US2821255A

US2821255A - Subformation oil production method

Info

Publication number: US2821255A
Application number: US574816A
Authority: US
Inventors: Spearow Ralph
Original assignee: Individual
Current assignee: Individual
Priority date: 1956-03-30
Filing date: 1956-03-30
Publication date: 1958-01-28
Anticipated expiration: 1975-01-28

Description

R. SPEAROW 2,323,255

sUBFoRMATIoN onJV PRODUCTION METHOD 2 Sheets-Sheet `l Jan. 28, 1958 Filed March 50, 1956 IN V EN TOR.

l *lll Illll 27 Pa/7 .jaaa/90W BY W TTORNEK 2 Sheets-Sheekl 2 V 5m @Hg if R. SPEAROW SUBF'ORMATION OIL PRODUCTION METHOD Jan. 28, 1958 Filed March :50, 195e ggg/X INVENTOR. 149040,@ pea/10W ,En fr0/mgm United States Patent This invention relates to methods of producing oil from oil sands by vertical drive gaseous pressurization and refers more particularly to such a method of producing oil wherein the oil is withdrawn from the earth formation from a level below the lowest level of the oil horizon whereby to permit production of all of the oil in the oilY horizon.

Previously, 1 have provided as in my-Patent Non 2,593,497, entitled Method and Apparatus for Producing Oil Wells, issued April 22, 1952, and my Patent No,

2,725,106, entitled Oil Production and issued November 29, 1955, methods of producing oil from oil horizons by vertical drive gaseous pressurization wherein gaseous pressure 1s applied to the uppermost portion of an oil horizon and liquid oil is produced from the lowermost portion of the oil horizon. As previously set forth in these patentsj it is desirable both to pressurize as close to the top of the` formation as possible and withdraw the oil from as close:

to the bottom formation as possible. In this wayas much as possible of the oil may be produced from the horizon. Existing methods of completion of the production area in the lower portion of the oil horizon make it impossible to scavenge out the entire formation due to the nature of the completions themselves, such as perforation of casings and surrounding cement columns and packing oi of casings against the oil formations themselves. Additionally, these production area completion methods which I have previously disclosed may fail to give complete sealing down to the top of the production area due to variations in the face of the well bore when a packer is set thereagainst and splitting or seaming of a cement column upon perforation. Such failures of sealing also tend` to prevent l% complete production of the' oil from an oil horizon.

Therefore, an object of the present invention is to prof` vide a method of producing oil from oil horizons utilizing a vertical drive gaseous pressurization method wherein oil is withdrawn only from below the horizon thereby permitting production of all of the oil in a formation'by such a vertical drive gaseous pressurization method.

Another object of the invention is to provide such a subformation oil well production method utilizing vertical drive gaseous pressurization wherein either combined pressurization and production wells or separate pressurization and production wells may be employed.

Another object of the invention is to provide a subformation oil well production method utilizing vertical drive gaseous pressurization which in combination with my previously disclosed methods of completing production well areas in the lower portions of oil sands, permits differential distribution of the total oil amongst several wells in a vertical drive gaseous pressurization eld with an oil contact with the well bore face in the oil horizon and oil is produced solely from the underside of the horizon, thereby getting vertical drainage of the liquid oil into the well.

Another object of the invention is to provide a subformation oil well production method utilizing vertical drive gaseous pressurization wherein a plurality of production well completion methods are provided for both combined and separate pressurization and production wells thereby to permit optimum adaptation to various well completion problems and horizon or sand types.

' Yet another object of the present invention is to provide a subformation oil well production method utilizing vertical drive gaseous pressurization wherein the lower portion of the oil horizon may be fractured to improve the productivity thereof, yet oil is recovered only from the underside of the horizon and not from the well bore face opposite the fracture.

Other and further objects of the invention will appear in the course of the following description thereof.

In the drawings, which form a part of the instant specifi- I cation and are to be read in conjunction therewith, there are shown several embodiments of the invention and, in the various views, like numerals are employed to indicate like parts.

