US2946382A - Process for recovering hydrocarbons from underground formations - Google Patents

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July 26, 1960 1- ETA 2,946,382 PROCESS FOR RECOVERING HYDRO BONS FROM UNDERGROUND FORMATI Filed Sept. l9, l9

INVENTORS M R. TEK A F BERTUZZI ATTORNEYS United States Patent PROCESS FOR RECOVERING HY DROCARBONS FROM UNDERGROUND FORMATIONS Mehmet R. Tek and Andrew F. Bertuzzi, Bartlesville,

0kla., assignors to Phillips Petroleum Company, a corporation of Delaware Filed Sept. 19, 1956, Ser. No. 610,753

8 Claims. (Cl. '166-11) This invention relates to a process for recovering hydrocarbons from porous underground formations containing carbonaceous material.

The recovery of oil and. other hydrocarbons from underground porous formations containing carbonaceous materials, such as oil and coal, by in situ combustion and by hot fluid drive utilizing hot gases and/or hot liquids is currently being emphasized as a production technique. A conventional in situ combustion method comprises initiating combustion of the oil adjacent a bore hole in the formation by any suitable means and injecting air through the bore hole into the formation so as to drive the combustion zone or front radially and laterally outwardly from the bore hole. A recent development in in situ combustion technique in the field, of oil recovery is disclosed and claimed in the copending application of John W. Marx, Serial No. 526,388, filed August 4, 1955, and comprises, establishing a combustion zone around a production well by conventional methods so as to provide a combustion zone and a heat reservoir of sufficient extent and temperature to permit cutting off the direct flow of air through the production well and injecting air into the formation through one or more spaced-apart Wells from the production well so as to cause the air to flow to the combustion zone at the production well and support combustiontherein so that the combustion front is advanced countercurrently. to the flow of air toward the injection well or wells. This technique is designated inverse air injection in situ combustion as opposed to direct air injection through the well or bore hole around which combustion is initiated.

Another recent development in recovery of oil by in situ combustion is disclosed in the copending application of I. C. Trantham and A. R. Schleicher, Serial No. 529,916, filed August 22, 1955, and comprises continuing the injection of air through one or more injection wells after the combustion front has'been advanced, by inverse air injection, to the injection well or wells so as to reverse the movement of the combustion front and drive the same back through the formation to the production well around which combustion was originally initiated. In this technique, designated thermal echo, the returning combustion front feeds on the residual carbon deposited in the formation during the inverse air injection phase of the process.

Oil recovery has also been effected by injecting hot combustion gas formed at ground level and/or superheated steam into a formation thru a well bore therein and the hot fluid is then driven thru the formation by fluid pressure so as to drive hydrocarbons from the forma tion thru a production well.

In these various production techniques an important problem is the conservation of heat in order to avoid unnecessary costs in the recovery of hydrocarbons. Substantial amounts of heat are lost to the overlying and underlying strata adjacent a carbonaceous formation and it is with the reduction and minimizing of these heat losses that this inventionis concerned.

. the borehole.

" ice Hence, it is an object of the invention to provide a process for recovering hydrocarbons from a porous underground formation containing carbonaceous material with a minimum of heat loss to the surrounding strata. Another object is to provide a more effective method of recovering hydrocarbons from an underground formation. A further object is to provide an oil recovery process which recovers hydrocarbons more efliciently and at a faster rate from a porous oil-bearing formation than is possible by other production methods. Other objects of the invention will become apparent from a consideration of the accompanying disclosure.

The invention comprises fracturing a porous or fluid pervious underground formation containing carbonaceous material, such as oil, at a level adjacent the center of the formation around a well therein and also fracturing the formation at higher and lower levels around one or more surrounding wells. The recovery of oil or other hydrocarbon from the formation is then effected by introducing hot fluid into the fracture adjacent the center of the formation and driving the hot fluid upwardly andv downwardly therefrom to the higher and lower level fractures so as to drive hydrocarbons from the formation. While the preferred technique involves establishing a combustion front in the fracture at the center of the formation and advancing the combustion front upwardly and downwardly therefrom so as to produce oil and other hydrocarbon from the formation, it is also within the scope of the invention toutilize hot gases and hot liquids heated. andinjected from the ground level or from within It is also feasible to effect the hot fluid drive fromvthe upper and lower fractures toward' the intermediate fracture but the heat losses to the overburden and underlying strata are greater with this type of recovery.

