Patent Application
20120227966
Not applicable.
The invention relates to in situ hydrocarbon upgrading system and method, and more particularly to an in situ oil upgrading for upgrading the crude oil before production.
Heavy oils such as bitumen and oil sands can be very difficult to access due to their high viscosity. In situ upgrading is an enhanced recovery technique that aims to upgrade heavy crude oil and bitumen while still within the subsurface of the earth, making the hydrocarbons easier to produce and transport. Attempts have been made to address this challenge by using in situ combustion approaches, solvent extraction, radio frequency (including microwave radiation) heating, and thermal resistive heating. Although each of these attempts has shown some technical merit, no method currently exists which addresses all of the requirements of a commercially viable process.
In situ upgrading has also been attempted by using a solvent process known as “Vapex.” In this approach, a solvent mobilizes the oil by decreasing its viscosity through a dissolution effect. During this process, asphaltenes, heteroatoms, and heavy metals may precipitate, resulting in upgraded oil. Solvent to oil ratios are high, however, and make this process economically unfeasible. In addition, as larger molecules precipitate, flocculation may occur which may lead to the clogging of the producing well.
A similar approach has been to simply use a catalyst bed around the producer well in a modified toe to heel air injection (THAI) process. This approach is limited to the amount of upgrading that may occur and does not utilize hydrogen.
Although the prior art methods have achieved success, they could be further improved with novel combinations of techniques and/or novel well configurations, to further increase production and/or decreases production costs. Thus, what is needed in the art are improved, cost effective methods of in situ upgrading of hydrocarbon deposits.
The use of the word “a” or “an” when used in conjunction with the term “comprising” in the claims or the specification means one or more than one, unless the context dictates otherwise.
The term “about” means the stated value plus or minus the margin of error of measurement or plus or minus 10% if no method of measurement is indicated.
The use of the term “or” in the claims is used to mean “and/or” unless explicitly indicated to refer to alternatives only or if the alternatives are mutually exclusive.
The terms “comprise”, “have”, “include” and “contain” (and their variants) are open-ended linking verbs and allow the addition of other elements when used in a claim.
The following abbreviations are used herein:
As used herein a “Fishbone” configuration is defined as a well having an initially vertical portion and a plurality of non-vertical, deviated portions connected to the vertical portion and extending in the oil reservoir. The non-vertical portions of a Fishbone well can further progress through the reservoir at angles different from the original angle.
As used herein, “in situ upgrading” refers to a system and/or process that upgrades crude oil, i.e. hydro-cracks the heavy oil, prior to production. In other words, the process occurs inside the ground or hydrocarbon reservoir.
The objective of the present invention is to upgrade mobilized oil within a reservoir prior to production of the oil to the surface. Generally speaking the invention requires pushing fluid through a reservoir, the lighter components of which then escape laterally through production wells. The heavier components sink to a lower horizontal production well, where it optionally filters through porous catalysts contained in the wellbore, thus being upgraded before production. The unique placement of the injector and producer wells optimizes production in this method.
In preferred embodiments, the present invention utilizes an injection well having a Fishbone configuration that facilitates the moving of a combustion front in the reservoir. In addition, by using two production wells having equi-spaced (parallel if only two) horizontal portions and another production well having a lower, but perpendicular horizontal portion, the mobilized oil can be more easily drained and produced through the lower production well, while gases escape through the higher production wells. In situ upgrading of the crude oil is realized by adding the catalytic reactor to the lower but perpendicular horizontal portion of the production well, so that the oil taken in the production well will first undergo hydro-processing in the catalytic reactor to further increase the mobility and quality of the oil. If desired, this lower portion can also be equipped with heaters to reduce oil viscosity and/or drive the catalytic reactions.
According to one aspect of the present invention, there is provided a system for in situ upgrading crude oil within an oil reservoir prior to production. The system includes at least one injection well, at least two first production wells, and at least one second production well. The at least one injection well has a vertical portion and a plurality of non-vertical portions connected to the vertical portion. The two first production wells are parallel to each other (but are roughly equi-spaced if more than two), and each has a horizontal portion with a first axial direction, wherein each said horizontal portion of the first production wells is horizontally spaced apart.