Fig. l is a cross-sectional view through an earth formation containing an oil horizon, the well drilled into the m tion containing an oil producing horizon, the well drilled into the horizon being solely a pressurization well, this well useable only in conjunction with a separate production well such as is shown either in Fig. l or Fig. 3. Fig. 3 is a cross-sectional view through an earth forma tion containing an oil producing horizon, the well drilled into the horizon being essentially the same as the well in Fig. l, the only difference being in the method of completion of the well and the fact that the face of the well bore has been fractured at a predetermined position in the lower portion of the oil horizon.

Fig. 4 is a cross-sectional view through an earth formation containing an oil producing horizon, the well drilled into theA horizon being a combined pressurization and production well, operable to produce oil from the horizon by itself, the lower portion of the horizon being shown fractured in this view.

Fig. 5 is a cross-sectional View through an earth formation containing an oil producing horizon, the well being drilled into the horizon being a combined pressurization and production well as in Fig. 4, the differences between the two lying in the method of completion of the well and the fact that the face of the oil horizon has been fractured both at the upper and lower positions thereof.

Referring rst to Fig. l, the inventive method comprises drilling of the borehole 10 of an oil well below the bottom level 11 of the oil horizon 12 to be produced, forming an open passageway 15 through the adjacent earth formations extending from a level below the horizon into the bottom of the oil horizon, running a casing or tubing 13 having a flow line 14 at the upper end thereof to the vicinity of the bottom of the hole bore and below the bottom of the oil horizon to be produced, said casing having at least one inlet opening 14a adjacent the lower end thereof, sealing said casing to the well wall from a level below the bottom of the oil horizon to a level above the top thereof, and producing oil through said passageway 15 into said casing and thence to the surface. In Fig. l, the method of sealing the casing to the well wall cornkprises packing off as at 16 at a level below the bottom portion of the oil horizon and lling the annulus above the packer between the casing or tubing 13 and the borehole wall with an annular sealing column of cement or other sealing substance 17. This sealing column extends to above the topmost level of the oil horizon 18 at least into the impermeable layers 19 thereabove. Tubing or casing 13 preferably has conventional T 20 at the upper end thereof to permit insertion of a pumping string (not shown) so that oil may be pumped from the tubing if desired. Flow line 14 preferably has valve 21 therein to permit withdrawal of the uid oil from the casing 13. Ground level is indicated at 22. Once the borehole has been drilled below the lower level 11 of the oil horizon 12, the open passageways may be formed either before or after the casing 13 is run and sealed. Such open passageways may be formed by angled perforation of the earth formation into the lower part of the oil horizon. Should there be cracking or sloughing of the formations below the oil horizon due to the perforation, it will 'not hinder the oil production but, in fact, usually aid it in offering a greater cross-sectional area of oil production so long as access is given to the borehole below the packer or other sealing means 16.

The inventive method as applied to original oil production under the original formation pressures within the oil sand is the same as set forth above without a step of applying gaseous pressure to the top of the oil horizon. In this case, once the casing 13 has been set in the Well bore, the passageways 15 formed and the sealing column 17 and packer 16 set to a level above the top of the horizon, oil may be flowed from the inlet openings 14 in the tubing 13 out of the flow line 14 merely by opening the valve 21, provided the original formation pressure is sufficient to raise the uid column to the surface. If it is not, a pumping string inserted in T 20 serves to raise the oil to the surface. Whether or not a gas cap exists originally in the oil horizon 12, the subformation production means shown permit complete production of the oil from the vicinity of the borehole 10 until the gas-oil interface at the bottom of the gas cap formed in the process of production reaches the passageways 15 where they enter the oil horizon 12. It is, of course, not possible to completely produce all of the oil within the horizon, even with the subject completion method, under the original formation pressures. Thus, any residue of oil left inthe horizon will have to be produced therefrom by a vertical drive gaseous pressurization method in secondary production as will now be described.

