US2967052A - In situ combustion process - Google Patents

Description

Jan. 3, 1961 F. w. CRAWFORD 2,967,052

IN SITU COMBUSTION PROCESS Filed March 51. 1958 AIR INJECTION (AIR K E STRATEJM INVENTOR.

F. W. CRAWFORD ates IN SIT-U COMBUSTIONPROCESS -9 Claims. (Cl. 262-3) This invention relates to .a .process --for ginitiating and effecting in situ combustion .in a carbonaceous stratum.

In situ combustion in the recovery vof hydrocarbons from underground strata containing carbonaceous material is becoming more prevalent in the petroleum industry. In this technique of production, combustion is initiated in thecarbonaceous stratum and the resulting combustion zone .is caused to move thru the stratum by either inverse or direct air drive whereby the heat of combustion of a substantial proportion of the hydrcarbon in the stratum drives out and usually upgrades a substantial proportion of the unburned hydrocarbon material.

The ignition .of carbonaceous material in :a {stratum around a borehole therein, followed by injection of air thru the ignition borehole and recovery of product bydrocarbons and combustion gas thru another borehole in the stratum, is a direct air .drive process for effecting in situ combustion andrecovery of hydrocarbons from the stratum. ln-this type of operation .the stratum usually plugs in ;front of the combustion zone "because a heavy viscous liquid bank of hydrocarbon .collects in .the stratum in advance of the combustion zone which .prevents movement of air to the combustion process. :To overcome this difliculty and ,to permit the continued progress of the combustion zone thru the stratum,.inverse .air injection has :been resorted to. By this technique, a .combustion zone is established around an ignit-ioniborehole by any suitable means and air :iS fed thru the stratum to the combustion zone from one ,ormore surroun ingboreholes- In either ;a zdirect or inverse air injection proces-s't'he stratum containing the carbonaceous material mustfirst be ignited around :a borehole therein where it is desired t i ti t e combu tion proce Some difficulty has been experienced in establishing combustion in .thecarbonaceous material around -a borehole because of :the hi h :hea l ss s t t e a ja n ro k nds r tum. Various types of theaters have been utilized ;to.-raise the temperature of the stratum around the ignition borehole -=to ignition temperature so that the combustion processtakes off When contacted with Q -containinggas, usually air. This invention is concerned with a method or process for {simultaneously drilling an {ignition borehole in a. carbonaceous stratum and igniting thestraturn around the borehole.

It is accordingly an object of the invention to provide an improved process for initiating in situ combustion in a carbonaceous stratum around a boreho'e therein. Another object of the invention is to provide a process for simultaneously drilling a borehole thru a carbonaceous stratum and igniting 1the1 tratum around :the :borehole. Arfurther object .is to .provide a process for establishing :in situcombustion in a carbonaceous stratum and simultaneously .initiatingmovement of the combustion zone thru the formation by inverse air injection. Other objects of the-invention will become apparent upon consideration of the accompanying disclosure.

atent ICE -A :broad .aspect of the invention comprises drilling :a borehole thru a carbonaceous stratum by means of a flame drill and simultaneously contacting the hot wall of tthetborehole with o -containing gas so as to initiate combustion of .the carbonaceous material adjacent the borehole. The initiation of combustion maybe eifected during any stage of the flame drilling step by contacting the wall of the borehole while at or above ignition temperature with tree-oxygen containing gas, such as air; however, it is preferred to feed air in excess to .the hot .drilling zone during the early stages of .the drilling so that combustion is initiated in the stratum from .the top to the bottomsection thereof.

=,Where the term air is utilized herein, it .is to be understood that other (D -containing gas or gases, such as diluted air or air enriched with oxygen, may be utilized inizlieu thereof providing the concentration of O .is sufli- .cient to initiate and/ or propagate combustion of the .carbouaceous material.

fDuring thermal or flame .drilling of the carbonaceous stratum air for combustion of the carbonaceous material may be supplied thru the ignition borehole by :suitable conduit means leading to the heated area such as thru the drill string or thru .conduit attached to the drill string.

The preferred method of contacting the heated section of :stratum .during the flame or thermal drilling process comprises injecting air into .the stratum thru one or more boreholes closely spaced to the ignition boreho'e being vdrilled so that the air passes thru the stratum to the hot area around the ignition borehole. .In this manner as ignition of the stratum takes place, the resulting com- ;bustion zone is :moved laterally outwardly from the ignition borehole toward the injection borehole or boreholes. This procedure establishes in situ combustion by inverse air injection simultaneously with the drilling of the ignivtion borehole.

