Patent Application
20130153217
The present invention provides a method for enhanced oil recovery using cryogenic fluids. In particular, cryogenic fluids are injected into subterranean reservoirs to enhance the recovery of oil.
In recent years, the demand for oil and natural gas has increased. The increase in demand for oil and natural gas is driving the oil and gas industry to produce more oil and natural gas using more cost efficient and effective techniques. Extracting subterranean fluids from depleted oil and gas reservoirs with new means is needed.
Generally, when extracting oil and natural gas from subterranean reservoirs, the skilled artisan must consider the properties of the reservoir, the types of fluids present in the reservoir, and the physical and chemical properties of fluids of the reservoir. Another important factor in enhancing the total recoverable reserves of hydrocarbons and other fluids form depleted reservoirs is related to the reservoir pressure of the fluids trapped in the reservoir. When a wellbore penetrates a reservoir, the reservoir pressure forces the subterranean fluids out of the reservoir into the wellbore and up ward toward the surface as a function of lower pressure at the surface. As fluids flow into the wellbore, the pressure of the reservoir decreases, or as commonly referred to in the industry the reservoir pressure depletes. As such, over a period of time of extraction, the reservoir pressure becomes insufficient to force hydrocarbon fluids from the reservoir into the well. Therefore, there is a need to maintain and/or increase the reservoir pressure in these depleted reservoirs in order to maximize the percentage of hydrocarbon fluids recovered from the reservoir.
A reservoir's ability to produce oil is also a function of the reservoir's drive mechanism. A reservoir's drive mechanism refers to the forces in the reservoir that displace hydrocarbons out of the reservoir into the wellbore and up to surface. Reservoir drive mechanisms include gas drive (gas cap or solution gas drive), water drive (bottom water drive or edge water drive), combination drive, and gravity drainage. An example of solution gas drive is when soluble gases in the oil expand and are carried into the well with liquid hydrocarbons. Reservoirs where soluble gases form a significant portion of the drive mechanism typically have the lowest reservoir primary recovery factors for hydrocarbons. Therefore, there is a need for a method to continually and rapidly replenish the reservoir energy depleted by the extracted soluble gases. This can be done with the injection of fluids that can energize the reservoir and still more desirable is injecting a fluid that is soluble in the reservoir fluid at reservoir pressure and temperature conditions.
Petroleum engineers often refer to the percentage of oil recoverable from a given reservoir versus the oil in place in a reservoir as the “recovery factor.” During primary recovery phase of a wells exploitation, the natural pressure of the reservoir created by the combination of forces like the earths overburden and subsequent compression of the reservoir fluids drives or forces hydrocarbons into the wellbore. However, only about 10 to 30 percent of a reservoir's original hydrocarbons in place are typically produced from the reservoir during the primary recovery phase. After a number of years of producing fluids from reservoirs under primary recovery methods, it becomes necessary to inject fluids from surface into the reservoirs to enhance fluid production from the depleted reservoir. This process is known as Enhanced Oil Recovery (EOR). The purpose of EOR is to increase the recovery of the reservoir fluids.
In general, Enhanced Oil Recovery is divided into two distinct phases, secondary recovery methods and tertiary recovery methods. Secondary recovery methods generally include injecting water or gas to displace oil and driving the hydrocarbon mixture to a production wellbore which results in the enhanced recovery of 20 to 40 percent of the original oil in place. After a reservoir has been flooded with water or other secondary recovery methods, tertiary recovery methods are used to increase the fluid recovery from the reservoir. However in some cases, tertiary recovery methods may be used immediately after the primary recovery method.
Generally, tertiary recovery methods include steam, gas injection, and chemical injection. Steam enhanced tertiary recovery involves injecting steam down an injection well to lower the viscosity of the hydrocarbon fluid. That is, heavy viscous oil reserves is made less viscous to improve their ability to flow out of the reservoir into a well. Gas injection tertiary methods employ gases such as natural gas, nitrogen, or carbon dioxide that expand in a reservoir to push additional oil to a production wellbore. In all these gas injection means, the fluids are at temperatures of more than −100° F. Fluids that are at a temperature below −100° F. are commonly referred to as cryogenic fluids. Preferred gases are those that dissolve in the reservoir hydrocarbon, which lower the in-situ hydrocarbons viscosity and improve the hydrocarbons flow rate from the reservoir to the well bore. Chemical injection involves the use of polymers to increase the effectiveness of water floods, or the use of detergent-like surfactants to reduce the surface tension that often prevents oil droplets from moving through a reservoir.