Referring now to the use of the production well in Fig. 1 in secondary production, it is necessary to provide means for applying gaseous pressure to the top of the oil horizon. Such means are shown in Fig. 2 wherein is shown a pressurization well providing a gaseous pressure flow line channel to the top of the oil horizon. This aspect of the method comprises the steps of drilling the borehole 23 of the pressurization well to or into the top of the oil horizon 12. If it is desired to have the top of the oil horizon fractured as shown at 24, the borehole of the pressurization well should be drilled into the top of the oil horizon 21 a sufficient distance for a fracturing packer assembly to be set in the well bore to fracture the oil horizon at the top or very close to the top thereof. A preferred fracturing packer assembly for fracturing localized areas of oil horizons is shown in my application Serial No. 563,089, tiled February 2, 1956, entitled Fracturing Packer and Method of Application Thereof. The top level of the horizon may also be cracked by a method as hereinafter set forth. Pressurization casing 25 having output openings 26 at the lower end thereof is then run to or into the top of the oil horizon, preferably gravel packed as shown at 27 with a layer of sealing substance (gelatinous or nely grained material) 2S placed on top of the gravel and sealed by an annular column 29 of sealing substance or cement from the top of the oil horizon to a level thereabove. Pressurization casing 25 has pressure flow line 30 connected into the sealed upper end thereof with valve 31 thereon. After gravel packing and cementing as described, the horizon may be cracked by running liquid into the casing 25 to f1ll it and then applying fracturing pressure thereto. The pressure is thus applied to the well bore face below the sealing column 27. After fracturing, the uid is removed from the tubing 25 for the input of air therein. T 32 having sealing plug 33 in the top portion thereof permits such a iiuid removal pumping operation or the fracturing fluid may be forced into fracture 24 by gaseous pressure.

To operate the combined apparatus of Fig. 1 and Fig. 2 in a pressure exhausted oil sand or very low pressure oil sand, gaseous pressurization media such as air or inert gases, is forced into the ow line 30 and out of the open or perforated lower end of the pressurization casing 25. The gaseous pressurization media ows into the top of the horizon and forms a gas cap which expands both outwardly and downwardly driving the liquid oil before it. A gasoil interface is formed by the periphery of this expanding gas cap and oil may be recovered from the open passageways 15 below the oil horizon until the gas-oil interface reaches and actually passes into the passageways 15. When this occurs, the production well of Fig. 1 is finished as a producer in the particular oil eld. The purpose of the fracture 24 at the pressurization well is to increase the rate of input of the gaseous pressurization media to reduce to a minimum the horsepower requisite thereto. It is also contemplated that the secondary recovery method be practiced in a plurality of pressurization and/or production wells analogous to production from a plurality of production wells in original production.

In Fig. 1, surface casing 32 has been set and cemented as shown in 33. Such surface casing 32 permits proper installation and positioning of tubing 13. It is also contemplated that the cementv or sealing column 17 be extended up to the vicinity of the surface thereby obviating the necessity of surface casing.

Fig. 3 illustrates a variation of the Fig. l production well illustrating a different completion method and also a method wherein the lower portion of the oil horizon is fractured to increase the oil production therefrom. It is also contemplated that the Fig. l construction be employed with such a lower horizon fracture and the fracturing step as described relative Fig. 3 will also apply to Fig. l. As in the Fig. l well, the well shown in Fig. 3 may be used either alone in original production or in combination with a pressurization well such as is shown in Fig. 2 in secondary production.

The'method as practiced in the Fig. 3 well in secondary production comprises the steps of drilling the borehole 34 of an oil'well below the bottom level of the oil horizon 12, running a casing 35 having a flow line 36 with valve 37 attached to the upper end thereof to the vicinity of the bottom of the hole bore and below the bottom of the oil horizon, sealing said casing to the well wall from a level below the bottom of the oil horizon to a level at least above the top thereof by an annular column 38 of cement or other sealing substance, forming an open passageway 39 through the casing, its surrounding annular seal and the adjacent earth formations 40 extending from a level below the oil horizon into the bottom of the oil horizon, applying fluid under pressure to the top portion of the oil horizon and producing oil from the casing at the surface. Casing 35 preferably has conventional T 41 at the upper end thereof to permit insertion of a pumping string (not shown) to per mit pumping oil from the tubing if such is desired.