The flame drilling of rock and mineral formations is conventional, as illustrated by US. Patents 2,674,993, 2j 693,9 37, and 2,628,817. An improved thermal drill suitable :for effecting the process of the invention is disclosed and claimed in the application of Martin AJRyan, S erial No. 515,940, filed June 16, 1955 now Patent No. 2,896,914. In the process of these patents the rock in the path of the borehole is melted and spalled and other- .wise disintegrated into fine particles which are blown :out of the borehole by means of the high velocity of the .cornbpstion gas from the .burner. The burner -of :the above-identified application imparts a spiral movement .to the rapidly expanding flame gases emanating from the burner, which aids in disintegrating the rock, and is particularly suitable for use in this invention.

.Elio illustrate the invention, reference is made to the accompanying schematic drawing which is an e'evation gin section thru a formation showing an arrangement of boreholes and apparatus for. eflecting the invention.

Referring to the drawing, a carbonaceous stratum 10 penetratediby .air injection borehole 12 and an ignition borehole 514. A flame drill 16 is provided with an .air line 18and ,a fuel gas line 20. Flame and hot combustion gas at 22 impinges upon the stratum in the area of 24 to heat, spall .and disintegrate the rock formation below the flame ,drill. 'During drilling air is injected thru line :26 and borehole 12 into the stratum 10 from which it travels to borehole 14 where it initiates combustion of the in-place hydrocarbon material when the temperature of the stratum at the ignition well reaches combustion supporting temperature. During the process combustion gases and produced gases are passed thru line 28 to suitable recovery equipment.

Well 12 is illustrative of a line of wells or a ring of wells encircling ignition well 14.

The injection of air for the combustion of carbonaceous material during the flame drilling of the carbonaceous stratum is preferably effected thru a ring of injection boreholes surrounding the ignition borehole being flame drilled. The injection borehole or boreholes should be spaced a short distance from the ignition borehole within the range of a few feet to 50 feet or more depending upon the permeability of the stratum. Usually the injection boreholes can be effectively spaced a distance of 5 to 25 feet from the ignition borehole. In coal seams and other carbonaceous stratum of extremely low permeability, the process can be readily efiected by horizontally fracturing the stratum at one or more selected levels therein by conventional methods such as by hydraulic or other fluid pressure, including air pressure. The fracturing is effected thru the injection boreholes by packing off the selected level around an injection conduit or Well tubing and applying fluid pressure to the stratum at the packed olf level thru an outlet in the tubing until the stratum separates thereby causing fracturing. Propping of the fracture or fractures with sand or other particulate solid material may be effected in order to keep the fractures open. When fracturing with a gas, such as air, alternately increasing and decreasing pressure rapidly thru the fracturing pressure, after fracturing has been effected, results in fluttering and creation of sufficient debris in the fractures to provide propping. However, the specific fracturing and propping procedure to be utilized is not a part of the invention and further discussion is believed unnecessary.

The invention is also applicable to in-line in situ combustion drive wherein a line of ignition boreholes is drilled only down to the stratum to be produced and, before flame drilling the boreholes thru the stratum, a line of injection boreholes is drilled thru the stratum substantially parallel to the line of ignition boreholes and spaced therefrom sufliciently close to permit injection of air thru the stratum to the line of ignition boreholes with reasonable air injection pressures. If the permeability of the stratum is low so as to require excessive injection pressures, the stratum should be fractured horizontally so that the fractures extend toward the ignition boreholes and preferably to the axis of the borehole, particularly, where the carbonaceous stratum is impermeable as in a vein of bituminous or anthracite coal. It is feasible to simultaneously drill more than one of the ignition boreholes with a flame drill thru the carbonaceous stratum and inject air thru the stratum to the flame drilling area or areas so as to initiate combustion in a plurality of the boreholes at substantially the same time. It is also feasible to initiate combustion during flame drilling in the carbonaceous stratum in one borehole at a time until all of the ignition boreholes in the line have been drilled and the area surrounding the same has been ignited.

