- CROSS-REFERENCE TO RELATED APPLICATION
Oil extraction systems and methods are generally discussed herein with particular discussions extended to systems and methods for extracting oil from oil reservoirs located in a prematurely abandoned oil field using, among other things, upward drilling.
This is an ordinary application of Provisional Application Ser. No. 60/689,308 filed Jun. 10, 2005.
Historically, oil has been produced by using primary, secondary and tertiary recovery methods. With primary methods, oil may be produced as long as there are sufficient reservoir pressure to create flow into a well bore. Primary methods include the natural drive due to formation pressure and/or artificial lift accomplished by either pumps or gas and oil lifting methods. Secondary methods consist of primary methods plus the addition of energy to the reservoir in the form of forced injection of gas or liquid to replace produced fluids and maintain or increase reservoir pressure. If primary and secondary methods fail to achieve the desired production results, then tertiary methods may be added if field conditions warrant. Tertiary methods generally consist of chemical and/or thermal techniques to lower the viscosity of the remaining oil-in-place and decrease the mobility of water. Despite the continued application of these conventional recovery methods, nearly two-thirds of the known original oil-in-place will remain in the reservoirs.
According to the United States Department of Energy's (“DOE”) Office of Fossil Energy, one of the United States' most serious energy problems is the premature abandonment of still-productive domestic oil fields. The DOE has stated that over half of the crude oil discovered in the United States lies in fields that were abandoned when they became no longer economically viable and the rate of abandonment is accelerating. The DOE further contends that after more than 135 years since the birth of the U.S. oil industry, the United States has twice as much oil remaining in its reservoirs than it has produced in all of its history; for every barrel of oil produced to date, two barrels have been left behind; and the U.S. oil industry has produced almost 160 billion barrels, but some 350 billion barrels remain as a target for improved recovery technologies.
There is a need for systems and methods for recovering the known oil from abandoned oil fields to thereby increase the amount of oil available for use.
The systems and methods of the present invention include the driving of a pipe from the earth's surface into an oil bearing formation. The pipe is then mucked out i.e., the dirt and other rock is withdrawn from the pipe leaving the pipe empty in the ground. An access tunnel is then drilled from the base or bottom of the pipe into the formation and bore holes are drilled from the access tunnel upwardly into the formation at various angles.
An oil water separation device is then provided at the base of the pipe for separating oil from water that flows from the bore holes into the access tunnel and thence along the access tunnel to the region adjacent the pipe. A pumping system is provided at the ground surface for pumping oil separated by the centrifuge from the bottom of the installed pipe to the ground surface for processing.
Aspects of the present invention further include a system for extracting crude oil from an oil formation below ground, the system comprising: a main shaft extending into the oil formation and terminating below the formation and in communication with an opening at ground surface level; a drift tunnel extending at an angle to the main shaft; a plurality of oil production bore holes extending between the oil formation and the drift tunnel, at least one oil production bore hole having a section positioned at an angle relative to the main shaft; and a manifold system for collecting oil mixture from the plurality of oil production bore holes located in the drift tunnel.
In yet another aspect of the present invention, there is provided a system for extracting crude oil from an oil formation below ground, the system comprising: a main shaft extending into the oil formation and terminating below the oil formation and in communication with an opening at ground surface level, the main shaft comprising a metal pipe and grout; a drift tunnel of a first general cross-sectional dimension extending from the main shaft a drilling station of a second general cross-sectional dimension in communication with the drift tunnel and spaced apart from the main shaft; a plurality of oil production bore holes extending between the oil formation and the drilling station, at least two oil production bore holes each having a section positioned at an angle relative to the main shaft; and a manifold system for collecting oil mixture from the plurality of oil production bore holes located in the drift tunnel.