-A more complete understanding of the invention and, particularly, further embodiments thereof may be had from a consideration of the accompanying drawing which is a schematic elevation of an arrangement of wells and fractures in an underground formation for the recovery of hydrocarbon in accordance with the invention.

Wells 10, 12, and 14 extending into the earth from thesurface 15 penetrate a porous oil-bearingformation 16 below overburden 18 and aboveformation 20. One or more fractures 22 and 23 are formed in conventional manner by perforation of the casing in well 12 at the desired level and pumping fluid into the formation in suflicient volume and at a sufficient rate to effect the desired horizontal fracturing. Fine, strong, granular material, such as sand, metal particles, and the like, are introduced to the fractures with the fracturing fluid injected near the end of the injection step so as to prop the fractures open. Fractures .26, 2'7, and 23. are then induced in the formation thruwells 10 and Mat levels above and below the level of fractures 22 and 23 so that a second group of fractures overlap the fractures effected,

thru well 12, Well 12 is imperforate at other levels than the level of fractures 22 and 23 andwells 10 and 14 are perforate only at the level of thefractures 26, 27 and 28 so that fluid under, pressure inducedthru wells 10 and 14 must pass generally vertically thru the formation inwells 10 and 14; andfractures 26, 27, and 28 extend' to the proximity of or to the area adjacent well 12.

The preferred method of operation is to' initiate combustioninfractures 22-- a-nd/ or '23 by conventional means and then drive the combustion front or zone substantially vertically thru the formation to the adjacent fractures leading to wells and 14. In this manner the heat developed in the formation and the hot fluid drive produces hydrocarbon from the formation which is recovered either fromwells 10 and 14 or from well 12 depending upon whether direct or inverse injection is utilized. If inverse injection is made use of, air is injected thruwells 10 and 14 so that it passes thrufractures 26, 27, and 28 and thence thru the formation of fractures 22 and 23 and to the combustion front established therein whereby the combustion front is advanced counter-currently to the flow of air so that it eventually arrives at the fracture at which air is being introduced to the formation. In other words, the combustion front established along fractures 22 progresses upwardly to fracture 26 and downwardly to fracture 27. -If additional fracture 23 is utilized, the combustion front established there is advanced upwardly to fracture 27 and downwardly tofracture 28. In this manner a substantial proportion of the hydrocarbons in the formation between the fractures is produced leaving a coke residue which can be burned out by continuation of air injection after arrival of the front at the injection fracture so that the front travels back to the fracture from which it originated, thereby producing the reminder of the oil in the formation (of course, less the amount of hydrocarbons consumed by the combustion process). The use of a plurality of fractures surrounding well 12 and overlapping fractures aroundwells 10 and 14 makes efficient recovery of the hydrocarbons possible with a minimum of heat loss to the overlying and subjacent strata. The more rapid recovery of oil effected thru the system shown in the drawing also contributes to the decrease in loss of heat to the surrounding non-oil-bearing formations.

'It is also feasible to initiate combustion infractures 26, 27, and 28 and inject air thru well 12 into fractures 22 and 23 so that the combustion front moves downwardly from fracture 26 both upwardly and downwardly from fracture 27 and upwardly fromfracture 28 to the adjacent fractures 22 and 23.

In case recovery is to be elfected by injection of hot fluid from the ground surface, it may likewise be introduced either thru wells 12 and 14 or thru well 10, but in order to minimize heat losses to the surrounding strata it is advantageous to inject the hot fluid thru well 10. Utilizing this technique hot combustion gas, hot water, superheated steam, and any other hot fluid nondeleterious to the hydrocarbon in the formation and to the equipment may be utilized. It is also feasible to heat the injection fluid by means of a heater (electrical or gas) placed downhole. Of course, any type of heat source may be utilized to heat the injection fluid.

