FULLY CONTROLLED COMBUSTION ASSISTED GRAVITY DRAINAGE
PROCESS
FIELD OF THE INVENTION
100011 The invention relates to the recovery, extraction, and production of hydrocarbons, including bitumen and heavy oil.
BACKGROUND
100021 With the world's reliance on fossil fuels and hydrocarbon based energy sources, many different processes have been investigated and developed to recover viscous hydrocarbons from underground deposits, such as the deposits found in the tar sands of Alberta, Canada, Venezuela, and the United States.
100031 Methods that have been developed include natural pressure depletion, water flooding or gas injection, steam based processes such as cyclic steam stimulation and steam assisted gravity drainage, polymer flooding, and in situ combustion.
[00041 The natural pressure depletion method may have low recovery factor and low production rate. The water flooding or gas injection method may consume a large amount of water with low recovery rates. Polymer flooding also has low recovery and production rates with a high consumption of water.
100051 While steam assisted gravity drainage has better production rates, the method consumes a large amount of water and requires significant investment in capital cost.
There is also significant carbon dioxide emission due to the need of generating a significant amount of steam by burning natural gas or other fuels for the steam production process.
[00061 Companies have tested the in situ combustion method in recovery of hydrocarbons. While the in situ combustion method has the advantage of not requiring the production of a large amount of steam, the current methods have potential problems with process control. For instance, the implemented methods cannot address the rates of oxidizing gas injection, hydrocarbon production, and flue gas ventilation properly. In addition, current methods of in situ combustion make it difficult to achieve sustainable and controllable in situ combustion within the reservoir. Furthermore, existing methods of in situ combustion may utilize the production well for removal of combustion gases generated from the combustion, causing the production rate of such production well to decrease in view of the dual-use of the production well.
[0007] Other known methods are described in patents and published patent applications such as Canadian Patent No. 2096034 to Kisman etal., Canadian Patent No. 2176639 to Greaves and Turta, Canadian Patent No. 2594414 to Chhina and Nzekwu, and 2678347 to Bailey and Canadian Patent Application No. 2692885 by Sarathi et al., all of which are incorporated herein by reference.
[0008] A need therefore exists for an improved method of extracting hydrocarbons using the in situ combustion method. Accordingly, a solution that addresses, at least in part, the above and other shortcomings is desired.
SUMMARY OF THE INVENTION
[0009] The invention relates to a method of extracting hydrocarbons using an in situ combustion method utilizing at least one injection well, at least one ventilation well, and at least one production well.
[0010] According to one embodiment of the invention, there is provided a method for extracting hydrocarbons from a hydrocarbon bearing reservoir, the reservoir being in fluid communication with at least one injection well and at least one production well, the method comprising, introducing at least one ventilation well in fluid communication with the reservoir;
injecting an oxidizing gas into the at least one injection well to support in situ combustion in an area of the reservoir to mobilize the hydrocarbons; controlling the ventilation in the in situ combustion area by way of the at least one ventilation well; and recovering the mobilized hydrocarbons by way of the at least one production well.
100111 According to one aspect of the invention, there is provided a method for extracting hydrocarbons from a hydrocarbon bearing reservoir wherein the at least one production well has a generally horizontal segment that is vertically spaced below the at least one injection well.
[0012] According to another aspect of the invention, there is provided a method for extracting hydrocarbon from a hydrocarbon bearing reservoir wherein the hydrocarbon is at a viscosity greater than 10,000 mPa.s.
[0013] According to another embodiment of the invention, there is provided a method of extracting hydrocarbons comprising selecting a hydrocarbon bearing reservoir, the reservoir being in fluid communication with at least one injection well, at least one production well having a generally horizontal segment and vertically spaced below the at least one injection well, and, at least one ventilation well; injecting an oxidizing gas into the at least one injection well to support in situ combustion in an area of the reservoir in proximity to the at least one injection well to mobilize the hydrocarbons; increasing, maintaining, or decreasing ventilation of the in situ combustion area by way of the at least one ventilation well; and recovering the mobilized hydrocarbons by way of the at least one production well.
[0014] According to one aspect of the invention, there is provided a method of extracting hydrocarbons wherein the hydrocarbon is heavy oil.
[0015] According to another aspect of the invention, there is provided a method of extracting hydrocarbons wherein the at least one injection well has a horizontal segment in the reservoir that is generally parallel to a horizontal segment of the at least one production well.
[0016] According to another aspect of the invention, there is provided a method of extracting hydrocarbon wherein the at least one injection well is at an angle between 00 to 1800 relative to the at least one production well.