The at least one second production well has a horizontal portion with a second axial direction. The catalytic reactor is placed at the horizontal portion of the at least one second production well such that oil coming through the second production well will first go through the catalytic reactor for hydro-processing. Preferably, the horizontal portion of the at least one second production well is vertically lower than the horizontal portion of the at least two first production wells to ensure better oil drainage and production. Preferably, the first axial direction of the first production wells is substantially perpendicular to the second axial direction of the second production well (or equi-spaced if more than two).
Of course, additional production wells can be used and the placement varied accordingly. Furthermore, when we refer to placement, the placement need not be exact, but can vary according to convenience, depending on surface structures or subsurface impediments. Thus, the placement of parallel or perpendicular wells, etc. is only a rough description.
In one embodiment, the catalytic reactor comprises a catalyst bed, a fluid inlet for introducing the fluid required for upgrading, and a plurality of slots for taking in the crude oil. In another embodiment, the catalytic reactor comprises a catalyst bed, a gas inlet, a plurality of slots for taking in the crude oil, and heaters for heating the reactor and/or the oil so as to facilitate the required temperatures necessary to upgrade the oil. In some embodiments, the heaters can be thermal resistive heaters, but other heating methods can also be used.
In one embodiment, the catalytic bed comprises hydro-processing catalysts. Examples of the hydro-processing catalysts include, but not limited to, metal sulfides, metal carbides, refractory type metal compounds or the combination thereof. The metal sulfides may include MoS2, WS2, CoMoS, NiMoS, or combinations thereof. The metal carbides can include Mo2C, WC, or combinations thereof. In another embodiment, the refractory type metal compound includes phosphosides, nitrides or borides of transition metals. In yet another embodiment, the refractory type metal compound includes hydrogenation catalysts such as Co2P, Ni2P, MoP, WP, NiMoP or Mo2N, Co4N, Fe3N, W2N or MoB, WB, Ni2B, Co2B, or the combination thereof, with optional support such as Al2O3, TiO2, MgO, SiO2 and the combination thereof.
The injection well, especially the non-vertical portions, may progress within the oil reservoir to any place depending on the need and technological limitations, except that preferably it does not extend deeper than 5 meters above the bottom of the pay.
According to another aspect of the present invention, there is provided a method for in situ upgrading crude oil within an oil reservoir prior to production. The method comprises the following steps: providing an injection well within the oil reservoir, the injection well having a vertical portion and a plurality of non-vertical portions connected to the vertical portion; providing at least two first production wells each having a horizontal portion with a first axial direction, wherein each said horizontal portion of the first production wells being horizontally spaced apart; providing at least one second production well having a horizontal portion with a second axial direction, wherein the horizontal portion of the at least one second production well being vertically lower than the horizontal portion of the at least two first production wells, the first axial direction being substantially perpendicular to the second axial direction, and a catalytic reactor being attached to the horizontal portion of the second production well; performing cyclic steam stimulation to heat the oil deposit with the oil reservoir; injecting a combustion agent into the injection well; and producing crude oil from the at least one second production well.
In a preferred embodiment, the method further comprises the step of introducing hydrogen through the gas inlet to the catalytic reactor.
In another embodiment, the combustion agent is selected from oxygen, oxygen-enriched air, or the combination thereof, although plain air and oxygen-depleted air are also applicable when the exotherm is large. In addition, chemical oxidants such as H2O2 or O3, or other organic and inorganic peroxides may also be used.
The present invention utilizes a novel well-configuration to facilitate the application of in situ combustion in a bitumen and/or heavy oil reservoir and offers a novel approach for upgrading the bitumen and/or heavy oil prior to surface production. The well configuration of interest is a fishbone well configuration as shown in
At the beginning, wells are drilled in a fishbone pattern. A single vertical well from the surface can facilitate this drilling. Multiple wells at angles varying from 30 to 120 degree from vertical will be drilled into the reservoir from the single vertical well. Additionally, these vertically deviated wells may progress through the reservoir at angles that differ from the original angle. This will facilitate the best placement of the well within the reservoir. These wells will be placed anywhere within the reservoir with the exception that the lowest well should be at least five (5) meters above the bottom of the pay. In addition, this process requires the use of three producer wells that will be completed through the use of horizontal drilling technologies. These horizontal wells can be placed near or at the base of the reservoir pay zone, where at least one or more producers are arranged perpendicular (or roughly equi-spaced depending on how many are used) to one or more producer wells situated vertically beneath the other well pairs. In
Once the wells have been placed within the reservoir, they will be used in a primary or preliminary recovery method known as cyclic steam stimulation (CSS) or similar technique. This process will facilitate the heating of the reservoir and preliminary recovery of oil. Once the pay between the wells has been heated (>80° C.), the CSS processes can be shut in. The main objective for the CSS process is to condition the reservoir by lowering the viscosity to a level that allows for fluid communication prior to the initiation of an in situ combustion process. CSS is a technology known to a skilled artisan in the field, and will not be elaborated here.