As to the provision of a fracture in the lower portion of the horizon, `either a suitable fracturing assembly may be run to the vicinity of the bottom of the oil horizon before running the casing 35 therein and the horizon fracture 42 at or slightly above the bottom of the horizon or, after the casing has been run and sealed at 38, the

casing and its surrounding annular seal may be perforated as shown at 43, the area below the perforations packed off and suiiicient gaseous or uid pressure ap-y plied within the casing 35 to fracture the horizon as shown at 42. The open passageways 39 may be formed by perforation or other method upwardly at an angle into the bottom of the horizon and into the fracture 42 to obtain optimum oil production from the lower portion of the oil horizon. It is evident that if the fracturing of the oil horizon is done by perforation of the casing and its surrounding annular seal, these perforations must be closed off in the oil production method whereby oil is produced only through the passageways 39 and not through the perforations 43. This may be done by putting a secondary tubing (not shown) within the primary tubing 35 and packing oft" at the level of the perforations and then draining oil only through the tubing below said packer. It is obvious that such a perforation method would not be as feasible in the completion method of Fig. l with the packer 16 positioned in the fracturing area. Thus it is preferred that the horizon be fractured before the setting of the casings 35 and 13 in both the Fig. 3 and Fig. 1 modifications.

The method and means for applying gaseous pressurization to the top portion of the oil horizon 12 has been previously described relative Fig. 2 and will not be described again. It is also contemplated that the method as shown in Figs. 2 and 3 be practiced in a plurality of pressurization and/or production wells.

In employment of the Fig. 3 method in original production, the Fig. 3 well is drilled as described above and finished as previously described but the step of applyingl gaseous pressurization to the top of the oil horizon is omitted. Again, pumping means may be employed to pump oil from the tubing or casing 35 if such is desired or necessary. The fracture 42 at the bottom of the horizon increases the access to the oil sand in the vicinity of the passageways 29 for improved oil production. When the gas-oil interface in the horizon passes into the passageways 39 below the lowest level of the oil horizon, the Fig. 3 well is through as a producer and all of the oil has been produced in the Vicinity of this production well, whether the gas-oil interface was produced by original or secondary production methods. As set forth relative the Fig. l modification, however, it is not contemplated that original pressures in the formation will produce all of the oil within the horizon and that at a late stage in such a production method, secondary pressurization with a pressurization well as shown in Fig. 2 will be necessary to completely scavenge the horizon of oil.

Fig. 4 illustrates a combined pressurization and production well. The method as practiced in Fig. 4 comprises the steps of drilling the borehole 44 of an oil well to a level below the lowest level 45 of an oil horizon 46, running a primary casing 47 into said borehole to a level below the bottom of said oil horizon and adjacent the bottom of the borehole, sealing said primary casing to the well wall from a level below the bottom of the oil horizon to a level above the top 48 thereof with an annular column of cement or other sealing substance 49, forming an open passageway 50 through the primary casing 47 and its Surrounding annular seal and the adjacent earth formations 51 extending from a level below said oil horizon into the bottom 45 of said oil horizon, running a secondary tubing 52 having an inlet opening at the lower end thereof 53 to a level at least below the topmost perforations in said primary tubing, said primary casing having been perforated 54 with its surrounding annular seal to provide access to the topmost portion of the oil horizon, packing oi as at 55 the secondary tubing against the inner face of the primary tubing to prevent uid ow through the annulus between the two casings therebelow, and producing oil from the secondary tubing through the passageways 50 below the packer 55. Primary casing 47 has conventional T 56 at the upper end thereof with pressurization tiow line 57 attached thereto with valve 58 therein. Secondary tubing 52 has iiow line 59 with valve 60 therein attached to the upper end thereof. Sealing gland 61 seals the secondary tubing into the T 56 of the primary tubing 47.