100171 According to another aspect of the invention, there is provided a method of extracting hydrocarbons wherein the at least one ventilation well intersects the at least one injection well within the hydrocarbon bearing reservoir.
[0018] According to another aspect of the invention, there is provided a method of extracting hydrocarbons wherein the at least one injection well and/or the at least one production well and/or the at least one ventilation well contains at least one sensor.
100191 According to another aspect of the invention, there is provided a method of extracting hydrocarbons wherein the at least one injection well and/or the at least one production well and/or the at least one ventilation well contains at least one temperature sensor.
[0020] According to another aspect of the invention, there is provided a method of extracting hydrocarbons wherein the at least one injection well and/or the at least one production well and/or the at least one ventilation well contains at least one pressure sensor.
[0021] According to another aspect of the invention, there is provided a method of extracting hydrocarbons wherein the in situ combustion area contains at least one sensor.
100221 According to another aspect of the invention, there is provided a method of extracting hydrocarbons wherein the at least one sensor is selected from a group consisting of temperature, pressure, and oxygen sensors.
[0023] According to another aspect of the invention, there is provided a method of extracting hydrocarbons wherein the at least one production well is at an angle at or between 0 to 30 degrees relative to the horizontal direction.
[0024] According to another aspect of the invention, there is provided a method of extracting hydrocarbons wherein the oxidizing gas contains additives such as low ignition point hydrocarbons and/or water mist.
[0025] According to another aspect of the invention, there is provided a method of extracting hydrocarbons wherein at least one the injection well contains circulation tubing to toe.
[0026] According to another aspect of the invention, there is provide a method of extracting hydrocarbons wherein the at least one production well contains circulation tubing to toe.
100271 According to another aspect of the invention, there is provided a method of extracting hydrocarbons wherein the at least one injection well is open hole or cased.
[0028] According to another aspect of the invention, there is provided a method of extracting hydrocarbons wherein the in situ combustion is initiated by a method selected from the group consisting of: steam circulation, oxidants, electrical heating, electrical-magnetic heating, or other physical/chemical heating methods.
[0029] According to another aspect of the invention, there is provided a method of extracting hydrocarbons wherein more than one ventilation wells are installed.
100301 According to another aspect of the invention, there is provided a method of extracting hydrocarbons wherein the at least one ventilation well has a segment that is substantially perpendicular to the horizontal segments of the at least one injection well.
[0031] According to another aspect of the invention, there is provided a method of extracting 5 hydrocarbons wherein the at least one ventilation well is at an angle between 0 to 1800 relative to the at least one production well.
[0032] According to another aspect of the invention, there is provided a method of extracting hydrocarbons wherein the oxidizing gas has an oxygen concentration of 0% to 100%.
[0033] According to another aspect of the invention, there is provided a method of extracting hydrocarbons wherein the at least one ventilation well is used to remove combustion gases generated by the in situ combustion in the reservoir.
[0034] According to another aspect of the invention, there is provided a method of extracting hydrocarbons wherein the combustion gases are redirected into the at least one injection well and/or the at least one production well through the at least one ventilation well.
[0035] According to another aspect of the invention, there is provided a method of extracting hydrocarbons wherein the in situ combustion occurs along the at least one injection well.
[0036] According to another embodiment of the invention, there is provided a method for sustaining a continuous in situ combustion in a hydrocarbon bearing reservoir comprising controlling ventilation in the in situ combustion by way of at least one ventilation well.
100371 According to another embodiment of the invention, there is provided a use of at least one ventilation well to sustain a continuous in situ combustion in a hydrocarbon bearing reservoir.
[0038] According to another embodiment of the invention, there is provided a system for extracting hydrocarbons from a hydrocarbon bearing reservoir by in situ combustion, comprising: at least one injection well; at least one production well; and at least one ventilation well.
[0039] According to another aspect of the invention, there is provided a system for extracting hydrocarbons from a hydrocarbon bearing reservoir by in situ combustion wherein the hydrocarbon bearing reservoir is in fluid communication with the at least one injection well and the at least one production well.
[0040] According to another aspect of the invention, there is provided a system for extracting hydrocarbons from a hydrocarbon bearing reservoir by in situ combustion wherein the at least one production well has a generally horizontal segment that is vertically spaced below the at least one injection well.
[0041] According to another aspect of the invention, there is provided a system for extracting hydrocarbons from a hydrocarbon bearing reservoir by in situ combustion wherein the at least one ventilation well intersects communicates with the at least one injection well.