In still yet other aspects of the present invention, there is provided a system for extracting crude oil from an oil formation below ground, the system comprising: a main shaft extending into an oil formation and terminating below the oil formation; a drift tunnel of at least 500 feet in length extending below the oil formation; a plurality of oil production bore holes extending between the oil formation and the draft tunnel; a manifold system for collecting oil mixture from the plurality of oil production bore holes located in the drift tunnel; and a pumping system for pumping the oil mixture to ground surface level.
BRIEF DESCRIPTION OF THE DRAWINGS
Other aspects and variations of the oil extraction system summarized above are also contemplated and will be more fully understood when considered with respect to the following disclosure.
These and other features, aspects and advantages of the present invention will be more fully understood when considered with respect to the following detailed description, appended claims and accompanying drawings wherein:
FIG. 1 is a schematic depiction of an oil well system provided in accordance with practice of the present invention incorporating an access pipe, an access tunnel and a plurality of bore holes drilled upwardly from the access tunnel;
FIG. 2 is a schematic showing the access tunnel and upwardly extending bore holes; and
FIG. 3 is a schematic plan view of a plurality of production holes extending from a drilling station.
In accordance with practice of the present invention, systems and methods are provided for extracting crude oil from an oil reservoir. The systems and methods of the invention can be understood by referring to FIGS. 1 and 2 which are schematic depictions of an oil well system 10, provided in accordance with practice of the present invention installed in an oil field 12. The system includes a main shaft 14, preferably formed and encased with a metal pipe, such a low grade steel which can be up to 10 feet or larger in diameter. The shaft is preferably grouted in and dewatered prior to production. The main shaft 14 may be formed via known pile driving techniques common in the mining industry or drilling techniques common in the oil production industry. The main shaft 14 is preferably drilled, using old logging information, to a greater depth than existing known oil traps or reservoir traps. In the following example, a reservoir trap of 1,000 feet is assumed and a main shaft of about 1,300 feet is drilled. However, the main shaft may be drilled to a much greater depth without deviating from the spirit and scope of the present invention, such as several thousand feet deeper, e.g., 3,500-5,000 feet deeper. This would allow the main shaft to be used to access multiple reservoir traps at different depths. In one exemplary embodiment, a production drift is excavated about 100 feet to about 600 feet or more below a known trap with 300 feet below a trap being more preferred. Thus, for example, if a first trap is located at about 600 feet and a second at about 1300 feet, then the main shaft would be drilled to about 1600 feet with horizontal drifts excavated at about 900 feet and 1600 feet respectively for drilling into both traps, as further discussed below. Changes in depths below a known trap may vary depending on rock formation, trapped gas, etc.
Returning to the example of a single 1000 feet deep trap, two vent shafts 16, 18 are drilled to approximately the same depth as the main shaft 14, with the depth being about 300 feet below an oil trap. The vent shafts 16, 18 are preferably located equally spaced apart from the main shaft and have a completed inside diameter of about 30 inches. Like the main shaft, the vent shafts incorporate hydrostatic steel casing, and are grouted, and dewatered. In one exemplary embodiment, the vent shafts are each located about 700 feet from the main shaft but may vary without deviating from the spirit and scope of the present invention. The vent shafts provide ventilation for the main shaft, when proper air blowers or fans are installed, as well function as emergency escape bullets. For added safety, additional vent shaft may be used with the minimum number being dictated generally by regulatory agencies.
The two vent shafts 16, 18 are connected to the main shaft 14 by horizontal drifts 20, 22. In one exemplary embodiment, only one of the vent shafts 16 or 18 is produced concurrently with the main shaft 14 while the second vent shaft is subsequently produced. This approach allows oil production to start while the second vent shaft is installed and connected. Prior to connecting the main shaft 14 to the two vent shafts, traditional venting and safety precautions may be used, such as equipping the main shaft with a 30-inch temporary auxiliary vent tube that also functions as an emergency escape bullet. Fan and vent bag system of ventilation may be also be used.
A hoist system, head frame, and guides will be installed in the main shaft. These devices are well known in the art and thus no further discussion is deemed necessary.