Should the well shown in Fig. 4 be desired to be produced under the original formation pressures, the valve 55 on ow line 57 to the primary casing 47 is kept closed so no oil sand fluid will pass into the annulus between the two casings through the perforations 54. With the valve 60 on now line 59 on secondary casing 52 open any original formation pressure existing in the sand may produce oil through the open passageways 50 at the bottom of the oil horizon until such pressure is so depleted that secondary pressurization is desired. When such secondary pressurization is desired, Valve 53 on iiow line 57 is opened and gaseous pressurization media forced into the annulus between the two casings 47 and 52 and out the pertorations 54 in the primary casing. Thus all of the oil may be driven from the formation. The formation of a gas cap and a gas-oil interface under such original production or secondary production is the same as has been previously described. lt it is desired to fracture either or both the top or bottom portion of the oil horizon to increase the productivity and pressurization input into the horizon, such may be done. The fracture as shown at 62 in the lower portion of the oil horizon is preferably made before the setting of the primary casing and its cementing by a fracturing packer assembly as previously described. The passageways 50 which may be formed after the casing 47 is set and cemented running into the fracture thus collect more oil per'unit time. if it is desired to fracture the top portion of the oil horizon to increase the secondary pressurization into the oil horizon, the horizon may first be fractured as in the fracture 62 and then the perforations 54 made opposite the fracture or the casing 47 set and sealed as at 49, perforations 54 made through the casing 47 and the seal 49 and then sufficient fluid or gaseous pressure applied through the perforations after the packer 55 has been set to fracture the upper portion of the horizon. Such a fracture is not shown in Fig. 4. it is, of course, contemplated that a plurality of conibined pressurization and production wells may be ernpioyed in the given oil horizon 46 or, the combination of combined pressurization and production wells as in Fig. 4 and separate pressurization and production wells as in Figs. l, 2 and 3. The arrangement of such wells would depend upon the thickness of the sand, the permeability of the various areas of the sand, etc.

Fig. 5 illustrates a modification of trie combined pressurization and production well in Fig. 4 with a different method of well completion and wherein, as before, either both the top and bottom portions of the oil horizon are fractured or merely one of these locations is fractured to aid both the input of pressurization media (gaseous) into the top of the oil horizon and withdrawal of the liquid oil from the bottom of the oil horizon.

The method as practiced in Fig. 5 consists in the steps of drilling the borehole 63 of an oil well below the bottorn level of an oil horizon, fracturing adjacent the bottorn or top portions of the oil horizon as desired, running a primary casing 64 at least to the top level of the oil horizon, sealing said casing 64 to the well Wall from the top of the oil horizon to a level above the top thereof,

running a secondary casing 66 having an inlet opening 67 at the lower end thereof, to the vicinity of the bottom of the hole bore and below the bottom 4S of the oil horizon, packing oi as at 68 the annulus between the secondary casing and the well wall face, the lower face of said packer being below the lower level of the oil horizon, filling the annulus between the secondary casing and the well bore face above the packer 68 with an annular column 69 of cement or other sealing substance from the top surface of the packer to a level adjacent to but below the upper level 48 of the oil horizon 46, forming an open passageway through the adjacent earth formations extending from a level below the oil horizon into the bottom of the oil horizon and communicating with the borehole of the well 63 below the oil horizon, either before or after the tubing 66 is run and sealed and producing fluid oil at the surface through said secondary tubing 66. Primary tubing or casing 64 preferably has conventional T 70 at the upper end thereof with flow line 61 having valve 72 connected therewith. Secondary tubing 66 has ow line 73 with valve 74 therein attached to the upper end thereof and sealing gland 75 in the top of T 70 seals the secondary casing within the primary casing at the top thereof.