[0042] According to another aspect of the invention, there is provided a system for extracting hydrocarbons from a hydrocarbon bearing reservoir by in situ combustion wherein the at least one injection well and/or the at least one production well and/or the at least one ventilation well contains at least one sensor.
[0043] According to another aspect of the invention, there is provided a system for extracting hydrocarbons from a hydrocarbon bearing reservoir by in situ combustion wherein the at least one sensor is a temperature sensor.
[0044] According to another aspect of the invention, there is provided a system for extracting hydrocarbons from a hydrocarbon bearing reservoir by in situ combustion wherein the at least one sensor is a pressure sensor.
[0045] According to another aspect of the invention, there is provided a system for extracting hydrocarbons from a hydrocarbon bearing reservoir by in situ combustion wherein the production well is at an angle at or between 0 to 30 degrees relative to the horizontal direction.
[0046] According to another aspect of the invention, there is provided a system for extracting hydrocarbons from a hydrocarbon bearing reservoir by in situ combustion wherein the at least one injection well contains circulation tubing to toe.
[0047] According to another aspect of the invention, there is provided a system for extracting hydrocarbons from a hydrocarbon bearing reservoir by in situ combustion wherein the at least one production well contains circulation tubing to toe.
[0048] According to another aspect of the invention, there is provided a system for extracting hydrocarbons from a hydrocarbon bearing reservoir by in situ combustion wherein the at least one injection well is open hole or cased.
[0049] According to another aspect of the invention, there is provided a system for extracting hydrocarbons from a hydrocarbon bearing reservoir by in situ combustion wherein more than one ventilation wells are installed in the reservoir.
[0050] According to another aspect of the invention, there is provided a system for extracting hydrocarbons from a hydrocarbon bearing reservoir by in situ combustion wherein the at least one ventilation well is substantially perpendicular to the horizontal segments of the at least one injection well.
[0051] According to another aspect of the invention, there is provided a system for extracting hydrocarbons from a hydrocarbon bearing reservoir by in situ combustion wherein the in situ combustion occurs along the at least one injection well.
[0052] Other objects, features and advantages of the present invention will become apparent from the following detailed description. It should be understood, however, that the detailed description and the specific examples while indicating preferred embodiments of the invention are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.
BRIEF DESCRIPTION OF THE DRAWINGS
[0053] Features and advantages of the embodiments of the present invention will become apparent from the following detailed description, taken in combination with the appended drawings, in which:
[0054] FIG. 1 is a front view illustrating the method of extracting hydrocarbons using in situ combustion according to an embodiment of the invention; and =
[0055] FIG. 2 is a side view illustrating the method of extracting hydrocarbons using in situ combustion according to an embodiment of the invention.
[0056] In the description which follows, like parts are marked throughout the specification and the drawings with the same respective reference numerals.
DETAILED DESCRIPTION OF THE EMBODIMENTS
[0057] The description which follows and the embodiments described therein are provided by way of illustration of an example or examples of particular embodiments of the principles of the present invention. These examples are provided for the purposes of explanation and not limitation of those principles and of the invention. In some instances, certain structures and techniques have not been described or shown in detail in order not to obscure the invention.
[0058] As part of this patent application, a number of terms are being used in accordance with what is understood to be the ordinary meetings of these terms. For instance, "fluid" includes both liquids and gases.
[0059] "Heavy oil" is defined as petroleum having an American Petroleum Institute gravity below 22.3 API (920 to 1000 kg/m3). "Bitumen" is defined as petroleum existing in semi-solid and solid phases with a density of greater than 1000kg/m3. While these terms are commonly used and are general categories, references to these terms in this application include the continuum of such substances and do not suggest some specific boundaries between the two substances. The term "heavy oil" includes within its scope "bitumen" of all forms.
100601 "Petroleum" means mixtures consisting primarily of hydrocarbons in different phases, including, liquid, gas, or solid phase. "Hydrocarbon" is an organic compound consisting entirely of hydrogen and carbon. In the context of this patent application, the words "petroleum" and "hydrocarbon" refer to mixtures with significant variations in composition.
[0061] A reservoir is a formation underneath the surface that contains natural accumulation of hydrocarbons.
[0062] Figure 1 is a front view illustrating a method of and a system 1 for extracting hydrocarbons such as heavy oil according to an embodiment of the invention. An injection well 10 is present in a reservoir 60 along with a production well 20. The production well 20 is spaced vertically apart below the injection well 10. The injection well 10 and the production well 20 are also situated in a hydrocarbon bearing area 70 of the reservoir 60. In addition, the reservoir 60 contains a ventilation well 30 that is inserted into an area near the injection well 10. A combustion area 40 represents the area in the reservoir 60 that would be subject to heating by the in situ combustion inside the reservoir 60. The injection well 10, the production well 20, and the ventilation well 30 are all in fluid communication with the hydrocarbon bearing area 70 of the reservoir 60.