The horizontal drifts 20, 22 are formed by first excavating a breakout chamber at the base of the main shaft on each side of the main shaft, i.e., 180 degrees apart with different spacing being acceptable. The break out chambers 24, 26 may be excavated by conventional drill-and-blast methods to a size of 16 feet×24 feet by 16 feet high, each. The breakout chambers are preferably equipped with steel roof supports and shortcreted. Muck produced from the excavation and drilling can be fed to a moving grizzly system and dumped into skips, which are hoisted to the surface for treatment and/or disposal. A 10 feet×10 feet drift is excavated from each break out chamber using conventional drill-and-blast methods. The drifts 20, 22 connect the main shaft 14 to the two vent shafts 16, 18. The drifts should be shortcreted and steel set for ground support with a concrete invert.
In one exemplary embodiment, a plurality of drilling stations 28 a-28 f are formed within each horizontal drift. In a preferred embodiment, three spaced-apart drilling stations are formed in each horizontal drift. However, fewer or more than three drilling stations are also acceptable with economic, safety, and efficiency being factors that may dictate the overall number. As further discussed below, each drilling station is configured for use in well preparation and production drills at various times or stages. Although the drilling stations can vary, each station is preferably excavated to about 24 feet×26 feet by about 20 feet high. The first drilling station 28 a, 28 d in each drift is about 100 feet from the base of the main shaft 14. Each subsequent drilling station is about 200 feet from the previous drilling station, i.e., at 300 feet and 500 feet, respectively, from the base of the main shaft. However, the drilling stations may be spaced apart from one another by a greater distance, such as 300 feet to 800 feet or greater, or a smaller distance, such as 100 feet to 300 feet.
Muck generated while forming the drifts may be removed using load haul dumps (LHDs) and transported to the muck bay at the main shaft station. There, the muck is fed to the grizzly and into the skips, which are hoisted to the surface for disposal or removal from the site. Muck may also be removed from the surface using automated roller belt installed at the main shaft and operated from the surface. Once the main shaft is connected to the two ventilation shafts, positive ventilation may be installed using one or more fans or blowers on the top of the ventilation shafts. The ventilation shafts may also be used as emergency escape routes.
A sump 30, 32 may be excavated in the general vicinity of each ventilation shaft 16, 18. In one exemplary embodiment, the sump is about 20 feet×20 feet×25 feet deep. The sump will serve as a collection pit for collecting production flow from the production sites, as further discussed below. An 8-inch production hole 34, 36 is drilled and cased at each ventilation shaft from the surface to the end of the drift in the vicinity of the sump 30, 32. Sand-oil-gas-water mixture will be pumped to the surface through the two cased production holes 34, 36. By incorporating production holes 34, 36, combustible fluids and gases may be isolated from the drifts and therefore enhance safety of the workers below. Additional production holes like 34 and 36 may be added along the drift sections.
Referring now to FIG. 2, a horizontal drift 20 is shown subjacent a reservoir trap 40. In one exemplary embodiment, a plurality of oil production boreholes 42 are drilled at each station (with only one drilling station 28 a shown). In a preferred embodiment, twenty-eight (28) boreholes each having a 4 to 8 inch diameter, preferably 4.5 inch diameter, are drilled upwards from the drilling station 28 a towards the reservoir trap 40. More preferably, the production boreholes are drilled at an angle from the drilling station 28 a towards the reservoir trap 40. A hydraulic drill (not shown) may be used to drill the production boreholes 42. A 125-horsepower electric pump can drill holes 2,500 feet in length. Depending on the logging information, directional drilling may be needed when drilling the production boreholes 42. The plurality of boreholes function as flow paths for the sand-oil-water-gas mixture in the reservoir trap 40 to flow and be collected and eventually lifted to the surface for recovery.