Once CSS operations are completed, the Fishbone well setup will now be used as injector wells for the introduction of combustion agent, for example oxygen or oxygen enriched air, into the formation. The major driver for the recovery of oil through the combustion process will be gravity drainage. In the present specification, “gravity drainage” refers to a recovery mechanism in which the oil is pushed or displaced into the production well by the force of gravity.
For example, as the combustion agent propagates from the Fishbone injector wells into the formation, oil and combustion gas products will drain to the base of the reservoir. The unique aspect of this well pair arrangement for the in situ combustion process is that it facilitates the ability to produce oil and gas products from separate wells. This phenomenon aides in the overall process by removing gas products from the reservoir, which allows the oil to flow more freely to the bottom of the reservoir where it can be produced by Producer 2 well in
Simulation results are shown in
An extension of the above mentioned process is that the fluid separation and gravity drainage mechanisms consistent with this approach offer a unique opportunity to upgrade bitumen and heavy oil subsurface.
Some examples of possible hydro-processing catalysts that may be applicable are metal sulfides (MoS2, WS2, CoMoS, NiMoS, etc.), metal carbides (MoC, WC, etc.) or other refractory type metal compounds such as metal phosphides, borides, etc. The refractory type metal compound includes phosphosides, nitrides or borides of transition metals. In one embodiment, the refractory type metal compound includes hydrogenation catalysts such as Co2P, Ni2P, MoP, WP, NiMoP or Mo2N, Co4N, Fe3N, W2N or MoB, WB, Ni2B, Co2B, or the combination thereof, with optional support such as Al2O3, TiO2, MgO, SiO2 and the combination thereof. It is not anticipated that reduced metal catalysts will remain active for a long period of time in this application.
Typical hydro-processing reactions will consist of impurity removal processes, such as the removal of sulfur, nitrogen and metals. This can improve the ultimate quality of the crude. Hydrogen assisted removal of oxygen can lower the acid number of the crude. Reduction of aromatics will produce “lighter” hydrocarbons thus lowering the API gravity of the crudes. Potential hydrocracking/isomerization reactions can provide lower carbon number branched hydrocarbons and will improve a lower viscosity crude. It is expected that some combination of all the above reactions will be realized thus giving an improved quality and less viscous crude oil.
The space velocity of the hydrocarbon in the catalyst/hydrogen zone should be between 0.05 to 1.0 hr−1 or more preferably between 0.2 and 0.5 hr−1. The unique aspect of this approach is that the hydrogen will be sufficiently separated from the high temperatures of the combustion front due to the fact that the main recovery mechanism is gravity separation. The producer tubing is placed vertically near the bottom of the reactor/producer, which promotes increased contact with the catalyst and hydrogen prior to production.
In a separate embodiment of this invention, thermal resistive heaters may be incorporated within the reactor/producer wells to facilitate the required temperatures necessary to upgrade the oil prior to production. An example of this is shown in
An advantage of this invention is that it allows for oils to contact catalyst and hydrogen at required upgrading temperatures prior to being produced. As the oil is upgraded, the viscosity will be further reduced which will lead to an increase in the overall recovery of the oil and limit or eliminate surface processing. Also, the present invention allows for the successful, both technically and economically, implementation of in situ combustion.
The foregoing description of the present invention is exemplary only, and other variation of the present invention can be readily contemplated by a person having ordinary skill in the art based on the teaching of the specification without deviating from the spirit of the present invention. The foregoing description is intended to be illustrative only, and not unduly limit the scope of the appended claims.
This application is a non-provisional application which claims the benefit of and priority to U.S. Provisional Application Ser. No. 61/450,872 filed Mar. 9, 2011, entitled “In Situ Catalytic Upgrading,” which is hereby incorporated by reference in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 61450872 | Mar 2011 | US |