Certain modifications of the invention will become apparent to those skilled in the art and the illustrative details disclosed are not to be construed as imposing unnecessary limitations on the invention.

We claim:

1. A process for recovering hydrocarbons from an underground permeable formation containing combustible carbonaceous material comprising providing in said formation a first well and a plurality of wells surrounding said first well, all of said wells extending to and being cased to a lower section of said formation; perforating the casing in said first well at an intermediate level of said formation and fracturing said formation horizontally thru the resulting perforations in said casing to form an intermediate fracture extending to areas adjacent the casings of the surrounding wells; perforating the casings in said surrounding wells at levels above and below said intermediate level and fracturing said formation horizontally thru the resulting perforations in said casings to an area adjacent said first well to form upper and lower fractures so that the fracture systems overlap and so that the fracture systems around said surrounding wells communicate directly with said wells and are sealed from said first well and the fracture system around said first well communicates directly with said first well and is sealed from said surrounding wells; propping the aforesaid fractures open; initiating combustion in said formation along the fracture communicating with said first well; feeding combustion-supporting gas into the resulting combustion zone thru at least one of said wells so as to move same toward both said upper and lower fractures; and recovering from at least one of said wells hydrocarbons driven from the formation by the combustion.

2. A process for recovering hydrocarbons from an underground permeable formation containing combustible carbonaceous material comprising providing in said formation a first well and a second well, both being cased to a lower section of said formation; perforating said first well at an intermediate level of said formation and horizontally fracturing same thru the resulting perforations to form an intermediate fracture extending to an area adjacent said second well; perforating the casing of said second well at levels above and below said intermediate level and horizontally fracturing said formation thru the resulting perforations to an area adjacent said first well to form upper and lower fractures so that the resulting fracture systems overlap and so that said first well is sealed from the fractures made thru said second well and said second well is sealed from the fracture made thru said first well; initiating combustion in said formation along the fracture communicating with said first well; advancing the resulting combustion zone both upwardly and downwardly toward said upper and lower fractures around said second well by passing combustion supporting gas to said zone thru one of the wells; and recovering from the other of the wells hydrocarbons driven from said formation by the combustion.

3. The process of claim 2 wherein said combustion zone is advanced by injecting air thru said upper and lower fractures and recovery is thru said first well.

4. The process of claim 2 including reversal of said combustion zone after it reaches the upper and lower fractures by continued air injection thereby driving same back to said intermediate fracture so as to recover additional hydrocarbon from the formation.

5. The process ofclaim 1 wherein said combustion zone is advanced by injecting air thru said upper and lower fractures so as to effect flow of air countercurrently to movement of the combustion zone, and combustion gases and hydrocarbons are removed thru said intermediate fracture.

6. The process of claim 5 including reversal of said combustion zone after it reaches said upper and lower fractures by continuing said air injection thereby driving same back to said intermediate fracture.

7. The process ofclaim 1 wherein said combustion zone is advanced thru said formation by direct air injection thru said intermediate fracture.

8. The process of claim 2 wherein said combustion zone is advanced thru said formation by direct'air injection thru said intermediate fracture.

References Cited in the file of this patent UNITED STATES PATENTS 7,479 Wolcott June 5, 1923 1,494,735 Cooper May 20, 1924 1,899,497 Doherty Feb. 28, 1933 2,413,765 Buddrus et al Dec. 17, 1946 2,497,868 Dah'n Feb. 21, 1950 2,630,307 Martin Mar. 3, 1953 2,642,943 Smith et al. June 23, 1953 2,687,179 Dismukes Aug. 24, 1954 2,754,911 Spearow July 17, 1956 2,780,449 Fisher et al. Feb. 5, 1957 2,818,118 Dixon Dec. 31, 1957

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