[0063] In one embodiment, in situ combustion may be started by injecting low ignition point material (such as oxidant) through the injection well 10 to create the combustion area 40 in the reservoir 60. Oxidizing gas 100 can be fed into the combustion area 40 through the injection well 10.
In other embodiments, the in situ combustion process may be initiated by ignition naturally, steam circulation, electrical heating, electro-magnetic heating, or other physical/chemical heating methods.
100641 In one embodiment, the oxidizing gas 100 is a mixture of oxygen and nitrogen. In other embodiments, the oxidizing gas 100 is oxygen enriched air.
[0065] The in situ combustion within the combustion area 40 will continue by burning a small portion of the hydrocarbons present in the hydrocarbon bearing area 70 of the reservoir 60 and the majority of the hydrocarbons in the hydrocarbon bearing area 70 will be mobilized upon being heated by the in situ combustion and drain to the production well 20 by gravity. The in situ combustion process within the combustion area 40 can be fully controlled by way of the injection well 10, the production well 20, and the ventilation well 30. This process does not rely on formation energy. In some embodiments, water or steam injection through the injection well 10 or the production well 20 may be applied to encourage circulation of fluids within the injection well 10 or the production well 20 to control the in situ combustion.
100661 Figure 2 is a side view illustrating a method of and a system 1 for extracting hydrocarbons according to an embodiment of the invention. The injection well 10 has a horizontal segment 12 in the hydrocarbon bearing area 70 of the reservoir 60. The production well 20 also has a horizontal segment 22 in the hydrocarbon bearing area 70 of the reservoir 60. The horizontal segment 22 is spaced vertically below the horizontal segment 12 of the injection well 10.
Multiple ventilation wells are placed vertically into the hydrocarbon bearing area 70 of the reservoir 60 and spaced apart along the horizontal segment 12 of the production well. As such, the ventilation wells 30 are perpendicular to the horizontal segments 12 and 22 of the injection well 10 and the production well 20.
[0067] Upon commencement of the in situ combustion in the injection well 10 and through the 5 horizontal segment 12 in the hydrocarbon bearing area 70 of the reservoir 60, the combustion area 40 is generated in the hydrocarbon bearing area 70 around the injection well 10.
As a result of the in situ combustion, which can occur across the hydrocarbon bearing area 70 along the injection well 10, the heavy oil in the hydrocarbon bearing area 70 mobilizes to become mobilized heavy oil 120 which moves via gravity into the production well 20. In addition, combustion gases 110 are formed 10 in the combustion area 40 as a result of the in situ combustion. The combustion gases 110 may include nitrogen, steam, carbon dioxide, trace amount of light hydrocarbons, and oxygen. Because of the presence of the ventilation wells 30 in the hydrocarbon bearing area 70 that are in fluid communication with such area, the combustion gases 110 can leave the combustion area 40 through the ventilation wells 30. In one embodiment, the ventilation wells 30 are open and the combustion gases 110 are released into the atmosphere. In another embodiment, the ventilation wells 30 are connected to a gas treatment facility where the combustion gases 110 are treated prior to their release into the atmosphere. In a further embodiment, the ventilation wells 30 may be connected to the injection well 20 whereby the combustion gases 110 can be recycled into the combustion area 40 through the injection well 10 as part of regulating the in situ combustion within the combustion area 40. In other embodiments, the ventilation wells 30 may be connected to the production well 20 whereby the combustion gases 110 can be recycled back into the production well 20.
[0068] By opening, choking back, or shutting each, some, or all of the ventilation wells 30, the ventilation of the combustion area 40 can be increased or decreased, such that the in situ combustion within the combustion area 40 can be regulated. For instance, if the in situ combustion is occurring too rapidly and the temperature within the injection well 10, the production well 20, and/or the combustion area 40 is becoming too high, then the ventilation wells can be completely or partially closed to reduce the amount of oxygen available to sustain the in situ combustion within the combustion area 40. Where the in situ combustion is unable to sustain across the horizontal segment 12 of the injection well 10 to allow for sustained combustion within the combustion area 40, the ventilation wells 30 can be completely opened or partially opened to allow oxygen to enter into the combustion area 40 to encourage further combustion. As such, temperature, pressure and oxygen levels can be controlled to desired limits within the system 1, within the in situ combustion area 40 and/or within each injection well 10, production well 20, and/or ventilation well 30. The control of temperature, pressure, and/or oxygen levels also enables one to control combustion and/or rate of flow of the mobilized heavy oil 120 within the production well 20.