In one embodiment of the invention two lines of injection boreholes are utilized for injecting air during the flame drilling of the carbonaceous stratum in the several ignition boreholes. In this procedure in-line injection boreholes are positioned on opposite sides of the line of ignition boreholes so that the combustion zone is moved radially outwardly from each ignition borehole and from the line of ignition boreholes toward the injection boreholes on both sides of the line of ignition boreholes. In this manner the recovery of hydrocarbons by in situ combustion is speeded up and is rendered more efficient.

In the various embodiments of the invention thus far described, the preferred procedure is to drill the ignition boreholes to the petroliferous bed and set the surface casing in the borehole with or without cementing and then proceed with the step of flame drilling thru the petroiiferous bed while injecting air thru said bed to the hot Wall of the boreholes so as to establish combustion of the petroliferous material.

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 of the invention.

I claim:

1. A process for completing an ignition borehole in a stratum containing carbonaceous material which comprises drilling a borehole to said stratum from the surface; drilling from said borehole thru said stratum with a flame drill by continuously directing a flame into said stratum whereby said stratum is heated to ignition temperature; and simultaneously contacting the wall of said borehole within said stratum with O -containing gas so to initiate combustion of said stratum radially around said borehole.

2. The process of claim 1 wherein said combustion is initiated by injecting said gas into said stratum thru at least one adjacent borehole during the step of drilling with said flame drill so that 0 passes into the heated zone to ignite said stratum.

3. The process of claim 2 wherein air is injected into said stratum thru a ring of boreholes surrounding said ignition borehole.

4. The process of claim 1 wherein air for combustion of said carbonaceous material is injected into said stratum thru said borehole to initiate combustion and thereafter air is injected into said stratum thru at least one other borehole, whereby said air passes to the resulting combustion zone and moves same countercurrently to flow of air.

5. The process of claim 1 including the step of moving said flame drill up and down in said borehole within said stratum so as to play said flame on the wall of said borehole thereby increasing the temperature of the surrounding stratum.

6. A process for simultaneously drilling an ignition borehole in a carbonaceous stratum and initiating in situ combustion therein which comprises drilling an ignition borehole to an upper section of said stratum; drilling at least one injection borehole thru said stratum adjacent said first borehole; horizontally fracturing said stratum thru said at least one injection borehole to provide at least one fracture extending to the line of said ignition borehole; thereafter drilling said ignition borehole thru said stratum with a flame drill by continuously directing a flame into said stratum so as to heat the wall thereof to ignition temperature; and while said ignition borehole is at said temperature and while continuing flame drilling, injecting air into said at least one injection borehole so as to pass air to the hot section around said ignition borehole and establish in situ combustion in said stratum.

7. The process of claim 6 wherein several injection boreholes ringing said ignition borehole are used in fracturing and in air injection so as to advance the resulting combustion zone outwardly from said ignition borehole.

8. The process of claim 6 wherein a row of in-line ignition boreholes are drilled, a generally parallel row of injection boreholes are drilled, fracturing is effected thru the injection boreholes, thermal drilling is efiected in the ignition boreholes, and air is injected thru the injection boreholes.

9. The process of claim 8 wherein a second line of boreholes on the opposite side of the line of ignition boreholes from said row of injection boreholes is also used for fracturing and air injection.

References Cited in the file of this patent UNITED STATES PATENTS 2,584,605 Merriam et al. Feb. 5, 1952 2,688,464 Payne Sept. 7, 1952 2,780,449 Fisher et al. Feb. 5, 1957 2,818,118 Dixon Dec. 31, 1957 2,833,516 Salomonsson May 6, 1958 2,889,882. Schleicher June 9, 1959

Claims (1)

1. A PROCESS FOR COMPLETING AN IGNITION BOREHOLE IN A STRATUM CONTAINING CARBONACEOUS MATERIAL WHICH COMPRISES DRILLING A BOREHOLE TO SAID STRATUM FROM THE SURFACE; DRILLING FROM SAID BOREHOLE THRU SAID STRATUM WITH A FLAME DRILL BY CONTINUOUSLY DIRECTING A FLAME INTO SAID STRATUM WHEREBY SAID STRATUM IS HEATED TO IGNITION TEMPERATURE; AND SIMULTANEOUSLY CONTACTING THE WALL OF SAID BOREHOLE WITHIN SAID STRATUM WITH O2-CONTAINING GAS SO TO

Images