It should be noted relative Figs. 4 and 5 that Ts may be inserted in the top of the

secondary tubings

52 and 66 to permit the insertion of pumping strings therein if it is desired to pump oil from the secondary tubings.

The open passageways 76 from below the oil horizon preferably penetrate any fractures 77 which may have been made in the lower portion of the oil horizon to permit greater oil production. The fracture 77 in the lower portion of the oil horizon is preferably made before the secondary casing 66 is run and sealed to the well wall. The fracture 78 at the top portion of the oil horizon, if made, may be made before the secondary tubing 66 is run or thereafter as desired. If made thereafter, once the sealing column 69 has set, liquid or gaseous pressure may be applied to flow line 7l into the primary casing at fracturing pressures to create the fracture above the sealing column 69.

As set forth relative Fig. 4, the well shown in Fig. may be produced under original formation pressure by shutting off valve 72 in flow line 71 on the primary casing. After all the feasible production under this method, gaseous pressure may be applied to the top portion of the oil horizon through flow line 71 after valve 72 has been opened whereby to drive any remaining Huid oil downwardly in the oil horizon to be recovered through the passageways 76 below the oil horizon. Again, all of the oil in the vicinity of the well bore 64 may be recovered.

In the completion of the well shown in Fig. 5, it is also contemplated that the well bore 64 be drilled to the top of the oil sand, the casing 64 be set and cemented as shown at 65 and then the well bore be completed to the vicinity of the bottom and necessarily below the bottom of the oil horizon by drilling or ratholing a well bore of lesser diameter downwardly from the bottom of the casing 64. This is conventional practice and is only set forth as a more convenient method of completing the well of the type shown in Fig. 5. Fig. 5 actually shows this modification of completion.

Referring to all of the wells shown in the five figures, it is necessary that all seals therein both above and within the oil horizon of casings and tubings be of such strength and cross-sectional area as to withstand any pressures exerted upon the sand either in original or secondary vertical drive gaseous pressurization production. The well bore seals must adhere to the well wall in the borehole t-o prevent any by-passing or flow of fluid or gas along the well bore face. If the seals are not properly completed, the method will fail due to the pressurization leakage.

From the foregoing it will be seen that this invention is well adapted to attain all of the ends and objects hereinabove set forth together with other advantages which are obvious and which are inherent to the method.

It will be understood that certain features and subcombinations are of utility and may be employed without reference to other features and-subcombinations. This is contemplated by and is within the scope of the claims.

As many possible embodiments may be made of the georges invention without departing from the scope thereof, it is to be understood that al1 matter hereinabove set forth or shown in the accompanying drawings is to be interpreted as illustrative and not in a limiting sense.

Having thus described my invention, I claim:

l. A method of producing oil from oil horizons having at least some of the original formation pressure stilll resident therein comprising the steps of drilling the borehole of a production well below the bottom level of the oil horizon to be produced, running a production channel to the vicinity of the bottom of the hole bore and below the bottom of the oil horizon to be produced, sealing said production channel to the well wall to produce an annular seal from a level below the bottom of the oil horizon to a level above the top thereof, forming at least one open passageway through the earth formations extending from a level below the horizon and within the well bore upwardly into the bottom of the oil horizon, producing oil through said passageway into said well bore below the bottom of the oil horizon under the impetus of the pressure inherent in the oil horizon, and thence to the surface in said production channel.

2. A method as in claim l wherein the open passageway extends upwardly into the bottom of the oil horizon from the open well bore below the bottom of the production channel.

3. A method as in claim 1 wherein the open passageway extends into the bottom of the oil horizon from therebelow and penetrates the production channel and its annular seal below the bottom of the oil horizon.

4. A method as in claim 3 including the step of fracturing the oil horizon closely adjacent the bottom thereto before running the production channel therein and wherein the passageway from below the oil horizon runs into the fracture.