[0069] In one embodiment, temperature sensors, pressure sensors, oxygen sensors, and other sensors known to persons skilled in the art are installed to monitor conditions in the injection well 10, the production well 20, the ventilation wells 30, and/or the combustion area 40 such as temperature, pressure, hydrocarbon production rate, and oxygen levels. In other embodiments, a computerized system is used to regulate the production of mobilized heavy oil 120 through interaction with the injection well 10, the production well 20, and/or the ventilation wells 30 based on results from the different sensors.
[0070] Through the use of the ventilation wells 30 situated along the horizontal segment 12 of the injection well 10, the combustion area 40 can be developed evenly along the horizontal section of the hydrocarbon bearing area 70 of the reservoir 60. The production of the mobilized heavy oil 120 through the production well 20 by gravity drainage is known in the art and is commonly used with other methods of hydrocarbon extractions such as steam assisted gravity drainage (SAGD).
[0071] As illustrated in FIG. 1 and 2, in one embodiment, the ventilation wells 30 are perpendicular to the horizontal segments 12 and 22 of the injection well 10 and the production well 20, respectively. In other embodiments, the ventilation wells 30 are not perpendicular to the horizontal segments 12 and 22 of the injection well 10 and the production well 20, respectively.
[0072] In one embodiment, the ventilation wells 30 are in the combustion area 40 and close to the injection well 10 and the production well 20. In other embodiments, the ventilation wells 30 intersect the injection well 10 at right angles. In other embodiments, the ventilation wells 30 intersect the injection well 10 at other angles that are not right angles.
[0073] As illustrated in FIG. 1 and FIG 2, in one embodiment, the injection well 10 has a horizontal segment 12 which is parallel to the horizontal segment 22 of the production well 20. In other embodiments, the injection well 10 does not have the horizontal segment 12 and is not parallel to the horizontal segment 22 of the production well 20. In other further embodiments, the injection well 10 has segments at an angle between 0 to 90 degrees relative to the horizontal direction.
100741 In one embodiment, the injection well 10 is cased. In other embodiments, the injection well is open hole. In one embodiment, the ventilation wells 30 are cased. In other embodiments, the 5 ventilation wells 30 are open hole.
[0075] In one embodiment, the injection well 10 and the production well 20 are completed with circulation tubing to toe. In alternative embodiments, the injection well 10 and the production well are not completed with circulation tubing to toe. In one embodiment, the ventilation wells contain corrosion resistant tubing. In other embodiments, the ventilation wells do not contain 10 corrosion resistant tubing.
[0076] In one embodiment, there is one injection well 10 and one production well 20. In other embodiments, more than one injection wells 10 may be used with one production well 20. In yet other embodiments, more than one injection wells 10 may be used with more than one production wells 20. In alternative embodiments, one injection well 10 can be used with more than one 15 production wells 20.
[0077] In one embodiment, there is one set of the injection well 10, the production well 20, and the ventilation wells 30 in the reservoir 60. In other embodiments, there are multiple sets of the injection well 10, the production well 20, and the ventilation wells 30.
[0078] The above embodiments may contribute to an improved method and a system of extracting 20 hydrocarbons and may provide one or more advantages. Firstly, the in situ combustion may be fully controlled from three different kinds of wells. Oxidizing gas injection rate, pressure, and temperature are controlled from the injection well; production rate and pressure (even temperature) can be controlled from the producer well; and flue gas production rate and pressure can be controlled from the ventilation wells. Secondly, the method may require lower capital and operation cost. Thirdly, the method may be easier to operate. Fourthly, the method may require use of little to no water.
Fifthly, the method may create less green house gas emission because natural gas is not needed for generating steam. Sixthly, the method may be adopted for use with different heavy oil -bearing formations, such as low oil saturation, lean zones, top water, top gas, low pressure, thin pay, and carbonates reservoirs. Seventhly, the method may allow flexible well configuration and completion.
Eighthly, the method may allow in situ upgrading of low quality hydrocarbons.
100791 The embodiments of the invention described above are intended to be exemplary only. Those skilled in this art will understand that various modifications of detail may be made to these embodiments, all of which come within the scope of the invention.
100801 All patents and patent applications referred to herein are incorporated by reference in their entirety to the same extent as if each patent or patent application were specifically and individually indicated to be incorporated by reference in its entirety. Nothing herein is to be construed as an admission that the invention is not entitled to antedate the cited references by virtue of prior invention.