be burned.
The scale removal technology of magnet in electric heating can effectively solve the scale phenomenon in the process of electric heating. Scale originates from the hard water quality. Magnets can soften water, which is environmental friendly, economical, convenient and safe. Ferrite permanent magnet, whose components mainly include BaFe12019 and SrFe12019, is made by ceramic technology, bears the characteristics of well temperature resistance, moderate price, and wide application. It is a preferred material for scale removal adapted to the environment of electric heating edge and bottom water layers.
According to the size of the reservoir, horizontal wells are drilled in the upper water layer of the edge-bottom water reservoir, near the oil layer. An electric immersion heater is installed in the upper slotted inner liner of the horizontal well to conduct electric heat to the water layer.
The structure of the electric heater of horizontal well is shown in
Several ferrite permanent magnet rods are fixed at the inner top of the upper slotted liner to prevent scaling.
Magnetized water scale prevention principle is cited as following:
The scale formed by water on the wall of the heater tube is hard scale CaCO3, which is called calcite. Its physical and chemical properties are similar to those of marble, with compact arrangement and hard structure.
After magnetic treatment, the particle group of water becomes smaller, the conductance increases and the activity increases. When heated, impurities in water create a thin layer of soft dirt on the wall of the metal tube. It is characterized by loose arrangement of molecules, disorder, poor adhesion to the metal pipe wall and easy to fall off. It can be reduced and eliminated by using reliable magnetizer for a long time which has the function of differentiating and eliminating scale on existing scale device.
The magnetizer can be divided into active and passive. Active is the electromagnet, which needs power and can control the magnetization. The passive source is made of permanent magnet, which is connected to the water pipe. The water can be magnetized at any time without power supply.
Curie temperature refers to the temperature at which a material can change between a ferromagnet and a paramagnet. When it is below Curie temperature, the material becomes a ferromagnet, and the magnetic field associated with the material is difficult to change. When the temperature is higher than Curie temperature, the material becomes a paramagnet, and the magnetic field of the magnets can easily change with the change of the surrounding magnetic field. It is reported that the Curie temperature of ferrite is about 450 degrees, usually greater than or equal to 450 degrees.
In some embodiment, a method of centralized thermal recovery based on an oil reservoir comprising centralized excavating the crude oil with at least one or more production wells comprising centralized recovering the mobilized oil with at least one or more production wells which are either vertical wells or horizontal wells, or any combination of these wells.
In another embodiment, a method of centralized thermal recovery based on an oil reservoir comprising centralized recovering the mobilized oil with at least one or more production wells comprising various oil recovery mechanisms are applied to exploiting oil efficiently including
This is a centralized thermal recovery method based on an oil reservoir unit, i.e. unified heating and unified oil recovery for the whole reservoir, reflecting the scale effect of the whole reservoir preheating and centralized construction operation. It is different from the conventional thermal recovery method which oil is produced while heating directly oil layers in a single well or group of wells. At the same time, it is also a kind of thermal recovery method which makes full use of natural formation water resources and their attributes and heats the whole oil reservoir by electric heating of formation water in horizontal wells. It can achieve the following beneficial effects: 1) The electric heating of formation water in horizontal wells is environmentally friendly, energy-saving, convenient, fast and easy to operate; 2) Thermal energy can be transmitted to reservoirs through water layers. Adequate heat can meet the needs of thermal recovery development, to solve the problems of reservoir thermal energy injection, small heating radius and short duration of thermal energy; 3) No use of surface water resources, no steam injection and sewage treatment processes, cost reduction, energy saving and environmental protection; 4) Reservoir in-situ thermal recovery method, no pipeline and wellbore thermal loss, thermal efficiency high, can effectively develop from deep to ultra-deep thermal recovery reserves; 5) High bottom water temperature, the whole reservoir crude oil in movable temperature conditions, combined with other driving energy, bottom water coning in the process of oil recovery can effectively form bottom water hot water flooding; 6) Unlimited requirements for reservoir geological characteristics, widely used in various oil reservoirs with edge and bottom water, 7) No damage to the reservoir and multiple recovery. The centralized thermal recovery method based on an oil reservoir by horizontal wells electric heating edge and bottom water layers has natural advantages, which can effectively solve many technical problems faced by conventional thermal recovery methods at present, and improve the production degree and ultimate recovery degree of reservoir reserves; 8) This method can be widely applied in thermal recovery of other similar types of mineral resources.
Label 1 in each figure refers to a slotted upper inner liner. Its function mainly has two points: one is to suspend the permanent magnet rods to protect the electric heater from the pressure of the upper stratum; the other is to allow the formation water to enter and leave the slotted screen pipe freely, so that the water and the electric heater can fully contact, so as to better play the thermal conductivity of water.