5. In a method of producing oil from oil horizons by vertical drive gaseous pressurization wherein gaseous pressure is applied to the top portion of an oil horizon through a pressurization channel extending at least to the top of the oil horizon in a well bore and sealed to the well bore wall at least from the top of the oil horizon to a level thereabove whereby to prevent leakage of gaseous pressurization medium thereabove, the improvement which comprises running a production channel in a well bore at least below the bottom of the oil horizon to be produced, sealing said production channel to the well wall to produce an annular seal from a level below the bottom of the oil horizon to a level at least adjacent the top thereof to prevent migration of pressurization medium through the annulus between the production channel and the well bore wall, forming at least one secondary production channel extending from the production channel well bore below the oil horizon outwardly therefrom and upwardly into the bottom of the oil horizon and producing oil from the oil horizon at least partially under the impetus of gaseous pressurization applied through a pressurization channel through said secondary channel into the well bore of the production channel below the oil horizon and then through the production channel to the surface.

6. A method as in claim 5 wherein the production channel is in a separate well bore from the pressurization channel, the production channel being sealed to its well bore wall to a level above the top of the oil horizon to be produced whereby to prevent any leakage of gaseous pressurization medium above the oil horizon as well as through it.

7. A method as in claim 5 wherein the production channel is in the same well bore as the pressurization channel and the production channel is sealed to the pressurization channel at some level along the length thereof whereby to prevent any leakage of gaseous pressurization medium above the top of the oil horizon.

8. A method as in claim 5 wherein the secondary channel extends from the open well bore of the production channel well bore into the bottom of the oil horizon.

9. A method as in claim 5 wherein the secondary channel penetrates the production `channel yand its annular seal below the bottom of the oil horizon to be produced.

10. A method as in claim 5 wherein the bottom portion of the oil horizon is fractured before the production channel is sealed to the Well bore wall and the secondary channel extends upwardly within the oil formation to contact the fracture.

11. A method of producing oil from oil horizons having at least some ui'd pressure existent within the horizon comprising the steps of drilling the borehole of a production well below the bottom level of the oil horizon to be produced, running a production channel to the vicinity of the bottom of the hole bore and below the bottom of the oil horizon to be produced, sealing said production channel to the well wall throughout the earth formations including the oil horizon to prevent any leakage of fluid pressure along the annulus between the production channel and the well bore wall either through, above or below the oil horizon to be produced, forming at least one open passageway through the earth formations extending from a level below the horizon and within the well bore upwardly into the bottom of the oil horizon, producing oil through said passageway into said well bore under the impetus of the uid pressure Within the formation and thence to the surface in said production channel.

12. A method as in claim 11 including pumping oil from said production channel when the pressure within the oil horizon being produced is not suicient to ow oil to the surface.

References Cited in the file of this patent UNITED STATES PATENTS

Claims

1. A METHOD OF PRODUCING OIL FROM OIL HORIZONS HAVING AT LEAST SOME OF THE ORIGINAL FORMATION PRESSURE STILL RESIDENT THEREIN COMPRISING THE STEPS OF DRILLING THE BOREHOLE OF A PRODUCTION WELL BELOW THE BOTTOM LEVEL OF THE OIL HORIZON TO BE PRODUCED RUNNING A PRODUCTION CHANNEL TO THE VINCINITY OF THE BOTTOM OF THE HOLE BORE AND BELOW THE BOTTOM OF THE OIL HORIZON TO BE PRODUCED, SEALING SAID PRODUCTION CHANNEL TO THE WELL WALL TO PRODUCE AN ANNULAR SEAL FROM A LEVEL BELOW THE BOTTOM OF THE OIL HORIZON TO A LEVEL ABOVE THE TOP THEREOF, FORMING AT LEAST ONE OPEN PASSAGEWAY THROUGH THE EARTH FORMATIONS EXTENDING FROM A LEVEL BELOW THE HORIZON AND WITHIN THE WELL BORE UPWARDLY INTO THE BOTTOM OF THE OIL HORIZON, PRODUCING