Generally, carbon dioxide is a common miscible tertiary EOR fluid. Carbon dioxide is the preferred EOR fluid in the current art because it can be delivered to wellbores in a liquid form above cryogenic temperatures. For example, carbon dioxide has a boiling point of −70° F. at ambient pressures, while other gases have a higher boiling point, e.g., methane has a boiling point of −259° F. at ambient pressures. The difference between these boiling points shows that carbon dioxide requires less energy to condense to a liquid phase in comparison to most other fluids that are miscible in hydrocarbon liquids. Nevertheless, over fifty percent of the cost when using carbon dioxide to flood the well is the initial purchase of the carbon dioxide. Further, the use of carbon dioxide in EOR methods has other disadvantages. For example, once carbon dioxide is injected into an injection well, it cannot be recovered and resold. Also, it is a greenhouse gas, the release of which into the atmosphere will likely be regulated. Moreover, it causes formation of carbonic acid in water that can lead to corrosions of pipes and other equipment. What is needed is a tertiary fluid that is soluble in the hydrocarbon fluids, can be commercialized as a part of the reservoir fluid recovery process, and is non-corrosive.
On the other hand, it is plausible for liquid methane or liquid natural gas, LNG, to be used to flood the reservoir in tertiary recovery methods if the liquefied natural gas supply can be replenished continually. When liquid natural gas (LNG) is used as a cryogenic flood fluid to enhance oil recovery, the LNG may be re-gasified under ground and separated from the tertiary recover of oil upon recovery of the combined fluids at the surface. The recovered LNG can be commercialized and sold as natural gas, using the existing equipment already in place to distribute oil and gas from the recovery sites to the market.
Further, it is difficult to inject gases into the reservoir, as it requires large high pressure compressors and prime movers at or near the wellbores. It is costly to construct the required compressor injection facilities at each EOR site, and it is even more cost limiting when the EOR site is offshore because the compressors and prime movers would have to be located on the offshore platforms where space is expensive and limited. This present disclosure provides for a solution where these same gases are liquefied as cryogenic liquids prior to injection to the wells, which allows them to be contained in significantly smaller spaces than their gas counterparts because the same volume of the fluid in liquid form contain several orders of magnitude more molecules than when the fluid is in gas form. For example, cryogenic liquefied methane and LNG contains 600 times more methane than an equivalent volume of methane gas. Consequently, a more cost effective method is needed to get large volumes of these cryogenic flood fluids delivered to the EOR sites to be injected into the subterranean oil reservoirs as flood fluids.
Further, currently, the oil and gas industry has many known reservoirs of natural gas that are stranded because the reservoirs are geographically located far from a commercial markets. As such, to commercialize the natural gas, large facilities are built at these stranded geographical areas to liquefied the natural gas produced at these sites. The LNG is transferred to large cryogenic tankers to commercialize the LNG and bring it to a market. The commercial activities, e.g., sales, of the produced cryogenic fluid, LNG, is limited in the world today because the markets for such LNG requires costly cryogenic facilities to receive and or re-gasify the cryogenic liquids at the destination market. These receiving stations at the destination market, or re-gasification stations, are expensive and require LNG carrying ships to come into ports and near populated areas to discharge their cryogenic cargo. The regasification facilities are often perceived as a potential health hazard; hence, public support for such facilities is difficult to obtain. What is needed are EOR facilities sufficiently far from population centers with facilities and wells equipped to accept the cryogenic fluid cargos as a flood fluid and to serendipitously commercialize the cryogenic flood fluid from production wells once it has served its purpose as a reservoir displacement or flood fluid and is naturally geothermally heated, re-gasified and/or separated from the recovered hydrocarbon produced to surface after the LNG is injected into the subterranean environment and used as the flood fluid.
The present invention provides a method for injecting large volumes of cryogenic liquids into subterranean reservoirs as very cold fluids, which are subsequently extracted from the reservoir with hydrocarbon fluids as a means of enhanced hydrocarbon recovery. As the geothermal energy warms the cryogenic flood fluid the fluid expands causing an increase in pressure in the reservoir. Additionally, the present invention provides a method for creating large conductivity paths for the cold fluids to enter into the reservoir matrix. Furthermore, this invention teaches methods to inject the cold fluid into wells by means of expanding tubular slip joints in the well. In addition, the present invention discloses methods of utilizing the existing equipment to commercialize LNG from stranded locations without having to build additional structures to re-gasify the delivered LNG in natural gas form.
The present invention provides methods and apparatus for enhancing the recovery of fluids from subterranean reservoirs using cryogenic flood fluids. In some aspects of the present invention the method for enhancing the recovery of fluids from subterranean reservoirs using a cryogenic flood fluids comprises the steps of providing a source of at least one cryogenic flood fluid, delivering at least one cryogenic flood fluid from the source to at least one wellbore, injecting the cryogenic flood fluid with at least one cryogenic pump through at least one wellbore into at least one subterranean reservoir, warming the cryogenic flood fluid, and transporting reservoir fluids produced from the subterranean reservoir into a storage tank through at least one wellbore. In some cases, the storage tank may be on, near or at the Earth's surface. In other embodiments, the storage tank may be aboard an oil platform, an oil tanker, underground and/or submerged under a body of water. In additional embodiments, the reservoir fluids produced from the subterranean reservoir may feed directly into a pipeline.