Label 2 refers to ferrite permanent magnet rods used to prevent scaling. According to
Y=178.27x0.2509
Note: y: Boiling point temperature; x: pressure MPa. Under the condition of electrically heated formation water, the boiling point temperature corresponding to formation water under 15 MPa is predicted to be 350 degrees Celsius and that corresponding to 28 MPa is about 450 degrees Celsius. Therefore, as long as formation pressure and the boiling point temperature of formation water are controlled to be lower than the Curie temperature 450 degrees Celsius of ferrite permanent magnet, the magnetism of permanent magnet will not be destroyed. At the same time, it must be noted that when the electric heater is DC, the magnetic pole of the ferrite permanent magnet rod must be in the same direction as the electromagnetic field produced by the electric heater. Otherwise, the magnetic force of the permanent ferrite magnet rod will gradually weaken.
Label 3 refers to waterproof spiral electric heater connected in series. The electric heater is connected to the ground power supply through a coaxial cable. When current is applied, the spiral electric heater will generate resistance heat to heat the edge and bottom water directly, the heated edge and bottom water will transfer mainly upwards and cold water will move downwards, which makes the surrounding water moving up and down produce electromagnetic induction heat. During this period, when the direction of the magnetic field is the same as that of the electromagnetic field, the ferrite permanent magnet rods will enhance the intensity of the electromagnetic field produced by the electric heater, and vice versa, weaken the induction phenomenon of the electromagnetic field.
Label 4 refers to heat insulation board. As shown in
Label 5 refers to a liner sealing board. It is well known that vacuum has good thermal insulation. The lower part of the inner liner is sealed in vacuum, which acts as a barrier to heat transfer downward together with the heat insulation board.
Label 6 in
Label 12 in
According to the size of a reservoir, horizontal wells which can be either single horizontal wells or multi-branch horizontal wells are drilled in the upper water layers, near the oil layer, which can store enough thermal energy to raise the temperature of the whole oil reservoir and delay the formation fracture due to premature boiling of the formation water and overpressure.
The number, length and trend of horizontal well are determined by the size of water body and reservoir volume. Gravel packed open hole completion works well.
If the horizontal well is sidetrack drilled from an oil production well, the conducting wire can be used as borehole or pumping rod electric heater so that the effect of cooling and heating can be realized; if the horizontal well is drilled individually, a skin heat tracing device needs to be applied to the conducting wire. High temperature resistant materials should be optimized to prevent the conducting wire from overheated in the borehole.
Pressure distribution curves in oil reservoir during centralized thermal recovery based on an oil reservoir by numerical simulation shows that the static pressure in the reservoir quickly changes to thermal expansion pressure after electric heating edge and bottom water layer, and the pressure distribution is relatively uniform, which corresponds to the boiling point temperature of formation water one by one. When the electric heating stops and enters the production stage, the reservoir enters the step-down production stage, and the pressure drop is relatively fast until the end of production, and the pressure drops to 2 MPa. Obviously, the magnitude of thermal expansion pressure plays an important role in the process of oil recovery.
Temperature distribution curves in oil reservoir during centralized thermal recovery based on an oil reservoir by numerical simulation shows that different from the characteristics of the pressure distributed in the oil reservoir, the temperature in the oil reservoir undergoes a gradual accumulation process during the centralized electric heating process. The temperature at the bottom of the reservoir is obviously higher than that at the top, and the temperature above the electric heating horizontal well is higher than that between wells. When the electric heating is stopped, the well closure is conducive to the further uniform diffusion of unbalanced heat in the oil reservoir. In the stage of centralized production, the reservoir temperature gradually decreases with the production of crude oil and becomes more uniform. Due to the thermal insulation of formation water, the reservoir temperature remained at a high level of about 180 degrees Celsius until the end of production.
After centralized electric heating the bottom water for 1100 days, the top temperature of the reservoir reaches 150 degrees Celsius. The production peak period produces 65-90 t/d of oil per day, the stable production time is 1405 days, and the recovery degree of primary production is as high as 53.8%.
Electric heaters are configured to be positioned in several horizontal wells drilled in an upper part of water layer of the reservoir, near the oil layers. The electric heaters heat the edge and bottom water layer of the reservoir so that the temperature of the whole reservoir can be increased. Several mechanisms are applied to recover oil efficiently, such as, the effect of heat transfer, the effect of steam flooding produced by water soluble gas overflow, the thermal expansion pressure from water formations and oil layers as well as the viscosity-reduction effect/wax-precipitation effect of in-place oil under high temperature.
It can be applied to thermally recover heavy oil reservoirs and high pour-point oil reservoirs with edge and bottom water layers, especially for those oil reservoirs in depth of middle-super deep depth which are difficulty recovered. This method can be widely applied in thermal recovery of other similar types of mineral resources.
| Number | Date | Country | Kind |
|---|---|---|---|
| 201310689685.0 | Dec 2013 | CN | national |
This application is a Continuation-in-Part application of pending U.S. Patent Publication No. 2017-0002637 A1 published May 28, 2015 and Ser. No. 15/039,454, which claims priority to China Application No. 201310689685.0 filed Dec. 12, 2013, all of which are hereby incorporated herein in their entireties by reference.
| Number | Date | Country | |
|---|---|---|---|
| Parent | 15039454 | May 2016 | US |
| Child | 16378613 | US |