In one exemplary embodiment, a pattern of 4 to 6 boreholes 42 fanning out in multiple directions from the drilling station 28a is used to drill the boreholes. The pattern of 4 to 6 boreholes in a particular targeted reservoir trap region decreases the spacing between boreholes thereby increasing the probability of finding the oil mixture. Each borehole 42 is preferably prepped by first drilling a 6-inch borehole 44 into the sandstone above the horizontal drift 28 a about 40 feet in length. This 6-inch entry point 44 will be cased, grouted, and equipped with a collar with a pressure-control device. Once the entry point is prepped, production drilling can begin. Preferably, the entry points 44 for the plurality of boreholes 42 are prepped prior to beginning production drilling. Other entry bore hole sizes are acceptable, such as one in the range of about 8 inches to about 14 inches.
In one exemplary embodiment, a header and/or manifold system is formed in each horizontal drift 20, 22. The manifold system collects flow from the plurality of production boreholes 42 and route the collection of flow towards the sump 30, 32 located at the end of each drift for pumping to the surface. In one exemplary embodiment, the collected mixture is fed into a receiving tank located at each sump 30, 32 and pumped to the surface through the respective 8-inch production hole 34, 36. Alternatively, the sumps can be covered or include enclosed collection tanks for collecting the drained oil-water-gas-sand mixture. This embodiment provides for an entirely enclosed system for isolating the fluid mixture from the air space in the drifts and main shaft. Pressured relief valves and other safety devices may be necessary to maintain adequate safety for the workers.
The produced sand-oil-gas-water mixture can be separated at the surface using known prior art methods such as a settling tank, a centrifuge, chemical treatment, etc. After separation, the oil can be stored in a storage tank for gathering, the water can be re-injected into the formation for reservoir re-pressure stimulation, and gas can be flared on location or used for heating. The spent sands can be stored on a lined surface for possible later use by construction or road construction. Alternatively, the mixture may be separated from below and only oil, or higher concentration of oil mixture, lifted to the surface. If the oil-water-gas-sand mixture is treated below ground, a centrifuge may be used to separate the mixture. Discharge bore holes may be drilled downwards in the vicinity of each sump for discharging byproducts.
Referring now to FIG. 3, a schematic plan view of the horizontal drift 20 viewed from just below the reservoir trap 40 of FIG. 2 is shown. As shown, a plurality of boreholes 42 are drilled from the roof of the drilling station 28 a. Depending on the logging information, testing, and coring information obtained during drilling, directional drilling may be used to drill certain boreholes. In FIG. 3, directional drilling is used to drill three of the production boreholes 42 a, 42 b, and 42 c.
In one exemplary embodiment, the production and handling system may be monitored from a central control unit on the surface, which may be equipped with controlling means for regulating flow rate at each production borehole. Underground air quality may also be monitored from the central control unit for safety.
Production may be facilitated by sampling and testing the recovered mixture as well as the reservoir. As examples, NMR oil logging may be used several miles underground to determine rock and fluid properties; MRI logging, which permits real-time analysis while drilling; electric log; gamma ray logging, and caliper logging, just to name a few, may also be used. Volumetric determination by labeling microspheres with a non-radioactive substance and introducing the labeled microspheres into a body of fluid for which a determination is to be made may also be used to measure flow rate of the recovered mixture. One such method is disclosed in U.S. Pat. No. 4,811,741, the contents of which are expressly incorporated herein by reference. An additional technique for measuring flow is to use labeled microspheres in combination with MRI or CT imaging. One such method is disclosed in U.S. Pat. No. 6,001,333, the contents of which are expressly incorporated herein by reference.
Although limited embodiments of the oil recovery system have been specifically described and illustrated herein, many modifications and variations will be apparent to those skilled in the art. For example, various logging techniques not specifically described may be used to analyze the production boreholes, different subsurface equipment and artificial lift may be used to bring the produced oil to the surface; different drilling techniques, such as horizontal and directional drilling, may be used to drill any of the shafts or holes discussed, and different completion devices may be used to develop the wells or boreholes and to cap the same. Accordingly, it is to be understood that the oil recovery system constructed according to principles of this invention may be embodied other than as specifically described. The invention is also defined in the following claims.