In other aspects of the present invention, the cryogenic flood fluid source is a liquid natural gas plant. In some embodiments, the cryogenic flood fluid source is a liquid air plant. In certain embodiments, the cryogenic flood fluid is liquid natural gas. In specific embodiments, the cryogenic flood fluid is liquid oxygen. In alternate embodiments, the cryogenic flood fluid is liquid nitrogen.
In some embodiments, the cryogenic flood fluid source is aboard a ship. In alternate embodiments, the cryogenic flood fluid source is provided by a truck in still other embodiments the cryogenic flood fluid source is a pipeline.
In some aspects of the present invention, the step of injecting the cryogenic flood fluid is performed by at least one cryogenic pump. The cryogenic pumps can be positive displacement pumps fed by low pressure cryogenic centrifugal pumps or a series high rate cryogenic turbo-pumps like the low pressure oxidizer pump and high pressure oxidizer pump used on the Space Shuttle. The high rate attribute of the cryogenic turbo-pumps is useful in rapidly unloading large volumes of LNG from LNG tankers offshore to reduce mooring times of the vessels.
In some cases, the wellbore is located offshore and the subterranean reservoir is an offshore oil reservoir. In other embodiments, the subterranean reservoir is an offshore gas reservoir. In specific embodiments, the subterranean reservoir is an aquifer. In other embodiments, the subterranean reservoir is a coal bed methane deposit, a shale oil deposit, and/or a shale gas deposit.
Additionally, the methods of the present invention may include the step of injecting a cryogenic flood fluid comprising a chemical additive. This chemical additive may be a solid, liquid and/or a gas. In some embodiments, the chemical additive is a solid. In some cases, the chemical additive is a polymer. In some cases, the chemical additive may comprise a tetrahalosilane. In specific examples, the tetrahalosilane is silicon tetrachloride.
Alternatively, the methods of the present invention may include the step of injecting a cryogenic fluid comprising a liquid chemical additive. In some embodiments, the liquid chemical additive is hydrogen peroxide. In yet another embodiment, the chemical additive is a gas.
In some embodiments, the reservoir fluid produced from the subterranean reservoir comprises a liquid. In some cases, this liquid comprises a liquid hydrocarbon. The liquid produced from the reservoir may comprise water and/or gas. In some cases, the gas comprises a hydrocarbon gas and/or steam.
In some embodiments, the step of warming the injected cryogenic fluid is performed by an electrical heater. In other embodiments, the warming step is performed by the geothermal energy of the well and reservoir wherein it is injected. The warming step can also be performed by a seawater heat exchanger. or a surface combustion fired heat exchanger.
In additional embodiments, the methods of the present invention further comprises the step of injecting a non-cryogenic flood fluid through at least one wellbore into at least one subterranean reservoir. In particular embodiments, a wellbore has at least one horizontal section.
The present invention provides for injecting at least one cryogenic flood fluid into a subterranean reservoir. In general, this apparatus has a wellbore extending into a subterranean reservoir, a first conduit that is located within the wellbore, a wellhead coupled to the first conduit, a second conduit is located within the wellbore, and a sealing elastomeric thermal expansion slip joint located near a distal end of the second conduit. In some embodiments, the wellbore extends from the surface into a subterranean reservoir. In some embodiments, the first conduit has a fluid path that extends from a location at or above the earth's surface to at least one subterranean reservoir. In certain embodiments, the wellhead that is coupled to the first conduit is located at or near the earth's surface. Additionally, the second conduit has a fluid path that extends from a location at or above earth's surface to at least one subterranean reservoir and the second conduit coupled to a subterranean reservoir at the earth's surface. In other embodiments, the elastomeric thermal expansion slip joint situated so that it is in contact with the inner diameter of first conduit and the outer diameter of the second conduit.
The foregoing has outlined rather broadly the features and technical advantages of the present invention in order that the detailed description of the invention that follows may be better understood. Additional features and advantages of the invention will be described hereinafter which form the subject of the claims of the invention. It should be appreciated by those skilled in the art that the conception and specific embodiment disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present invention. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the invention as set forth in the appended claims. The novel features which are believed to be characteristic of the invention, both as to its organization and method of operation, together with further objects and advantages will be better understood from the following description when considered in connection with the accompanying figures. It is to be expressly understood, however, that each of the figures is provided for the purpose of illustration and description only and is not intended as a definition of the limits of the present invention.
For a more complete understanding of the present invention, reference is now made to the following descriptions taken in conjunction with the accompanying drawing, in which:
As used herein, “surface” refers to locations at or above the surface of the
Earth, ice, ocean bottom, river bottom, lake bottom, and/or body of water, such as a lake, river, or ocean.
As used herein, “fluid” refers to substance that continually deforms and/or flows under an applied shear stress. This term includes gases and liquids.
As used herein, “cryogenic” refers to a liquid that boils, i.e., changes from a liquid to a gas, at temperatures less than about 110 Kelvin (K) at atmospheric pressure, such as hydrogen, helium, nitrogen, oxygen, air, or methane (natural gas).
In
In the preferred embodiment, liquid natural gas 2 is injected into subterranean reservoir 6 as a cold liquid. The cold fluid has advantages over previous methods of EOR injection of gases as the cold fluid causes cracking and rubbilizing of the subterranean reservoir thereby exposing a new fluid path for the flood fluids to sweep hydrocarbons from the reservoir. As LNG 2 begins to heat up in the reservoir 6, a flood bank of liquid natural gas 16 is formed near injection points 15 of well bore 5. As the LNG 2 is being injected through wellbore 5, wellbores 7 and 8 draw liquids like oil and gas fluids from the same reservoir 6. As LNG 2 moves through wellbore 5, the flood front pushes toward production wellbores 7 and 8. In other embodiments, other fluids besides LNG like liquid air, nitrogen, and oxygen, can be used as the cryogenic flood fluid. In
Additionally,
Also, the present invention provides the method for stopping and/or restarting the injection of cryogenic fluids, like liquid natural gas 2, into reservoir 6. This is done to allow geothermal energy 18 of the earth to heat the cryogenic flood fluids in-situ and to allow for LNG ship 1 to arrive with a fresh supply of LNG 2. In another aspect of the present invention, liquid natural gas is injected down a different wellbore like 7 when the next cycle of liquid natural gas 2 is injected into reservoir 6.
Additionally, the water from tank 20 or sea water may be injected into reservoir 6 and used as an alternative flood fluid in between the injection cycles of cryogenic fluids. This water may be used in alternating injection cycles, alternating between water and cryogenic flood fluid. These waters may be heated prior to injecting into the reservoir to further assist in the thermal cracking of the reservoir to enhance reservoir conductivity and to heat the injected cryogenic fluids. In an additional embodiment, chemical additives, such as solids, liquids and gases may be added to the cryogenic flood fluid and the water injection cycle and injected into reservoir 6 from the flood fluids from tank 22 through an injection pump 23. The chemical additives may include, but are not limited to polymers, surfactants, corrosion inhibitors, caustics, ammonium carbonate, hydrogen peroxide, sulfuric acid, urea, butanol, N-alkylacrylamides, terpolymers of acrylamide, N-decylacrylamide, and sodium-2-acrylamido-2-methyl-propane sulfonate (NaAMPS), sodium acrylate (NaA), sodium-3-acrylamido-3-methylbutanoate (NaAMB), partially hydrolyzed polymer polyacrylamide, polyacylamide, bentonite clay, polydimethyldiallyl ammonium chloride biopolymers, exopolysaccharide produced by Acinetobacter, Xanthan, Wellan, Pseudozan, silicon tetrahalides (halide refers to a halogen atom such as, fluoride, chloride, bromide, iodide and/or astatide), silicon tetrachloride, silicon tetrafluoride, silicon tetrabromide, and/or silicon tetraiodide.
Although the present invention and its advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims. Moreover, the scope of the present application is not intended to be limited to the particular embodiments of the process, machine, manufacture, composition of matter, means, methods and steps described in the specification. As one of ordinary skill in the art will readily appreciate from the disclosure of the present invention, processes, machines, manufacture, compositions of matter, means, methods, or steps, presently existing or later to be developed that perform substantially the same function or achieve substantially the same result as the corresponding embodiments described herein may be utilized according to the present invention. Accordingly, the appended claims are intended to include within their scope such processes, machines, manufacture, compositions of matter, means, methods, or steps.
This application is a continuation of U.S. patent application Ser. No. 12/763,650, filed on Apr. 20, 2010, and entitled “METHOD AND APPARATUS TO ENHANCE OIL RECOVERY IN WELLS,” which claims the benefit of U.S. Provisional Application No. 61/170,966 filed on Apr. 20, 2009, both of which are incorporated herein in their entirety.
| Number | Date | Country | |
|---|---|---|---|
| 61170966 | Apr 2009 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 12763650 | Apr 2010 | US |
| Child | 13770414 | US |
